Why some rapid chargers cutoff at 90% SoC

Here is the guide to Why some Rapid Chargers cutoff at 90% SoC

Something which has been noticed by the electric vehicle users is that some of the DC rapid chargers cut off after the battery of the car reaches 90% state of charge (SoC). So the question arises why does this happen? Is it to prevent the battery health from degradation? If we charge the battery of our electric car to 100% using a DC rapid charger will the battery get damaged?

To answer all the questions of Rapid Chargers cutoff no, there is nothing stated like this, not in any report or review. It is just speculation among the electric vehicle users because some chargers automatically cut off once the battery reaches 90% state of charge (SoC). We will try to clear all these speculations in this post.

Rapid Chargers cutoff: 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.

It is reported by the EV users that it takes nearly the same time to go from 80 to 100% state of charge (SoC) as it takes to go from 0 to 80% state of charge (SoC). The driver might use some other rapid charging points after this point if needed. This shows that if someone continues to charge till the battery reaches 100% state of charge (SoC), it will nothing but a waste of time not only his but also of some other people who need the rapid charging.

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Rapid Chargers cutoff: 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 in Rapid Chargers cutoff. 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.

Why some Rapid Chargers cutoff at 90% SoC

Why some Rapid Chargers cutoff at 90% SoC

Rapid Chargers cutoff: 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 Rapid Chargers cutoff in 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.

So, Rapid Chargers cutoff when your dashboard shows you a 100% state of charge (SoC) you can assume that it is somewhere near 80 to 90% state of charge (SoC), and the same for the lower margins when the dashboard shows a 0% state of charge (SoC) you might be having 10 to 20% state of charge (SoC) left which the battery management system does not allow to be consumed.

Why some Rapid Chargers cutoff at 90% SoC

Level 1 vs. Level 2 Electric Vehicle Charging Stations

These upper and lower Soc buffers do not always remain the same in Rapid Chargers cutoff, they change over time as the life of the battery degrades. This is also the reason why it is not advisable for old electric vehicles to go more than 80% state of charge (SoC) in any condition because the buffers might not be working and the battery might actually be charged to 100% state of charge (SoC), which will degrade the battery life faster.

Charging point operators who cut the power automatically after the battery reaches 90% state of charge (SoC) should not be blamed but should be appreciated. In my opinion, the charging limit at the rapid-charging station should be fixed at somewhere around 75 to 85%, and if someone stays at the charging point even after the battery reaches the defined state of charge (SoC) a penalty should be added to the final cost of electricity consumed to recharge their vehicle.

Plug-in hybrid cars should be suggested not to use the Rapid chargers as it is not that beneficial for them, but each charging station should have one separate Rapid charger in case any hybrid cars need it as these cars genuinely need to charge up to 100% state of charge (SoC).

The infrastructure of charging stations is growing continuously, even so, the addition of Rapid Chargers cutoff is not practical as it is not cost-efficient as of now and to set up a charging station a large area is needed if the electric vehicles owners and drivers follow the guidelines given by the vehicle manufacturers and charging point operators in Rapid Chargers cutoff on how to utilize rapid charging stations then the available rapid chargers can be utilized by everyone in need without any problem. Although, it is true that there is a need for fast chargers as the sales of electric cars are increasing day by day.