NinerBikes wrote:
The 12.81 V was probably some surface charge still remaining. I'd say 12.72 V is pretty dog gone good and charged darn near fully to 100%.
The best V I have ever seen, after a day or two of top charge, then an hour or two of equalization, then a day or two of losing the surface charge after EQing, was 12.73V.
I've seen my T-1275 go through 4 or 5 cycles, top charging every single time, then doing an EQ session every single time after doing a 30 to 45% discharge, before all the cells pretty much came up as much as they were going to, and the voltage was at 12.73. The most important part for me was that the range of SG tightened up significantly per cell. I also saw top SG's of 1.285, uncorrected for temperature.
I think doing this sort of treatment before I put my battery away for storage completely disconnected, is the best condition, storage wise, for the battery.
Yes, my whole goal was to get the sg readings tighter; for two reasons. One being the obvious need for battery health/maintenance, but the other being a need to figure out whether the batts are compromised, or the pm4b is malfunctioning?
Yesterday I spent hours considering all the variables, and concluded it was either the batts, the charger, or both. :( so I still don't know for sure. I will deal with this dilemma in -EDIT-- my post to BFL.--
As for resting voltages, I was hard pressed to find a % soc chart that accurately reflected my batts' behaviours. but I did find one that seems close, and it has 12.8v as full, 12.2v as 50%, and a couple more soc's in between. I have expanded on this chart by filling in the blanks, and the numbers seem true to my situation; at least initially, based on actual Ah usage and discharge/recharge results, i.e; various resting voltages before and after charge cycles. Clearly I still have more data to collect, but my preliminary findings seem to line up well with these numbers.
However, this was all well and good until i did the half-azz eq charge. For the first time since owning these batteries, the resting voltage dropped below 12.78v; thus my question as to whether this was normal after eq'ing? And knowing as little as I do regarding battery chemistry, I suspected (guessed, really) that the electrolyte concentration may have changed, thus changing the voltage readings. I know I'm in the early stages of figuring this all out, and perhaps the resting voltages will eventually fall in line more with the numbers you've seen, but for now, I'm just not convinced my batts are full at anything less than 12.78v; especially after seeing them rise back up after the nautilus charge. Again, just guessing, but it seems the eq simply shook things up, and the nautilus brought things back to "normal". And the changing temps every morning, lately, may not be helping.
And a related issue is the fact that after splitting the 430Ah bank in two, the resting voltages seem to have risen to 12.81/12.82. And yes, this could very well be residual surface charge, so I will carefully look through my notes, again, paying close attention to resting time. But this all raises another question:
??? do smaller banks generally hold a surface charge longer than larger banks? if so, this could certainly explain the apparent, sudden, increase in resting voltages.
Thanks for all you input.
