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Old 01-05-2022, 12:45 PM
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edwardc edwardc is offline
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Joe,

This is one of the (many) architectures I have considered, and is still in the running.

On the Pro side, using the alternator to only charge the LA starting battery insures that a BMS disconnect won't fry your alternator and electronics.

On the Con side, the DC-DC converter has some efficiency losses. If I'm just cruising around the Chesapeake, this is not a concern. But in the Bahamas, especially in the Exumas, fuel availability is limited, so much so that its the number one resource constraint, above even water or food!

I'm hoping that my new increased solar array size(from 200W to 400W) will all but eliminate my need to run the engine to charge. This would lessen the impact of the efficiency loss, as I would rarely need to run the engine just to charge.

Another related architecture is to use the alternator to directly charge the LiFePO4 bank, and a smaller DC-DC charger to keep the LA starter battery topped off. The presence of the DC-DC charger's input on the house bank should keep the alternator properly loaded in the event of a BMS disconnect, but I have yet to confirm this. And the tiny amount of power needed to keep the starting battery topped up will make the efficiency loss negligible.
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