Challenges Keeping Batteries Up at Anchor

[Maine Sail]

Maine stated in this thread (and elsewhere) "25 - 30% of Ah capacity when HOT". My US Battery 6V GC data sheet shows a charging recommendation Bulk Rate of: "Constant current @~10% of C/20 Ah in amps to 2.45+/-0.05 volts per cell (e.g. 7.35 volts +/-0.15 volts per 6 volt battery). Ensure that you verify with the manufacturer your maximum charge rate; otherwise, you run into the ramifications of overcharging. Ensure that you program your new regulator with the settings as recommended by MS and you are well on your way to Admiral (and skipper) happiness.

This is hot alternator output. An alternator, when hot, will not put out the same current it can at when cold. You don't size it for cold performance you size it for max hot performance.

As for the USB deep cycle batteries they can easily be charged at .3C (30% of Ah capacity) just as the East Penn GC15 etc. can. USB only publishes the "general recommendation" used in most industrial or golf course applications but Mike M. or Fred W. at USB can easily confirm that charge rates of up to .3C / 30% of Ah capacity will not harm their flooded batteries. Also be aware that our charging, in the marine industry, is what USB considers "two stage" or CC/CV constant current (bulk) and constant voltage (absorption & float). What they call three stage is CC>CV>CC and that does not exist in the marine market only in fixed industrial applications....

 

[capta]

I think it's interesting that some on here are charging their batteries with a 50 horsepower plus diesel engine. I'd think they would be up somewhere around 1600 RPM's to get the amperage they desire. Certainly not a bad system IF one is using the engine anyway, but not a very efficient or environmentally friendly one, if they are not.
We haven't had an alternator on our engine since I bought the boat, mainly because we use it so little. As we are having some problems with our generator, we are adding an alternator to the engine as a back up to the solar/wind. But we're certainly not going to be charging our batteries with an 86 HP diesel, except in an emergency.


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[Gunni]

It is more like maximizing energy extraction when you have the auxiliary running. So much of that power is going out the block as heat and noise, you might as well capture it and store it. The Balmar alternator system is no ordinary alternator. The temp sensored external regulator allows it to put out lots of amperage at fast idle. And it is just a cost effective upgrade, you would struggle to get 100 Amps from some combination of PV, wind and hydrogenerator for a $1,500 bolt-on alternator replacement. And for the guys with no room or interest in a genset, a smart alternator system is a good option.