Hi Bob,

Greetings from one old OTLISTer to another.  ;-)

Yes, it applies to all healthy lead acid batteries.  (More on the "healthy"=
=20
aspect below.)  Basically pulse charging is "snake oil" when it is touted a=
s=20
better than standard manufacturer recommended charging methods.... somethin=
g=20
no one here has done  There is no advantage to the battery from delivering=
=20
current in short higher voltage pulses except (addressing the healthy aspec=
t=20
now) when the goal is to "desulfate" a seriously and chronically undercharg=
ed=20
battery that is so heavily sulfated that it won't accept a charge by standa=
rd=20
methods.  If it will accept a charge, then standard methods of recharge are=
=20
always better.  And recovery of such unhealthy batteries only recovers a=20
battery that is of no lasting value in any situation requiring even a=20
moderate level of reliability.  It needs to be replaced immediately anyhow,=
=20
so I don't even recommend pulse charging in that case.  Such recovered=20
batteries are technically recharged, but are essentially end of life junk d=
ue=20
to the effect of the prior heavy sulfation.  It can result in evolution of=
=20
hydrogen in SLA designs. which leads to loss of water from the electrolyte=
=20
due to hydrogen venting.  SLA designs depend on preventing the evolution of=
=20
hydrogen so that water never needs to be added.

Pulse charging increases IR and I^2R losses and in the case of older=20
batteries suffering from normal (or abnormal) levels of plate corrosion for=
=20
their age, it can stress partially corroded internal components to the poin=
t=20
of premature failure.

There's really nothing involving benefit to the battery to recommend pulse=
=20
charging.





Stepping outside my 35 years of experience with lead-acid batteries from th=
is=20
point onward...

In the sailboat situation, it seems to me that if the very long leads to th=
e=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 o=
f=20
the two batteries from each other during charging... something that will ne=
ed=20
to be done with pulse charging anyhow.... or separate charging systems - tw=
o=20
alternators.

The OPs idea of an "old timey" on-off regulator on the nearby battery while=
=20
(I assume) the farther battery remains directly connected to the alternator=
,=20
seems like a reasonable solution.  Or maybe a second alternator for the aux=
=20
battery if one can be installed.

JimH


Received from Bob Blick at 02/08/2014 04:54 UTC:

>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 materi=
al
> > 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 pu=
lse
> > 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 a=
s
> > possible detrimental effects on the battery depending on the nature of
> > the
> > battery system and its load.  The latter probably isn't a factor in thi=
s
> > case, but it is very much a factor in UPS systems.


--=20
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