Jim:

I originally was going to use a DC-to- DC converter to charge the start
battery, but that struck me as over-kill. Actually, the way I use the
boat (we live aboard it all summer), the engine doesn't get used too
much. I use a 185 watt solar panel to charge the house batteries, and
can also charge the start from them if I chose. If we are in a marina, I
can use the battery charger to take care of both batteries.

But occasionally we do travel under power for a few hours, and that's
when I'd like to have the start battery charged from the alternator.

I've got a few ideas from this group on how to proceed.
--=20
Larry Bradley =20
Orleans (Ottawa) Canada=20

On Sat, 2014-02-08 at 18:16 +0000, Jim Higgins KB3PU wrote:

> Hi Bob,
>=20



> Stepping outside my 35 years of experience with lead-acid batteries from =
this=20
> point onward...
>=20
> In the sailboat situation, it seems to me that if the very long leads to =
the=20
> aux battery cause such a loss of voltage that recharge must be unduly=20
> extended, or source voltage raised at the expense of another battery=20
> connected closer to the charging source, the better solution is isolation=
 of=20
> the two batteries from each other during charging... something that will =
need=20
> to be done with pulse charging anyhow.... or separate charging systems - =
two=20
> alternators.
>=20
> The OPs idea of an "old timey" on-off regulator on the nearby battery whi=
le=20
> (I assume) the farther battery remains directly connected to the alternat=
or,=20
> seems like a reasonable solution.  Or maybe a second alternator for the a=
ux=20
> battery if one can be installed.
>=20
> JimH
>=20
>=20
> Received from Bob Blick at 02/08/2014 04:54 UTC:
>=20
> >Hi Jim,
> >
> >Does this apply to SLA and AGM as well as flooded lead acid?
> >
> >Friendly regards, Bob
> >
> >On Fri, Feb 7, 2014, at 07:48 PM, Jim Higgins KB3PU wrote:
> >
> > > I will say that my comments re: Pulse Charging come from 35 years as =
a
> > > Process Engineer in the lead-acid battery industry where I wrote mate=
rial
> > > specs and designed processes for battery manufacturing as well as had
> > > plenty of hands-on experience.  The same company also manufactured=20
> > chargers and
> > > UPS systems.  And its research labs did extensive investigation into =
pulse
> > > charging.  The short story is that it has no advantage over constant
> > > potential or modified constant potential charging and it has several
> > > disadvantage in terms of greatly increased IR and I^2R losses as well=
 as
> > > possible detrimental effects on the battery depending on the nature o=
f
> > > the
> > > battery system and its load.  The latter probably isn't a factor in t=
his
> > > case, but it is very much a factor in UPS systems.
>=20
>=20
--=20
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