Startability limit

The APM calculates a lower and an upper startability limit for the battery:

• The lower startability limit corresponds to the minimum charge state of the battery so that the vehicle can still be started.
• To counteract discharge down to the lower startability limit, a certain charge volume is kept as a reserve. To achieve this, the upper startability limit is calculated.

The startability limit is calculated by evaluating the following measured variables:

• Average ambient temperature with vehicle parked.
• Ambient temperature of the last journey.
• Current state of charge.
• Voltage dip of the last engine start (trend for ageing of the battery).

The startability limit is therefore dependent on the ambient temperature: The colder the ambient temperature, the more energy required for the engine start. Therefore the startability limit is higher for cold ambient temperatures:

• Startability limit is approx. 30% state of charge at 15 °C.
• Startability limit is approx. 50% state of charge at -15 °C.