If a gel battery bank can handle 22 amps at 48-60 volts, what can it handle at 24-30 volts?

softdownsoftdown Solar Expert Posts: 2,989 ✭✭✭✭
A neighbor sold me some 110 Ah gel chemistry batteries. I contacted the listed "manufacturer"...which happens to be the owner of Outback. They informed me that these batteries can handle 22 amps charging without damage.

Now they are being used on a 24 volt system. Does that mean they can handle 44 amps on a 24 volt system?


First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries

Comments

  • Raj174Raj174 Solar Expert Posts: 740 ✭✭✭✭
    edited September 2016 #2
    If four in series equal 48 volts and the charge current is 22 amps then, I would think, for two in series it would be 11 amps. A 5% charge rate is common with gel batteries.
    3600W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 54.4V 195AH LiFePO4 no BMS, Kohler Pro 5.2E.
  • PhotowhitPhotowhit Solar Expert Posts: 5,146 ✭✭✭✭
    It can handle 22 amps...

    Nothing changes other than the system voltage. If you have multiple strings in parallel it would handle more, but each battery can handle 22 amps, so if they are 12 volt batteries and they can handle 22 amps, then a string of 2 can handle 22 amps at 24 volt, and a 48 volt string can handle 22 amps at 48 volts...
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • softdownsoftdown Solar Expert Posts: 2,989 ✭✭✭✭
    Photowhit said:
    It can handle 22 amps...

    Nothing changes other than the system voltage. If you have multiple strings in parallel it would handle more, but each battery can handle 22 amps, so if they are 12 volt batteries and they can handle 22 amps, then a string of 2 can handle 22 amps at 24 volt, and a 48 volt string can handle 22 amps at 48 volts...
    There are six 12 volt  batteries on 24 volt system. So....three strings. This was his "introduction" to solar. He has already bought a replacement 48 volt system with intentions of using this 24 volt system as well.

    So.....still at 22 amps I am thinking?

    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • BB.BB. Super Moderators, Administrators Posts: 30,219 admin
    3x parallel strings * 22 amps per string (per individual series connected battery string) = 66 amps for battery bank

    Is that the question?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Raj174Raj174 Solar Expert Posts: 740 ✭✭✭✭
    Photowhit said:
    It can handle 22 amps...

    Nothing changes other than the system voltage. If you have multiple strings in parallel it would handle more, but each battery can handle 22 amps, so if they are 12 volt batteries and they can handle 22 amps, then a string of 2 can handle 22 amps at 24 volt, and a 48 volt string can handle 22 amps at 48 volts...
    Thanks for the correction Photowhit, of course it's 22 amps
    3600W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 54.4V 195AH LiFePO4 no BMS, Kohler Pro 5.2E.
  • softdownsoftdown Solar Expert Posts: 2,989 ✭✭✭✭
    BB. said:
    3x parallel strings * 22 amps per string (per individual series connected battery string) = 66 amps for battery bank

    Is that the question?

    -Bill
    So.....the answer is 66 amps?  Using six 12 volt batteries yielding three 24 volt strings....That is a huge difference.

    Gels are often thought to charge best at "5% rate". Charging them at 66 amps would, I think, far exceed a 5% rate.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • BB.BB. Super Moderators, Administrators Posts: 30,219 admin
    There are some GEL batteries that say they will support >>5% rate of charge. (European brands mostly?)

    Make sure to understand the charging voltages and I/V profile.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • softdownsoftdown Solar Expert Posts: 2,989 ✭✭✭✭
    I contacted the listed manufacturer over 1.5 years ago. Was told they were good for 22 amps at 48 volts. That was one string....none parallel.

    So I thought maybe 44 amps at 24 volts. Now...I am not sure what to think. Perhaps I should stick to 40 amps. But if the batteries boil.....big problem.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • Marc KurthMarc Kurth Solar Expert Posts: 732 ✭✭✭✭
    As already explained, if the individual battery is happy with 22 amps:

    - A single string of 4 or 6 or 10 batteries in series is limited to 22 amps.
    - If you remove two batteries from the single string to make it a 24v string, the limit is still 22 amps.
    - If you reconfigure to make two strings of two batteries, each string is still limited do 22 amps - but the two in parallel can handle 44 amps.
    - If you put all four in parallel, you can now go to 88 amps.

    Remember that a string of batteries in series should be treated as a single battery of the cumulative voltage.

    Marc
    I always have more questions than answers. That's the nature of life.
  • softdownsoftdown Solar Expert Posts: 2,989 ✭✭✭✭
    A few different explanations have been offered. With no proven mathematical/electrical explanation. More of a "This is how I would view it." Answers have ranged from 22 amps to 66 amps.

    Because of the parallel batteries (six 12 volt batteries for 24 volt string)...it seems like 44 amps would be acceptable.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • PhotowhitPhotowhit Solar Expert Posts: 5,146 ✭✭✭✭
    edited September 2016 #12
    No, Pretty much just one explanation, you just are not understanding.

    Spec's are, as you have said, each battery can handle 22 amps.

    If you have a string of 4 then, they can handle 22 amps, at 48 volts.

    If you put them in strings of 2, they can handle 22 amps at 24 volts.

    If you have 2 strings of 2 (for 24 volts), side-by-side in parallel, Then each string can handle 22 amps X 2(strings) = 44 amps. They will be drawn down in unison and charged in unison, one battery bank.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • PhotowhitPhotowhit Solar Expert Posts: 5,146 ✭✭✭✭
    edited September 2016 #13
    More information that may help, Most of this stems from the basic equation Watts = Volts x Amps.

    Your original question is actually vague, If you had said will 4 batteries used in a 48 volt system are used as 2 parallel strings in a 24 volt system, can they handle 44 amps. The answer would be a simple yes. See my original response.

    That is NOT what you asked! You asked if they batteries could handle 44 amps in a 24 volt system, with no delineation as to the number of strings.

    Back to the math, so these are 110 Amp Hour batteries at a draw of 1/20th of their capacity per hour. So you can look at the amp hour charge rate as a percent of their capacity, or 22/110=.2 or 20%, so if you know your battery bank's capacity you can use a 20% of capacity figure to define the charging rate.

    Now let's look at the battery bank capacity, in the original configuration of a single string of 4 batteries, this is obviously 110 Amp Hours at 48 volts, so a charging rate of 22 amps at 48 volts would be correct. The battery bank has a total capacity of 48 volts x 110 Amp = 5280 watts. Charging rate at 20% of battery capacity of 110 amps at 48 volts, 22 amps at 48 volts

    Now if you take the same 4 batteries and combine them as 2 strings of 2 batteries, you have 2 strings of 2 batteries. Each have a capacity of 110 Amp hours at 24 volts. 2 x 110 amps = 220 amp hours at 24 volts. Total capacity 220Amps x 24 volts = 5280 watts. Charging at a 20% rate of 220 amp hour battery bank at 24 volts = 44 Amps at 24 volts.

    Marc did a nice job of explaining it also, just forgot to say 4 batteries in parallel "at 12 volt" The charge rate would be 88 amps.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • softdownsoftdown Solar Expert Posts: 2,989 ✭✭✭✭
    Thanks for farther breakdown. Though I did say this: "There are six 12 volt  batteries on 24 volt system. So....three strings." And this: "Using six 12 volt batteries yielding three 24 volt strings....That is a huge difference."

    My initial question was an attempt at delineating the simple charge rate at 48 volts vs 24 volts. That number does not change. Parallel batteries and strings of batteries does change the number. Six batteries on a 24 volt system yields 66 amps.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • BB.BB. Super Moderators, Administrators Posts: 30,219 admin
    The current for charging does not really "care" if the bank is 12/24/48 volts... Each battery "wants" its own current flow (22 amps in this case).

    What matters is the actual bank configuration. If you have a 48 volt battery bank with 4x1 string of 12 volt @ 110 AH batteries, you would have a 22 amp maximum rate of charge.

    If you reconfigure the battery bank to 24 volts with 2x of of the same batteries in series and and 2x of these string in parallel--Then you would have a 2s x 2p battery bank which would take 44 amps (maximum) for charging.

    However, it you had just 2x batteries in series for a 2s x 1p battery bank, you only have one string of batteries and then the maximum charging current would be 22 amps (one string of batteries, each battery "sees" the 22 amps).

    The 48/24 volt question does not really give enough information--If you are reconfiguring the battery bank (keeping the same number of batteries from 4s*1p 48 volts @ 110 AH bank into a 24 volt @ 220 AH battery bank with 2s*2p) that is one answer--But if you are splitting it into two different 24 volt battery banks (or tossing 2x "weak batteries", as an example), then you have a different answer.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Marc KurthMarc Kurth Solar Expert Posts: 732 ✭✭✭✭
    edited September 2016 #16
    How about:

    1) Using your batteries, you are limited to 22 amps per string of batteries in series. That doesn't change based on string voltage.
    2) If you add additional strings, each one will handle an additional 22 amps, regardless of string voltage.

    Add up the number of strings to get your maximum battery bank amperage.

    Please note that voltage isn't part of the conversation. :)



    I always have more questions than answers. That's the nature of life.
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