Any way to test actual capacity of batteries?

[Supernam]

Sorry for being a noob, but I'm guessing you would load the battery with a fixed current draw and measure voltage vs time. If we say something has 1000mAh and load it at 1A, it would take an hour to drain? Is this until it gets to 0v? or is it like flashlights where we measure until 50%? Additionally, has anyone actually tested and published actual capacity of popular flashlight cells? I've seen runtime charts for various cells but not actually expressed in mAh.

 

[MatajumotorS]

I think not 0V but 0,9V for HiMH and 3,0V for Li-On. Correct me if i am wrong. And as far as i know, the capacity of a cel will wary, demanding on current. For example: nimh at 1A discharge 2000mah, but at 500mA - 2300mah something like that.

 

[mzzj]

Sorry for being a noob, but I'm guessing you would load the battery with a fixed current draw and measure voltage vs time. If we say something has 1000mAh and load it at 1A, it would take an hour to drain? Is this until it gets to 0v? or is it like flashlights where we measure until 50%? Additionally, has anyone actually tested and published actual capacity of popular flashlight cells? I've seen runtime charts for various cells but not actually expressed in mAh.

Sure it's possible. I built such a circuit couple of weeks ago. Can test with adjustable current between 0.5A and 12A, have adjustable low-voltage cutoff 0.6v-12v and uses inexpensive $3 quartz watch as a timer/counter.

 

[SilverFox]

Hello Supernam,

You may find the information in this thread informative.

Tom

 

[soffiler]

Original questions have been numbered by me for easier reference.

1) Sorry for being a noob, but I'm guessing you would load the battery with a fixed current draw and measure voltage vs time.

2) If we say something has 1000mAh and load it at 1A, it would take an hour to drain?

3) Is this until it gets to 0v? or is it like flashlights where we measure until 50%?

4) Additionally, has anyone actually tested and published actual capacity of popular flashlight cells? I've seen runtime charts for various cells but not actually expressed in mAh.

1) This device does exactly what you request:

http://www.westmountainradio.com/CBA.htm

2) Yes.

3) Different cell chemistries have different cutoff voltages; no, you don't ever go to 0V. NiMH for example is typically cutoff at 0.9 volts. Alkaline is typically 0.8V. Li-ion can be damaged if they are discharged below 2.0 volts and "protected" Li-ion are specifically protected from just that (plus a couple other protections). And so on...

4) Follow the link provided by Silverfox to see a large amount of actual test data.