Dick wrote: "I have become aware that internally regulated alternators often do not fully charge house batteries. I'm wondering if solar panels overcome that problem.
Thanks for any input.'

Dick,

Why do you think internally regulated alternators don't fully charge batteries?

What will happen depends on several variables, including the size of the battery bank, the capacity of the alternator, the ability of the alternator to run for prolonged periods while controlling its own operating temperature, and the temperatures of the batteries being charged, themselves.

OEM alternators on engines less than 350hP tend to be smallish: like maybe 50A to 60A range for rated output.  When they get hot, they cut back their output, so maybe only 25A on average.  If you have a lot of DC nav devices running, there may not be power left over from the alternator to charge the batteries, or the rate of charge would certainly be very slow, but the batteries will charge (maybe take so many hours that its not practical, but they will charge).  Even dual engine boats with two OEM 50A-rated alternators will only average maybe 25A available to charge batteries.  That's not much.

In the above scenario, if an alternator can only output 25A on average, and the draw for total DC loads is 30A on average, the batteries will discharge by 5A per hour..

NONE OF THE ABOVE IS THE FAULT OF THE ALTERNATOR.  It's the fault of an inadequate system design.  Whether internally or externally regulated, the alternator has to be capable of handling the ambient DC loads on the boat AND HAVE POWER LEFT OVER to charge the batteries.

Yes, solar panels can help...    Sometimes...  Maybe...

That depends on alternator voltage regulator designs and solar controller designs.  All regulators must be designed so they can output their full capacity EVEN IF other power sources are also present in the system.  For example, the Balmar ARS-5 and MC-614 will shut down if they think the batteries are fully charged.  If a solar controller is working in that system, the battery terminal voltage will be too high for Balmar external regulators, and the alternator(s) will not contribute to charging.

Hope this helps.

Jim

Peg and Jim Healy, living aboard Sanctuary
http://gilwellbear.wordpress.com
Monk 36 Hull #132
MMSI #367042570
AGLCA #3767
MTOA #3436

As it has been pointed out to me in the past, all caps in an email is the
same as yelling; nobody likes to be yelled at. Emphasis should be done with
other appropriate methods more suited to the written word, especially in
emails.
.

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*BRINEY BUG-a 34' Sail-Assisted Trawler *
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