Quote:
Originally Posted by Cal Coon
They make "jump boxes" small enough, light enough, and most importantly, powerful enough to start a cold (dead) V8 easily. They are not much money. Well worth the investment. Keep it right on board all the time. It is a "must have" on my boat, and snowmobile.
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Those are great, but keep in mind that the alternator on a typical boat engine is really small and will probably take 8 or more hours of cruising RPM to bring a dead battery back to a fully charged state, maybe longer if the boat has a big electrical load and/or more than one battery. There are two other problems with letting the batteries go dead too:
1. When you discharge a lead acid battery below 50% capacity, you damage it. This will reduce it's capacity and lifespan. The further below 50% the worse the damage. This rule includes deep-cycle batteries, BTW.
2. When you leave a boat battery in a partially discharged state, it will suffer from sulphation which reduces the battery capacity and lifespan.
One option to avoid dead batteries with the switch left on is to shut off whatever is drawing the batteries down rather than rely on the valet crew to shut the switch off. A valet-stored boat is typically won't have many circuits so it should not be hard to figure out what the load is that's killing the battery.