Long Live the FLA! Please post about your long lived battery bank

carleriksen · September 2021

Hello all,

I am interested in collecting use cases of long life FLA banks. I see posts as part of many topics and I have asked a number of people for their experience directly. I hope this topic can bring out some great examples of FLA battery banks that went the distance. Let say going the distance is at least 7 years for GC, 8 years for L16, more than 10 years for industrial batteries as a rough guide.

It would be great if people would post information that includes:

Battery brand/model, bank voltage, configuration (string/parallel)
typical DOD
Was it cycled/fully charged daily?
EQ regime
How long the bank survived, to 80%, to end of life/disposal
Summer temp it was exposed to
anything else that you feel was important to know/that you believe contributed to long life.

stillchillin · September 2021

Hi Carl, I will share
I have a 48V bank of 12 Rolls 4KS25 batteries in series that are going on 12 years of off grid service with no noticeable loss of capacity.
They live in my basement in a box up here in northern VT and stay around 68 degrees year around. I have about a 3.5KW solar array with a 11KW generac propane generator for charging during the short days of winter. I run that on average about 250 hrs per year.
I have my AGS set to start the generator when I get down to 65% and stop at 90%. Typically my bank is fully charged in the morning during the summer months. I water every 5 weeks, about 2.5 gallons. I EQ monthly in the winter months maybe once in the summer. Sometimes in the winter I will EQ with both the sun and my generator for about 110 Amps in. Usually see 60A input with just my panels. I see a high temp of 80 degrees during a EQ cycle, I have my outback set for a 64V EQ but never see it over 62.5V. I have absorb set for 1 hr in the summer but push it up to 3 hrs during the shorter days, bulk charging and absorb are set for 57.5 V. I do take SG readings monthly and hope for 1.265 or better. Twice a year I take and record all cell SGs and voltages after a good EQ. Hoping to get 10 more years from
them! Thanks for asking, Steve

706jim · September 2021

I had 12 220A-hr Dunlop GC's set up in three series parallel strings as my battery bank. They lasted for 19 years 6 months from May to November. They normally reached float from my 430 watts of panels. Equalized occasionally maybe three times a season. Stored in the freezing cold for those 19 winters. Eventually lost capacity after being drained accidently by my daughter's friends. Normal DOD about 20%.

19 years

Ralph Day · September 2021

Eventually lost capacity after being drained accidently by my daughter's friends.

That's why no-one else is ever in charge of my system...so far.

freelivingman · September 2021

Steve - wow what an information packed post. Thank you so much. . I have a 48V system made up of 16 6 volt Crown batteries. 8 in series one side and 8 the other then joined parallel. This is my second set of Crown batteries in the past 8 years, I ignored the warning signs and neglected them for several months, low water, over charge, high heat etc.
This new set is about 3 mths old and I am going to keep a close eye on the, including monthly watering, EQ every 40 days or so, hydddrometer readings, etc.

BB. · September 2021

While it is nice to exchange long term history on batteries and battery suppliers/mfgs.... I do worry that, for example 10 years, is a long enough time for "other things" to happen (Walmart, Costco, etc. change battery vendors, vendors move to Mexico/off short manufacturing). And even good vendors seem to have "lost the recipe" at times (bad lot, bad few lots). Then there are others in the supply chain. Battery distributor mixes wrong acid concentrations, tipped batteries on pallet leak electrolyte, a pallet of batteries left in the back corner of the warehouse for a number of months and not properly charged/maintained.

So, it is critical that you do some basic steps when you receive the batteries.

check delivery (no leaks, cracked cases, etc.).
Log each battery (mark a number, lot code, check specific gravity of each cell, resting voltage). If old lots mixed in raise an issue with distributor. Low SG, low resting voltage, low electrolyte levels--May be a reason to return to vendor (basically lead acid batteries at less than 75% state of charge are at risk for early sulfation). You have X number of batteries and Y number of cells--they should all be closely matched for readings (SG, voltage, date codes, etc.).
In the Rolls manual, they even say to check battery polarity is correct (with meter) on initial inspection (that would be big surprise).

Example of battery manual (Rolls):

https://www.rollsbattery.com/wp-content/uploads/2018/01/Rolls_Battery_Manual.pdf

Make sure you banks are wired so that each parallel strings has equal resistance in their cable runs:

http://www.smartgauge.co.uk/batt_con.html

Do the normal monthly maintenance required for your battery type (check and log specific gravity of each cell resting voltage of each battery, battery connections are clean and tight, plates are not exposed to air, etc.). Any differences that stand out (high SG or low SG in one cell, etc.) needs to be investigated.

We have several folks that sell/maintain battery systems--And the #1 battery killer is under charging. Make sure you have enough solar/genset/etc. power to get your bank charged (>90% at least once or several times a week). Do not let Lead Acid banks sit for more than ~1 month (flooded cell at room temperature) without recharging (AGM ~6 months max between recharging)...

-Bill

carleriksen · September 2021

@stillchillin / Steve: Thank you very much for that detailed rapport on the Rolls'. Industrial strength bank. Maybe we one day will get a second report when you cross the 20 year mark! fingers crossed for that. Nice to see your EQ voltage mentioned.

@706jim That is an unusually impressive life span. Even if you factor in half of the time was not under load just the time alone. The temperature surely helped.

@freelivingman: Do I read you correctly that first bank essentially lasted 8 years before a lapse in maintenance destroyed it? Would you mind mentioning the specific model of the battery? What kind of DOD did those Crowns typically see?

@BB. Duly noted. I agree that one must be careful in assuming that results are repeatable; there are factors out of our control as you detail. Thank you for the pointers on good maintenance. I know those in the know already.. well.. know and I think getting these things repeated can only be a good thing. A very clear picture from all the questions I ask, in other forums as well, echo what you detail. Don't fail to fully charge, Don't let them sit. Keep up with the full maintenance program. And your point/procedure to personally making sure you actually start with good product is very important too.

Fenachrone · October 2021

My 6-volt Rolls S-460s, in series strings for 24 volts, went almost 15 years (warranted for 7). And that was with not the greatest care, including not a consistent equalization schedule, complete discharges a couple of times, and low water in some cells from time to time. Summer temps never got above 90F. DOD got down pretty low routinely in the fall.

Long Live the FLA! Please post about your long lived battery bank

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