How long can i leave my battery at full state of charge after initial top balance?

[Sprks]

Just finished building and top balancing (24V 230ah), but maybe too soon? Not yet ready to put it into my system (delays added up) and im not sure how im going to discharge down to 50% with what ive got on hand. Ive got all the other equipment on hand and will be installing it over the next week, and was originally trying to time the completed top balancing with having all installed and then discharging the battery... Only inverter i have is a 12V 300W cigarette plug type, and a 24/12 step down.... i suppose i might be able to cobble together a load to do that... According to @FilterGuy on his top balance how to he says not to "leave it at full state of charge for multiple days". My questions is, how long might be ok?? If i need to discharge with my dinky 300W any idea how long i might need to do so for 50%? I might be able to borrow a bigger inverter form a neighbor... Im in a bit of a pickle here..... Thanks

 

[rmaddy]

A 24V 230Ah battery is 5888Wh. 50% is 2944Wh. You would need to run a 300W load for 9.8 hours to deplete 2944Wh.

If you are going to start using the battery in a week I wouldn't worry about getting to 50%. 90% is probably more than enough. Your 300W load would need to run 2 hours to burn off 10%.

 

[AntronX]

Discharge it to 3.35V per cell. It should not take long.

 

[Sprks]

A 24V 230Ah battery is 5888Wh. 50% is 2944Wh. You would need to run a 300W load for 9.8 hours to deplete 2944Wh.

If you are going to start using the battery in a week I wouldn't worry about getting to 50%. 90% is probably more than enough. Your 300W load would need to run 2 hours to burn off 10%.

Probably wont be able to find an AC load exactly at 300W through dinky inverter. If i hook it up and measure load amperage with dc clamp meter on battery terminal may i assume since batt is 230ah can i stop after 115ah is consumed? example: load = 15a, so 115/15 =7.6 hours? Beginner needing a math check here.... Thanks

 

[Sprks]

Discharge it to 3.35V per cell. It should not take long.

Battery is assembled so im assuming 8 cellsX3.35 or 26.8V to stop discharge? Thank you

 

[rmaddy]

If i hook it up and measure load amperage with dc clamp meter on battery terminal may i assume since batt is 230ah can i stop after 115ah is consumed? example: load = 15a, so 115/15 =7.6 hours? Beginner needing a math check here.

That's correct if you want to take it down 50%. Keep in mind that you'll need almost 400W to get 15A out of a 24V battery. That will be hard to do with a 300W inverter.

 

[AntronX]

Battery is assembled so im assuming 8 cellsX3.35 or 26.8V to stop discharge? Thank you

Yes, it should pretty quickly drop to 3.3V resting voltage or 26.4V for 8S pack. From what I understood from reading battery research papers it's the voltage + temperature that influences rate of capacity loss and that is directly tied to state of charge. But with LFP chemistry the voltage curve is almost flat so discharging them by 5% from full to 95% SOC should be sufficient.

 

[Sprks]

Yes, it should pretty quickly drop to 3.3V resting voltage or 26.4V for 8S pack. From what I understood from reading battery research papers it's the voltage + temperature that influences rate of capacity loss and that is directly tied to state of charge. But with LFP chemistry the voltage curve is almost flat so discharging them by 5% from full to 95% SOC should be sufficient.

Much appreciated.

 

[BradCagle]

Just finished building and top balancing (24V 230ah), but maybe too soon? Not yet ready to put it into my system (delays added up) and im not sure how im going to discharge down to 50% with what ive got on hand. Ive got all the other equipment on hand and will be installing it over the next week, and was originally trying to time the completed top balancing with having all installed and then discharging the battery... Only inverter i have is a 12V 300W cigarette plug type, and a 24/12 step down.... i suppose i might be able to cobble together a load to do that... According to @FilterGuy on his top balance how to he says not to "leave it at full state of charge for multiple days". My questions is, how long might be ok?? If i need to discharge with my dinky 300W any idea how long i might need to do so for 50%? I might be able to borrow a bigger inverter form a neighbor... Im in a bit of a pickle here..... Thanks

You're fine, I wouldn't consider worrying about it unless you're talking months.