Testing Battery For Mah Capacity - RC Groups
Feb 26, 2002, 09:12 AM
Registered User

Testing Battery For Mah Capacity

Hello,
How do you test a single battery to determine it's MAH capacity?
I have several batteries that came out of some old packs that I found, but they are not marked with the MAH capacity.

Thanks,
Steven
 Feb 26, 2002, 09:44 AM Registered User Cycle them with a charger that can work with individual cells.. Now you start to see why we recommend you start with the best charger you can afford.. needs change over time.. ..a
 Feb 26, 2002, 09:50 AM Registered User Andy, I'm using a Tekin BC112 C charger. I can do a single cell charge, so how do I go about determining the Mah of the cell? I should know this, but I'm having a brain fart I guess. Steven
 Feb 26, 2002, 11:09 AM Registered User You do a single-cell discharge also.. My I2 can do it, don't know anything about that charger, but if it can cycle, it should do the job.. ..a
Feb 26, 2002, 12:22 PM
Registered User

Poor Man's Capacity Measurement

Well, if you have a good DVM, some electronics experience, and LOTS of free time, then you can make a poor man's discharge acquisition system. It can give approx mAH values:

(1) Take a wild guess at the cell's capacity. Don't worry about being wrong, but attempt to nail it as close as possible.

(2) Charge the cell at a C/10 rate (per your guess) for 14-16 hours. Second best is to use a quick charger set to single cell mode.

(3) Divide the guessed capacity by 5 (C/5). This will be your discharge rate. For example, a 600mAH cell will be discharged at 120mA.

(4) Choose a resistive load that provides the C/5 current draw. A 3V flashlight bulb makes a good load. It does not have to be exactly C/5. But you must record the load current for later use.

(5) Continue discharging until your cell measures exactly 1.0VDC. The voltage monitoring will require you to check every 5-10 minutes. When the voltage is met, then record the number of hours it took. Re-measure the current draw at the lower voltage.

(6) Calculate the average load current: mA = (Current1 + Current2) / 2.

(7) Calculate mAH: mAH = mA X Hours.

After doing this once or twice I expect that you will decide that those unmarked cells are best used in the kids' toys.
 Feb 26, 2002, 12:27 PM Registered User Thanks for all the info. I'll try charging them at a C1 or maybe even half that and see what happens. I thought there may be an easy way to do it , that I was aware of. Steven