AGM Battery Charging - Temperature Dependent
Posted by Max Dunn Sat, 24 May 2008 02:00:00 GMT
As we have seem, the biggest per mile cost of running an electric vehicle is not the electricity, it is the battery depletion. So it is important to maximize the life of your batteries. One trick that works with all battery techologies is to take short trips and recharge after each one. By minimizing your depth of discharge (DOD) you will maximize the total energy that the batteries will deliver over their life.
Another very important factor is to charge the batteries correctly. Especially for sealed lead-acid batteries like gel or AGM, correct charging is critical. Deka states that if their batteries are continuously charged with a voltage that is only 0.70 volts over the proper charging voltage, it will reduce the battery life by 60 percent! This is because if sealed batteries are overcharged, they will dry out and there is no way to replace the lost moisture. It is likely that all sealed lead-acid batteries will suffer from this, not just Deka batteries.
Here is the kicker: the proper charging voltage varies depending on the temperature. It ranges from 15.10 volts when it is below 40 degrees 13.60 volts when it is above 120 degrees. And it is not good enough to just measure the air temperature, instead it is important to measure the temperature of each battery since they will often be warmer than the outside air.
So unless your charger or BMS has a temperature probe on each battery, it is almost guaranteed that the batteries are not being charged correctly and that their potential life span will be reduced.