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/
>
>
> _______________________________________________
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>


-- 
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
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<michael.e.r...@gmail.com>
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