[RE-wrenches] replace part of rolls battery bank

Mon Apr 3 12:08:40 PDT 2023

My 2 cents:  L16s are not a good choice in the first place. Compare the 
cycle life vs cost.
2nd that sounds like way too many batteries/ strings and definitely a 
candidate for larger format 2 v cells or Li+.

I second William's idea of creating 2 strings of the best cells, and 
start shopping for a better solution. You're going to start playing wack 
a mole, replace a couple of batteries now, a couple more in 2 months, 
and so on, until both you and the client are in tears. Put all that 
money and effort towards a new battery.

If they want sealed, Li+ is really the only decent choice, I've seen 
less than 5 years from sealed L16s like Trojan.  Full River is about the 
best in that field, and still only going to see 7 to 8 years.  It just 
doesn't pencil out compared to HUPs or Li+.

Ray Walters
Remote Solar

On 4/3/2023 12:39 PM, William Miller via RE-wrenches wrote:
>
> Daniel:
>
> I feel your pain:  In October of 2021 one of our off-grid clients had 
> failed flooded L-16 batteries.  We needed 16 replacement batteries and 
> chose Rolls VRLA batteries.  We could not get 16 due to supply chain 
> constraints so we went for 8 with a back order for another 8.  It took 
> until May of 2022 before we could get 8 more.
>
> The Rolls batteries subsequently failed.  We were denied warranty 
> relief in part because we mixed the exact same batteries but delivered 
> 7 months apart.  The cost of resolution came out of my pocket.
>
> If you can’t mix the same batteries of slightly different age, I would 
> extrapolate that you can’t mix batteries of different manufacturer.  
> My guess is if you mix batteries the entire array would experience a 
> hastened decline.  This conclusion is consistent with research done 
> over many years.
>
> I looked up the S550 batteries and learned they are 6 volts units.  
> Assuming the system is 48 volt nominal this would be 3 strings of 8.  
> Three strings is pushing the envelope of acceptable design.  Multiple 
> parallel strings encourage circulating currents resulting in a process 
> I call “battery cannibalism”:  Lower voltage batteries discharge the 
> higher voltage batteries over time.
>
> If it were me I would rearrange the batteries into two strings of the 
> best batteries and wait for the rest of them to fail.  I would then 
> redesign the system for one string with an appropriate AH rating.  Two 
> volt cells are a practical way to achieve this.
>
> Also look carefully at your thermal compliance.  Make sure you are 
> using the proper temperature compensation value applied to all 
> charging sources.  Avoid re-radiated heat from sunlit surfaces and 
> proved good ventilation.
>
> I hope this helps.
>
> William Miller
>
> Miller Solar
>
> 17395 Oak Road, Atascadero, CA 93422
>
> 805-438-5600
>
> www.millersolar.com <http://www.millersolar.com/>
>
> CA Lic. 773985
>
> *From:*RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] 
> *On Behalf Of *Daniel Young via RE-wrenches
> *Sent:* Monday, April 3, 2023 11:04 AM
> *To:* RE-wrenches
> *Cc:* Daniel Young
> *Subject:* [RE-wrenches] replace part of rolls battery bank
>
> Hello Wrenches,
>
> Have a client with 24 x Rolls S550’s. 2 of the batteries have given up 
> the ghost. Rolls will replace them under the pro rated warranty.
>
> The issue us, the client is wanting to replace them with non Rolls 
> batteries to save $. They can get 400AH 6V L-16 form factor FLA 
> batteries from a local battery house for the same price I am going to 
> get the new Rolls for. And that also means they don’t need to pay for 
> freight. The net result is that they could save $4-500 by getting the 
> batteries locally. No freight, and no markup on the batteries we 
> provide (I can technically add the lost markup back in as labor, we do 
> need to make something off of the 3hr one way drive to swap the batteries)
>
> Question is, has anyone got experience mixing battery brands like this?
>
> 3 x strings of 8 c S550’s (L-16HC would be the replacements) both dead 
> batteries are on the same string.
>
> Whole battery bank is near the 5yr old mark.
>
> The last rolls battery bank the client had lasted them 10 years. (they 
> baby the battery bank to be sure, and take maintenance seriously)
>
> I understand where the client is coming from, but do not want to let 
> them shoot themselves in the foot, and I simply do not know what the 
> chances are of swapping in batteries from a different brand. In my 
> head, I don’t see a big issue, even if they are sub par, they will 
> likely just get older faster, and fail around the same time as the 
> rest of the 4-5yr old battery bank. But I’m unsure if there are any 
> more subtle issue that these other batteries would cause.
>
> Client has been loyal for more than a decade, so I want to give them a 
> fair shake at saving some $ now, as they plan to move to lithium when 
> the whole battery bank finally gives out.
>
> 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>
>
>
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