Why charging your electric car to 100% every time is a bad idea, especially at public chargers

Electric car recharging is different to refuelling a petrol car because when your car battery is nearly empty it charges fast and when it’s mostly full it charges slowly.

We asked an MG Australia spokesperson to explain:

“Like most other EVs’, we suggest charging to 80% State-of-Charge (SOC) because EVs require essentially the same amount of time to reach 100% from 80% as they do to reach 80% from 0%. This allows maximum output in the shortest period of time.”

“Additionally, lithium-Ion batteries work longest and perform their best when they are within the mid-range of charge. This help manage the longevity of the battery and allows it to perform at its optimal level.”

“The ZS EV defaults to 80% state of charge to maintain battery life, however, you can adjust this up to 100% if you’re preparing for a longer drive”.

This doesn’t just apply to MG electric cars but to all brands, below is a graph of a Polestar 2 charging up (credit: jojje80 on Reddit) which shows how the charging speed drops over time.

jojje80 also makes the point that keeping your car attached to a public charger once it passes 70-80% is bad manners because charging up that last 20-30% takes so long and blocks others from using the charger.

Another excellent explanation, this time in video form can be watched below which gives several charging tips including that a car will charge faster once the battery is warmed up after a bit of use compared to a cold start from parking:

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