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View Full Version : Need help from battery guru/electronics guru - charging


dodgey
06-17-2006, 05:30 AM
I'm trying to ressurect a 4s4p pack I've messed up. I replaced a bank of 4p cells and I'm individually charging each 4p 3.7v "bank" of cells before I use the pack again to get them all perfectly balanced - and, to check they are all OK (i.e. taking and giving the same Mah). Two questions

1) The fact they are all linked in series should not make any difference when I attach leads to each bank of 4p and charge as an individual 3.7v 8000Mah? As far as my understanding of electronics goes the fact they are connected should make no odds as I'm going directly to each 4p pack?

2) the pack is rated at 8000Mah, so each bank of 4p should be made up of 4 x 2000Mah 3.7vcells. BUT - I certainly can't charge an individual bank of 4p at 8amps (like I can charge the whole pack at 14.4 v 8Amp). Anything over about 1.5Amps triggers the end of the charge cycle, or a charging error. I'm guessing that this has something to do with volts and amps ratio?

Logic says 4 x 2000Mah cells, in parallel, gives 8000Mah 3.7v, and shoudl be able to charge at 8Amps - but it does not work in practice - any idea why?

Efliernz
06-17-2006, 10:44 PM
Your charger obviously is capable of charging 8amp but is the power supply feeding it?
Logic says 4 x 2000Mah cells, in parallel, gives 8000Mah 3.7v, and shoudl be able to charge at 8Amps - but it does not work in practice - any idea why?
Yes it should work, as long as the charger and powersupply can handle it.

dodgey
06-18-2006, 04:28 PM
My PSU gives 25Amp continuous. I can charge two packs in series at 16Amp easily ;-) - it's a bit of a beasty!

Going to strip the pack right down this week and find where I have messed up. I have a funny feeling where I added balance leads, the soldering "activity" has separated one or two tabs on the 4p bank that is getting hot.