Reverse Capacity Test?

[12vDC]

Can you infer capacity by monitoring the end result of a full charge from BMS low voltage disconnect?

I purchased two 100Ah Renogy lithiums in Nov2019 and mounted them in parallel in a tray underneath my van chassis. With the recent tech advancements creating "Mini" lithium deep cycle batteries I am now able to fit three 100Ah batteries in the tray (I was not able to find one suitable 300Ah battery to fit previously). Got them on sale $200ea!

I used one of the replaced batteries (Renogy) to power my Starlink (from full charge) on a trip last week to Utah. At some point on the last day the battery disconnected BMS on low voltage. On my return I put the battery on a 10A charger and let it go overnight. The result is somewhere around 99Ah received up to 14.6V.

Im not sure exactly how to correlate this data however, can I infer this 4year old battery is still at least 99% effective to capacity from the latest monitored charge?

 

[Bob B]

There would be efficiency factors to take into account ... but the result should be in the ballpark.

If you have Renogy stuff .... any chance you can help out this guy? He has discharged his Renogy batteries excessively low and doesn't know how to get them started taking a charge again.

Emergency ? Help

You need a charger to wake the bms up you will have to do this for each battery individually the bms has shut down for low voltage if possible charge each battery to full capacity then hook them back up after verification of correct voltage which should be over 13 volts once they settle out...

diysolarforum.com

 

[MattiFin]

Li cells have nearly 100% coulombic efficiency with moderate charge currents. For 0.1C charge the coulombic(ah) efficiency is somewhere 99% to 99.8% and in practice 100Ah in is 100Ah out