Re: LiFePo4 batteries: Twin 24V Alternators on the main engine

Bill Kinney

I think we might have a better generator backup alternative than you credit.

When we are underway, we normally cycle our batteries from something  between 93% and 100% (depending on solar input that day) down to 60-70%. Without running the main engine, the generator runs for 70 to 90 minutes to come back to 93%, and we are good for another 24 hours or so. That cycle from 70% to 93% is about 110 Amp hours. Our total battery discharge might come close to double that if we assume zero solar input.

Our little small case alternator outputs about 48 amps continuously, and with a conservative average consumption of 13 Amps, that leaves us with a net charging capability of 35 amps.  In other words, without counting any solar input at all, our little alternator can keep up with our entire routine underway usage running only 6 hours a day.  Even if we ran the engine at normal cruising speed (1 gal/hr) for those 6 hours, that would give us almost 2 weeks of fuel starting at a half tank. Cut back to the minimum 1500 RPM needed to get full output from the alternator, and you are looking at nearly double that. And we still arrive with BOTH freezers running... and no empty jerry jugs. :)

I am pretty comfortable with our emergency backup generation capability. It's not pretty, or efficient, but it's backup...

After almost 350 hours of operation, we continue to be very happy with our WhisperPower generator.  The whole system is well designed and has worked exactly as we hoped.

On exhaust elbows, I think they really need to be considered a routine maintenance item both for generators and drive engines.  Some last longer than others, but realistically, none of them have design and metallurgy to last for the life of the engine. The catch is that it is hard to predict failure ahead of time since the lifespan can vary a lot depending on the usage cycle even on identical engines.  WhisperPower doesn't list a replacement schedule for theirs.  On my list for next year is to pull it off and have a look. The engine runs pretty heavily loaded all the time, so I don't expect a lot of soot buildup... but you never know until you look!

Bill Kinney
SM160, Harmonie
Port Louis, Grenada

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