At 10:04 PM 3/14/2011, Daryl Christensen wrote:
>OK�My van charges at about 13.6 to 13.8 or9 max. 
>All the spiffy temp/voltage AGM battery chargers I see are 120V AC input..
>Is there an onboard �charger widget� for upping 
>the charge voltage to the 14.4 the AGB batts need?

Yes, but you're not going to like it.  Because 
getting up there is easy (at least on Bosch 
alternators) - drop-in adjustable regulators are 
easy to get.  It's getting back down that's the 
problem, 'cause if you keep the voltage up there 
you'll boil the thing dry.  Charging AGM and gel 
deep-cycle batteries properly involves first 
stuffing amps into them hard and fast until the 
terminal voltage rises to {the right amount based 
on battery temp}, then holding that voltage for 
an hour or two, then dropping back down to the 
{temperature-dependent} float voltage while the 
engine continues to run.  That means the 
alternator will be running hard for a while, 
either at its maximum output or at the maximum 
rate that you have decided the battery bank can 
safely accept (which is something like C/3 for 
these batteries, C being the capacity in 
amp-hours).  It also means a much smarter 
regulator than the ones used for cars.

The conventional way is to start with an 
alternator that expects an external regulator, 
and that also expects to be run hard.  Here's the 
setup my brother is putting in his Vanguard class 
sloop, to be powered by a 30 hp Atomic Four engine:

Balmar 621, 70 Amp alternator and MC-612 multi 
stage regulator with battery and alternator temp 
sensors.  Total damage just under $800.

Here's the Balmar lineup with list prices: 
http://www.balmar.net/2011-Balmar-Product-Guide.pdf

===============================

The second way would be use the existing 
alternator, modify it to accept external 
regulation, and get one of the fancy regulators 
from Balmar, Ample Power or another 
supplier.  That halves the cost at least.  The 
mod might be pretty easy - it wouldn't be very 
hard on the Bosch to fake up the regulator module 
so it was really mostly a brush carrier with the 
smarts outside.  And the alternator might be up 
to the job, or it might need additional cooling 
air supplied to the back of it to keep from 
burning up.  In addition to the continuous-duty 
rating, the Balmar and similar alternators cost 
more because they're what we used to call 
explosion-proof, meaning they won't cause 
one.  Now they say "ignition-protected."

=========================

A third possible, a kluge, would be an inverter 
driving one of the AC chargers you 
mentioned.  You'd have to determine whether it 
would need to be a full sine-wave inverter or 
would one of the cheap ones do.  This would have 
the virtue of giving you a smart charger 
available to plug in whenever you had AC 
available, and if it would run on a "modified 
sine" inverter the additional cost over the 
charger would be small.  That would let your 
starting battery get along in starting-battery 
mode which is perfectly satisfactory for starting 
and has been for the last century or so.  The 
potential would again exist of needing extra 
cooling on the alternator to keep it from frying.

Yours,
d