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

Wed Apr 5 16:23:52 PDT 2023

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 <danny at sesre.com> <mailto:danny at sesre.com>
> To: "offgridsolar at sti.net" <mailto:offgridsolar at sti.net> <offgridsolar at sti.net> <mailto:offgridsolar at sti.net>, RE-wrenches
> 	<re-wrenches at lists.re-wrenches.org> <mailto:re-wrenches at lists.re-wrenches.org>
> Subject: Re: [RE-wrenches] replace part of rolls battery bank
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> 
> 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)
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