Wrenches, especially the
grizzled ones,
I was referred to a couple for off grid service about 75
miles from here. They have an older homeowner-built 24V
system (that I haven't seen yet) and have lived with it for
decades. They have ten L16s in two parallel strings. I
questioned this when I first heard it, but the owner told me
that the most positive cell is the one that always fails
first, and he hates the effort of periodically rotating his
batteries, so the battery nearest the positive cable has
another L16 in parallel with only this battery. He explained
that he has lived this way for thirty years. I don't yet
know what life they have gotten from their battery sets, but
until recently they lived on 750W of PV, and now have around
1kW - not a large array.
I respectfully replied that in nearly thirty years in the
field, this is the first time I had heard of this approach.
My own experience is that while sometimes I had sometimes
seen marginally more water consumption in the lead positive
cells as they aged, when I had tested for failed cells in
old strings, the failed cells tended to be randomly located,
and not frequently enough at the positive end to suggest a
pattern. I had also long ago read (Surrette's manual?) that
rotating the lead cell is good practice, but unless a system
has a single series string, wired to make this possible,
nobody ever did this rotation, and it didn't appear to make
a noticeable difference in long-term performance.
Has anyone else heard of this approach? Is there validity to
the logic? What can I learn here that I didn't know?
Thank you,
Allan
--
Allan Sindelar
al...@sindelarsolar.com
NABCEP Certified PV
Installation Professional
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder (Retired), Positive Energy, Inc.
505 780-2738 cell
