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ALLGRAND 200a/h Gel Batteries: Charge settings recommendations please


profa
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So I have a crappy pwm 3kva/3000w inverter. 24 v. 

I have two Allgrand 200a/h 12v batteries connected to the inverter in series. The inverter is set to ONLY charge the batteries from solar power. The inverter is also set to switch to the grid/utility supply should the solar panels no longer be providing any current. So at night I am on utility. Because they are gel batteries, my thinking is to not "waste" cycles for night usage when the grid is available. The inverter however will switch to the batteries should the grid go down at night. 

I do not have a separate battery monitoring/management system connected to the inverter so cannot accurately tell state of charge. I don't even know if my inverter supports connecting one? So here is my problem....what to set the various voltages for charging and low DC cut-off on the inverter. 

  1. Bulk charging voltage (C.V voltage): Default is 28.2, I raised it to 28.4
  2. Float charging voltage: Default is 27.0, I raised it to 27.2
  3. Low DC cut off battery voltage setting: Default is 20.4 which I think is ridiculous and cause damage to the battery, so I set it to 24.0 which is the maximum
  4. Battery stop discharging voltage when grid is available: Default is 23.0 which I again thought was too low, so raised it to 24.5
  5. Battery stop charging voltage when grid is available: default is 27.0 and I raised this to 27.2 to match the float voltage in (2) above.

I have attached the spec sheet to the battery that I got off the net. 

GEL Battery 6CNFJ200 12V200Ah.pdf

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  • 3 weeks later...

1.)Bulk 28.4V

2.)Float 27V

3.)I would lower the low voltage cut-off to 23V which is 11.5V per battery. Once it kicks in you'll be left in the dark so there's no point in setting it any higher than this.

4.)Highest possible

5.)Depends on the inverter behaviour. If set to float voltage, will it prevent the batteries from bulk charging?

 

Edited by tetrasection
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  • 2 weeks later...
On 2020/11/01 at 2:25 AM, tetrasection said:

1.)Bulk 28.4V

2.)Float 27V

3.)I would lower the low voltage cut-off to 23V which is 11.5V per battery. Once it kicks in you'll be left in the dark so there's no point in setting it any higher than this.

4.)Highest possible

5.)Depends on the inverter behaviour. If set to float voltage, will it prevent the batteries from bulk charging?

 

Thanks for the response. Just a few questions. I agree with 1 and 2. 3,4 and 5 however, if possible could you explain to me?

3. Is 23V not too low (could perhaps take the batter past 50% DOD)? 

4. Highest possible is 29V. Wouldn't that make my inverter use the solar to keep charging the battery while always while it gets its power for use from the grid as my inverter is set to use solar and battery and only when solar is not available does it switch to grid. Unless grid is also not available then it switches to battery. It doesnt run from solar only.

5. Mine matches my float voltage. Should I set it ever so slightly higher or lower if it doesnt bulk charge? I however do think seeing battery voltages at 28.4 now and then. So I do think mine does bulk charge despite it being set to the same value as the float charge.

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  • 2 weeks later...
On 2020/11/15 at 11:06 AM, profa said:

Thanks for the response. Just a few questions. I agree with 1 and 2. 3,4 and 5 however, if possible could you explain to me?

3. Is 23V not too low (could perhaps take the batter past 50% DOD)? 

4. Highest possible is 29V. Wouldn't that make my inverter use the solar to keep charging the battery while always while it gets its power for use from the grid as my inverter is set to use solar and battery and only when solar is not available does it switch to grid. Unless grid is also not available then it switches to battery. It doesnt run from solar only.

5. Mine matches my float voltage. Should I set it ever so slightly higher or lower if it doesnt bulk charge? I however do think seeing battery voltages at 28.4 now and then. So I do think mine does bulk charge despite it being set to the same value as the float charge.

Sorry for the late reply, haven't been around here for a while.

3.Yeah it might take it past 50% DOD but would you rather sit in the dark or use your batteries which still have 50% capacity left?

Off-grid people cycle their batteries every single night so DOD becomes much more of an issue. Your batteries are basically just on float apart from the occasional load shedding at night which even at 80%DOD would still be considered very minimal cycling.

4. "Battery stop discharging voltage when grid is available" means it will continue to use your battery power even while grid is available until your batteries reach the set voltage. Setting it to the highest setting tells the inverter to switch to grid immediately instead of running your batteries down.

Again it depends on the inverter behaviour, if setting it to the highest setting causes the inverter to switch to grid even when the sun is shining then I would set it to just below the float voltage, like 26.8V, maybe a bit lower if you get voltage drops due to heavy loads switching on during the day (you'd have to check that by looking at the screen while turning whatever load you have on and then set the voltage to just below that), but even if the voltage does drop below the set point during heavy loads it would only switch to grid for a short time which shouldn't be much of a problem.

Basically you want it to switch to grid as soon as the sun goes down so that your batteries remain full.

5. I would set it to any setting above bulk since you want it to be able to reach bulk charge voltage and you don't really want it to ever stop charging (best scenario for battery longevity would be floating 24 hours a day). 

 

Hope that helps a bit, let me know how it goes.

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