Cell Balancing!!!

[RogerW]

Hello everyone.

Got a question again. What's the right parameter that has to be set for the cell balancing? I notice one of mines BMS's. Tend to go different on the balancing. Is it normal.
Another thing. Anytime I turn off the charge switch and I turn back on the battery percentage automatically drops. I think the voltage stays the same, but the percentage changes. Is this normal.

 

[sunshine_eggo]

start voltage 3400
delta 20
turn off bal only when charging.

Your cells look pretty good to me.

Toggling the switch might force the BMS to estimate based on voltage.

EDIT: Also, change cell full voltage to 3500

 

[42OhmsPA]

You still need to change your low temps...
Post in thread 'BMS PROBLEM!!!' https://diysolarforum.com/threads/bms-problem.75008/post-951607

 

[740GLE]

I found turning off “balance only when charging” was a huge game changer, now set the absorption time to 2-3hrs

 

[740GLE]

Also is this a different set up than the previous thread you started about “BMS PROBLEMS”?

 

[shvm]

I'm not sure what your cells are doing at 3.5 V with practically no current going into the cells.
LFP batteries are supposed to go into float at a much lower voltage as soon as that happens. For 16S, you can use anywhere from 53.9 to 53.6V as float Voltage.

Once the battery goes into float at the end of a full charge cycle, balancing can commence.

I don't get why anyone would include option like 'balance only when charging' in a BMS.
Any battery will have some internal resistance. In the presence of current (whether charging or discharging) , the voltage at the terminals will deviate from the chemistry voltage. Why anyone would try balancing here is beyond me.

It should be EXACT OPPOSITE of that - balancing should only take place when there's no current going in/out of the battery.

Also, 3.35 V for LFP is like 98% SOC not 90%.

Anything above 3.37 ish V is 100% and overcharging.

 

[sunshine_eggo]

@RogerW Please ignore @shvm. He's new to this and thinks because he has an advanced technical degree in a different field, it makes him an expert in this one.

 

[RogerW]

This is the same setup. I've just been trying to get all parameters set the right way. So is there like a standard parameter? Or it varies with lifepo4 type battery ?

 

[sunshine_eggo]

This is the same setup. I've just been trying to get all parameters set the right way. So is there like a standard parameter? Or it varies with lifepo4 type battery ?

This:

start voltage 3400
delta 20
turn off bal only when charging.

Your cells look pretty good to me.

Toggling the switch might force the BMS to estimate based on voltage.

EDIT: Also, change cell full voltage to 3500

and this

You still need to change your low temps...
Post in thread 'BMS PROBLEM!!!' https://diysolarforum.com/threads/bms-problem.75008/post-951607

This is referring to charge under temp value.