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:[email protected]]
*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)
[email protected] <mailto:[email protected]>
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