Why some Rapid Chargers cutoff at 90% SoC

Why some Rapid Chargers cutoff at 90% SoC

The reason behind the cutoff of rapid chargers is more related to business and common sense than technical

When we use a Rapid charger, it charges with high charging power until the battery reaches the SoC of 80%, once the battery touches the 80% state of charge (SoC) the charging power gets reduced and gets the same speed as other AC home chargers and portable chargers. So, even if we connect to a rapid charger our vehicle will still charge at a slow speed after the battery reaches a certain state of charge (SoC). Because of this very reason the charging point operators use an intelligent system that detects the state of charge (SoC) of the battery and disconnects once it reaches the defined mark, making the charger free for someone else who needs rapid charging.Is it to prevent the battery health from degradation?

The answer is both yes and no. The electric vehicles have a battery pack, and it is never advisable to charge any battery to its full capacity, and the batteries in the cars have lithium-ion inside them which does not like a high flow of current for a long time.

We have heard of some lithium-ion batteries catching up the fire, we can understand how dangerous it is to overcharge a battery. The power stations do not cut it to save your car’s battery from degradation but it is done so that you can hit the road back and the charger can be vacant for someone else to use.

What happens if we still charge up to 100% state of charge (SoC)? Will it affect battery health?

Considering the words of researchers, it’s never a good idea to charge any battery up to 100%, as it impacts the life of the battery. The batteries are made up of lithium-ion which do not like high voltages for a long period of time because the higher the voltage the faster is the degradation process, that is why it is suggested to charge any kind of battery only up to 80% state of charge (SoC).

However, the newer battery management system comes with its own tricks to handle some of these situations. Just like the reserve fuel system in gas cars, the electric cars have state of charge (SoC) buffers at higher and lower limits, in which they keep some of the cells true capacity in reserve and never use it to prevent it from being overcharged and the lower limit to prevent it from being over-discharge.

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