Showing posts with label Fyi. Show all posts
Showing posts with label Fyi. Show all posts

Wednesday, March 19, 2014

how battery works 4

Understanding battery capacity: Ah is not A

Posted by Jan on 12 November 2010
I used battery holders for eight “C” alkaline cells on my robot after not finding a 12V, 1A battery.
My earliest electronics projects and my first robot were powered by regular alkaline batteries, and I didn’t think about current or the capacity of those batteries. The batteries were prominently labeled “1.5V”, and I was happy in my understanding that putting four in a battery holder got me to 6 volts; when the motors slowed down, it was time for new batteries. When I began designing my second robot, I found some 12V, 1A motors (what a “1-amp motor” might mean is a topic for another post) and promptly wasted many hours dragging parents and teachers to Radio Shack and car parts stores looking for a 12V, 1A battery. No one understood that the batteries were labeled with capacity, not current, and since the smallest 12V motorcycle and alarm system batteries in town were 3Ah or 4Ah, I went home empty handed. I ended up using alkalines. Apparently, once the battery capacity wasn’t in my face, I forgot about my concern that they would force too much current into my motors.
I made many common mistakes in going about my battery selection:
  • Not understanding that my circuit would draw whatever current it wanted from the battery, as opposed to the battery forcing a given amount of current into the circuit.
  • Thinking that my motors would draw a fixed amount of current.
  • Confusing current and capacity.
  • Ignoring the “h” in “Ah”
  • Forgetting about a property, such as capacity, as soon as it wasn’t in my face.
The first two points are complex enough that further elaboration would merit their own posts; today I want to focus on some technical details of battery capacity and current and touch on the sloppy attitude that leads to the last two mistakes.
A battery stores energy; the “capacity” is how much energy it can store. Energy is measured in joules, abbreviated J, but it can also be expressed in different units such as watt-hours, abbreviated Wh (for larger quantities, such as residential electricity use, kilowatt-hours (kWh) are used; a kWh is a thousand Wh). This is similar to the way area can be measured in acres or in square miles: there are units specifically for area, such as acres, but you can also arrive at a measure of area by multiplying length by length, to get mile-miles, or the less awkward square miles. (The hyphenation imposed by English grammar does not help matters since the hyphen looks like a minus sign when we are actually multiplying the units together.) Watts and watt-hours are generally good units for electronics since they are easily related to voltage and current and since typical batteries that you can hold in your hand will have a capacity of a few dozen watt-hours.
In the case of a typical battery, where we can assume a constant voltage, we can replace watts with volts multiplied by amps. A 12-volt, 1 amp-hour (abbreviated Ah) battery and a 6-volt, 2Ah battery each store 12Wh, but the voltage is usually a critical parameter for a battery, and once a voltage is selected, the capacity can be specified by the amp-hour rating. The value in using the amp-hour is that it makes explicit our multiplication of rate, the amp, and time, the hour: a battery rated for one amp-hour can provide a current of one amp for about one hour, two amps for about half an hour, or 0.1 amps for about ten hours. I say “about” because the exact capacity will depend on the current.
The current and capacity for a battery are like the speed and range of a car. If your car has a range of about 300 miles, you can go 30 miles an hour for ten hours, or 60 miles an hour for five hours. Your efficiency will get worse with speed, so by the time you go 60 miles per hour, you might run out of gas after only four hours, for a range of 240 miles. Going back to my battery search, looking for a 1-amp battery was like looking for a car with a speed of 60 miles: 60 miles isn’t even a speed, and even if I revised my search to a car that could go 60 miles per hour, it still wouldn’t be a useful specification to look for. Most batteries on the scale I was looking at can deliver one amp, just like most cars can go sixty miles per hour. The maximum available current, like the maximum speed of the car, might be a more reasonable specification to search for, though providing those kinds of specifications might make the respective manufacturers nervous.
It is reasonable, though, to consider the maximum current a battery can safely deliver. That value will depend on all kinds of things, including the chemistry of the battery, but the maximum discharge rate is almost always tied to the capacity. That means that given a particular technology, a battery with double the capacity can deliver double the maximum current. Batteries are often specified with a discharge rate in terms of C, where C is the capacity of the battery divided by hours. For example, for a 2Ah battery, C is 2A. If the battery has a maximum discharge rate of 10C, the maximum current is 20 amps. It’s good to keep in mind that a 10C discharge rate means a battery life of less than 1/10th of an hour, and with the loss of capacity that a high discharge rate generally causes, the battery life would be less than five minutes.
As I tried earlier to recall what happened with my failed battery search, I was struck by the extent to which I ignored the “h” in the “Ah” specification and the ease with which I forgot about my critical “1-amp battery” requirement when I returned to the alkaline batteries. Unfortunately, this kind of carelessness or sloppiness is common, especially for beginners who might already be overwhelmed by all the information they need to sort through and who have not yet had the experience of losing time and destroying hardware because of inattention to details. I do not have any particular solution to this problem beyond reminding you to pay attention and think about how things should work before just hooking things up. Be on the lookout for contradictions; seeing “Ah” where you expect “A” should definitely make you very uneasy and lead you to reevaluate your expectations.
I will wrap up this article with some example battery capacities.
AA batteries.
  • A typical alkaline or NiMH battery in the standard “AA” size has about 2000 to 3000 mAh (or 2 to 3 Ah). With a cell voltage of 1.2 V to 1.5V, this corresponds to 2 to 4 Wh per cell. When multiple cells are used in series, as with the use of a battery holder or most pre-made battery packs, the voltage goes up but the capacity in amp-hours stays the same: an 8-cell NiMH pack made of AA cells will have a 9.6 V nominal voltage and a 2500 mAh capacity. There can be quite a range in capacities depending on the quality of the batteries. For larger cells, such as C and D size, the capacity should go up approximately proportionally to volume, but some cheap units (they’re usually light) can have the same capacity as the smaller cells. Alkaline cells have a more pronounced drop in capacity as the current drawn out of them goes up, so for applications requiring several hundred mA or more current, NiMH cells of the same size could last significantly longer. For low-current applications that need to run for months, alkaline batteries can last much longer because NiMH cells can self-discharge in a few months.

9V battery.
  • 9V alkaline batteries can be convenient for their high voltage in a small size, but the energy density (watt-hours per given volume or weight) is the same as other batteries with the same chemistry, which means the capacity in amp-hours is low. In approximately the same size as an AA cell, you get six times the voltage, so you also get about six times less in the Ah rating, or about 500 mAh. Given the high losses incurred from discharging in anything under a few hours, 9V batteries are impractical for most motors and therefore for most robots.

Coin or button cell batteries.
  • Coin or button cell batteries vary in size and chemistry, but you can generally expect 1.5 to 3 volts with a few dozen to a few hundred mAh.

12V, 8Ah sealed lead-acid battery.
  • Lead-acid batteries are popular for larger projects since they are usually the lowest-cost option and are widely available. Sealed lead-acid or gel-cell batteries are available in 6 V and 12 V versions (other multiples of 2 can be found), with the 12 V versions weighing about a pound per amp-hour. 12 V car batteries store a few dozen amp hours, and they weigh a few dozen pounds.

11.1V, 1800mAh Li-Po battery.
  • Lithium-based rechargeable batteries have around double the energy density of alkaline and NiMH batteries by volume and even better improvements by weight. These newer batteries are far less standardized in terms of battery size and shape, but since they are usually intended for applications where capacity or maximum battery life are important, these batteries usually have their voltages and capacities prominently labeled.

how battery works 3

Battery Basics

How Do Lead Acid Batteries Work?

Lead Acid batteries have changed little since the 1880's although improvements in materials and manufacturing methods continue to bring improvements in energy density, life and reliability. All lead acid batteries consist of flat lead plates immersed in a pool of electrolyte. Regular water addition is required for most types of lead acid batteries although low-maintenance types come with excess electrolyte calculated to compensate for water loss during a normal lifetime.

Battery Construction

Lead acid batteries used in the RV and Marine Industries usually consist of two 6-volt batteries in series, or a single 12-volt battery. These batteries are constructed of several single cells connected in series each cell produces approximately 2.1 volts. A six-volt battery has three single cells, which when fully charged produce an output voltage of 6.3 volts. A twelve-volt battery has six single cells in series producing a fully charged output voltage of 12.6 volts.
A battery cell consists of two lead plates a positive plate covered with a paste of lead dioxide and a negative made of sponge lead, with an insulating material (separator) in between. The plates are enclosed in a plastic battery case and then submersed in an electrolyte consisting of water and sulfuric acid (see figure # 1). Each cell is capable of storing 2.1 volts.A battery cell.
In order for lead acid cell to produce a voltage, it must first receive a (forming) charge voltage of at least 2.1-volts/cell from a charger. Lead acid batteries do not generate voltage on their own; they only store a charge from another source. This is the reason lead acid batteries are called storage batteries, because they only store a charge. The size of the battery plates and amount of electrolyte determines the amount of charge lead acid batteries can store. The size of this storage capacity is described as the amp hour (AH) rating of a battery. A typical 12-volt battery used in a RV or marine craft has a rating 125 AH, which means it can supply 10 amps of current for 12.5 hours or 20-amps of current for a period of 6.25 hours. Lead acid batteries can be connected in parallel to increase the total AH capacity.
In figure # 2 below, six single 2.1-volt cells have been connected in series to make the typical 12-volt battery, which when fully charged will produce a total voltage of 12.6-volts.
A typical 12-volt battery.

Lead Acid Batter Discharge Cycle

Fully charged battery provides electricity to a light bulb.
In figure # 3, above a fully charged battery is connected to a load (light bulb) and the chemical reaction between sulfuric acid and the lead plates produces the electricity to light the bulb. This chemical reaction also begins to coat both positive and negative plates with a substance called lead sulfate also known as sulfation (shown as a yellow build-up on plates). This build-up of lead sulfate is normal during a discharge cycle. As the battery continues to discharge, lead sulfate coats more and more of the plates and battery voltage begins to decrease from fully charged state of 12.6-volts (figure # 4).
Discharging battery.
In figure # 5 the battery is now fully discharged, the plates are almost completely covered with lead sulfate (sulfation) and voltage has dropped to 10.5-volts.
NOTE: Discharging a lead acid battery below 10.5 volts will severely damage it!
Fully discharged battery.
Lead sulfate (sulfation) now coats most of the battery plates. Lead sulfate is a soft material, which can is reconverted back into lead and sulfuric acid, provided the discharged battery is immediately connected to a battery charger. If a lead acid battery is not immediately recharged, the lead sulfate will begin to form hard crystals, which can not be reconverted by a standard fixed voltage (13.6 volts) battery converter/charger.
NOTE: Always recharge your RV or Marine battery as soon as possible to prevent loss of battery capacity due to the build-up of hard lead sulfate crystals!

Lead Acid Battery Recharge Cycle

The most important thing to understand about recharging lead acid batteries is that a converter/charger with a single fixed output voltage will not properly recharge or maintain your battery. Proper recharging and maintenance requires an intelligent charging system that can vary the charging voltage based on the state of charge and use of your RV or Marine battery. Progressive Dynamics has developed intelligent charging systems that solve battery problems and reduce battery maintenance.
The discharged battery shown in figure # 6 on the next page is connected to a converter/charger with its output voltage set at 13.6-volts. In order to recharge a 12-volt lead acid battery with a fully charged terminal voltage of 12.6-volts, the charger voltage must be set at a higher voltage. Most converter/chargers on the market are set at approximately 13.6-volts. During the battery recharge cycle lead sulfate (sulfation) begins to reconvert to lead and sulfuric acid.
Discharged battery connected to a converter/charger.
During the recharging process as electricity flows through the water portion of the electrolyte and water, (H2O) is converted into its original elements, hydrogen and oxygen. These gasses are very flammable and the reason your RV or Marine batteries must be vented outside. Gassing causes water loss and therefore lead acid batteries need to have water added periodically. Sealed lead acid batteries contain most of these gasses allowing them to recombine into the electrolyte. If the battery is overcharged pressure from these gasses will cause relief caps to open and vent, resulting in some water loss. Most sealed batteries have extra electrolyte added during the manufacturing process to compensate for some water loss.
Fully recharged battery.
The battery shown in figure # 7 above has been fully recharged using a fixed charging voltage of 13.6-volts. Notice that somelead sulfate (sulfation) still remains on the plates. This build-up will continue after each recharging cycle and gradually the battery will begin to loose capacity to store a full charge and eventually must be replaced. Lead sulfate build up is reduced if battery is given an Equalizing Charge once every 10 discharge cycles or at least once a month. An Equalizing Chargeincreases charging voltage to 14.4 volts or higher for a short period. This higher voltage causes gassing that equalizes (re-mixes) the electrolyte solution.
Since most RV and Marine craft owners seldom remember to perform this function, Progressive Dynamics has developed the microprocessor controlled Charge Wizard. The Charge Wizard will automatically provide an Equalizing Charge every 21 hours for a period of 15 minutes, when the battery is fully charged and not in use. Our 2000 Series of Marine Battery Chargers have the Charge Wizard feature built-in.
One disadvantage of recharging a lead acid battery at a fixed voltage of 13.6-volts is the recharge time is very long. A typical 125-AH RV or Marine battery will take approximately 80 hours to recharge at 13.6 volts. Increasing the charge voltage to 14.4-volts will reduce battery recharge time for a 125-AH battery to 3-4 hours. Once a battery reaches 90% of full charge, thevoltage must be reduced from 14.4-volts to 13.6-volts to reduce gassing and water loss. The optional Charge Wizardautomatically senses when a battery has a very low state of charge and automatically selects its BOOST MODE of operation.BOOST MODE increases the voltage of a PD9100 Series converter/charger to 14.4 volts. When the battery reaches the 90% charge level, the Charge Wizard automatically reduces the charge voltage down to 13.6 volts to complete the charge. Again, this is a standard feature on our Marine Chargers.
Another disadvantage of recharging a lead acid battery at a fixed voltage of 13.6-volts is that once it is fully charged, 13.6 volts will cause considerable gassing and water loss. To prevent this from occurring the charging voltage must be reduced to 13.2-volts. The Charge Wizard will automatically select its STORAGE MODE of operation (13.2-volts) once the battery reaches full charge and remains unused for a period of 30 hours. This feature is standard on all of Progressive Dynamics Marine Battery Chargers.
At a charging voltage of 13.2 volts, the converter/charger will maintain a full charge, reduce gassing and water loss. However, this lower voltage does not provide enough gassing to prevent a battery condition called Battery Stratification. Battery Stratification is caused by the fact that the electrolyte in the battery is a mixture of water and acid and, like all mixtures, one component, the acid, is heavier than water. Therefore, acid will begin to settle and concentrate at the bottom of the battery (see figure #8).
Battery stratification.
This higher concentration of acid at the bottom of the battery causes additional build-up of lead sulfate (sulfation), which reduces battery storage capacity and battery life. In order to prevent Battery Stratification, an Equalization Charge(increasing charging voltage to 14.4-volts) must be applied periodically. The Charge Wizard automatically selects itsEQUALIZATION MODE (14.4 volts) every 21 hours for a period of 15 minutes. This Equalizing Charge feature is standard on our Marine chargers.
As you have learned, in order to properly charge and maintain a lead acid battery you must use an intelligent charging system. Progressive Dynamics, Inteli-Power 9100 Series RV converters with a Charge Wizard installed, or one of our Inteli-Power Marine Battery Chargers will provide the intelligent charging system your battery needs for a long life, with low maintenance.

Answers to Common Questions about Batteries

Do lead acid batteries discharge when not in use?
All batteries, regardless of their chemistry, will self-discharge. The rate of self-discharge for lead acid batteries depends on the storage or operating temperature. At a temperature of 80 degrees F. a lead acid battery will self-discharge at a rate of approximately 4% a week. A battery with a 125-amp hour rating would self-discharge at a rate of approximately five amps per week. Keeping this in mind if a 125 AH battery is stored for four months (16 weeks) winter without being charged, it will loose 80 amps of its 125-amp capacity. It will also have severe sulfation, which causes additional loss of capacity. Keep your batteries charged while not in use!
Do lead acid batteries develop a memory?
Lead acid batteries do not develop any type of memory.
Do I need to completely discharge my lead acid battery before recharging it?
No, in fact you should never discharge your lead acid battery below 80% of its rated capacity. Discharging it below this point or 10.5 volts can damage it.
When do I need to perform an equalization charge?
Equalizing should be performed when a battery is first purchased (called a freshening charge) and on a regular basis (every 10 discharge cycles or at least once a month). Reduced performance can also be an indicator that an equalizing charge is needed.
What is an equalizing charge?
An equalizing charge for a 12 volt battery requires that it be charged with a voltage of at least 14.4 volts for a period of at least one hour once a month, or every 10 discharge cycles. An equalizing charge prevents battery stratification and reduces sulfation, the leading cause of battery failure.
When should I add water to my batteries?
How often you use and recharge your batteries will determine the frequency of watering. Also, using batteries in a hot climate will require more frequent watering. It is best to check your battery water level frequently and add distilled water when needed. Never add tap water to your battery. Tap water contains minerals that will reduce battery capacity and increase their self-discharge rate.
Warning - A brand new battery may have a low electrolyte level. Charge the battery first and then add water if needed. Adding water to a battery before charging may result in overflow of the electrolyte.
What is the proper electrolyte level?
Battery electrolyte levels should be just below the bottom of the vent well, about ½ - ¾ inch above the tops of the separators. Never let the electrolyte level to drop below the top of the plates.
Do I ever need to add acid to my battery?
Under normal operating conditions, you never need to add acid. Only distilled or deionized water should be added to achieve the recommended electrolyte levels.
Can my batteries freeze?
If your battery is partially discharged, the electrolyte in a lead acid battery may freeze. At a 40% state of charge, electrolyte will freeze if the temperature drops to approximately -16 degrees F. When a battery is fully charged the electrolyte will not freeze until the temperature drops to approximately -92 degrees F.
What are the most common mistakes made by owners of lead acid batteries?
  • Undercharging - Generally caused by not allowing the charger to restore the battery to full charge after use. Continuously operating a battery in a partial state of charge, or storing the battery in the discharged state results in the formation of lead sulfate (sulfation) on the plates. Sulfation reduces the performance of the battery and may cause premature battery failure.
  • Overcharging - Continuous-charging causes accelerated corrosion of the positive plates, excessive water consumption and in some cases, damaging temperatures within the battery. Lead acid batteries should be charged after each discharge of more the 50% of its rated capacity and during or after prolonged storage of 30 days or more.
  • Under-watering - In lead acid batteries water is lost during the charging process. If the electrolyte level drops below the tops of the plates, irreparable damage may occur. Check your battery water level frequently.
  • Over-watering - Excessive watering of a battery results in additional dilution of the electrolyte, resulting in reduced battery performance. Add water to your battery after it has been fully charged, never when the battery is partially discharged.
Can I reduce the need to add water to my battery by lowering the charging voltage to 13 volts or less?
Lowering the charging voltage will reduce the need to add water, but this will cause a condition known as battery stratification. Battery stratification is caused when the sulfuric acid in the electrolyte mixture separates from the water and begins to concentrate at the bottom of the battery.
This increased concentration of acid increases the formation of lead sulfate (sulfation). To prevent stratification, your battery should receive a periodic equalizing charge (increasing the charging voltage to 14.4 volts or above).

how battery works 2

Battery ratings

Because batteries create electron flow in a circuit by exchanging electrons in ionic chemical reactions, and there is a limited number of molecules in any charged battery available to react, there must be a limited amount of total electrons that any battery can motivate through a circuit before its energy reserves are exhausted. Battery capacity could be measured in terms of total number of electrons, but this would be a huge number. We could use the unit of the coulomb (equal to 6.25 x 1018 electrons, or 6,250,000,000,000,000,000 electrons) to make the quantities more practical to work with, but instead a new unit, the amp-hour, was made for this purpose. Since 1 amp is actually a flow rate of 1 coulomb of electrons per second, and there are 3600 seconds in an hour, we can state a direct proportion between coulombs and amp-hours: 1 amp-hour = 3600 coulombs. Why make up a new unit when an old would have done just fine? To make your lives as students and technicians more difficult, of course!
A battery with a capacity of 1 amp-hour should be able to continuously supply a current of 1 amp to a load for exactly 1 hour, or 2 amps for 1/2 hour, or 1/3 amp for 3 hours, etc., before becoming completely discharged. In an ideal battery, this relationship between continuous current and discharge time is stable and absolute, but real batteries don't behave exactly as this simple linear formula would indicate. Therefore, when amp-hour capacity is given for a battery, it is specified at either a given current, given time, or assumed to be rated for a time period of 8 hours (if no limiting factor is given).
For example, an average automotive battery might have a capacity of about 70 amp-hours, specified at a current of 3.5 amps. This means that the amount of time this battery could continuously supply a current of 3.5 amps to a load would be 20 hours (70 amp-hours / 3.5 amps). But let's suppose that a lower-resistance load were connected to that battery, drawing 70 amps continuously. Our amp-hour equation tells us that the battery should hold out for exactly 1 hour (70 amp-hours / 70 amps), but this might not be true in real life. With higher currents, the battery will dissipate more heat across its internal resistance, which has the effect of altering the chemical reactions taking place within. Chances are, the battery would fully discharge some time before the calculated time of 1 hour under this greater load.
Conversely, if a very light load (1 mA) were to be connected to the battery, our equation would tell us that the battery should provide power for 70,000 hours, or just under 8 years (70 amp-hours / 1 milliamp), but the odds are that much of the chemical energy in a real battery would have been drained due to other factors (evaporation of electrolyte, deterioration of electrodes, leakage current within battery) long before 8 years had elapsed. Therefore, we must take the amp-hour relationship as being an ideal approximation of battery life, the amp-hour rating trusted only near the specified current or timespan given by the manufacturer. Some manufacturers will provide amp-hour derating factors specifying reductions in total capacity at different levels of current and/or temperature.
For secondary cells, the amp-hour rating provides a rule for necessary charging time at any given level of charge current. For example, the 70 amp-hour automotive battery in the previous example should take 10 hours to charge from a fully-discharged state at a constant charging current of 7 amps (70 amp-hours / 7 amps).
Approximate amp-hour capacities of some common batteries are given here:
  • Typical automotive battery: 70 amp-hours @ 3.5 A (secondary cell)
  • D-size carbon-zinc battery: 4.5 amp-hours @ 100 mA (primary cell)
  • 9 volt carbon-zinc battery: 400 milliamp-hours @ 8 mA (primary cell)
As a battery discharges, not only does it diminish its internal store of energy, but its internal resistance also increases (as the electrolyte becomes less and less conductive), and its open-circuit cell voltage decreases (as the chemicals become more and more dilute). The most deceptive change that a discharging battery exhibits is increased resistance. The best check for a battery's condition is a voltage measurement under load, while the battery is supplying a substantial current through a circuit. Otherwise, a simple voltmeter check across the terminals may falsely indicate a healthy battery (adequate voltage) even though the internal resistance has increased considerably. What constitutes a "substantial current" is determined by the battery's design parameters. A voltmeter check revealing too low of a voltage, of course, would positively indicate a discharged battery:
Fully charged battery:
Now, if the battery discharges a bit . . .
. . . and discharges a bit further . . .
. . . and a bit further until its dead.
Notice how much better the battery's true condition is revealed when its voltage is checked under load as opposed to without a load. Does this mean that its pointless to check a battery with just a voltmeter (no load)? Well, no. If a simple voltmeter check reveals only 7.5 volts for a 13.2 volt battery, then you know without a doubt that its dead. However, if the voltmeter were to indicate 12.5 volts, it may be near full charge or somewhat depleted -- you couldn't tell without a load check. Bear in mind also that the resistance used to place a battery under load must be rated for the amount of power expected to be dissipated. For checking large batteries such as an automobile (12 volt nominal) lead-acid battery, this may mean a resistor with a power rating of several hundred watts.
  • REVIEW:
  • The amp-hour is a unit of battery energy capacity, equal to the amount of continuous current multiplied by the discharge time, that a battery can supply before exhausting its internal store of chemical energy.
  • An amp-hour battery rating is only an approximation of the battery's charge capacity, and should be trusted only at the current level or time specified by the manufacturer. Such a rating cannot be extrapolated for very high currents or very long times with any accuracy.
  • Discharged batteries lose voltage and increase in resistance. The best check for a dead battery is a voltage test under load.

Related Links

Thursday, April 18, 2013

Time Stops for None (but Eventually for All)










The Plot Thus Far...




If history were taught in the form of stories, it would never be forgotten.


- Rudyard Kipling



5 - 3 billion years ago - The sun was born, throwing off giant gas balls and spewing out elements that eventually coalesced into planets; earth, formerly a boiling ball of molten rock, began to cool and solidify; plates of solid land formed over the surface; water collected, forming oceans; the most basic forms of life (bacteria and blue-green algae) appeared in the electrochemical soup of the oceans.

600 - 200 million years ago - Fossils records appeared; the surface of the planet teemed with primitive life including a few still around today; non-aquatic plants appeared; extensive lava flows - perhaps accompanied by an asteroid impact - caused the Permian mass extinction wiping out 90% of all life on the planet although reptiles soon returned in force - then Pangaea formed when huge volcanoes exploded to the surface - only Eastern and Southeastern Asia and maybe Western North America (including Alaska and east Siberia) weren't included.





Lots about Pangaea remains conjectural - the first map is from Essentials of Geology p 432, the second from wholeo.net

67 - 65 million years ago - Mammals appeared; shortly thereafter (geologically speaking), a 6-mile-wide asteroid hit Chicxulub in the Yucatan with the force of 100 million megatons of TNT - the resulting heat pulse incinerated life on the planet in just a few hours; only those that were in burrows or underwater likely survived.

30 - 2 million years ago - Primitive monkeys and apes appeared in Africa; mammals began to acquire modern characteristics; dogs, modern-type horses, manlike apes appeared; the earliest hominid ancestors appeared, including "Lucy"; Ice Ages caused glaciers to advance and recede; ice carved the Great Lakes and created grasslands where humanoid evolution exploded; stone tool use began; primitive humanoids lived in communities, used fire, hunted, gathered; Homo erectus left Africa.

400,000 - 100,000 BC - Europeans lived in wood shelters and used weapons to kill big game; ocean-going vessels first used; clothes made from processed animal skins were developed and animals were domesticated.

69,000 - 35,000 BC - The last Ice Age; 1/3 of earth's surface was sheathed in ice for much of the period and world geography underwent a drastic change - revealing land bridges and creating ice bridges that assisted migration to all parts of the globe; fire was first used; medicines were developed; homo sapiens appeared.

12,000 - 4,000 BC - Glaciers restricted to Antartica and Greenland; giant mammals became extinct; someone painted graffiti all over a beautiful cave in France, the Christian god created the universe, modern human culture development and spread; settlements become cities; the wheel, pottery, and improved methods of cultivation occur in Mesopotamia and elsewhere; according to theBible, a Great Flood killed almost everything and everybody on the planet.

4000 - 3,000 BC - Man started experimenting with metals; in the Middle East, the first cities were founded and the first constellations recorded; as the southern glaciers were done melting, worldwide sea-levels had risen over 300 feet; the Egyptians built the Sphinx and the Great Pyramid at Giza; Stonehenge was begun (taking 1,500 years or so to complete); Gilgamesh lived and wrote.

2,000 - 1,400 BC - The Egyptian alphabet was produced; the first code of laws was developed; Moses led the Israelites out of Egypt into Canaan in search of a homeland.

1,000 - 600 BC - The Old Testament was begun; the Iliad and Odyssey were composed; the first Olympic games were held and the first music written; money changed everything when people in the Middle East started using coins in trade; Lao-tse, Chinese philosopher and founder of Taoism was born; Alexander the Great lived.

600 to 200 BC - Confucius was born; the Parthenon was built; Plato lived and wrote his Republic; Pythagoras did math; shortly after, Buddha was born, Socrates was executed, Euclid and Aristotle lived and worked and the Mayan calendar was developed; the building of the Great Wall of China was begun.





The Badaling Section of the Great Wall Source: images.cnd.org

200 BC - 100 AD - The Roman Empire; astrology was invented; Spartacus led a failed slave revolt; Cleopatra lived and died; paper was developed in China; Julius Caesar, Augustus Caesar and Jesus of Nazareth were born; Jesus was executed; the Roman persecutions of Christians was begun; the Gospels were written; the Library of Alexandria rose to prominence - it contained lecture halls with 5,000 seats, was the first university and contained by far the largest collection of manuscripts to be seen for centuries thereafter.

100 - 350 AD - Hadrian ruled Rome; by this date, the Romans had paved 50,000 miles of road and begun a postal system; Christianity began to spread from a small cult to become the dominant religious and political power in civilised Europe; the Han dynasty ended in China; Mayan civilisation began its peak.

A manuscript was recently unearthed during building work in Rome. Written in colloquial, even chatty, Latin (the translation can only be an approximation), the text is a 1st-century guide to etiquette during Saturnalia, the pagan festival which Christmas replaced....

350 - 700 AD - The Mongols invaded Europe; the Roman Empire broke up; a plague spread through Europe; King Arthur lived; the silk industry developed; Mohammed founded Islam which grew quickly; the Chinese kept inventing stuff; in 585 AD the earliest recorded date of zero on copper plate occurred in India but it wasn't fully explained until the 7th century, making its way into Arabic books in 770, carried to Europe by the 8th century.





Roman Empire







The Western World in 526AD
Source: pitt.edu


The fall of the Roman Empire heralded the beginning of the Dark Ages, which was followed by the Middle Ages (about the 9th century) - the age when a sense of a national identity (the concept of a nation-state) was created. At that time, there were no real countries as such, but rather a hodge-podge of city-states. Kings were not absolute monarchs during that period but instead had to pacify noblemen because it was they who supplied the peasants for the king’s army.




700 – 850 AD - The Arab empire extended from Lisbon to China; Charles Martel ("The Hammer"), savior of Europe, defeated the Arabs at Tours, halting the Arab advance; Caliph Harun al-Rashid ruled the "Golden Age" of Arab culture; pagodas spread to Japan from China; Vikings attacked Britain; Machu Picchu flourished in Peru; Charlemagne became the first Holy Roman Emperor.

875 AD - Russia was founded by Vikings.





Crusades







Major Crusades
Source: tea.state.tx.us


The Crusades had an enormous influence on the European Middle Ages. At times much of the continent was united under a powerful Papacy, but by the 14th century the old concept of Christendom was fragmented, and the development of centralised bureaucracies, the foundation of the modern nation state was well on its way, in France, England, Burgundy, Portugal, Castile and Aragon partly because of the dominance of the church at the beginning of the crusading era. Although Europe had been exposed to Islamic culture for centuries through contacts in Spain and Sicily, much Islamic thought, such as science, medicine, and architecture, was transferred to the west during the crusades; for example, European castles became massive stone structures, as they were in the east, rather than smaller wooden buildings as they had typically been in the past. The crusades also aided the beginning of the Renaissance in Italy, as various Italian city-states from the very beginning had important and profitable trading colonies in the crusader states, both in the Holy Land and later in captured Byzantine territory.

Source: en.wikipedia.org/wiki/The_crusades




1000 - 1100 AD - Vikings, Arabs and Jews mingled freely in the streets and marketplaces of Europe's major cities; musical notation was systematized; Turks forged high-quality steel; the Anasazi lived in the American southwest; Leif Ericksson discovered America; Beowulf was written; the Chinese invented gunpowder but used it only for fireworks; the Università di Bologna in Italy was founded under a charter from Frederick I Barbarossa making it the longest-lived university in the Western world (today, it is called the Alma Mater Studiorum); the first of many Crusades is launched in an attempt to defend the crumbling Byzantine Empire from encroaching Muslim armies - unlike most of the following Crusades, the First was a success and pushed the Muslim forces back, even recapturing the Christian city of Jerusalem.





The Specola, the former astronomical observatory of Bologna; Copernicus made his observations from there.
Source: pd.astro.it

1100 - 1300 AD - The mostly Turkish Muslim armies regrouped and overan Edessa, then followed up by reconquering Jerusalem - this triggered a good half dozen Crusades, but none managed to duplicate the success of the First; the best was the Third (which fought Saladin to a draw), the worst was the Fourth, which got mixed up in the byzantine politics of the Byzantine Empire - its main accomplishment was sacking the capital of the very empire it was attempting to to defend; a dozen or more crusades followed against any number of targets but met with very little success in the Middle East and were increasingly disassociated from the church, whose temporal power was quickly fading; the leader of the only Crusade to even briefly recapture Jerusalem, the Emperor Frederick II, spent most of his life at war with the Papal States and was excommunicated twice (the Pope of the time was referred to him as the anti-Christ). But as organised religion's power was fading in Europe, it was growomg in Asia - the temple complex Angkor Wat was completed in Cambodia - then the largest city on the planet with over one million citizens; Genghis Khan conquered China, Persia, Russia - then died; the Magna Carta was signed in England; the Inquisition expelled Jews from Spain and Portugal and burned non-believers at the stake; Kublai Khan ruled the Mongols; Marco Polo went to China; the first Parliament was established in England. (Phew!)



European Kingdoms





Plus ça change plus c'est la même chose...(The more things change, the more they stay the same) Source: asmilan.org

The tournament is supposed to have been invented mid-11th century in France and developed as a popular form of regular training in the handling of weapons and horses. It rapidly became highly organised and hedged around with rules and elaborate pageantry. Ambitious knights travelled round Europe fighting in tournaments at fortnightly intervals. It is probable that such itinerant participants in tournaments helped to spread the usages and conventions of heraldry across Europe. Later in the Middle Ages the bearing of arms came to be accepted as an essential prerequisite of participation in a tournament.

The growing importance of military pageantry and its association with the tournament would have excluded those of insufficient social standing who were unable to meet the expense, and this would have helped to restrict the use of arms to the knightly class. Thus, arms came to be seen as a mark of noble status, and were granted by the Holy Roman Emperor and the European kings as a corollary to ennoblement. In early days, however, most arms were self-assumed, and their owners sometimes changed them at will but even in the 12th century, and before the rapid proliferation of armorial devices led to a growing measure of royal control, there was some equation between nobility of blood and armorial bearings. This clue suggests an alternative theory for the origins of heraldry. Although heraldry came to have strong military associations, it may have developed from the civil personal mark, the seal device, of certain north European ruling families descended from Charlemagne, who perpetuated some of the administrative organisation and possibly the symbolic devices of his court. The latter included the sun and the moon, the symbols of the Evangelists: St Mark's lion and St John's eagle, and the fleur-de-lis (which later became the symbol of royalty in France).

Consequently, the origin of heraldry was not Norman but Flemish. It is most likely, therefore, that the origins of English and Scottish armory are to be found not in Normandy (the Normans were of mixed Scandinavian and Frankish descent), but in the system adopted by certain ruling families descended from the Emperor Charlemagne, the military and political colossus who ruled the Frankish Empire of northern Europe from 768 to 814. These families perpetuated much of the administrative organisation of the Carolingian Empire, including the use of dynastic and territorial emblems on seals, coinage, customs stamps and flags. There is evidence to suggest that these devices were common to families or groups linked by blood or feudal tenure, and were of necessity hereditary. With the redistribution of lands following the Norman Conquest, the cadets in England of Flemish families who were of Carolingian descent, and the devices used by them, became integrated in Anglo-Norman society. During the first Crusade, only 30 years after the Conquest, the mass cavalry charge of mail-clad knights remained the standard tactic of warfare. Order was maintained in the ensuing fight by the use of mustering flags bearing the personal devices of commanders and it is clear that these were sufficiently distinctive to be recognised, even in the heat of battle. It is likely that they also possessed a peacetime function - that of marking territory and symbolising authority - and that the devices used for this purpose also came to be engraved on seals by which documents were authenticated. The proto-heraldic devices were displayed on seals and banners. Hereditary devices may have been known in 1066, and symbolic banners seem to have been carried at the battle of Hastings and in the First Crusade.

Source: ceu.hu




1300 - 1400 AD - The Renaissance began; the Aztecs flourished in Mexico; gunpowder found its way to Europe and small cannon were soon developed; the Black Death spread across Europe killing 1/3 of the population; the Ming Dynasty began in China; an Italian invented the gun.
The Terror of the Black Death





The Spread of Black Death
Source: tea.state.tx.us

The Black Death wiped out nearly one half of medieval Europeans. The first reports of the Black Death come from Sicily in October 1347. 12 Genoese galleys, which were said to have come from the Crimea, entered the harbour of Messina in Sicily. The crews were said to have "carried such a virulent disease in their bones that anyone who only spoke to them was seized by a mortal illness and in no way could evade death." A symptom of the black death was hæmorraghagic spots caused by blood seeping from damaged blood vessels beneath the skin - they were known as "God's Tokens". The average rate of spread of the medieval plague was between 1 and 5 miles (2 to 8 kilometres) a day, which suggests that it was mainly carried by infected people travelling on foot rather than on horseback.

The plague probably arrived in Britain at Melcombe Regis (now called Weymouth), in Dorset, then an important town and port on the south coast - although Bristol and Southampton have also been suggested as the entry point. It may also have come from the Channel Islands, where it was already rampant and the fishermen were unable to pay their taxes because they were all stricken. Its arrival has been variously dated between June and early August 1348. The general direction of the spread of the Black Death in Britain can be determined from ecclesiastical records describing how the bishops in each diocese hastily had to appoint new clergy to replace those who had died.

Historians disagree about the total number of people who died from the plague in London. Some have suggested a figure of 100,000 but a more reasonable estimate would probably be between 20,000 and 30,000 deaths out of a population of 60,000 to 70,000 - which would be in line with the death rates in other English cities. Because the devastation of the Black Death was outside their comprehension, people accepted unquestioningly the doctrine of the Pope and the Church that the visitation was God's punishment for their manifold sins. This unhelpful doctrine prevailed for the next 300 years and beyond.

The Black Death moved from the most southerly point of Europe northwards to the freezing, inhospitable Arctic Circle, some 2200 miles (3500 kilometres) in less than three years. Plague victims suffered a sudden and high fever and developed large, foul-smelling boils; they were sometimes delirious and a severe headache was the usual prelude to death.

The black death disappeared in 1670. It had been the scourge of Europe for 323 years. Note that it is distinct from Bubonic Plague - so named because of the swellings of the lymph glands (called buboes) which appear - which is still with us today. These two diseases are completely unrelated to each other.

The average time from the point of infection to death was 37 days - of this the first 10 to 12 days was a latent period; the next 20 to 22 days was an infectious period before the appearance of symptoms. Therefore, 32 days was an incubation period. Physical symptoms would show for five days and then the sufferer would die. The total infectious period where the disease could be transmitted was 27 days (22 + 5). This long infectious period without showing symptoms accounted for its spread.

Prior to 1670, the regions afflicted by hæmorrhagic and bubonic plague overlapped only on the Mediterranean coast. The former became established in Europe, with occasional forays into North Africa and the Eastern Mediterranean, while the latter had its stronghold in Asia and the north African coastlands, with rare outbreaks in Italy, Southern France and Barcelona that did not persist.





Marcello's Drawing of the Black Death in Italy 1348 AD
Source: msimonetta.web.wesleyan.edu



Here Is What the Black Death Might Be Like if It Reappeared Today...

Sometime in the 21st century...

The infection is brought back to the Western world by biologists who have been working closely with primates in the high forests of Central Africa. They return home to New York and unwittingly spread the infection widely when travelling daily on the crowded public transport. The subway, packed with constantly-changing passengers, allows transmission of the virus to a great many victims coming into the city over a wide radius. Some are visitors from all over the world. Trips to sporting venues, theatres and cinemas all disseminate the infection widely before the symptoms appear in any of the victims.

When the primary cases die, the health authorities realise that their patients had contracted a serious, unknown disease; they take proper precautions with full protective clothing when nursing them and the bodies are sealed into special bags. Beyond that, there is nothing else that they can do. It is only when the multitude of secondary and tertiary cases began to appear all over the country and worldwide that the scale of the epidemic becomes apparent. Too late, the damage has been done. It proves impossible to establish any form of quarantine because the disease is spreading so rapidly. It is uncontrollable. This terrible bug particularly favours clubs, shopping malls, cinemas, sporting events, centrally heated offices and schools. These are all closed by law.

The food supplies run out and looting and petty thieving are now rife. Gangs armed with knives and with whatever other weapons they can lay their hands on rove the streets seizing any food they can discover. The authorities, very sensibly, issue advice to the effect that it is dangerous for people to congregate at places of work - but then when the power workers refuse to report for duty, electricity supplies fail. Electricity, not petrol, is the life-blood of the developed economy and many people are now unable even to sterilise drinking water by boiling it.

The complex fabric of life in the 21st century collapses completely. The rugged independence and self-sufficiency of their ancestors has long gone and they have been living a completely artificial existence based on computer technology, driven by international finance and a world economy. They had been cocooned by central heating, refrigerators, TV, rapid transport, convenience foods, microwaves, an array of electrical goods and the pharmaceutical industry. People were adept at surfing the Internet but had lost the basic instinct to survive. The global technology civilisation was precarious and any spanner in the works could have caused catastrophe - so this mysterious and horrific epidemic was an accident that was waiting to happen.

The effects when the pandemic spread to India and China were truly catastrophic. It was unstoppable. Emergency health measures were limited and largely ineffective and supplies of painkillers and sedatives were rapidly exhausted. Terrified, everybody showed the usual response and fled by bus and train, carrying the disease far and wide. When authorities prohibited all forms of transport, people tried to flee on foot, dragging handcarts behind them. All to no avail - the epidemic spread steadily and remorselessly – an inexorable, gigantic evil wave of unimaginable terror and agonising suffering. The conditions were ideal for the bug and the teeming millions provided a seemingly endless supply of susceptible people. It was later estimated that the final death toll would be counted in billions. The Black Death had returned - 700 years after its first appearance. Its pattern of spread was broadly similar to that of the original pandemic, except that there was now an endless supply of victims all tightly packed together. Transmission was ridiculously simple and the economy of developed countries collapsed completely.

Could the world recover from such a catastrophe?

Source: firstscience.com based on the book Return of the Black Death: The World’s Greatest Serial Killer by Dr Susan Scott and Professor Christopher Duncan - they are at the School of Biological Sciences, University of Liverpool, England (e-mail:sscott@liverpool.ac.uk). The book can be purchased at Amazon.com. Also the science magazine Nature has another what-if scenario for a flu pandemic set in December 2005



Something Like That Might Even Happen...
Bird Flu Virus Mutating, Posing Bigger Threat Says World Health Orgamisation

Hong Komg - The spate of human bird flu cases in Vietnam this year suggests the deadly virus may be mutating in ways that are making it more capable of being passed between humans, the World Health Organisation said. The finding points to the greatest fear of health experts that the H5N1 virus could unleash a pandemic and kill millions around the world if ever it gained the ability to be transmitted among humans efficiently.

While investigators could not prove human-to-human transmission had occurred, the report said that "the pattern of disease appeared to have changed in a manner consistent with this possibility. They (the findings) demonstrate that the viruses are continuing to evolve and pose a continuing and potentially growing pandemic threat," the WHO said in a report.

Klaus Stohr, WHO's global influenza programme coordinator, told a news briefing in Geneva: "We don't know whether the pandemic will occur next week or next year ... We should continue very intensively with pandemic preparations."

H5N1 made its first known jump to humans in Hong Kong in 1997 and experts have always established that the mode of transmission was through direct contact with birds. But the virus has mutated since, raising fears among experts that it may one day adapt in humans and become easily passed between them, setting off a pandemic. In the 6-page report, produced after an expert meeting in Manila earlier this month, the WHO said at least 92 adults and children in Vietnam, Thailand and Cambodia had become ill after being infected with H5N1 since late 2003, and 52 of them had died. Stohr said the toll had risen to 97 cases with 53 deaths.

In an update issued late on Thursday, the WHO said more clusters of infections involving household members have occurred, opening the possibility that "person-to-person transmission" may have taken place. Eight such clusters were observed in north Vietnam this year alone, with recent cases spanning over a longer period. "What we are seeing so far is a slight increase in clusters which could indicate more transmission," Stohr said. There was "circumstantial evidence" for such transmission - which could not be proved - but based on belief that a person became sick after being exposed only to an infected person and not to a sick chicken or duck, according to the expert. "Then you can talk about very strong evidence for human-to-human transmission. That has happened in three clusters, two in Vietnam and one in Thailand," he added.

Regional Variations

Recent cases raised the possibility that apart from being exposed to ill birds, the victims might have been infected through prolonged exposure to birds that did not appear sick but which were shedding the virus, or through contact with other sick people. The report also said that the age range of people infected in Vietnam this year had widened to between less than a year old to 80 years old. Equally worryingly, human H5N1 viruses isolated from Vietnam were genetically distinct from strains in 2004. Scientists also found that viruses from northern Vietnam and Thailand had begun to form a separate cluster from those isolated from south Vietnam and Cambodia. "It is possible that the avian H5N1 viruses are becoming more infectious for people, facilitating infection in a greater number or range of people and resulting in more clusters," it said. "It is possible that avian H5N1 viruses are becoming more capable of human-to-human transmission."

Additional reporting by Stephanie Nebehay in Geneva

Source: alertnet.org 19 May 2005 Reuters




1400 - 1600 AD - The first bank was founded; the Incas thrived in Peru; the Byzantine Empire finally collapsed and the Ottoman Empire was founded upon its ashes; Gutenberg created the printing press; during a never-ending quest to get more spices and silk, Columbus accidentally stumbled across the Americas - failing to notice that there were already millions of people living in the "new" world, Europeans moved in and slavery of native peoples and Africans began almost at once; one of Magellan's ships made it around the world; Shakespeare lived; Dutch painters flourished.

But wait! There's more... (click "Next" below)




For more on modern history including both widely-known and little-known facts, opinions (mine and others), a few political cartoons, some photos, a map or two, rants, politicians, geology, speculation and more, click the "Up" button below to take you to the Index for this History section.






The Topics Index offers access to a different approach to lots of topics - among them poisonous insects, eating dogs, what's addictive, training versus teaching, tornados, unusual flying machines, humour, wearable computers, IQ tests, health, Y chromosomes, share options, NJ's positive side, oddities, ageing, burial alternatives, capital punishment, affairs, poverty, McCarthyism, the most beautiful city in the world, never-ending work and lots more (it would take you a year to read it all)...







Credit:

http://flatrock.org.nz/topics/history/plot_thus_far.htm