Thanks, that was instructive. When you say lead is the fuel - how does that work? I wouldn't have expected it unless it means the grids (my word for whatever they are called. plates?) are bigger...
I guess you could make the grids heavier better life in severe conditions. How do you know the extra weight is in grid area and not structure? Or do I have the wrong idea altogether? On Wed, Apr 30, 2014 at 9:56 PM, EVDL Administrator <evp...@drmm.net> wrote: > On 30 Apr 2014 at 20:36, Michael Ross wrote: > > > So what should I be paying for? Weight? $/lb value? $/Ah value? I am > > hoping at least for directed opinion. > > Who was it who categorized all falsehoods as lies, damn lines, and battery > pitches? I think it may have been Lee Hart. ;-) > > Especially with cheap, no-name batteries, amp-hour ratings can be iffy. > There are many ways that battery salesmen can fudge the numbers. > > If you're a battery manufacturer, you can make a battery's capacity seem > higher by rating it at a very slow discharge - perhaps C100 (100-hour > discharge, common for PV systems for some reason) instead of the standard > C20 (20 hour discharge). OTOH, some of the good batteries are actually > rated at C5. > > Or you can measure capacity at some absurdly high temperature that would > degrade the battery in a few weeks if you actually used it that way. > > Or you can measure highly optimized lab samples made with high quality > materials, but conveniently ignore the poorly made junk that actually comes > off the asembly line. > > Or you can just outright lie about it. > > So I'd say that price/amp-hour is pretty iffy. > > Weight is a better indicator of real capacity. Lead is your fuel. Again, > make sure your vendor is telling the truth! > > This can also change if you're drawing large currents. You might find that > a battery with a lower C20 capacity than another one actually has a higher > C1 capacity. > > The factor which models capacity loss at high currents is the Peukert > (pronounced POY-kairt) exponent. If you have a capacity rating for your > battery at two different currents, or if you have C20 and reserve capacity > (and you can actually trust the manufacturer's rating), you can calculate > the Peukert exponent with this calculator: > > http://evdl.org/uve/battery.html > > The lower the Peukert exponent, the more capacity the battery will have at > high currents. Some (but not all) AGM batteries can approach a Peukert > exponent of 1.1. > > David Roden > EVDL Administrator > http://www.evdl.org/ > > > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > For EV drag racing discussion, please use NEDRA ( > http://groups.yahoo.com/group/NEDRA) > > -- Put this question to yourself: should I use everyone else to attain happiness, or should I help others gain happiness? *Dalai Lama * Tell me what it is you plan to do With your one wild and precious life? Mary Oliver, "The summer day." To invent, you need a good imagination and a pile of junk. Thomas A. Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html> A public-opinion poll is no substitute for thought. *Warren Buffet* Michael E. Ross (919) 550-2430 Land (919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone (919) 631-1451 Cell (919) 513-0418 Desk michael.e.r...@gmail.com <michael.e.r...@gmail.com> -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140430/c43726a2/attachment.htm> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
