backchannel: this week in battery mistakes

not a deep cycle

> I put a single [1400Ah (700 useable) wet cell]( in my travel trailer at 170 pounds. No solar yet

Uh, no.  OP bought a marine battery with 1400 CCA.  Not a deep cycle, as s/he will find out within a year.

killing me softly

> 655ah of  batteries! ... I got 960w of solar on the roof to charge them too!
  1. it’s a mismatched bank of one excellent AGM (Lifeline) and two other SLAs, presumably AGM.  Good luck with that, and my condolences to that nice Lifeline (excellent batteries, this example is ~$650)

  2. AGM requires C/5 charging current at a minimum.  Example:  lifeline says they require a minimum of .2C (C/5) charging or “the cycle life of the battery may be negatively affected”.  Ie, they will die early.

  3. The solar will provide  70A of charging on a good day (960w - at least 15% heat derating and DC-DC losses  = 816w,   816w / 12v = 68A.    .2C charging would be 131A for a 655Ah bank.   Kids in grade school can tell you that 70 is much less than 131.  About half.