48v 280ah 3.29v cells. best settings?

TLJester

New Member
Joined
May 24, 2020
Messages
32
Hi all.
Well i have my 48v 16cell bank up and running with Daly (Non-SMART) BMS.
The cells are marked 280ah 3.29v
Setting up my MPPT system withWatchPower to set Bulk/Float/Min etc settings looking for some advice.

Assume Bulk should be 16x3.29v = 52.6v
Float something a bit lower ie 50v or 48v?
Not sure about min and all the others etc

Not looking to run the cells to their max thresholds unless that is a better/longer life solution that not doing it (really want these to last a LONG time)
Using a pair of MPP Solar 3kw Charger/Inverters to power the bank. And not sure exactly what settings i should configure within that for this 48v bank
( i did find a LOT of info for 12v, but some was conflicting, others appeared to not scale to 24-48v systems, hence my current confusion...)

Thanks in advance!
 

TLJester

New Member
Joined
May 24, 2020
Messages
32
Unless this is all i need (though somewhere else it said these values where too high .... ! )?

48V 16S LiFePO4 Battery w/ BMS
  • Absorption: 58V
  • Float: 54.4V
  • Inverter Cut-off: 42.8V-48V
 

smoothJoey

mumble...
Joined
Nov 30, 2019
Messages
9,315
Unless this is all i need (though somewhere else it said these values where too high .... ! )?

48V 16S LiFePO4 Battery w/ BMS
  • Absorption: 58V
3.625 volts per cell(quite high for a diy pack)
Assuming top balanced commodity cells, you will very likely trip the bms on high cell disconnect every time you charge.
Did you top balance?
Are these commodity cells?
  • Float: 54.4V
3.4volts per cell
Most would be ok with that.
I like 3.35 volts float, but depending on your circumstances you might want to go lower or higher.
3.35 is the highest voltage that doesn't cause unnecessary voltage stress on your cells.
  • Inverter Cut-off: 42.8V-48V
3.0 volts per cell which is well into the low knee
Set that to 48.

2.5 volts is dead empty but its not reasonable to set the value that low with commodity cells as you would expect the bms to trip before the all_in_one disconnected every time.

Disconnecting a bms while pulling/pushing significant current is pretty stressful for the bms.
The bms protects the cells.
The all_in_one should be configured to protect the bms.
 

RCinFLA

Photon Sorcerer
Joined
Jun 21, 2020
Messages
1,026
3.29v is just the marking when they made the cell voltage measurement. It means the cells are at close to 50% state of charge for storage and shipping.

Max charge voltage per cell is 3.65v so for 16s that is 58.4 vdc maximum.

For balancing, most BMS do not activate dump until a cell is above 3.4v. So you need to charge a bit higher than that to get any balancing time. 3.5v x 16 = 56v. You don't need to go that high every time you charge but need to do it periodically to keep up with balancing.

Floating cells at 3.35v x 16 = 53.6v will keep you over 90% full charge and not stress cell too much. But you will get no balancing.

3.35v per cell is typically used for UPS applications.
 
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