Cell imbalances in electric vehicle batteries can result in reduced driving ranges, and premature battery degradation, if not addressed. Dealer service managers need to recognize the early warning signs, which include slower charging and battery overheating. We provide a summary of the factors leading to these imbalances, according to a report we saw on the Midtronics website.
Cell Imbalances in EV Battery Packs
The average electric vehicle battery contains hundreds, even thousands of individual battery cells. These are in modules that comprise the battery itself. A battery management system controls the flow of electricity when charging and discharging, and monitors battery health.
When such an electric vehicle battery is new, the individual cells receive and discharge electricity at approximately the same rate. However, nothing is perfect in this world, and so imbalances in electric vehicle battery cells gradually develop.
These symptoms may be the result of inconsistent manufacturing, patterns of use, or gradual degrading. Whatever the case, the net result is some individual battery modules lose some of their capacity, or charge at different rates.
The battery management system tries its best to iron out these imbalances. However, it can only go so far to maintain consistency. The net outcome may be shorter driving ranges, slower charging, and / or diminished vehicle power.
The Outward Signs of Degrading EV Batteries
- The first and obvious warning sign is slower charging, and / or not topping up fully due to failing cells.
- This loss of storage capacity translates into reduced driving range. The driver may notice a loss as great as 20%.
- A technician at a service center may detect a significant capacity difference between different battery modules.
- The battery runs a little warmer due to these inconsistencies. A driver may notice greater user of the battery cooling system.
- These imbalances in electric vehicle batteries can significantly slow charging, as the system adapts to the weaker cells.
An astute electric vehicle driver will ask a technician to service their battery regularly, and take action if those warning signs begin to show.
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