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- Oct 16, 2019
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It was mentioned earlier that putting the first bit of charge goes quickly but to fully charge from an alternator takes hours. And a higher capacity alternator isn’t necessarily the answer because the batteries have a limit on how much current they can accept.
When I had my sailboat I had two 200Ah deep cycles and one 120 Ah starting battery.
I was running a 50 A alternator with a smart charge controller that topped off the starting battery first so I could always start the Diesel engine. Once that was topped up it switched to charging the deep cycle batteries.
If I had been at anchor for a few days, it would take hours of motoring to bring the deep cycle batteries up to full charge.
I also had a 15A Xantrax 120v shorepower charger that I used when docked. Even that would take several hours to recover the deep cycle batteries. I was very conservative with my power use, mainly lights and portable electronics off a 1000w inverter.
All this to say that the design of a DC power system is a bit involved if it’s going to work properly and not roast your expensive batteries.
When I had my sailboat I had two 200Ah deep cycles and one 120 Ah starting battery.
I was running a 50 A alternator with a smart charge controller that topped off the starting battery first so I could always start the Diesel engine. Once that was topped up it switched to charging the deep cycle batteries.
If I had been at anchor for a few days, it would take hours of motoring to bring the deep cycle batteries up to full charge.
I also had a 15A Xantrax 120v shorepower charger that I used when docked. Even that would take several hours to recover the deep cycle batteries. I was very conservative with my power use, mainly lights and portable electronics off a 1000w inverter.
All this to say that the design of a DC power system is a bit involved if it’s going to work properly and not roast your expensive batteries.