A Battery Management Systems( BMS) is a very important part of an electric bike lithium battery, it is an electronic regulator that monitors and controls the charging and discharging of rechargeable batteries. it monitors the battery state such as voltages and currents and the battery internal and ambient temperature, Protects the battery from being over-charged (cell voltages going too high) or over-discharged (cell voltages going too low), calculates the data such as the charging voltage, balancing the charging current or temperature etc.
There are three main aims common to all BMS
1. Protect the battery cells or battery pack from damage
2. Prolong the battery lifetime
3. Maintain the battery in a state in which it can fulfill the function of the application specified.
To achieve these aims the electric bike lithium battery BMS would incorporate following 8 functions generally.
1. Temperature protection – monitor the battery cells temperature and control the temperature in a safe area.
2. Battery balancing protection – there is PTC which will make adjustment when the temperature or current is higher or bigger.
3. Short circuit protection – Monitor the real-time information of the electric bike, shut down the power once any short circuit.
4. Charging over-voltage protection – When charging, BMS would monitor and calculate the charging voltage to prevent the higher voltage damaging the battery.
5. Charging over-current protection – When charging, BMS would monitor and calculate the charging current to prevent the battery damage.
6.Anti-reverse Charging protection – There is an anti-reverse Charging protection board when the charging cable is inserted in reverse.
7. Discharging over-current protection – When discharging, BMS would monitor and calculate the discharging current to prevent the over-discharging current damaging the battery.
8. Battery under-voltage protection – When discharging, BMS would monitor and calculate the battery voltage, prevent the battery when it is smaller than the working voltage.
In addition to these functions, there are more functions such as ON/OFF switch, Bluetooth connection, UART communication etc in some smart BMS.
There are two types of the E-bike battery BMS. one is divided port- that is the power negative and the Charger negative are divided, the other type is same port- that is P- and C- are connected in the same port.
For different voltage battery, it needs different BMS. 7S for 24V, 10s for 36V, 13S for 48V, 16S for 60V. Seen from the following image, it is 10S-36V BMS.