State of health (SoH), a variously-defined measurement of the remaining capacity of the battery as % of the original capacity.State of charge (SoC) or depth of discharge (DoD), to indicate the charge level of the battery.Voltage: minimum and maximum cell voltage.Computation Īdditionally, a BMS may calculate values based on the below items, such as: This can be reduced by pumping the coolant faster through the system, creating a tradeoff between pumping speed and thermal consistency. Indirect cooling has the potential to create large thermal gradients across the BMS due to the increased length of the cooling channels. The batteries can either be directly submerged in the coolant or coolant can flow through the BMS without directly contacting the battery. Liquid cooling has a higher natural cooling potential than air cooling as liquid coolants tend to have higher thermal conductivities than air. The additional components of the cooling mechanism also add weight to the BMS, reducing the efficiency of batteries used for transportation. Large amounts of power must be used to operate the cooling mechanism, far more than active liquid cooling.
The major disadvantage of air cooling is its inefficiency. Commercially, the Honda Insight and Toyota Prius both use active air cooling of their battery systems. Such systems can be passive, relying only on the convection of the surrounding air, or active, using fans for airflow. Air cooling is advantageous in its simplicity.
Current: current in or out of the batteryĮlectric vehicle systems: energy recovery.Coolant flow: for air or liquid cooled batteries.Temperature: average temperature, coolant intake temperature, coolant output temperature, or temperatures of individual cells.Voltage: total voltage, voltages of individual cells, or voltage of periodic taps.Safety circuit for four-cell LiFePO4 batteries with a balancer Monitor Ī BMS may monitor the state of the battery as represented by various items, such as: