We’ve teamed up with Shell Recharge to answer the questions everyone asks, bust some myths and help clear the air around electric cars. So here’s one for you…

Why should I only charge my electric car to 80%?

There are lots of reasons which we’ll cover below. In short, there are benefits to battery health and efficiency, and it can also save you time. But it’s not compulsory and it won’t invalidate your warranty if you go past 80% - it can be overridden if you’re heading off on a longer journey and need that maximum range. Here we will look at all this in a little more detail.

My car’s manual says that I should only charge to 80% if possible. Why is that?

It’s all to do with keeping your battery as healthy as possible, for as long as possible. And while it’s perfectly safe to charge your electric car to 100%, the Lithium-Ion batteries that power most electric cars are most efficient working in ranges from roughly 20 to 80%. So while you can charge to 100% when you’ve got a long journey ahead, or scrape those last few miles from the range to get you home at night, if you can avoid it the battery will thank you in the long term. Think of it like not revving your engine in a petrol vehicle to the maximum every time you drive it: you’re just being a little bit more gentle with the hardware, which tends to mean it’ll last longer and be more efficient in the future.

Even though electric car batteries are lasting far longer than even the most positive of predictions - several hundreds of thousands of miles in some cases - it’s always good to look after your things, even if you won’t be the person that has to deal with them in 10 years’ time.

Charging to 80% is being kind to your car

What happens if I DO charge to 100%? 

Nothing - you’ll just have the maximum amount of possible range for the battery and efficiency of your car, which is obviously what you’ll need if you have a particularly long journey, or a hectic day covering significant miles with few chances for a charge. And if you need a charge while out and about, then there are 230 Shell Recharge forecourt and destination points in the UK, with more being added every day. They range from rapid 50kW chargers to 150 and 175kW ultra-rapids - you need never be caught short.  

I can’t watch my car to make sure it gets to 80% and no more! 

You don’t have to. Most modern electric cars have a control in the menu setting that allows you to choose how much charge you put in - simply set the amount (say 80%) and the car can be plugged in and will stop charging when it reaches that set level. Some chargers - both home and public - offer this facility as well.

There are 230 Shell Recharge forecourt and destination points in the UK, so you need never be caught short

How can NOT charging my car up the whole way save me time? 

Sounds counterintuitive to say this, but this really is true. Some cars actually take nearly as long to charge from 10-80% as they do from 80-100%, so it might well be quicker to charge to 80% and then find another charger further on when the charge is low again if you’ve got a very long journey. 

One of the best ways to visualise it is to imagine the battery is a glass of water, which you are trying to fill using a jug. You can slosh in as much as you like at the start without issues, but as you get closer to the brim, you have to slow down to avoid spillage. 

The same happens in your battery, with the charger having to work harder to find ‘space’ in the cells as it gets to nearly full. So if you are on a long journey, driving for a while after charging to 80% is like taking a few gulps from that glass of water before topping it up again at a faster rate later on. 

For instance, on a Shell Recharge 175kW charger, some cars will be able to take the full amount in the right conditions but charge will tail off above 80% so that by the time they are at 90% they might be taking less than 10kW. The last few percent could be at less than 2kW – the same as you’d get from a 3-pin plug. 

So just put in the miles that you need to safely continue your journey, and head on. It’s also worth noting that cars with bigger batteries obviously have a bigger ‘sweet spot’ between 20-80%, so they’ll generally add more miles more quickly.

Charging to 80% when on a longer journey could actually save you time - even though it seems counterintuitive

How does charging to 80% make me more considerate? 

This is an etiquette issue. Basically, sitting on a public charger waiting for an extended period to get those last few miles of charge into your car - especially when above 80% and therefore likely very slowly - stops other people using the charger. So unless that’s the difference between getting home in one go or not, it’s often more polite to charge quickly and efficiently to 80% and then vacate the charger for someone else to use. It keeps the charging experience as seamless as possible for everyone! 

Sometimes there are slower chargers near to the rapids. They are usually cheaper too, so if you really do need to go to 100%, it will be better for everyone if you can move to one of those – it won’t take you any longer, will cost you less and will free up the fastest charger for someone else to use.

So what else should I be thinking about in terms of keeping my battery in tip-top shape? 

Well, there’s a couple of things that are worth taking into consideration. First up, watch the battery temperature. Most electric cars have built in heating and cooling to keep them like Goldilocks’ porridge – not too hot and not too cold. But if you drive quickly in hot weather, rapid charge and then repeat you could find that the temperature creeps up and it could take longer to charge as the car’s electronics will try to protect it.

Similarly, running from 100% full to 0% - or as close as you dare - also makes the battery work hard, meaning that it will tire out more quickly. Plus there are things like extreme temperatures which batteries aren’t fond of - one of the reasons why we get less real-world range in winter.

It’s also not advisable to leave the battery at 100% or near to empty for extended periods of time – like while you are away on holiday. If you are going away, try to charge to 80% or less before leaving.

But it’s worth noting that all electric cars have built-in buffers aimed to prolong battery life - even when your car says 0% or 100% battery, the car manufacturers will have made sure that there’s a little bit of spare capacity left over to keep everything running smoothly.

If you are leaving your car for an extended period, try to keep the battery at a mid-level charge