Battery management system

Such systems can be passive, relying only on the convection of the surrounding air, or active, using fans for airflow.

Commercially, the Honda Insight and Toyota Prius both use active air cooling of their battery systems.

[6] The additional components of the cooling mechanism also add weight to the BMS, reducing the efficiency of batteries used for transportation.

[6] Additionally, a BMS may calculate values based on the items listed below, such as:[1][4] The central controller of a BMS communicates internally with its hardware operating at a cell level, or externally with high level hardware such as laptops or an HMI.

For high-voltage systems the seeking time of all cells is another restriction, limiting minimum bus speeds and losing some hardware options.

[8] Combination of hardware and software restrictions results in a few options for internal communication: To bypass power limitations of existing USB cables due to heat from electric current, communication protocols implemented in mobile phone chargers for negotiating an elevated voltage have been developed, the most widely used of which are Qualcomm Quick Charge and MediaTek Pump Express.

More recently, the USB Power Delivery standard aims for a universal negotiation protocol across devices of up to 240 watts.

A BMS may have a circuit that can check whether a relay is already closed before recharging (due to welding for example) to prevent inrush currents from occurning.

It must communicate with at least a charger (or charging infrastructure), a load, thermal management and emergency shutdown subsystems.