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post #8 of Old 03-19-2003
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Electrical Power Recharging Options for Extended Cruise

Stormer, you''ve got a basically suitable electrical system for your passage plans but I think you misunderstand how a hicap alternator & lead acid batteries work and therefore think you have needs which in reality might not exist.

The charging regimen you describe is exactly what is supposed to happen, and having a hicap alternator (let''s assume it''s a small frame 100-110 amp unit, with perhaps less output at max temp) does not provide for rapid, full bank charging, something I get the impression you think should be available and adviseable. This isn''t suitable because the lead acid batteries can''t sustain it. One you''ve passed the bulk rate charge, the batteries are what dictates the acceptance rate of charge; this will be true whether you''re working off a generator, alternator or whatever else you might use (so long as you care for the batteries properly).

Given that you have the typical ''100 amp/day boat'' and especially with your cruise plans - frequent docking/anchoring at times (engine running), perhaps the occasional plug-in, routine living aboard and cruising - you should IMO be fine using the 50-80 rule. This refers to the fact that you don''t really want to draw down the house bank below 50% in order to max the lifespan of the bank, and you don''t want to charge much above 80-85% of bank capacity simply because the efficiency of doing so becomes less and less (just as you describe). This 30-35% ''band'' of your 440AH bank is roughly 140-150 amp hrs, or about 1.5 days of average electrical consumption with refrigeration before a charge is required, followed by an initially high bulk rate charge (I would expect your system would charge a 50% full bank at the 80-90 amp rate; if it doesn''t, your alternator is overrated or your regulator isn''t doing it''s job) that should put most of another day''s electrical capacity back in your bank within one hour.

This is where alternative energy comes in, as the process described above introduces a slowly dropping curve with slowly increased battery charging times in order to insure the 50% capacity level is never exceeded. But for a finite cruise period such as you anticipate, and with moving the boat being a norm, I agree that the purchase of ancillary charging sources is probably not needed...and that would include a generator.

However, if you consider a generator, realize that it might not be controlled by your regulator (this can be a real problem with smart systems and dumb generators) and you''ll likely have to bypass that system entirely and connect the generator directly to the house bank.

Don''t think you should be working from 100% capacity ''down'', but rather expect that you''ll be oscillating between 50-80% capacity, at which point you might conclude as I do that there isn''t a problem you need to solve.

Good luck on a safe, enjoyable cruise!

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