Danny, My experience is if you are careful and use _equal length
conductors_ for all 3 strings you can get good results. The main
problem I have with 3 strings of 6 V cells @ 48 vdc is leaving the
customer with 72 cells to check and fill. That's a lot of work if you
don't have a watering system.
I totally get why you'd want to give them 2 strings in case they lose a
battery or 2. Most of my off grid customers live quite a ways from the
battery store and it's not uncommon for it to take a month to get
replacements - during the best of times.
Another option I've done is give them a string of 25 - 2V cells for a
48V system. You just set the charging parameters accordingly and go.
That way if they lose a cell or two, the remaining battery bank should
be able to keep them limping along until the replacement battery(s) show
up. Need to check and _make sure_ your charge controller and inverter
can charge at the slightly higher V but usually that's not a problem.
Best,
Greg Egan
Remote Power Inc.
g...@remotepowerinc.com
Message: 1
Date: Tue, 4 Apr 2023 20:45:44 +0000
From: Daniel Young<da...@sesre.com>
To:"offgridso...@sti.net" <offgridso...@sti.net>, RE-wrenches
<re-wrenches@lists.re-wrenches.org>
Subject: Re: [RE-wrenches] replace part of rolls battery bank
Message-ID:
<bl1pr12mb5921cde5991f65fa842bc82cbb...@bl1pr12mb5921.namprd12.prod.outlook.com>
Content-Type: text/plain; charset="utf-8"
Thanks all for the advice. I figured it was not worth trying on a different
battery brand. I honestly needed to be able to tell them I researched it and
asked my peers.
The client really uses the 3 x strings they have and did not really want to go
down to 3. They are currently choosing to get the two Rolls under the prorated
warranty, and hopes to get another 2 useful years out of the bank before
planning to replace.
Already prepared him on the cost of the equivalent Li+ at todays prices. So he
knows roughly where he is heading.
Side note: I am in the camp of trying for 2 x strings when possible (agree that
3 x strings is the absolute limit, and not the best option), simply because if
a single cell goes bad, I don?t want a client with essentially nothing
available until we can get a replacement and get on site. With 2 strings, they
can make due at least. That?ll go out the window with Lithium though. Looking
at Fortress Power for the next battery bank for this client. But we will see
what changes in the market by the time it?s needed.
With Regards,
--
Danny Young
NABCEP PV Installation Professional #031508-90
Engineering Team Lead
Solar Energy Solutions
Lexington | Louisville | Bloomington | Cincinnati | Evansville | Indianapolis
513-448-5176 (mobile)
877-312-7456 (Main Office)
da...@sesre.com<mailto:da...@sesre.com>
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