Volvo Group Trucks Technology has found a need for a new way to present the battery status and electricity consumption of their on-board batteries in combustion engine trucks. Many battery related issues the drivers are facing could be prevented if a tool was developed that could assist with energy planning in an intuitive way. In many cases, the climate control system will constitute the bulk of the energy supplied by the battery. In addition, the climate system energy demand is dependent on both user settings and factors beyond the driver’s control. This work describes the process of developing a grey-box Simulink model able to predict the battery charge depletion rate based on signals already sampled by many Volvo truck versions. The resulting model is able to estimate the time remaining until the battery state of charge (SOC) is getting close to the crankability (starting engine) limit or risks causing battery damage. The settings of the climate system are shown to have great impact on the battery charge depletion rate. Predicting the time until the battery will reach a critical limit, and adjusting the climate system settings accordingly, can make the difference between the battery charge lasting overnight or not. A way to implement additional influences, such as sunlight, are discussed and recommendations are given.