How should batteries be charged in an electric vehicle to last as long as possible?
Electric cars

How should batteries be charged in an electric vehicle to last as long as possible?

How do you handle batteries in an electric vehicle so that they last as long as possible? To what level should you charge and discharge batteries in an electric vehicle? BMZ specialists decided to test it.

Table of contents

  • To what level should an electrician's batteries be charged?
    • What is the best duty cycle in terms of vehicle life?

BMZ manufactures batteries for electric vehicles and supplies them, among other things, to German StreetScooters. BMZ engineers checked how long Samsung ICR18650-26F elements (fingers) can withstand, depending on the method of handling. They assumed that the end of a cell's life was when its capacity dropped to 70 percent of its factory capacity, and they charged and discharged them at half the battery's capacity (0,5 C). Conclusions? They are here:

  • most cycles (6) of charge-discharge of durable batteries operating according to the scheme charge up to 70 percent, discharge up to 20 percent,
  • Least cycles (500) of charge-discharge of durable batteries operating according to the scheme 100 percent charge, 0 or 10 percent discharge.

This is illustrated by the blue bars in the diagram above. The study's findings are in good agreement with the recommendations that another battery expert gave Tesla owners:

> Battery Expert: Only charges the [Tesla] vehicle to 70 percent of its capacity.

What is the best duty cycle in terms of vehicle life?

Of course, the number of cycles is one thing, because the 100 -> 0 percent digit gives us twice the range as the 70 -> 20 percent digit! Therefore, we decided to check how many batteries will serve us depending on the selected charge-discharge cycle. We assumed that:

  • 100 percent of the battery equals 200 kilometers,
  • every day we drive 60 kilometers (EU average; in Poland it is 33 kilometers according to the Central Statistical Office).

And then it turned out that (green stripes):

  • the longest we will use a battery that has a cycle of 70 -> 0 -> 70 percent, because for a whole 32 years,
  • shortest We will be using a battery that runs on a 100 -> 10 -> 100 percent cycle because it is only 4,1 years old.

How is it possible that the 70-0 cycle is better if the 70-20 cycle offers 1 more charge-discharge cycles? Good when we use 70 percent of the battery capacity, we can drive more on a single charge than when we use 50 percent of the power. As a result, we are less likely to connect to the charging station, and the remaining cycles are consumed more slowly.

You can find our table from which this diagram is taken and you can play with it here.

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