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<font face="Times New Roman, Times, serif">What you have there is a
set of completely hammered batteries. </font>It sounds like an
off-grid system with parallel strings of batteries of different ages
being chronically undercharged., which is the renewable energy
equivalent of a car full of teenagers with guns and whiskey.
Something bad inevitably happens.<br>
<br>
I'd recommend that you get an automotive style battery load tester
and clamp that on to each one in turn. Measure the voltage with your
multimeter, because those load testers have iffy analog meters. I'll
bet one will collapse under load.<br>
<br>
Does this customer also have a generator? Sometimes with undersized
PV arrays and a generator you get a "gorge and starve" charging
pattern. The customer lets the batteries get totally flailed and
then grudgingly goes out and starts the generator. The batteries get
blasted with high amperage for a while, shedding positive plate
material, and then get starved again. Perfect storm.<br>
<br>
Tell her that she needs a new set of matched batteries. If she
balks, politely tell her you can't help her, and let someone with
less judgement deal with it.<br>
<br>
Good luck,<br>
<br>
Hilton<br>
<br>
<pre class="moz-signature" cols="72">--
Hilton Dier III
Renewable Energy Design
Partner, Solar Gain LLC
453 East Hill Rd.
Middlesex, VT 05602
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