Countries like India have 80% of their vehicles as 2 wheelers and 3 wheelers. These batteries do not have active cooling. Ambient temperature exceeds 45ᵒC for significant time. Smaller sized batteries used in such vehicles implies that higher C rate is used during driving. This further worsens the situation. Battery-life is influenced by factors such as charging and discharging rates, operating temperature, depth of discharge, temperature gradient within the pack, voltage imbalance and internal resistance. In adverse climatic conditions any of the battery-cell may deteriorate very rapidly. One needs to monitor every cell of the battery on a continuous basis and identify if any of them starts to misbehave, and give advance warning that the battery would soon become unusable. The paper presents monitoring and analysis of battery parameters so as to possibly take corrective actions to prolong battery-life.
We have thus added a number of probes in the design of such batteries, to measure temperature, current, voltage and estimate State of charge (SOC) of each cell on a continuous basis and use the Battery Management System (BMS) to collect and upload this data to a back-end server periodically. Voltage imbalance between cells is a strong indication that a cell is not behaving well. The weakest cell in a pack tends to charge and discharge faster than others. Further, some cells degrade more than others resulting in voltage imbalance.
The critical factors that could lead to battery malfunction are (i) the higher cell to cell voltage Delta V, (ii) higher temperature gradients Delta T, (iii) temperature of electronic components used in BMS and the (iv) lifecycles the battery has undergone. These four parameters are plotted in a 4-dimensional space to identify potential issues with a specific battery. The same data is then presented in three dimensions, by excluding cycle-life information and the space is now divided into 9 regions, indicating state of the battery.
The nine regions, presented in attached abstract, indicates the present risk-state of the battery and possible causes due to which the battery cells are in that region. Further if the battery is in risk-regions, measures are suggested in the for corrections, so as to prolong its usage.
Thus, the paper presents that monitoring of certain battery parameters while the battery is in use in adverse operating conditions and analyzing the results enable us to determine the risk-state of the failure of the battery. This would help us take suitable corrective actions, so as to prolong the battery life.