Battery Equalization Interrupted

sub3marathonman Solar Expert Posts: 300 ✭✭✭
I was doing the equalization procedure on the four Surrette (12CS-11PC) batteries I have set up as a 48V system. Everything was going fine until ... the Charger Block function kicked in and stopped it. The batteries were just starting the charge current reduction after going through the constant current charge. The voltage read about 58.5 (I think). After the equalization stopped the voltage returned to normal or maybe even slightly higher than normal. I think it was 51.1 volts.

So, what should I do next? Should I try to do the full equalization again? If the cells are within specifications and showing they are fully charged, does it need to be equalized again? Do the batteries even need to be equalized if the cells are within the specifications for the voltage variation? It seems they need to be equalized to prevent the acid from becoming stratified, so is it on a time basis too, such as every six or eight months? Does equalization hurt the battery or just use some extra water? I also tried to do the equalization when it was cooler so the batteries wouldn't get so hot.


  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Battery Equalization Interrupted

    You should be a lot higher than 58.5 , 64V is standard for EQ for LA batteries

    Fire it of again and again ( or increase either the charge current or EQ timer ) until you can get the battery's to hit 64V and then absorb
  • blackswan555
    blackswan555 Solar Expert Posts: 246 ✭✭
    Re: Battery Equalization Interrupted

    Were your batteries FULLY charged before commencing EQ ? They have to be, (I give my site`s 4 - 5 hrs of absorb before I get there) Also do you have auto temp compensation or are you doing it yourself ?

    There is some good reading on here

    Have a good one
  • sub3marathonman
    sub3marathonman Solar Expert Posts: 300 ✭✭✭
    Re: Battery Equalization Interrupted

    Well, I found the problem. The XW6048 was doing exactly what I told it to do.

    It interrupted the first equalization because I had the charger block set.

    OK, so I took Solar Guppy's advice, and started another equalization. And this time, I made sure I charged the batteries first, as blackswan555 said. And the XW6048 shut it down again. This time for "Battery Over Voltage."

    This time I was able to figure it out myself. I had set the "Battery Under Voltage" cut out at 46.5V, and the "Battery Over Voltage" at 60.0V. That would explain things.

    So the third time apparently worked exactly as it should. It made it through the entire procedure. The only thing I wondered about was that it seemed to be timed for only one hour at the equalization voltage, I was expecting a longer time. I can't find any settings for that though, although somewhere I might have changed it.

    So now hopefully the batteries are happy again for awhile.
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    Re: Battery Equalization Interrupted

    Seems to me that 64.0 V is on the very high end of the recommended EQ Voltage. Am unfamiliar with the XW line, but think that the EQ voltage is usually NOT temp compensated, so your EQ voltage may need to be compensated manually by the user.

    Personally, I always EQ from Solar input. The MX-60 appears to not temp comp VEQ, so usually I look at the Temp comped VFloat and the actual Vbatt, and manually compensate the VEQ by that amount, starting from 62.0 Volts. Our bank experiences very light discharges, usually down to 92-95% SOC, so our EQ has never been too aggressive. (Surrette recommends EQ time between 2-3 hours).

    Everyone seems to develop their own way of interepreting manufacturer's recommendations, and FLA batteries seem to generally be very forgiving.

    I do wish that Surrette had a Forum, where we all could do Q/A and benefit from collective wisdon, but alas have not found it. Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,500 admin
    Re: Battery Equalization Interrupted

    Via Dave Sparks:
    I learned this strategy from Dave Surrette (Rolls) in the late 70's. Pretty much the bible on how I design my systems for offgrid.
    • Assume that the system will never reach more than a 90% state of charge.
    • Try not to go below 50% SOC, ever! Complete absorption over 90% of the year
    • Use the energy stored from 70% to 90% SOC for your daily cycles.
    • Save the energy from 50% SOC to 70% SOC for aging to get long battery life.
    I know Surettes has changed their recommendations over the years but I also know they are in the business of selling batteries! If you do the above you will get 10 to 15 years on their batteries with decent maintenance....!

    Equalization, in my humble opinion, is to be done only when needed (cell to cell specific gravity miss-match outside of 0.030, "tall batteries" that can stratify charge).

    Equalization performed often and with heavy currents/boiling otherwise would seem to age a battery rather than extend its life (excess gas generation damaging plates and oxygen induced corrosion of the positive plates).

    There is this oldie but goodie thread about "Time to Question the 3 d
    Day Rule?
    "... In there, I offer that a battery bank that is 2x-4x larger will last 2x-4x longer, but at roughly the same, or slightly less overal costs as a smaller bank that has fewer batteries to replace but needed replacement more often because of the deeper cycling.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset