Recommended settings for a homemade ( out of 18650 used cells ) lithium ion battery 7S60P 135 Ah ( 24V )

Pindrix

New Member
Hello folks !

I need help to set up my solar charge controller for a 24V Li-ion homemade battery.

Before I ask, I browsed this wonderful forum ( Thank you Will Prowse for that ! ;) ) but I only found set up for LiFePo4 battery, which is different from Li-ion ( 3.2V VS 3.7V )

In the custom mode of my SCC ( USER mode, right column on the picture ), I have to modify a lot of parameters, but I don't make a difference between some of them.

Epever 5415 AN user mode.jpg

I would be grateful if someone could tell me what would a "safe" value for each parameter according the battery I want to charge ( for recall, a homemade 7S60P Li-ion battery, not a LiFePo4 )

I f someone can explain to me as clearly as possible what every parameter do, it would help me to take the right decisions about this set up ( I don't want my battery to be damaged, or worse, to explode, it's for using in a RV ! )

Thank you very much, I'm waiting for your advices :)
 

Supervstech

Administrator
Staff member
Moderator
AFIK, lipo cells can safely be charged to 4.2V per cell... so, 7S would be 29.4, and a safe low cutoff would be 21V, there shouldn’t be a float charge, so, CC to 4.2/cell @ 29.4, and the BMS monitoring cell bank voltage, cutout above 4.2 or 4.15 to give a margin...
 

Supervstech

Administrator
Staff member
Moderator
I would want a temp monitoring charger though... those cells can explode, and create a runaway fire condition with no way to extinguish...

cool charging is key.
 

Pindrix

New Member
Thank you for your quick response, Supervstech :)

But what about all the other parameters ? I don't understand what they are for and I don't want to enter a wrong/dangerous value.

My battery has a BMS which limits the charge/discharge to 45A, so each cell will charge/discharge at 7501 mA maximum ( 45A / 60 cells = 0.75 A )
 

Ampster

Renewable Energy Hobbyist
Hopefully these Lithium Ion batteries you are using are NMC and not LIPO. If LIPO, then I would be even more conservative. There us a good explanation of the logic and some rules for settings at the bottom of that sheet. Why dont you take the suggestion of @Supervstech and adjust accordingly then post here and let us comment? There is some logic in the relationhip of those numbers that might be clear if you give it a try.
 

Pindrix

New Member
Ampster, you're absolutely right, I've to confess I didn't notice the "rules" at the bottom of the sheet ( I believed it was the order of the different steps, i didn't notice the signs < and =, shame on me ^^ )

Just to be sure, accordinf to Supervstech, the value for "Charging limit voltage" should be 29.4V and "Discharging limit voltage" should be 21V, am I right ?

Even if I still don't understand every parameter, I have now a better idea to figure out with them, I just hope it won't affect the integrity of anything.
I'll keep you informed of my attemps.

But if someone have additionnal advices, I'm still a taker :)

Thank you very much ! :)
 

Ampster

Renewable Energy Hobbyist
No worries. Is the chemistry NMC or Lipo?
My only suggestion is to disable EQ by making thevtime zero. BTW Boost is the same as Absorb or the CV set point that @Supervstech referred to. Most others have a relationship above or below that setting. Float and EQ should be disabled. Float may be useful depending how these are being used.
 

Master Dalor

Self made Master
Hello folks !

I need help to set up my solar charge controller for a 24V Li-ion homemade battery.

Before I ask, I browsed this wonderful forum ( Thank you Will Prowse for that ! ;) ) but I only found set up for LiFePo4 battery, which is different from Li-ion ( 3.2V VS 3.7V )

In the custom mode of my SCC ( USER mode, right column on the picture ), I have to modify a lot of parameters, but I don't make a difference between some of them.

View attachment 22721

I would be grateful if someone could tell me what would a "safe" value for each parameter according the battery I want to charge ( for recall, a homemade 7S60P Li-ion battery, not a LiFePo4 )

I f someone can explain to me as clearly as possible what every parameter do, it would help me to take the right decisions about this set up ( I don't want my battery to be damaged, or worse, to explode, it's for using in a RV ! )

Thank you very much, I'm waiting for your advices :)
@Pindrix
I found An example:
Design and manufacture by Yousun
Overcharge Detection Voltage: 4.200V
Overcharge Release Voltage: 4.170V
Cell-balancing Detection Voltage: 4.160V
Cell-balancing Release Voltage: 4.150V
Overdischarge Detection Voltage: 2.800V
Overdischarge Release Voltage: 3.00V
2pcs Mosfet Work safety current: 15A
Tweak it for your use.
Now I saw they are used 18650 that you have,
@Supervstech With used batteries isn't it advisable to lower the up voltages by 1 V and raise the low voltages by 1V (per cell) also, to allow for difference in speed of charge/discharge, and leave time to balance
 

Pindrix

New Member
Then, thanks to yor advices, I dared starting my set up as following :

Over voltage disconnect voltage : 30.4
Charging limit voltage : 29.4
Over voltage reconnect voltage : 29.4
Equalize charging voltage : 29.4 ( can not set it to 0 )
Boost charging voltage : 29
Foat charging voltage : 27.4 ( can not set it to 0 )
Boost reconnect charging voltage : 26.2
Low voltage reconnect voltage : 25
Under voltage warning reconnect voltage : 24.2
Under voltage warning voltage : 23.8
Low voltage disconnect voltage : 22
Discharging limit voltage : 21
Equalize duration : 0 minutes
Boost duration : 120 minutes

It as worked at the beginning of the day, around 9:30AM, I was producing about 290W ( 100V - 2.9A ) with 3 PV of 255 W each.

But around 11AM, PV voltage was still around 100V but the AMPs were around 0, and since, I'm not producing more than 2-3W, even with the sun shining.

And although the green light meaning the PV is charging the battery ( green light flashing ), the battery doesn't seem to charge.

Even if I plug a 350W lamp in my inverter, the AMPs on the SCC are not increasing.

I don't understand...
 
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