Battery preconditioning

Preconditioning brings the battery to a suitable temperature before fast charging or driving. It can reduce lithium plating risk and speed up charging in cold conditions, but it does not make charging free of ageing.

What preconditioning does

Many EVs can heat, and sometimes cool, the battery ahead of a planned fast-charging stop, typically when you navigate to a charger or activate the function manually. The goal is a cell temperature at which the battery can accept high current with less stress. Some cars can also condition the pack before a scheduled departure while still plugged in.

The energy for heating comes from the battery or, when plugged in, from the grid. Preconditioning while connected to a charger avoids spending driving range on it.

The science behind it

Cold cells are more prone to lithium plating during charging, because lithium diffuses into the graphite more slowly. Research has shown that raising the cell temperature during fast charging can suppress plating, and studies of ageing versus temperature place the slowest ageing near room temperature, with plating dominating below it.

Preconditioning therefore moves the cells away from the plating-prone zone. A warmer pack also has lower internal resistance, which is why the BMS allows more charging power once the pack is warm.

What it does not do

Preconditioning does not make ageing zero. Fast charging still involves higher currents than slow AC charging, and warm cells experience faster SEI growth. Even with a warm pack, high SOC and high current still add stress, so ending a session at a moderate SOC remains a battery-preserving alternative.

In hot weather the concern can be the opposite: an already warm pack may need cooling. Active thermal management handles this, but sustained heat still contributes to calendar ageing.

How Voltgevity models preconditioning

Voltgevity accounts for preconditioning by assuming a higher pack temperature for the fast-charging sessions concerned, which lowers the plating-related stress term. The calendar and SEI-related terms still apply. The size of the benefit is uncertain and depends on the vehicle's thermal management, so it is shown as a range.

Key takeaways

Preconditioning warms the pack before fast charging, reducing lithium plating risk in the cold.
A warm pack charges faster because the BMS allows more power.
Preconditioning reduces stress but does not make fast charging free of ageing.
Ending a session at a moderate SOC remains useful even with a preconditioned pack.