[RE-wrenches] RE-wrenches] replace part of rolls battery bank

Wed Apr 5 18:30:40 PDT 2023

Just attended the NABCEP conference last week and took in CEU classes from
Rolls and Midnite on battery charging and design. Just awesome classes and I
walked away thinking the FLA were kind of like my old 7.3 Powerstroke
diesel.I could work on them and could see when issues were developing. The
lithium batteries are kind of like my 6.7 PSD. Great power, fast but when
something happens with a BMS.no idea except to go to the manufacturer.

Just wanted to share this after reading your awesome post.

Scot

From: RE-wrenches <re-wrenches-bounces at lists.re-wrenches.org> On Behalf Of
Tump via RE-wrenches
Sent: Wednesday, April 5, 2023 6:24 PM
To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
Cc: Tump <tump at swnl.net>
Subject: Re: [RE-wrenches] RE-wrenches] replace part of rolls battery bank

I would suggest that adding additional batteries to increase battery
voltages is fine 48 to 54V or what ever, I too have used this many times on
very remote sites. Please also increase your inverters hi voltage cut out
settings, as this can be a real bummer having the system shut down in full
sun. 

Another thing; IF you have battery strings,  cables of equal length from
each string should be connected to a buss bar then buss bar to inverter or
inverters, this will reduce wiring headaches, voltage drop as well as
providing equal charging to all strings. (depending on internal resistance).

I would also suggest fewer batteries of bigger cells. My preference is 2
volt cells, less holes to water, less copper interconnects. Yeah there heavy
but for hi charging & discharging, a large battery is always my choice.  OR
the Surrette 6CS25P has been the MOST reliable battery Surrette has put out.
After almost 30 + years of installing their batteries this one has been the
best. They do have a EX series 2 Volt cell that has the same plate thickness
as the 6 CS but I have had issues w/ them. IF you are using the EX 2 volt
check the polarity PRIOR to installing them & mark the positive side. I have
had the plastic covers installed incorrectly and it plays havoc on your
install.

Yep LEADITE I am, refractometer and a DVOM and I have a client that can spot
problems way before things become critical. AND that Surrette warrantee Pit
BULL Mr. Higgins & your client will be very happy when Steve OKs a
replacement because you have recorded your Spg readings.

My $.02 TUMP

On Apr 5, 2023, at 5:26 PM, greg egan via RE-wrenches
<re-wrenches at lists.re-wrenches.org
<mailto:re-wrenches at lists.re-wrenches.org> > wrote:

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.

greg at remotepowerinc.com <mailto:greg at remotepowerinc.com> 

Message: 1
Date: Tue, 4 Apr 2023 20:45:44 +0000
From: Daniel Young  <mailto:danny at sesre.com> <danny at sesre.com>
To:  <mailto:offgridsolar at sti.net> "offgridsolar at sti.net"
<mailto:offgridsolar at sti.net> <offgridsolar at sti.net>, RE-wrenches
   <mailto:re-wrenches at lists.re-wrenches.org>
<re-wrenches at lists.re-wrenches.org>
Subject: Re: [RE-wrenches] replace part of rolls battery bank
Message-ID:

<mailto:BL1PR12MB5921CDE5991F65FA842BC82CBB939 at BL1PR12MB5921.namprd12.prod.o
utlook.com>
<BL1PR12MB5921CDE5991F65FA842BC82CBB939 at 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)
danny at sesre.com <mailto:danny at sesre.com>  <mailto:danny at sesre.com>
<mailto:danny at sesre.com>

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Tump
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