Second battery

[John Hofstetter <hofs@domain.elided>]

>From: Tom Mandera <tsm1@domain.elided>
>Subject: Re: Con-Ferr Shackles...Spare Batteries...
>
>On Tue, 13 Jan 1998 jmbrodsky@domain.elided wrote:
>
>>         Also, what are the recommendations for mounting an extra battery
>>      in a '75 T'all.  What about isolators, and mixers?  I was going to
>>      run the accesories off the spare batt. and run a high-current relay
>>      between the two batts to charge the spare only when I need to.  I
>>      was thinking of a deep-cycle boat battery for the second.  Any
>>      ideas?
>
>FYI, remember that a deep cycle battery will NOT put out as much "juice"
>as a regular "starter" battery.. so, for a WINCH, you *do not* want the
>Deep Cycle, but rather a good Starter Battery.

Just for the sake of clarification, I hope, when people talk about a deep
cycle boat battery or marine battery they are usually talking about a
battery that has enough cranking amps to start the engines on the boat
rather than a true deep-cycle battery.  What Tom is saying is less true for
a marine battery and absolutely true for a deep-cycle battery. There are
some other ramifications that Tom didn't deal with directly. You can't
correctly charge two different types of batteries at the same time with one
charging source by sending the charge to the two batteries wired in
parallel. Worse yet, this doesn't even work very well with batteries of the
same kind if they are of different ages or made by a different company. I
had two batteries in my Travelall and they were connected with a marine
battery switch that allowed me to draw from, or charge to, either battery
or both batteries. This worked OK and was necessary because I was a
winching fool in those days, but I had to control the charging by changing
the switch or my battery life was very short. At that time I was using
lifetime guaranteed batteries and I would replace them within a year, and
lied every time about how I was using them.  Their life was so short
because, as Tom says below, I was discharging the batteries pretty near to
nothing, and regular batteries can't take that kind of discharge treatment.
I saw a paper put out by some battery maker that talked about the number of
total discharges the different kinds of his batteries could take. For
regular batteries like we have in our cars, 3 or 4 discharges and the
battery was gone. (I actually only remember the number was very low, not
the exact number)  A deep cycle battery like used on golf carts, on the
other hand can withstand a 100 or so total discharges. My advice, for what
it's worth, go with two batteries, consider the marine starting batteries
if you want, but plan on buying two new ones of the same size, or put in
another battery and battery switch and plan on thinking out how much
remembering you're going to have to do to remember  to keep both batteries
charged and such, or install two new regular starting batteries wired in
parallel and never draw them way down. If you do this you do not need to
have particularly high cranking amps. Remember: the more amps that a
battery will put out, the more plates it has, the thinner the plates are,
and the more susceptable to damage both from internal and external sources
the battery is. A deep cycle battery has a few very thick plates and
consequently puts out few amps but are very resistant to damage.
End of battery lesson.
John
>
>Even lights.. if you're running a few high powered ones, should be run
>from a "starter" battery..
>
>OTOH, if you want to use a DC--> AC inverter to run a TV set while
>camping, a deep cycle may be your choice.. you can severely discharge a
>deep cycle and bring it back to life a number of times, whereas a
>"starter" battery kinda falls apart after a few good super-deep discharges.
>
>Note this also means you don't want to use a deep-cycle to start your
>truck.. take a look at CA and CCA on a deep-cycle (if it has a rating)..
>I was just looking at some Exide NASCAR series batteries for my Scout
>II.. 1100CA available.. I bought the 850 or so @ $75 (less $5 core)
>
The 1100 probably has a third more plates than the 850 to illustrate my
previous point.
John

John Hofstetter a.k.a. Ol'Saline, who's been a lot of places none of us is
allowed to go anymore and that's a real tragedy, and who to quote the
senator from Texas, "has more guns than he needs but not as many as he
wants"
79 Scout Terra with 8000 lb. Warn Winch, Detroit Locker in rear and limited
slip in front, 4" Trailmaster lift kit, Holley Electronic Fuel Injection,
Mallory Unilite Distributor                                  MSD ignition
"It's a legend", but it's too darn long and too darn wide sometimes to go
where I ask it to go.

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