From: John De Armond
Newsgroups: rec.outdoors.rv-travel
Subject: Re: More Battery Recharging Questions
Date: Thu, 22 Dec 2005 23:41:07 -0500
Message-ID: <52vmq1drbf92ain8avcsph6tcur0ps5fma@4ax.com>

On Thu, 22 Dec 2005 16:29:36 -0800, altar wrote:


>--------------------
> http://www.windsun.com/Batteries/Battery_FAQ.htm
>
>
>Life span of average use batteries: Golf cart: 2-6 years
>
>Battery life is directly related to how deep the battery is cycled
>each time. If a battery is discharged to 50% every day, it will last
>about twice as long as if it is cycled to 80% DOD. If cycled only 10%
>DOD, it will last about 5 times as long as one cycled to 50%.
>----------
>Further:
>---------
>
> The most practical number to use is 50% DOD on a regular basis. This
>does NOT mean you cannot go to 80% once in a while. It's just that
>when designing a system when you have some idea of the loads, you
>should figure on an average DOD of around 50% for the best storage vs
>cost factor. Also, there is an upper limit - a battery that is
>continually cycled 5% or less will usually not last as long as one
>cycled down 10%. This happens because at very shallow cycles, the Lead
>Dioxide tends to build up in clumps on the positive plates rather in
>an even film.
>

Use those general FAQs as a guide and not a bible.  This kind of stuff
varies a lot with the type of battery and even the manufacturer.

I know, for instance, that a single full discharge to 0 volts will
kill a pair of newish Sam's Club cart batteries.  I had that happen
when a vandal pulled the shore power on my rig and I didn't notice it
for a couple of weeks.  When I pulled the pair and put them on my
battery tester, the capacity was below 20%, even after several
charge/discharge cycles.

I rely on the manufacturer's  guidance when I can get it with enough
specificity and on my experience.

>All of the above is the reasoning for my original statement:
>
> No way am I going to live on 25% percent of capacity. Or wait to
>charge them at 10-12 amps.

Of course not.  This sounds like some who fret about babying an AA
NiMH battery.  Who cares if it only lasts a year?  At a buck and a
half ea, it's a non-issue.  I'm gonna cram a 15 minute charge into
them and use them until they quit.  Strangely enough, none have yet.

I have the same attitude about house batteries.  My pair of Group 29
Stowaways cost about $140 plus tax.  I wouldn't give it a second
thought if I had to replace them every year.  Why, $140 would almost
buy a tank of gas! :-)  My attitude is run 'em hard and put 'em up
wet.  What I've learned is that if I don't run 'em TOO hard, the
effect on life is very minimal.  I routinely run mine to 80% DOD.  My
heart doesn't palpate if I occasionally let 'em run down to 10 volts
or less in the middle of the night.

I give the batteries in my EV a bit more care because at nearly a
kilobuck for the pack, the money involved is starting to get serious.
I never go below 80% DOD and try to keep it above that.  However! The
end of the discharge cycle occurs when I arrive at my destination and
not when the E-meter hits a magic number!

I charge 'em as hard as my charger is capable of because I've yet to
see any credible evidence that it does any harm and I don't like my EV
to be down for hours charging.

John