231 - The Battery Health Episode

Gary C: Hi, I'm Gary and this is EV Musings, a podcast about renewables, electric vehicles and things that are interesting to electric vehicle owners. On the show today we'll be looking at battery health, specifically for second-hand cars. Before we start I want you to say a big vote of thanks to listeners who support me via ko-fi.com. I talk about it in the closing credits every week but there are people out there such as Neil McCall and Rob Prior who donate every month to the podcast through ko-fi. com, plus all the others who give one-off donations, KevTHC and Michael Edwards for example.

Thank you all, very much appreciated. Our main topic of discussion today is battery health. Let me paint you a picture.

You've got your eye on a second-hand Porsche Taycan, too expensive to buy brand new but quote-unquote easily affordable with some of the depreciation levels we've seen on that particular vehicle. You take a test drive and it all feels good, the range looks good and you're seriously tempted by the price but you still have a niggling doubt about whether the battery is still in a good state of health. While most second-hand batteries at the moment are still under the eight-year battery warranty, there are some from the earlier phase of the EV rollout that might be out of warranty.

So how can you be sure that you're not going to end up with a battery that will need replacing within a couple of months? And the short answer is, you don't. But that's not going to be the case going forward.

We've touched on this before in previous episodes but that was more from the point of view of, this is what you need to do to make sure your battery works well and remains in good condition. Today I want to have a think about the next step of the battery journey, second-hand cars, and how you can determine whether the batteries are any good. With most modern EV batteries the chemistry used to make them run will degrade over time and by that I mean that the range you can expect from a 100% battery charge will reduce.

This is perfectly normal and usually is quite limited. This is because the battery has a complex software battery management system to protect it and prolong the lifespan. As an example of how good this software is, take a look at any modern smartphone after about three years.

Smartphones don't have the complex BMS software on them like EV batteries do. On an iPhone go to the battery settings and check state of health. My last battery at around three years old was down to about 82% state of health and what this means is that when the battery is shown as 100% charged it's only actually 82% charged.

This has an impact on how long it can go without needing to recharge it and how quickly it discharges during the day. So this obviously causes issues when you're looking at people who are equating a phone battery with an EV battery. Fundamentally they're the same basic technology maybe even the same basic chemistry in certain vehicles but any similarity in how they operate stops there.

So it's understandable why people who are used to replacing their phone or phone battery on a regular basis because it needs charging twice a day to keep working are concerned that the same thing will need to happen with their EV. While replacing an iPhone battery is relatively inexpensive - I bought a replacement part with the associated tools needed to do the repair off Amazon for around £30 recently - The costs associated with a new EV battery are much much bigger. Various figures are bandied around for replacement costs and it depends of course on battery size, battery chemistry, supplier and age , are you replacing the brand new one or one that's been taken from for example a written off version of your car.

It's always going to be a reasonably big outlay for a new EV battery. Figures of £20,000 and higher can be seen being paraded around social media. So put all these things together and you have members of the public thinking if this EV is more than three years old it'll need a new battery and it'll cost me £20,000 to replace it and indeed I've seen more than one post on social media and in certain parts of the mainstream media where this is the case.

But it couldn't be further from the truth and today I want to look at why that's not the case indeed. First let's talk about battery health in general and why thinking iPhone batteries and EV batteries are the same is a big mistake. Firstly the key thing that hurts batteries of pretty much any sort is heat.

When you use them, charge them and recharge them they get hot and this heat contributes to the degradation in the battery. Ironically though heat is actually required to make EV batteries charge at an optimum speed. If you can heat your battery up to a certain point, charge it and then immediately cool it down you get the best of both worlds, a rapidly charging battery with a relatively long life.

But when you look at your smartphone I bet you do things like leave it charging all night plugged in on the bedside table or you use it in the heat of the summer making sure that it gets. you know, almost too hot to touch or you do lots of video for your Instagram pages meaning the processor and the batteries working extra hard right? How many of you do the double whammy of reading in bed with the phone charging, connected and then fall asleep with it under the covers next to you or under the pillow? All these things will increase the heat of the battery.

In some cases they'll help the battery charge quicker but in most cases they'll provide some sort of damage to your phone and this is because smartphones don't have a battery management system on them. Actually to be accurate some of them do but it's fairly basic and rudimentary and it's nowhere near as complex as that that's on an EV. Also they don't have the temperature management systems.

These manage heat coming into and out of the battery. No smartphone has this and guess what? If your phone is under the covers with you plugged in all night once it gets to 100% it'll get warmer and warmer degrading the battery more and more as it does so.

There's a lot more about batteries in an earlier episode of the podcast with battery electric chemist Dr Ewan McTurk. Episode 61 is the doctor in. Links in the show notes.

So let's look at a bit of data. Geotab who were guests on last season's episode on geospatial planning also gather battery health information from thousands of cars that they monitor. In a recent report they released they cover battery health extensively.

Let me read from their web page. "At the average degradation rate of 2. 3 percent per year an EV battery would take 15 years to decline to 70 percent maximum charge and that's well beyond the average lifespan of a car in the UK" end quote.

They also say that battery degradation is not a linear thing there's an initial drop in health within the first year or so after that it declines a lot slower. When the battery is approaching the end of its useful life the degradation will start to increase quicker.

Vehicle batteries respond differently to the test of time depending on their make and model year. Why does some vehicles seem to on average degrade faster than others? Well two potential contributors are battery chemistry and the thermal management of the battery pack.

The Nissan LEAF has a lot higher battery degradation because it has no thermal management of its battery pack and this means that a LEAF can have an average degradation of 4.2% vs say Tesla with 2.3%.

So what can we do to provide a level of comfort and assurance when looking at battery health? Well there are a number of ways to do so. The first one is to take the car for a drive.

Fill it to 100% and run it down to around 10% state of charge. This will give you some idea of the distance you can get with a battery at its current state of health. If you're tracing the efficiency of the battery you can then also determine what the capacity is for the whole battery.

It's a bit complicated but bear with me. Start at 100% and run the battery down to around 10%. This means you've used 90% of the battery.

Check the efficiency of the journey using the software in the vehicle. Divide that into the distance travelled to get the battery usage and then divide the usage by 90 and multiply it by 100 and this will give you the value for the capacity of the battery. Sounds complicated?

Well let's do a specific example. You run your battery down to 10%. The onboard computer tells you you've achieved an efficiency of 250wh per mile or 4 miles per kilowatt hour.

If you travel 250 miles on that battery you can calculate that the usable battery in your car is 250 divided by 4 which is 62.5 kWh for 90% of that battery because you've used 90% and left 10% in the state of charge. So you divide that 62.5 by 0.9 to give you 69.4 kWh for total capacity.

If your original battery was 70 kWh that means you've lost a little over half percent of the capacity. So let's assume you're a little bit heavy footed with that same car and you only bring back 330wh per mile or 3 miles per kilowatt hour and you only cover 188 miles so you do the same calculation 188 divided by 3 is 62.6 divide by 0.9 for the 90% and you get 69.6. Now the issue with this is that there are other factors that play into the calculations and there is room for inaccuracy to creep in.

What you really need is something that can physically get into your battery and check what the state of health is. Now last season we spoke with Irish EV car dealer Simon Acton and one part of the interview that was not broadcast at the time related to a segment of his business where he provided battery health for used EVs.

Simon A: I suppose if I could touch very quickly on the battery health side of things.

So obviously one of the things that we've been doing is testing cars and making sure we have a read on the state of health of the battery. And also there's consideration that you know cars used vehicles have traditionally been valued based on their condition and their mileage and largely that is still the case with EVs but in the future well it shouldn't be that way because battery health is actually a more important metric than mileage and for a number of reasons I won't go into now. A vehicle with less mileage could have lower battery health than a vehicle with higher mileage so obviously that in theory has an impact on the value.

So what we're not seeing in the market really at all and I don't think you're seeing it in the UK either to the extent that needs to happen is that there's visibility to the consumer of battery health and that is important in two ways. It's important like I said for value but it's also important to give confidence because of this whole narrative around the batteries don't last whereas the reality is that you know you could pick pretty much any you know five-year-old EV that even some that have done high mileage and they're going to have north of 90% battery health. So you can figure out from that how long that car's going to last before you have an issue with longevity of the battery.

So yeah that is an important factor that doesn't get talked about enough and the tools are available there they're here now for dealers and consumers to use to get this information but it just isn't happening and there needs to be more knowledge raised of this. You know consumers should be aware that it's something they should ask about when they buy a used electric car both to protect themselves but also you know to make sure that you know they're working with a dealer who actually knows what they're selling. The tool I use is obviously the company Avalu they're a commercial business so they do store all that data centrally in their own data cloud and all of that data is used in the calculations that they make to consider the health of a particular battery and how that benchmarks against similar vehicles.

So that information isn't publicly available but I mean they have worked with a number of OEMs to offer that information. It's not freely available but it is there.

Gary C: Now Simon mentioned Avalu an Austrian company that provide battery health testing.

It's a commercial business which will evaluate the state of health for battery. It works very simply: you have a specific piece of kit which plugs into your car's OBD port, you charge the car to 100%, plug the monitor in, run the car to 10% then send the data back to Avalu. All the data is sent to the cloud where it's analysed and they'll send you a detailed battery health certificate within two working days.

the time of writing - October: 2024

If you're after peace of mind with second hand EV this is absolutely prime. There are other companies which do similar things. If you get a Cleveley EV for your mobile servicing, or more accurately if they come to you, they can perform an evaluation using a diagnostic tool they have in their vehicles.

It runs right into the meter of the battery and it calculates lots of different variables to provide a state of health report for your car. Now another tool to look at is called ClearWatt. It's an app on your phone and what they do is, once you register, you make a number of journeys while running the ClearWatt app and it gathers telemetry data on your driving style.

It uses some sort of AI to manage what's happening and presumably at some point it captures data manually regarding state of charge etc. This is then processed to produce a battery status report. It isn't a battery health report like the Avalu output capturing degradation of the battery. What it does is it determines a rating based on reference data for your vehicle vs observed data from the app telemetry. It will tell you what your expected range is on a full charge and compare that with the expected range on a new battery and calculate this rating, A plus down to D, as well as plotting that on a graph showing the range vs the age of the car so you know how it stacks up against similar vehicles in the space.

Remember the whole reason you'll want to have something like this is so that when you come to buy a second hand EV you can have a level of confidence that the vehicle itself isn't going to land you with a large bill for replacing a battery. But it is worth reminding you that your car comes with a very very good battery warranty itself. From new most EVs offer an 8 year or 100,000 mile warranty.

If you're buying a second hand car and it's within the warranty that will still apply. If anything goes wrong with the battery and it needs replacing, this warranty will cover the work. What the warranty won't cover is a battery which has a higher degradation than expected.

I.e. supposing you bought a 4 year old car that had 10% degradation when an average example of this age had 5%.

This isn't covered by the warranty. But if that degradation then drops down to below the warranty level prescribed by the manufacturer which is usually around 25-30% degradation within the warranty period, the battery will be replaced or repaired free of charge to you. So if it's peace of buying from large bills you want the warranty will go a long way to stopping that.

If you're outside the warranty period there is an amount of caveat emptor, buyer beware, when buying second hand EVs. But the same can be said for any second hand car. There are numerous tales of people who bought old Fiestas and Astras and Renault Megans only to find that they need an expensive clutch replacement or even a gearbox replacement.

The 911s I used to drive before I went electric were famous for losing pressure in certain cylinders over time. This involved a top end rebuild which cost a minimum of about £5,000. So remember this isn't just an EV thing, it's an old car thing.

If you're buying from an auction site such as BCA they'll usually provide you with a very detailed appraisal of the vehicle including checks performed, any bodywork issues, tyre depth, they'll even run the car for about 10 miles on the road to check for noises and driving issues etc. But what they don't do is provide the battery health check for you. So if you're buying from an auction there's always that to bear in mind.

The other thing to remember is that battery problems don't always mean a complete battery replacement, unless you're driving an EV that's designed with a completely sealed battery pack unit. Many EVs allow you to open the battery pack and replace specific cells within the pack itself. This is much cheaper and a more convenient way of repairing a battery than throwing the whole lot away and buying a new one.

In fact if you want to know what to do if you've bought a car that's a bit of a lebon when it comes to batteries, podcaster Andrew Till has a great video when someone he knows bought a Nissan Leaf with a battery problem. It's a series of three videos and it's well worth your time if you want to have a look at it. But if you want the quick overview the car wouldn't hold a charge, it threw a traction battery error every time it was driven so they took it to a HEVRA certified repairer, they had one cell replaced at a cost of around £900 including labour and it solved their problems.

So let's wrap things up here with a quick summary. Nobody wants to be surprised with a big bill to replace a battery if they buy a second-hand EV. The easiest way to avoid this is to ensure you only buy second-hand within the warranty period but this won't guarantee there isn't degradation only that the degradation is within the warranty limits.

If you want a better idea of the actual battery state of health there are a number of solutions you can go for which will help put your mind at rest. This season we're looking at raising the awareness of carbon literacy with our listeners and one way we're doing that is with the carbon fact as read by carbon literacy trainer Anne Snelson.

Anne S: We all know that plant-based diets are best for the planet but if you love meat there's a halfway step you can take.

Ruminant animals especially cows cause way more emissions than non-ruminant ones so swapping from beef to chicken or pork can cut your emissions by about two-thirds. Think about how much you're eating too because things like bacon bits or spicy sausage can give all the flavour with only a fraction of the amount used.

Gary C: It's time for a cool EV or renewable thing to share with your listeners.

The world's largest wind-powered cargo ship called Animus recently made its first delivery from France to New York carrying wine and spirits. This innovative ship uses large lightweight sails and advanced technology to primarily rely on wind power reducing reliance on fossil fuels. TOWT the company behind Animus plans to expand its fleet and help brands meet climate goals through sustainable shipping.

What's that old saying? Everything old is new? Sails coming back, can't complain about that.

If you have any thoughts, comments, criticisms or other general messages to pass on to me I can be reached at info@EVMusings.com

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I know you’re probably driving or walking or jogging now. But if you can remember- and you enjoyed this episode drop a review in iTunes, please. It really helps me out. Thanks.

If you've reached this part of the podcast and are still listening thank you. Why not let me know you've got to this point by tweeting me at @musingsev with the words 'There's positives and negatives. #ifyouknowyouknow Nothing else. Thanks as always to my co-founder Simone.

You know I once asked him if he was at all worried about the huge number of Christmas toys that get used once then thrown away as kids need more and more stimulation to keep them interested. He seemed less concerned about that than he was about something found inside the toys.

Simon A: I suppose if I could touch very quickly on the the battery health side of things.

Gary C: Thanks for listening. Bye.