Jump Starting And Charging Vehicles With Battery Management Systems

Jump starting and charging a 12 V battery with a battery management system (BMS) may not be as simple as connecting cables to the battery. Most newer vehicles are equipped with a BMS and may have specific instructions on how to jump start and charge the battery.

What is a battery management system? A BMS monitors the battery state of charge and all power entering and exiting the battery. Ensuring the battery state of charge is maintained appropriately prevents the battery from becoming discharged or over charged.

The BMS also communicates with the rest of the vehicle systems to ensure power is maintained at the correct voltage levels. The system allows the vehicle to identify if the battery is operating outside of its parameters, or if there are any issues. This is possible because vehicles with a BMS will typically have a sensor mounted to the negative battery terminal.

Unlike older vehicles, it is not as simple as attaching a positive and a negative clamp to the battery and jump starting or charging. Every make and model may have a specific procedure that should be followed.

When charging the vehicle battery, it is critical that the correct type of battery charger is used. Many of the 12 V batteries, like absorbed glass mat (AGM), can only be charged at low current levels and may have different cut-off voltages compared to traditional flooded cell batteries.

The charging procedure may require the leads be connected to points other than the battery terminals. This allows the BMS to monitor all energy going into the battery. If unmonitored energy is put into the battery, the BMS may not have accurate information as to the battery’s actual state of charge.

Jump starting and charging information can typically be found in the service manual and/or owner’s manual. If the vehicle-maker specifications and procedures are not followed, the battery and other electrical components could be damaged. Always follow vehicle-specific battery instructions to ensure a complete, safe, and quality repair.

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