Why is the State of Charge (SoC) in EVs Is Important

When charging electric vehicles, the charge level, or State of Charge (SoC) is important because the battery life degrades if you continuously charge your battery to full capacity. When you purchase a new car, it will be rated for a fixed range, say 100% battery gives 300 miles range. If the battery degrades to 90%, you have lost 30 miles from your range, and now you are getting 270 miles for a full charge. This is why it's important to know the range, and SoC that the vehicle has been charging at.

Without going too much into the details, we look at some vehicles' data that are on the Keemut platform for a better understanding of SoC for the community at large.

Tesla Model X = 80% SoC

This vehicle has been driven for about 16,000 miles and has had its charge rate set to 80% - 85% for most of its time. You can see in the chart below, that the blue dots are about 95% battery health.

This falls basically in the middle of the community where batteries are holding their charge between 92% - 99%.

Good Battery Range, Average SoC =82%

Tesla Model X - SoC 100%

In comparison to the first Model X, the second one is regularly charging to 100% SoC. After driving 100,000 miles, it should keep its charge up to 85%, but its charge is at 65%. Both vehicles are city driven with highway driving and have the same battery 90D.

Model X - 118k miles 65% battery, 100% SoC

The key difference is the SoC. Now, the second car may be an outlier, but after looking at other vehicles that charge at 95% - 100% regularly, we see similar trends.

Which Model X Would You Buy?

All things being equal, the vehicle with a 100% SoC will have a lower range of distance and you will need to charge it more often compared to one that has been recharging at 80% SoC.