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Old 03-14-2007, 01:42 AM   #1
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Unhappy Batteries, they can't all be duds surely? It's either that or the charge source.....

Ok, while I'm waiting for parts to get my new car (off-road as it happens) on the track I decided to cycle all my batteries and take fresh accurate readings with my latest gadget a Watt's Up watt meter.

Anyway the batteries are:

2 x 1400 mah scr +
2 x GP 3700 (unmatched)
2 x Intellect 3600 (matched)
2 x GP 3700 (matched).

Charging source is a 12v battery from a light truck.

I charged in the order they are listed and the first 1400 pack gave a reading of 1484mah (the second 1400 was very similar) and on the 20amp discharger it used 1250mah.

So from there the rated mah of the batteries as they were charged was 3700/3700/3600/3600/3700 and 3700. Note that after the second 3700 the source was charged overnight before continuing with the last 4 batteries.

The first 3700 gave a reading of 3600mah on charge and the second gave a reading of 3382mah.

After charging the source overnight the first 3600 read 3334 and the second read 3137. The second to last 3700 read 2901. The last battery is on as I type this.

Progressively each battery is giving a worse reading than the one before it, but the really weird part is that even after an overnight charge of the source battery the readings are getting worse with each battery in turn.

Even more weird the meter said the charger was delivering the charge it was supposed to.

Edit: The last battery actually went up by 116mah over the previous one.

Last edited by Mabuchi540; 03-14-2007 at 03:56 PM.
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Old 03-14-2007, 03:57 PM   #2
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Old 03-14-2007, 04:15 PM   #3
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A battery is not like a bucket that can be filled with exactly 5 gallons of water over and over for forever. The chemicals used in the reaction don't last forever, and the amount of charge and discharge decreases with additional use and time. Charging is only 90% efficient at best, and the higher the discharge rate, the lower the measured battery capacity. Just the way it is.

Basically, if you have a brand new battery rated at 1500 mah, it will take 1650 mah or so to charge, and if you discharge it at 30 amps, you may only get 1200 mah out. But if you discharge at 1 amp, you would get 1500 mah or so. As the battery gets older, all the numbers will go down.

Your batteries are acting normal.
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Old 03-14-2007, 06:48 PM   #4
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Post Thanks.....

Quote:
Originally Posted by Manning
A battery is not like a bucket that can be filled with exactly 5 gallons of water over and over for forever. The chemicals used in the reaction don't last forever, and the amount of charge and discharge decreases with additional use and time. Charging is only 90% efficient at best, and the higher the discharge rate, the lower the measured battery capacity. Just the way it is.

Basically, if you have a brand new battery rated at 1500 mah, it will take 1650 mah or so to charge, and if you discharge it at 30 amps, you may only get 1200 mah out. But if you discharge at 1 amp, you would get 1500 mah or so. As the battery gets older, all the numbers will go down.

Your batteries are acting normal.
but I'm not entirely sure that explains why with a fully charged source battery my worst mongrel pack (the third to be charged in this sequence), and used so many times I've lost count, of 3700 unmatched GP cells gives better numbers (in every department including watt hours/energy) than my expensive not used more than 12 times each matched packs (which were charged 5th-8th)?

Here are the numbers:

Worst 3700 pack/supposed to be my best pack:

Peak watts into battery at charge = 39.8/38.70

Mah = 3600/2901

Watt hours (energy) = 31.00/25.10

On discharge.....

Peak watts delivered to 20amp discharger = 194.70/193.80

Mah into discharger = 3238/2815

Watt hours (energy) = 22.8/15.60

All my matched packs have had less than 12 runs/charges but they all still give worse readings than my worst packs which I tested first. Everything you said made sense but I don't see how the numbers I'm seeing fit into what you've said?

NB: I know the number of times each good pack was used because none was used twice in a race day and there were only two of those a month and after 6 months of use I gave up for a year (studying) until checking them out now. Sorry make that 14 times each because during the year of not racing I did cycle them a couple of times each to keep them conditioned.

Last edited by Mabuchi540; 03-14-2007 at 06:58 PM.
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