MSXIV’s LG Chem MJ1 18650 batteries had an operating temperature range of 0 ~ 45°C for charging and -20 ~ 60°C for discharging. The internal temperature of the cells cannot exceed 45°C if they are to be charged by the solar array and regenerative braking. It is estimated that the average high temperature in the US Midwest will be around 35°C. Thus, sufficient cooling is needed to ensure the temperature of the cells does not exceed 45°C from the starting point of the ambient temperature of 35°C.
Temperatures above 45°C will force the shutdown of solar array charging and regenerative braking.
Temperatures above 60°C will lead to accelerated degradation.
Temperatures above 130°C have a risk of thermal runaway and explosion.
Optimal Discharge Temperatures
There is only a 5% deficit of capacity from the optimal discharge temperature of 23°C to the max discharge temperature of 60°C. The difference in capacity is negligible so the focus of cooling system should be to maintain temperatures under 45°C.
Best case scenario: A cooling system that can match the heat output during peak currents + maintain uniform cooling throughout battery + that cooling capacity doubled for a safety factor of 2
Worst case scenario: A cooling system that can mitigate heat accumulation such that the battery reaches 45°C at end of leg