Home special-report How do you know how good your EV’s battery is?

How do you know how good your EV’s battery is?

How do you know how good your EV’s battery is?

Right from the start, the question has been how long will the batteries last. Ever since electric cars first broke onto the market, and long before battery power became the be-all and end-all of modern motoring, there were concerns raised about how robust EV batteries would be, and how expensive they’d be to replace if everything went wrong.

Car makers tried to placate potential owners with generous warranties and reassurances that replacing the entirety a battery would be a one-in-a-million event.

While that’s broadly true — generally what happens is that individual battery cells degrade, rather than the whole battery, and these can be replaced at relatively reasonable cost— recently, we’ve seen tales, in The Irish Times, of consumers being asked to pay as much as €19,000 (plus VAT…) to replace the battery of an ailing EV.

In increasing number, electric cars are filtering through to the second hand market, and while the used car buyer — a conservative beast at the best of times — is likely to mostly shun them in favour of supposedly more dependable petrol, diesel, or hybrid cars for some time yet, the fact is that checking the health of a car’s battery is going to become a task, like checking the tyres, the service history, and the fluid levels, that all of us will have to do when buying a used car.

So how do you do that? You can’t clasp an EV battery between finger and thumb, like a Duracell, and see what the little green bar tells you. Indeed, if you could do that the 400-volts of an EV battery would kill you stone dead. No, you’re going to need something a little more high-tech than that.

The battery test

Thankfully, there is now a solution — both for those looking to buy or sell and EV with a clean bill of battery health.

It’s called the Aviloo EV Battery Test, and it’s being brought into Ireland by Next Eco Car, the Dun Laoghaire-based used EV specialists.

“There’s basically what they call a premium test, and then there’s a flash test” Simon Acton from Next Eco Car tells breakingnews.ie. “The premium test product is a very detailed test. You basically plug it into the ODB port of the car, and you charge your car 100 per cent. And then you drive it until it goes down ten per cent, and that gives you a full battery test certificate.

“That was the initial product that they had, which was great in as much as it’s giving you a completely independent analysis of the capacity of the battery based on the discharge that has been completed. Now that sounds great, but quite inconvenient as you can imagine, especially on longer range vehicles.

“The second product which they launched quite recently is called a flash test about basically a static test. You do it in the same way, by plugging this device into the car, but it completes the test in about three-to-five minutes. Then you immediately get a set of results back.”

Acton says that one of the great advantages of the Aviloo test is that the company has a huge amount of data in the background, of tests that it’s run on thousands of EVs around the world.


So not only can the test give you the instant snapshot of your car’s battery health (or a car you’re interested in buying…), it can also compare that health to a vast database of tests carried out on the same make and model, so it can tell you if your battery is batting above or below average.

The premium test, the one that involves charging and running the car down to ten per cent capacity, is done at home with a kit that comes in the post, and which costs €99. This is the one that’s more suitable for those looking to sell a car, and who want to provide a prospective buyer with a certified battery health form.

The flash test has to be performed on-site, either at Next Eco Car’s premises or one of its appointed partners (the first of which has just been appointed in Finglas, north Dublin) but it only costs €60.

Again, it’s probably better suited to a dealership which wants to sell a car with a big green tick next to battery health in the advert, but you could easily imagine someone taking a test drive in a used EV and popping in — convenience allowing — to get a quick check done on the battery.

“This is for consumers, so consumers could use this to test their own car, or if they’re thinking of buying a car, but it’s also very useful for people like me, firstly to make sure we’re choosing good cars, and secondly to give reassurance to customers” says Acton.


“And that’s really the key piece. This is a hot topic because there’s a lot of information, or even misinformation, out there about degradation of EV batteries. For the most part, EV batteries are very good. Obviously, like buying any car, you don’t want to pick the one that hasn’t been treated correctly and maybe isn’t as good as it should be.”

Battery health is not a logical constant among EVs, says Acton. From his experience, an early Nissan Leaf from 2014, could have a battery health rating of 90 per cent, while an identical model next to it could be down to 70 per cent.

It’s older Leafs that tend to suffer the worst degradation from repeated fast-charging, says Acton, because the original battery design did not include any active cooling, which helps to prolong battery health. More modern designs are proving vastly more robust.

“Like any technology things can go wrong” says Acton. “And there are examples where batteries have gone wrong and need to be replaced, but I haven’t — touch wood — in all the cars I’ve sold in five years, had a situation where I’ve had a battery that’s been a problem or needed to be replaced. Traditionally we buy cars when we look primarily at mileage, but the thing with an EV is that mileage isn’t the only contributing factor to battery degradation in the same way it is for engine.”

The Aviloo test could be useful to consumers in another way.

If a battery does develop a problem, and needs warranty work, it’s an independent and verifiable test that can demonstrate beyond a reasonable doubt that there is an issue which needs dealing with.

“If you bring a car with what you think is a damaged battery back to a main dealer, they’re going to check it on their equipment, which is not an independent test” says Acton.

“It’s what the car maker has given them, whereas Aviloo is 100 per cent independent and can be used across multiple brands and models. We’ve seen situations where a dealer is telling a customer that there’s nothing wrong with their car, but Aviloo has been able to dig into it for the consumer and provide enough evidence to go back and say ‘look, there’s a genuine issue here’ and those customers have been given a replacement battery under warranty.

“So that process has been proven, and it works, and it provides evidence that dealers and car makers will follow up on.”