[NLRS] Battery charge regulator

Wed Sep 7 13:28:25 EDT 2011

Several years ago I got a Vector 2/10/15A smart charger. It has a setting
specifically for gel cells. I'd recommend something like that. I think when
I got it, the regular price was something like $65 but Farm & Fleet had them
for sale for $45.

It's the best battery charger I've owned.

73, Zack W9SZ

On Wed, Sep 7, 2011 at 12:06 PM, Jim Klassen <klas0037 at umn.edu> wrote:

>
>
> There are two issues here.
>
> The first is that Gel batteries (and to a lesser extent AGMs) cannot
> tolerate being over charged and this means a charger that is both voltage
> and current limited.  In particular, if you actually have a Gel battery,
> they have a lower max voltage than AGM and flooded so they would be easy to
> cook with a car charging system.
>
> If the charger is properly current limited, I don't see a problem (except
> possibly noise/hash from the inverter) from leaving the charger connected
> while operating.  The charger will supply whatever current it is limited to
> (which needs to be set at a safe continuous duty level for the charger) and
> the voltage will fall off until the battery will fill in the rest.
>
> If you have a voltage regulated charger (matched to the battery float
> voltage), the really simple  (and suboptimal from a power efficiency and
> longer than necessary charging time) answer, would be to connect the charger
> through the resistor and the load via a separate connection to the battery
> positive terminal.
>
> In practice a 1.4 ohm resistor will limit the charging current to much less
> than 10 amps in a 12 volt system.  While the charger voltage may be near 14
> volts (which is too high for a Gel battery, but probably ok for cycle use of
> an AGM), the battery voltage probably shouldn't be allowed to get below 11
> volts, so you would only have about a maximum 2 amps charge rate and that
> will drop quickly as the battery voltage recovers as it is re-charged.
>
> Jim
> KB0UAZ
>
> On Sep 7, 2011, at 11:42 AM, Bill Ockert wrote:
>
> >
> >
> > Hi John,
> >
> > Not sure if it is applicable to the overall situation but...
> >
> > The trolling motor on my boat uses 24V so has two 12V batteries in
> series.
> > The boat
> > overall therefore has three batteries, on for cranking and two for the
> > trolling motor. This
> > is a common situation. I bought a charger from Cabelas that changes all
> > three in place.
> > In addition to changing all three batteries from 120VAC, the model that I
> > have will charge
> > the two 12V series batteries from the charge current the boat motor puts
> out
> > to the cranking
> > battery.
> >
> > I do not recall the make and model of the charger but looking at Cabelas
> web
> > site there
> > are several models that do this.
> >
> > Hope this is of some help.
> >
> > 73 de Bill ND0B
> > ----- Original Message -----
> > From: <tosca005 at umn.edu>
> > To: "NLRS Reflector" <nlrs at mailman.qth.net>
> > Sent: Wednesday, September 07, 2011 11:30 AM
> > Subject: [NLRS] Battery charge regulator
> >
> >
> >>
> >>
> >> Well, I managed to "cook" one of my 31 AH gel cell batteries while
> trying
> >> to recharge it. It didn't explode or rupture spilling acid all over the
> >> place, but the case sure looks funny as it pushed outward from internal
> >> gas
> >> liberation. Fortunately, it held together without cracking open, but...
> >>
> >> Anyway, not wanting to repeat that experience, I am looking for a
> battery
> >> charge regulator. I realize that a 1.4 ohm 150 watt resistor in the
> >> positive lead of the (replacement) battery would limit the charge
> current
> >> to about 10 amps, but it would also limit the drain current to the same
> 10
> >> amps or so, which is not enough when roving when some of the "low
> >> microwave" amps kick into high gear. I would like a device or circuit
> that
> >> would limit the charging current into the battery to whatever is optimal
> >> for a gel cell battery, but not limit how much current is drawn out of
> the
> >> battery under severe load.
> >>
> >> An even tougher need is a way to put two 12v gel cells in series to
> >> provide
> >> 24 volts at high current for a few of the amplifiers that need 18-26
> >> volts,
> >> and still be able to safely charge the pair of batteries from the
> >> vehicle's
> >> 12 volt electrical system. I have a 12V to 24V inverter that can deliver
> >> about 30 amps at 24 V, but some of the amplifiers want even more than 30
> >> amps when driven to the max. I figure that a pair of healthy gel cells
> in
> >> series could provide all the current I need for short periods of time,
> as
> >> long as I can keep them properly charged. Using the 12-to-24V inverter
> >> output across the series-connected 12V batteries would potentially work,
> >> if
> >> not for the problem of lack of charging current regulation leading to
> >> another catastrophic battery failure, which would not be nice on the
> road.
> >>
> >> Ideas, anyone?
> >>
> >> 73 de W0JT
> >> ______________________________________________________________
> >> NLRS mailing list
> >> Home: http://mailman.qth.net/mailman/listinfo/nlrs
> >> Help: http://mailman.qth.net/mmfaq.htm
> >> Post: mailto:NLRS at mailman.qth.net
> >>
> >> This list hosted by: http://www.qsl.net
> >> Please help support this email list: http://www.qsl.net/donate.html
> >>
> >>
> >
> >
> > ______________________________________________________________
> > NLRS mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/nlrs
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:NLRS at mailman.qth.net
> >
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
>
> ______________________________________________________________
> NLRS mailing list
> Home: http://mailman.qth.net/mailman/listinfo/nlrs
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:NLRS at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>