Steve_S
Offgrid Cabineer, N.E. Ontario, Canada
To properly Match & Batch cells (of any kind): Simple breakdown
VENDOR TESTS:
The little Voltage Matching & Minimal IR testing vendors do is ONLY to match cells quickly. They take the set of cells and verify ea cell is at the same voltage IE 3.20V then they verify the Internal Resistance is the same or very close at THAT Voltage. So if all 16 cells are 3.20V and have an IR between 10-12 they'd get batched together. JUST USING EXAMPLE NUMBERS. They don't cycle test through testing machines which are Very Expensive !
There are many references & tech papers on this... very dry & boring BUT here is some very handy reference info worth reading that is not too unreadable.
BU-803a: Cell Matching and Balancing – Battery University
Pre-Balancing Cells | Orion Li-Ion Battery Management System
- each cell must be mounted into a testing machine,
- each cell has to be fully charged to 100% and IR tested.
- Each cell is discharged at Varying Rates and at specified setpoints, IR evaluated & recorded @ that Volt Setpoint.
- Each cell is tested under Light & Heavy Load & Charge Rates as the cycle proceeds. IR and other factors change in these conditions. Testing only under "No Load Idle" would not be accurate.
- Once fully discharged to 0% SOC, the Recharge cycle testing begins in reverse.
- Typically this process runs through 3-5 times. Depending on Cell Capacity, the time it takes varies and can be DAYS.
- Once completed a print-out report of the complete "batch" is produced.
- All cells with Matching IR @ Setpoint Voltages (within 1% or less) are Batched is "Matching Cells"
- Any cell which falls outside of test params is then declassed as Grade-B or down to "Utility" or even for "recovery/recycle"
VENDOR TESTS:
The little Voltage Matching & Minimal IR testing vendors do is ONLY to match cells quickly. They take the set of cells and verify ea cell is at the same voltage IE 3.20V then they verify the Internal Resistance is the same or very close at THAT Voltage. So if all 16 cells are 3.20V and have an IR between 10-12 they'd get batched together. JUST USING EXAMPLE NUMBERS. They don't cycle test through testing machines which are Very Expensive !
There are many references & tech papers on this... very dry & boring BUT here is some very handy reference info worth reading that is not too unreadable.
BU-803a: Cell Matching and Balancing – Battery University
Pre-Balancing Cells | Orion Li-Ion Battery Management System