NiMH pack self discharge to zero
#1
Currently I have a NiMH pack charging at 0.5A, at 525 minutes (8 1/2 hours) and has currently pumped roughly 4100mAh into it, Cells are Intellect 4200s.
Overnight I charged it at 0.4A to get C/10, it finished around 7am and I let it cool down and whatnot then put it on a 0.7A discharge to (roughly) get C/6, it pulled 3000mAh out of the pack when it hit 5.4v. I let it cool for about a half hour, then put it on the charger with current settings, I had to restart the charging after about ten minutes due to a very brief power outage of under a minute, been charging ever since.
Does this sound right to anyone? I have the peak detection at 5mV/Cell, capacity limit is at 4200mAh, and using my temp gun 3 cells are at 100*F and the other three are at 105*F.
I'm really wanting to think the pack may be dead, looking for a second (or third) opinion on what's going on. Thanks in advance for any responses.
Overnight I charged it at 0.4A to get C/10, it finished around 7am and I let it cool down and whatnot then put it on a 0.7A discharge to (roughly) get C/6, it pulled 3000mAh out of the pack when it hit 5.4v. I let it cool for about a half hour, then put it on the charger with current settings, I had to restart the charging after about ten minutes due to a very brief power outage of under a minute, been charging ever since.
Does this sound right to anyone? I have the peak detection at 5mV/Cell, capacity limit is at 4200mAh, and using my temp gun 3 cells are at 100*F and the other three are at 105*F.
I'm really wanting to think the pack may be dead, looking for a second (or third) opinion on what's going on. Thanks in advance for any responses.
#2
Tech Champion

Joined: Oct 2007
Posts: 7,341
Peak detection won’t work properly at that low of a charge rate. If you are charging at a low rate you need to time the charge manually.
It might get better after a few cycles. Perhaps with a longer rest between cycles, nimh generally don't like being cycled quickly, need some time to recover.
It might get better after a few cycles. Perhaps with a longer rest between cycles, nimh generally don't like being cycled quickly, need some time to recover.
Last edited by Dave H; 07-25-2010 at 10:04 PM.
#4
Joined: Jul 2008
Posts: 11,530
From: Houston, TX
Continue for a few cycles to establish what the disch numbers are doing. If they're improving, pack may have life left. If the numbers don't improve or get worse, pack is prob done.
Even if they show marked improvement, you may have a pack that will self disch very quickly. Time are zero voltage seems to increase self disch if the cells come back.
Even if they show marked improvement, you may have a pack that will self disch very quickly. Time are zero voltage seems to increase self disch if the cells come back.



