EV’s & Battery Health by Ivan Endicott

In all the history of motor vehicles switching to an Electric Vehicle (EV) has to be the biggest change we all face, it’s not like we have a choice when purchasing a new car in 2035, as in the UK as there will be a complete ban on the sale of ICE cars.

EV’s are certainly not new in design and one of the first documented EV’s was built around 1832, so they actually pre-date ICE cars by a number of years. Only in the last 8 years are EV’s are at a stage where they can be used as a daily commuter vehicle.

Now the one thing that has been in the media spotlight in the past few years is the life span of an EV traction battery. How to keep the battery in the best condition so degradation is kept to an absolute minimum is one of the biggest worries an EV driver faces as this is singerly the most expensive part of an EV. On this I wanted to make sure I understood the best way to keep the traction battery in tip top condition.

My go to source of information nowadays like a lot of people is the internet and more specifically YouTube. I started a search on YouTube for videos about “How to minimise EV battery degradation” and found a bewildering range from channels saying, “don’t rapid charge” to others saying, “rapid charging is good for your battery”.

One thing that has always stuck in my mind and has been reinforced by a lot of YouTube channels are that Lithium-ion batteries are generally only good for about 1000 cycles, meaning that they can only be charge from empty to full 1000 times before they are rendered useless for an application in an EV.

I then came across a channel suggesting that you can effectively quadruple your charge cycles to over 4000 charges, so I watch the video to see what the secret was. It turns out the creator was telling people that they should only allow the battery to drop down to a minimum charge of 50%, and a maximum charge of 80%, which if you own an EV means you will be charging often to keep the cars battery in the sweet spot, but this is not really a sustainable option for most people.

One channel mentioned that a number of taxi firms in Scotland only rapid charge their Nissan Leafs and they have had no issue with them in terms of battery degradation but no figures were quoted of the State Of Health on the batteries after a few years only that the taxis had covered over 150,000 miles on the same traction battery.

I decided to search my usual channels, Fully Charged, Plug Life TV and Transport Evolved. Now these channels seem to back up a lot of their claims with facts and technical knowledge so they seem to be a good source to fund out information.

I have come up with the following conclusions and please note these are my own personal opinions based on my findings and I suggest to others that have the same questions to do their research. But here goes……

  • It appears that Lithium-ion batteries work best between 20% – 80% state of charge.
  • Heat is a killer of batteries and will drastically shorten a batteries life, if you happen to live in a hot country battery degradation will generally happen quicker. In the UK as the climate is not to hot or cold and so this is a good preserver of batteries.
  • Battery life is extended dramatically if the battery pack is actively cooled, this backs up the point above about heat being a killer of batteries.
  • Charging a traction battery to 100% at least once every 2 weeks is good for it and helps balance cells that are not performing well (Some cars are different so consult your manual before you do this, for example the Kia E-Niro manual tells you to charge to 100% at least every month)
  • Rapid charging a battery from time to time can actually help the health of a battery, but continual overuse of rapid chargers can have a net negative effect.
  • If you ever leave your car for a long period of time do not charge the battery to 100% as this will damage the chemistry in the battery. The sweet spot to store an EV traction battery is said to be around 50%.

So keeping your EV traction battery state of health as high as possible is still a bit of an art. We have general guidance but if there is one myth that has been debunked recently is that EV’s traction batteries only last between 2-3 years.