Date: Thu, 4 Sep 2008 10:20:45 -0700
Reply-To: Jim Cochran <mxsailor@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Jim Cochran <mxsailor@GMAIL.COM>
Subject: Thoughts on batteries
In-Reply-To: <1b3c5f060809040844v633df79ep587c35f2924e8e41@mail.gmail.com>
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Hi List,
I can appreciate the wisdom gained from the ham setup.
I live on a sailboat most winter months and live off my batteries
during much of that time. Have for 11 years.
On my boat I use an external voltage regulator that allows me to dial
up how many amps I want to push into the batteries, or set it to
automatic and the regulator will figure how much my batts can take at
any given moment when I run my diesel. I use 2 banks of Napa "Special
Use" (Exide) 6 volt batteries, 4 in each bank wired to output 12 volts
per bank, plus a group 27 starting battery. My regulator or 120 vac
charger can charge 3 banks at the same time, sending different charge
to each bank as needed. Also equipped with solar panels and wind
generator.
Now that my Westy is running, I'll replicate that system using a smart
charger for a bank of two Napa 6v batteries, with some solars on the
poptop. The bank will live under the rear seat. The 6v can be
discharged to zero and still come back (I've even had them run dry on
me and still come back to life). Point is that the Exides sold by Napa
are just as good as Trojans, without spending a fortune on them. If
I'm camping on the water or dry land, I want the 6 volt wet cells.
If you stop at 11.5 volts, you aren't going to have any capacity
unless you have a monster bank of batteries. Most equipment with built-
in battery savers kick in at 10.5v.
On Sep 4, 2008, at 8:44 AM, Bill Prats wrote:
>> 3. Did I hurt my Aux Battery?
>
> I have a large ham radio and have lots of battery experience, some
> of the
> brands don't last more than a few years. Here is any easy way to
> test the
> capacity of a smallish battery. Wire a tail light across it by
> itself and
> time how long the light burns a decent glow. Since the wattage is
> on the
> bulb you will get a good idea about the condition of the battery.
> Power in
> Watts = Voltage times current. 6 watt bulb on 12 volts draws a 1/2
> amp, 12
> watt lamp on 12 volts draws 1 amp. 24 watt lamp on 12 volt draws 2
> amps.
> A 100 watt sound system full on will draw around 9 amps and more
> depending
> on other features and volume level. A older 40 amp hour battery
> might be
> good for 2 hours in my opinion.
>
> Try not not to drain any battery below 11.5 volts, that level varies
> by
> battery but its generally accepted as the bare minimum before the
> battery
> plates warp and short together, bad news.
>
> Its possible the battery is ageing and the sound system draws far
> more power
> than estimated. Put an amp meter in series with the system to
> measure.
>
> The only sure way to find out the battery chemistry type is to
> research the
> brand/model number. Sometimes a deep cycle/gell or AGM will weigh a
> few
> pounds more than it automotive type cousin. Well at least you get a
> rough
> idea. I have the same problem, a 55 amp battery that weighs a ton.
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