I have 3 of these batteries: http://www.hobbyking.com/hobbyking/stor ... duct=18631
Took them out for their first test ride yesterday, and everything was working great. I stopped after about a mile and grabbed my voltmeter to check the cells. Things were looking good. The first pack was at 3.73 for all 4 cells, the second pack was at 3.72 for all 4 cells, and the third pack was at 3.74 for all 4 cells. This was after 1 mile of riding. I take it about another mile and a half, and stop to check the cells again. Suddenly, there was a MUCH higher drop in voltage than there was after the first mile. Before I set out, the cells were all at 3.79v, across all 3 packs. After 1 mile, they had dropped down to 3.73v, 3.72v, and 3.64v, so a loss of about .04v to .07v over 1 mile.
Now, that second mile and a half, for some reason, drained the batteries much, much more. Whereas before, 1 mile took an average of .05 volts across all cells, that second 1.5 miles took the first pack from 3.74 to 3.29, the second pack down from 3.72v to 2.66v, and a couple cells at 2.8v, and the third pack down from 3.74 to 3.34v! Why would the second leg of that ride have taken so much more out of the pack? If 1 mile takes approximately .05 from each cell, then 1.5 miles should take approximately .075v from each cell. Of course there will be differences between uphill/downhill, speed, wind resistance, etc, but THAT much of a difference doesnt make sense. The second leg of the ride was actually abour 40% downhill, and there was no more wind than the first part, although I did go slightly faster for the non-downhill part.
But, even with all that take into consideration, it still doesnt make sense that it would be that drastically different. I mean, i can understand if the first mile took out .05v, and the second mile and a half took out, say, .15v (which is triple the first mile). But, going from .05v loss to over .5v loss, and even 1.02v loss in the middle pack?! WTF?
Another thing I dont understand, is why the middle pack would have been drained so much more. I realize not all packs will be drained exactly evenly, but for two of them to be drained by .5v, and another to be drained by 1.01v is a very big difference.
So, all that being said, my biggest concern is this: When I got home, I plugged all 3 batteries in to charge, each with one of these: http://www.hobbyking.com/hobbyking/stor ... duct=21044
being powered by a 12V 5.4A SLA car battery. The two packs that werent drained as much (the ones that ended up at 3.29v and 3.34v) charged up just fine, no issues. But, the middle pack, the one that dropped down below 2.7v per cell, wont charge at all. When I plugged it in to charge, the pack was at 10.8v total. A few hours of charging later, it had actually DROPPED down to 10.5v total! Whats even more confusing is that after leaving them all unplugged and not charging overnight, it had gone UP to 11.3v WITHOUT being charged! I understand that not going below 2.7 is one of the 'Golden rules of Lipo" but this still doesnt make sense. Everything Ive read just says that going below 2.7v will result in an overall shorter lifespan for the batteries. As in, go below 2.7v and you might only get 3000 cycles instead of 10000. Ive never read anything that said a lipo battery wont charge AT ALL after dropping below 2.7v.
None of this seems to make sense, so any help is greatly appreciated.
So, to recap, the main issues I need help with are:
- Why would the battery pack(s) be drained by only .05v on the first mile of the ride, but then drained by over 1.01v over the next mile and a half?
- Why would the middle pack be drained by so much more than the other 2 packs?
- Why wont the middle pack charge at all any more?
- Why/how would the middle pack not charge when plugged in, but go from 10.5v to 11.3v overnight when NOT plugged in at all?
- Is there any way to 'fix' the middle pack so that it will charge again and get back up above 2.7v?
First lipo setup, running 3 of this battery http://www.hobbyking.com/hobbyking/stor ... duct=18631
Took it for a ride, first mile took each cell down by about .05v, second mile and a half took each cell down by over 1.01v, and that doesnt make sense.
The pack in the middle was drained far more than the other 2, going from 3.72 all the way down to 2.6, whereas the other two packs went from 3.73 down to 3.3-ish. Why would the middle pack be drained so much more than the packs on the left and right?
Now, the middle pack wont charge at all. Is there any way to make it charge again?
Any and all help is greatly appreciated.