Join Date: Feb 2010
Location: Narragansett Bay
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Re: Battery Sizing - am I crazy?
Well, I ended up buying two Everstart Marine 29DC (selection #95), 845 marine cranking, 122AH@1amp batteries.
Something is fishy. Industry standard is to rate batteries at a 20hr discharge rate. 1amp discharge suggests these batteries would last 122hrs, but if you increase the draw to 2amps, the hours drop by more than half due to resistance.
Increase the draw to a fairly light 5 or 6 amps and, while the linear math would suggest 20+ hours, I'm sure it would be substantially less. Maybe only a few hours.
Further compound this by best practice not to draw your batteries down by more than 50% of their capacity for longest life and these sound like they may be a little light.
Going to one or two smaller batteries sounded like a good idea, its just that something doesn't sound right about these, if they are advertised at 1amp. There are some battery gurus around here that may know better than I.
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