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Another QUCC/ Xoixiang / Overkill question

BigGElmo

New Member
Joined
Feb 2, 2022
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Hi this is my first post so here goes....
Basic system.
150w van roof mounted PV.
100ah LiFePo4 (4x Varicore 3.2v 100ah cells).
MPPT solar charge Controller ( Unknown make )
QUCC 4s 100a BMS.
3000w Inverter ( More of this later )

So here goes....After watching numerous videos from Will I took the plunge and upgraded my old 70ah Lead Acid leisure battery to a 100ah LiFePo4 battery.
The Varicore 100ah cells arrived at a 3.2v SOC and all 4 cells were well balanced within 0.02v of each other.
The problem is that since building the pack and connecting it to the charge controller the pack will not charge above 13.3v ( 3.3v per cell ), the QUCC/Xioxiang Android app shows that the pack is at 90% SOC but there is no PV charge current shown that would take the pack 100%.
I have not yet top balanced the pack upto 3.6v as I'm still waiting for a bench power supply to be delivered.
I'm not sure if I have a BMS or Charge Controller problem.
Any ideas ???

Ohh yeah, the inverter is junk and won't power more than 1200w.
 

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Hi this is my first post so here goes....
Basic system.
150w van roof mounted PV.
100ah LiFePo4 (4x Varicore 3.2v 100ah cells).
MPPT solar charge Controller ( Unknown make )
QUCC 4s 100a BMS.
3000w Inverter ( More of this later )

So here goes....After watching numerous videos from Will I took the plunge and upgraded my old 70ah Lead Acid leisure battery to a 100ah LiFePo4 battery.
The Varicore 100ah cells arrived at a 3.2v SOC and all 4 cells were well balanced within 0.02v of each other.
Just because the shipping voltage was within 20mv in no way implies that the cells are well balanced.
Actually 20mv is a large delta for shipping voltage.
But even if they were the same down to the milli-volt it doesn't mean the cells are top balanced.
You need to do that process.
The problem is that since building the pack and connecting it to the charge controller the pack will not charge above 13.3v ( 3.3v per cell ), the QUCC/Xioxiang Android app shows that the pack is at 90% SOC but there is no PV charge current shown that would take the pack 100%.
I have not yet top balanced the pack upto 3.6v as I'm still waiting for a bench power supply to be delivered.
I'm not sure if I have a BMS or Charge Controller problem.
Any ideas ???
Make sure the BMS app agrees with your reference meter.
Ohh yeah, the inverter is junk and won't power more than 1200w.
3000 ac watts / .85 inverter efficiency / 10 volts low cutoff = 352.941176471 service amps
352.941176471 service amps / .8 fuse headroom = 441.176470588 fault amps.
Your bms is limited to 100 amps which works out to 850 ac watts at cutoff voltage.
Your cells should not really be discharged at higher than .5c(50 amps) which is 425 ac watts at cutoff voltage.
To run your inverter at full bore you need 9 of those batteries.
Lets make it 10.
 
Thanks smoothJoey.
I managed to connect a Motorcycle battery charger to the pack in the van this afternoon and the BMS accepted the charge so I'm now thinking it's a Charge Controller issue.
 
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