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 |