OK, so maybe it's not fair asking YOU why WE test something the way we do. ;)
Here's the thing -- Our company uses AGM Lead acid batteries in some products. The testing methods are ancient (but so is lead-acid technology). There's nobody left in the company to ask these questions of. We have "what" well documented, but rarely is "why" written down.
Our application is most similar to a golf cart or fork lift. "Traction batteries" I believe these would be called.
I've asked the battery manufacturers but I can't get a straight answer. I suspect this may be a case of Llama Dung
For a 12V battery (example) we do 150 cycles of the following:
- Discharge battery at 13A until voltage reaches 8V
- Rest 3 minutes (during this time, the battery voltage will recover)
- Discharge at 5A until voltage reaches 10V
- Perform slow charge (about 8 hours) until battery is fully charged
- Repeat ad nauseum
The part nobody can explain is why we do a 2nd, lower current drain of the battery before recharging.
This may be a chemistry question (in which case I'm not qualified to really understand the answer I'm sure).
Anybody know something about this that I've failed to be able to Google?? (Believe me, I tried!!!)
Heck I even read the relevant sections of Lindens "Handbook of Batteries". All I could find was this one sentence..
" Intermittent discharge, which allows time for the electrolyte to recirculate, or forced circulation of the electrolyte will improve high-rate performance. "