Funny, happened to us, too, some years
back... six sets of 2V cell pairs in a 24V bank, with one case
showing 0.05 volts DC, the difference in resting voltage between
the two cells. We opened up the cover (the case was red, as I
recall, Mick), disconnected the internal cell-to-cell connection
and made it work until the pair could be replaced.
Allan
Allan Sindelar
[email protected]
NABCEP Certified Photovoltaic
Installer
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder and Chief Technology Officer
Positive Energy, Inc.
3209 Richards Lane (note new address)
Santa Fe, New Mexico 87507
505 424-1112
www.positiveenergysolar.com
On 10/15/2012 9:32 AM, Kirpal Khalsa wrote:
Mick.....we had this happen once too.....Luckily it
had already become standard procedure for us to check and notate
voltage of each battery prior to connecting battery cables....we
had installed 11 of the 12 batteries and the 12th battery turned
out to have reversed polarity......While we didn't send it back we
made clear markings on the battery case and wired it
appropriately.....Whew!
lesson of the day: always check each battery for voltage and
polarity at or before installation......
OK, now time to go replace a customers battery bank, Note to
self:- check battery polarity!
Be safe, cheers!
--
Sunny Regards,
Kirpal Khalsa
NABCEP Certified Solar PV Installer
Renewable Energy Systems
www.oregonsolarworks.com
On Mon, Oct 15, 2012 at 6:24 AM, Mick Abraham <[email protected]> wrote:
Hello, Wrenchies~
Mac Lewis wrote about battery strangeness on the Sunny Island
system for his clients. Here is a theory to consider, Mac.
I once bought a 48v string of >famous brand< two volt
cells in which one cell had been loaded backwards into its
case. When hooked up according to the +/- markings on the
case, this cell was discharging at the same time the rest of
the string was charging so even though the others were running
high during the charge, the end to end voltage immediately
slumped to relatively low values after the charge was ended.
The one cell was effectively missing in action.
My client was a DIY type who was distant from my location but
he owned a voltmeter that was still in the box. I coached him
through a "voltage walk" up the string and sure enough we
found the one increment that was subtracting from overall
string voltage instead of adding to it. The >famous<
battery supplier said this was impossible, they are checked
three times, this never happens & can't happen, blah
blah...and they were only convinced when the cell was back in
their shop and they could measure this for themselves.
Even after they checked it, they said, "It's the first time in
our 20 + years with that brand that we have ever seen this."
Black swan.
At my request, the company paid to ship back the entire string
and ship all new replacement cells to the client. This seemed
important because the other 23 cells had been subjected to a
high voltage per cell and had gotten a bit hot before the
problem was discovered.
++++++++++++++++++++++++++++
Perhaps this theory is worth checking on site. Whatever you
find to resolve this problem, Mac, be sure to report back on
list so we can all learn.
Jolliness,
Mick Abraham, Proprietor
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