Quote:
Originally Posted by cRiPpLe_rOoStEr
Is there alternative other than a marine battery that you would consider to try? What about a lithium battery?
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If you went with LiFePO4, you would have a "nominal" voltage of 12.8v with 4 cells, and it should maintain said voltage (or slightly higher) from charged right up until it's dead. Rather than dropping steadily from 12.6v until it's dead at 10v with a lead-acid.
Cells are ~$1.20 per amp-hour, so a 100ah battery with 4 cells in it would be nearly $500.
They would need some control circuitry on them to protect them from over or under charging and to keep them balanced. Under $50 will do the job. You'd be fine charging it without an alternator, but you would have to figure out how to make it work properly with one, if you did. Unless the control circuit is deigned for it.
You'd get a lot more cycles out of it then you would for a lead-acid, so it would end up cheaper in the long run.
OTOH, basic LiFePO4 aren't good below freezing temps, so come winter, you'd need a battery warmer. Or a different chemistry. There is a slightly different chemistry that is basically the same, other than weighing a bit more for the same capacity and it's good for -20c or so.
My original thought was to use a regular lead-acid deep-cycle and throw in a buck booster (readily available on ebay for like $20) and some diodes, so that the ECU/ignition always got a set voltage (13v? 14v?) in spite of what the rest of the system voltage was. The diodes are there in case it fails, then it would still get battery voltage.