EVRA
Used battery pack assessment process. DRAFT 1 February 2024
A. Potential dangers
When recovering cells or modules from used packs you must be aware of the potential dangers due to the following causes:
- Mechanical damage to the cells from shock loading or distortion may not be immediately apparent but can lead to internal cell damage, reduced capacity and higher heating rates which only becomes apparent under high electrical loads.
- Water ingress from failed seals or casing corrosion leading to cell damage or residue making connections to casing parts or cables/wires.
- Coolant leaks inside the pack due to failed joints, this may be caused if the pack was in a collision or has been dropped. Coolant can compromise the structure of some types of cell leading to damage or high temperatures in use.
- Excessive discharge cells due to long storage times or malfunction leading to excessively higher temperatures when charging or in use.
- Bus bars and cables/wiring have the potential to come into contact with each other or the outer casing if the bus bars or cables/wiring are exposed due to corrosion or overheating.
B. Pack assessment
When using complete packs for use in an EV conversion the following procedure is recommended:
- Establish as far as is possible the condition of the vehicle that the pack has come from. A full fault code reading and check of the BMS and SRS is recommended.
- If the SRS indicates a severe collision then the pack must be stripped for inspection.
- Inspect the vehicle for signs or collision or flood damage. Take pictures for your records.
- Any signs of physical damage to the pack require full pack strip and inspection, damage includes, dents in the pack casing, warping or bending of the case or mountings, excessive corrosion that may have let moisture in to the pack. For air cooled packs check the air inlet and outlet area for signs of moisture ingress.
- If the HRC fuse has failed then the cells may have experienced a significant over current and should not be used.
- Obtain a readout of the BMS recorded SOH and cell voltages. If this is not available then a dash instrument reading may be used as an approximation only.
- All cell voltages must be checked and recorded, if any are outside the manufacturers recommended limits then those cells must not be used.
C. Module/cell assessment
When using modules or cells from a stripped pack the following procedure is recommended:
- Always buy a complete pack or car, avoid buying individual cells/modules unless their history can be shown by the vendor.
- If the vehicle has crashed to a severity that would normally cause airbags to go off then the cells must be inspected by a competent person.
- Inspect cells/modules for coolant or water ingress.
- Do not use corroded or excessively swelled cells.
- If the HRC fuse has failed then the cells may have experienced a significant over current and should not be used.
- Obtain a readout of the BMS recorded SOH and cell voltages. If this is not available then a dash instrument reading may be used as an approximation only.
- All cell voltages must be checked and recorded, if any are outside the manufacturers recommended limits then those cells must not be used.