BMW i3: What is preconditioning and how it works

One of my favourite features of the i3 is the ability to precondition (heat or cool)  the battery as well as the passenger cabin. 

This allows you to begin their journey with a properly heated or cooled battery and cabin, while still having the state of charge at or near 100%. 

Since electric vehicles have a shorter range and longer refuelling times than their combustion counterparts, it’s important to save the energy in the battery for its main purpose; to move the vehicle, and not waste too much of it on luxury power draws.

Warming the battery and the seating area uses a lot of energy, completing this while the vehicle is plugged in charging will save you precious energy for your intended journey.

A properly warmed battery increases the range and you start your journey with 100% battery store.

This is of great importance for i3 owners in cold weather including frosty mornings. 

It is also great to precondition on warmer days to cool the cabin.

A cold battery can reduce its range up to 30%. A hot battery does not reduce the car’s range, it has an adverse effect on the overall life of the battery. Preconditioning the battery on hot days is also are recommended.

To make use of the battery preconditioning you need to do this when your i3 is plugged in to charge. Using it 20-30 minutes by the remote app before a journey will only condition the space not the battery.

Thermal preconditioning eliminates the transient climate control load on the battery. In this situation, the onboard power supply has only to provide the steady-state climate control load.

Battery ageing is caused by multiple phenomena related to both cycling and calendar age. Battery degradation is accelerated with the depth-of-discharge (DoD) of cycling, elevated temperature, and elevated voltage exposure, among other factors. 

Worst-case ageing conditions drive the need to oversize batteries to meet warranty requirements. Systems and controls, such as thermal preconditioning, may be able to lessen the impact of some of these conditions. 

These two effects can be correlated with power and energy loss that cause battery end-of-life in an application. Mechanisms for resistance growth include loss of electrical conduction paths in the electrodes, fracture and isolation of electrode sites, growth of film layers at the electrode surface, and degradation of electrolyte. Mechanisms for capacity loss include fracture, isolation, and chemical degradation of electrode material, as well as loss of cyclable lithium (Li) from the system as a byproduct of side reactions.

Pre-cooling of electric vehicle batteries is predicted to reduce capacity fade by 2% to 7% and resistance growth by 3% to 14% in hot (35°C) ambient conditions. Vehicles that benefit most from battery pre-cooling will be those with small battery thermal mass or high heat generation rates (i.e., PHEVs with a short electric range) and those with limited battery active cooling systems.   Off-board powered thermal preconditioning has benefits to the consumer via CD range extension and less expensive energy costs (electricity versus liquid fuel and/or battery capacity), as well as vehicle manufacturers via extended battery life and avoided warranty claims.

Electric car plug charging in the winter. Amsterdam, Netherlands

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