Very Low OCV on Full Batts???
I've been seeing lower than usual resting ocv this winter, compared to last. Figured it was either wear and tear, too high a charging voltage, or a parasitic draw. So I tried throwing a lower vol...
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As I mentioned, I warmed up the bank before charging on Thursday. The result was resting ocv rose from 12.57v at 12F, to 12.63v at 44F. So apparently cold temps do have an effect on resting voltages; as well as discharge rates, charging voltages, and SG readings. I cannot find anything on line regarding the effect of cold temps on resting voltages though.
So, before the charge, ocv was 12.63 (and rising?). T.C. SG readings were in the 1.265 - 1.280 range... so a little low. I let the pm4b do its 15 min thing at 14.76v, which ended with the bank accepting 8a. I tweaked it to 15Vabs and 9a, and charged for an additional 6 1/2 hours, which ended with the bank accepting 5.6a. By this point, cabinet temp was 50F... No idea what temp the electrolyte was.
Resulting SG readings varied a lot... some rose while some remained the same, but overall were slightly higher... 1.265-1.285 range.
I disconnected all wiring and left batts to sit individually.
Two days later (Saturday), T.C. SG readings had risen ever so slightly, but appeared to be a bit better balanced. One thing I noticed, as I have in the past, was the batts with the higher resting voltages had lower SG readings. String A (the two "weaker" batts, based on SG readings) were at 6.52v (A1) and 6.53v (A2) while B1 was at 6.50v and B2 was at 6.49v.
Today (Sunday), voltages were A1 6.49, A2 6.51, B1 6.48, and B2 6.46 volts... each down about .02-.03v... at 17F. So now the waiting game, to see the long term results of Thursdays charge. My initial thoughts are the low ocv's I was seeing were from undercharging, but time will tell.
So, before the charge, ocv was 12.63 (and rising?). T.C. SG readings were in the 1.265 - 1.280 range... so a little low. I let the pm4b do its 15 min thing at 14.76v, which ended with the bank accepting 8a. I tweaked it to 15Vabs and 9a, and charged for an additional 6 1/2 hours, which ended with the bank accepting 5.6a. By this point, cabinet temp was 50F... No idea what temp the electrolyte was.
Resulting SG readings varied a lot... some rose while some remained the same, but overall were slightly higher... 1.265-1.285 range.
I disconnected all wiring and left batts to sit individually.
Two days later (Saturday), T.C. SG readings had risen ever so slightly, but appeared to be a bit better balanced. One thing I noticed, as I have in the past, was the batts with the higher resting voltages had lower SG readings. String A (the two "weaker" batts, based on SG readings) were at 6.52v (A1) and 6.53v (A2) while B1 was at 6.50v and B2 was at 6.49v.
Today (Sunday), voltages were A1 6.49, A2 6.51, B1 6.48, and B2 6.46 volts... each down about .02-.03v... at 17F. So now the waiting game, to see the long term results of Thursdays charge. My initial thoughts are the low ocv's I was seeing were from undercharging, but time will tell.
