Spring has arrived and temperatures are climbing. Have you noticed that an electric vehicle battery gives off heat while charging? As the cold winter passes and the weather warms, this will again become a worry for electric vehicle owners!

So here we briefly introduce the principles behind battery heating, hoping it helps everyone.

Battery heating in an electric vehicle comes in two cases: heating during discharge and heating during charging.

1. Heating during discharge

The main reasons for discharge heating are discharging too fast, possibly because the battery capacity is small and the discharge current exceeds 0.5C for a long time.

1) When the motor’s rated voltage is low, the battery capacity is small, and the working current runs high, the voltage drops sharply and the capacity is consumed quickly, which is hardest on the battery.

2) The battery’s electrochemical reaction rate can barely sustain the ride, and with frequent full charge-discharge cycles, a little carelessness leads to over-consumption.

Headwinds and hills draw very heavy power, forcing the plates into intense reaction, so the case grows quite hot; this damages the battery and shortens its life.

3) The ideal situation is the electrochemical reaction fully supplying enough energy. If the battery case shows no unusual heat, its capacity is adequate.

2. Heating during charging

Heating in the charging process may come from these faults:

1) The battery itself: aging of the battery, rising internal resistance, dried-up electrolyte, or an internal short circuit causing heat.

As the battery is used more, through both discharging and charging, water molecules inside are gradually lost, the so-called gassing and water loss, which makes the battery heat up in its electrochemical reactions.

Also, during charge-discharge cycles the battery solution forms sulfate crystals that stick as paste on the lead plates, raising the battery resistance and producing heat.

These two kinds of problems can be solved by adding water or by desulfation techniques. If the heat is caused by a shorted or dead cell inside, it is best to replace the battery with a new one.

2) The charger, the most common cause. Most families own one or several electric vehicles, often of different brands, so their chargers naturally differ too.

But in daily use they get mixed up, and such mismatched chargers make the battery take in excess heat while charging, so it turns hot. On this point, our advice is: do not casually use another brand’s charger.

If your own charger breaks, we suggest buying a replacement from the dealer where you first purchased the vehicle, so you avoid ending up with one that does not fit.

Of course, if you can get a dedicated charger customized for the battery, it will match the characteristics of your battery even better, whether in charge-discharge cycles or in safety and stability.

To solve charger-caused battery heating at its root, you must choose the right electric vehicle charger. Charging is an electrochemical process: a slight warmth during it is normal, while abnormal heat from a battery in good condition points to the charger.