No Idea
New Member
Hello,
My questions are on minimising battery stress on old cells. Not worried about giving up capacity by limiting voltage and amps.
Question 1: 0.5C discharge and 0.2C charge OK?
Question 2: Operate between 3.00v and 3.40v per cell and NOT balance or operate between 3.00v and 3.60v and BMS balance? Or just play with both options and find out what works with no danger of screwing things up?
More info:
I bought cheap to learn with for my first build so no point paying more until I am ready to make big $$$ order direct from Alibaba with a bit of experience under my belt.
I have built two banks of old 3.2v 50Ah cells for two ammo box builds. No history available which is typical of locally sourced LiFePO4 here but they were cheap ?. They are in 2p4s arrangement for 100Ah batteries. No bloating based on a steel ruler check on their bodies.
New cell specs in pic at end of post.
JBD BMS 80A 4S.
I tested the two cells with highest IR of 0.76mΩ and 0.75mΩ at a 0.2C discharge and they came out at 50.20Ah and 51.88Ah. IR range for all 16 cells is 0.57mΩ to 0.76mΩ.
Max discharge will be 0.5C and max charge will be 0.2C which will also be my planned capacity test before putting them into service.
In use I will operate between 3.0v and 3.4v so 12v and 13.6v. They are for standby use for emergencies hence not wanting to leave them at a higher voltage.
They are spaced with 2mm gaps and not compressed, with PTFE BBQ sheet between each cell.
Anyone foresee any issues with the test or operating voltage range? The high IR is a concern to me but the 0.2C capacity results were surprisingy good.
I paired the cells to give lowest spread of average IR of the paired cells across the 4S. All were parallel top balanced to 3.65V then IR measured.
My questions are on minimising battery stress on old cells. Not worried about giving up capacity by limiting voltage and amps.
Question 1: 0.5C discharge and 0.2C charge OK?
Question 2: Operate between 3.00v and 3.40v per cell and NOT balance or operate between 3.00v and 3.60v and BMS balance? Or just play with both options and find out what works with no danger of screwing things up?
More info:
I bought cheap to learn with for my first build so no point paying more until I am ready to make big $$$ order direct from Alibaba with a bit of experience under my belt.
I have built two banks of old 3.2v 50Ah cells for two ammo box builds. No history available which is typical of locally sourced LiFePO4 here but they were cheap ?. They are in 2p4s arrangement for 100Ah batteries. No bloating based on a steel ruler check on their bodies.
New cell specs in pic at end of post.
JBD BMS 80A 4S.
I tested the two cells with highest IR of 0.76mΩ and 0.75mΩ at a 0.2C discharge and they came out at 50.20Ah and 51.88Ah. IR range for all 16 cells is 0.57mΩ to 0.76mΩ.
Max discharge will be 0.5C and max charge will be 0.2C which will also be my planned capacity test before putting them into service.
In use I will operate between 3.0v and 3.4v so 12v and 13.6v. They are for standby use for emergencies hence not wanting to leave them at a higher voltage.
They are spaced with 2mm gaps and not compressed, with PTFE BBQ sheet between each cell.
Anyone foresee any issues with the test or operating voltage range? The high IR is a concern to me but the 0.2C capacity results were surprisingy good.
I paired the cells to give lowest spread of average IR of the paired cells across the 4S. All were parallel top balanced to 3.65V then IR measured.
