Charge controller settings for 12s29p NMC pack

[Burton4290]

Hey all, looking for some extra reassurance on my calculations for bulk and absorption settings on my victory charge controller that’s charging a 12s29p 44.4v NMC battery.

The battery specs say max charge of 49.8v and discharge cutoff of 38v. If I want to give a little buffer zone of safety and only charge to a max of 49v, what should I have my bulk, absorption, float and tail current settings at?

 

[AntronX]

Can you measure cell voltages?

 

[MisterSandals]

that’s charging a 12s29p 44.4v NMC battery

12 cells in series and 29 of those in parallel?

 

[Burton4290]

Can you measure cell voltages?

I can measure the 12 series packs voltage but not individual cells. BMS does an excellent job and has each series pack at 3.70-3.701

 

[Burton4290]

12 cells in series and 29 of those in parallel?

That is correct. It is a generac pwrcell pack. Here’s a picture back when I had them opened up

 

[MisterSandals]

That is correct.

So each 12S battery would need a BMS.

If it were 29P12S, a single BMS could work. One balance wire for each 29P "cell".

 

[Burton4290]

So each 12S battery would need a BMS.

If it were 29P12S, a single BMS could work. One balance wire for each 29P "cell".

Each 12S pack is controlled by BMS. This is a generac Pwrcell unit. Here is a picture (not a good one) of the BMS.

 

[Burton4290]

Each 12S pack is controlled by BMS. This is a generac Pwrcell unit. Here is a picture (not a good one) of the BMS.

 

[MisterSandals]

Each 12S pack is controlled by BMS.

Great, you made it sound like a single BMS.

So onto your original question:

battery specs say max charge of 49.8v and discharge cutoff of 38v. If I want to give a little buffer zone of safety and only charge to a max of 49v

what should I have my bulk, absorption, float and tail current settings at?

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I’m trying to determine the correct bulk/float voltages for my batteries to set in my inverter. Inverter is growatt 12000T Batteries are an LG NMC Lithium battery. Each battery is 6.5KW, so over the 7 batteries in the pack, 45kw total. These batteries were planned for an off-grid...

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[AntronX]

BMS does an excellent job and has each series pack at 3.70-3.701

Can it stop charging if one cell gets above 4.2V ?

 

[Burton4290]

Can it stop charging if one cell gets above 4.2V ?

Yes, each of the 12 series cells of 29 parallel cells is monitored for over voltage

 

[AntronX]

In that case charge to 3.9V/cell (46.8V total) or 80% SOC for longevity. Stop discharging at 3.5V/cell (42V) or 10% SOC. Edit: better NMC voltages below.

 

[Burton4290]

In that case charge to 3.9V/cell (46.8V total) or 80% SOC for longevity. Stop discharging at 3.2V/cell (38.4V) or 10% SOC.

Great, i can get on board with all that. As far as the settings on the victron charge controller however, it’s got bulk, absorption, float and tail current. Any ideas of good settings for those? I appreciate the help

 

[AntronX]

I set bulk, absorption and float to the same voltage. I cycle my batteries every day. I'll let others chime in about what may be better. If you are going to leave your battery charged and in standby for a long time (like in UPS application) then maybe lower float voltage to 3.7v/cell or 44.6V to extend battery life even more. Here is NMC voltage curve.

 

[MisterSandals]

Stop discharging at 3.2V/cell (38.4V) or 10% SOC.

Your graph shows 10% is 3.5V.

 

[AntronX]

fixed

 

[Burton4290]

I set bulk, absorption and float to the same voltage. I cycle my batteries every day. I'll let other chip in about what may be better. If you are going to leave your battery charged and in standby for a long time (like in UPS application) then maybe lower float voltage to 3.7v/cell or 44.6V to extend battery life even more. Here is NMC voltage curve.
View attachment 190528

You freakin rock, that’s exactly what I was looking for. I personally will be cycling them every day as well. Not fully, but they will be charged up/ loaded during the day and then minimally loaded over night. I’ve seen so much conflicting information online about the float settings for a lithium ion battery. So essentially if I set bulk, absorption, float etc all to the same 80% voltage of 46.8, I’ll virtually never have a risk of overcharging as it will get it to 46.8v and then quit?

 

[Burton4290]

Your graph shows 10% is 3.5V.

Good eye! His reccomendation was correct based on my specific manufacturers specs on this battery. For a 44.4 nominal it’s got an abnormal min voltage of 38 and max voltage of 49.8 But good to mention for others that may see this