From: John De Armond
Subject: Re: More Battery Recharging Questions
Date: Thu, 22 Dec 2005 23:41:07 -0500
On Thu, 22 Dec 2005 16:29:36 -0800, altar wrote:
>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%.
> 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
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.