[TriEmbed] Battery Discharge Testing

[Michael Monaghan]

Hi everyone,

I've been looking for a good guide for doing Battery Discharge Testing. The
guides I'm finding look like someone copied someone's homework and added a
bunch of words to ensure they met the 10k word requirement. Most seem to be
missing a good discussion of the math and testing procedures or spend a lot
of time discussing related topics and then glossing over the core subject.

As I understand it, I need either a known fixed resistance load or constant
current sink within the battery's discharge rate. I'm testing lithium-ion
battery packs that are 40v and have a discharge rate of C/2. As the packs
are 2A, 4A and 6A that means 1A/2A/3A discharge rates.

My current process is to use a 100 ohm load and calculate the discharge
time from full charge, 41v, to discharge, 25v. Doing it this way, I know
the current across my load will reduce as the battery voltage decreases.
Initially that's 0.411A based on measured resistance of the entire load.

My Questions:


   1. Is my method sound?
   2. Should I be using a different method like constant current?
   3. Is there a way to compensate for the reduction in current in the
   results other than using a constant current device?
   4. Is [starting current] * [run time in hours] = [Amp Hours] or should I
   be using something like [average current]?
   5. Is there a good guide to the math or actual testing procedures?

Here's a link to my first test data.
<https://docs.google.com/spreadsheets/d/1iMTTGLH9aOz2s1oqccSRw4_gO97dHxm4nJX7ln7vmDA/edit?usp=sharing>

Thanks for any insights.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.triembed.org/pipermail/triembed_triembed.org/attachments/20250502/c804ed44/attachment.htm>