Join Date: Feb 2011
Location: San Francisco Bay area
Thanked 80 Times in 80 Posts
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Re: Battery options for starting and accessories, outboard has an alternator
The best approach is to measure the current your radio etc. is using, and then size the battery so you don't go below say 50% after a long day sailing.
That's because going below 50% battery capacity shortens the life a lot.
Note that your alternator won't take the battery over 85%. So that actually gives you 35% (from 85% down to 50%) of the battery capacity to power the radio for a day.
Bristol 31.1, San Francisco Bay