In the past electric vehicles used nickel caladium, nickel-metal hydride or lead acid batteries but todays the manufacturers tend to use lithium based ones due to their numerous advantages. The lithium based batteries have much better energy density and specific power (which are important to make the vehicle lighter but extend the usable range too), but have some disadvantages. These type of batteries are prone to quickly wear if they are used outside of their designed operating envelope. Exceeding these parameters can not only cause wear, but make the batteries dangerous. In certain cases the batteries can heat up or catch on fire.
There are many electronic control units in today’s modern hybrid or pure electric vehicles. One of which monitors and controls the onboard battery called battery management system (BMS).
The BMS system main purpose is protect the battery by monitoring and controlling its operating conditions and act if it’s outside of the design envelope. The secondary function is to provide derived parameters like state of charge or state of health.
In my thesis I show a BMS system which I designed and built for a pure electric vehicle made to compete in the Shell Echo-marathon.