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Old 03-12-2005, 04:26 AM
lttakas lttakas is offline
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How to find out how many MAH does your old batteries have?????????

Alright so this is the deal i got 3 packs from my frend i the batteries are used and i dont know how many MAH they have.Is there a way i could find out whats my capacity of my batteries without buying topof the line chargers plz help
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Old 03-12-2005, 04:30 AM
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Grizzbob Grizzbob is offline
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Well, if you know how many amps your current charger uses to charge a pack, then you could first discharge the pack, & then fully charge it & time just how long it takes to peak. Then if we have the time to peak & amp rate, we might be able to guesstimate at the pack's capacity....
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Old 03-12-2005, 04:40 AM
lttakas lttakas is offline
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can i use my multi meter to check how many amps my charged batteries have?
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Old 03-12-2005, 12:47 PM
darncars darncars is offline
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Quote:
Originally Posted by lttakas
can i use my multi meter to check how many amps my charged batteries have?
Still trying to figure that out too.
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Old 03-12-2005, 03:18 PM
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Only if it can read how many amps are going into the pack, it won't tell you how much the pack itself has accepted. When you see a high-end charger saying how many mah a pack took on its display, that's only an estimation based on how many amps the charger was putting into the battery & how long it did it(just like what I said before). And in all honesty, we can't really know exactly how much a battery has actually accepted(since all of them tend to lose some to their internal resistance), it's only estimated by what the charger tells us & by how long it can run when we place a particular amp load on it when we discharge it....
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Old 03-13-2005, 04:16 AM
AudiTT-Quattro AudiTT-Quattro is offline
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Right, as Grizzbob mentioned, there is really no accurate way of doing this. What the charger reads is the amount of current it outputs to the charger but because of the internal resistance of the cells and everything, the battery does not actually accept all of it where some of it is lost to heat.

A more practical test to estimate the capacity of a battery would be using a motor. Run a fully charged packof known capacity, say 1500mAh, down on a motor and measure the amount of time it takes to discharge. Repeat the experiment with the fully charged mystery battery pack and find the time it takes that to discharge. Assuming the motors performance is fairly consistent over the two trials, the capacity of the mystery pack can be determined by

mystery mAh = (mystery pack runtime)(mAh of known pack)/(known pack run time)
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Old 03-14-2005, 01:08 PM
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cheerwhiner cheerwhiner is offline
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do you happen to have a discharger? If you KNOW FOR SURE how many amps you are discharging at, simple math will help out here. I would suggest having a discharger anyway, and you can build one. 5 quantity 1157 auto lamps would give you a 10 amp discharge rate, with 2 amps per auto lamp. 3.3 amps takes an hour to discharge on a 3300 mah battery. 2.4 amps takes an hour to discharge a 2400mah battery- mah means milliamp HOURS. Thus 10 amps would drain a fully charged 2400mah battery in about........15 minutes. SO knowing exactly what your discharge rate is, you can figure out what was in the pack. Just need to have a watch to do it.

Or if this is a stick pack with an opaque covering, you COULD just cut open the pack and see if the individual cells are labeled, they usually are. However this number may not be accurate, because NICDs will lose their ability to hold their rated charge over the years, especialy if not discharged completley before charging. This would be a good thing to do because you can actually see if they looked burned (yes I mean BURNED) or if there is dirt in the pack, the plastic ends are cracked, etc. You can replace the shrinkwrap and the plastic ends, just need to pop new plastic ends on and heat the new shrink to cover the pack and hold it all together. Trinity makes rebuilding kits for battery packs. Its also cool to see the numbers on your pack.

I have a few GP 3300 packs that came with opaque wrap on them. SO I cut that off and put on clear wrap. I know its not critical but I care! Plastic ends of stick packs to get damaged and cracked. Don't be afraid to rebuild them. Get any dirt out too. It is super easy.

Here is some stuff to look at:

re-shrink with this its cheap http://www2.towerhobbies.com/cgi-bin...?&I=LXDZ18&P=7

and your plastic end caps are cheap too: http://www2.towerhobbies.com/cgi-bin...?&I=LXJZ85&P=M

Last edited by cheerwhiner; 03-14-2005 at 01:16 PM.
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Old 03-14-2005, 01:43 PM
kschauwe kschauwe is offline
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I use one of these , a low voltage cutout (5.4v) and a Bulb discharger to monitor my battery capacity.
It's not what's going in, but what comes out that matters.
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Old 03-14-2005, 02:01 PM
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exactly, which is why discharging is a better way to determine anyway!
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