I spend my day at a keyboard, helping EV owners learn about their cars and understand battery degradation. For a discussion on battery replacements, it seemed important to get out of the office and visit a team that replaces EV batteries each day. That led me to Matt Lamontagne, EV technician extraordinaire at Leo & Sons Auto Shop in Lawrence, MA. I had the pleasure of a lovely chat with him to talk about what the shop is up to, trends he sees in battery replacements, and predictions for the future of the EV market. 

Although Matt drives an older LEAF and a 2021 Ford Mustang Mach-E, there are often a ton of other EVs in his shop’s lot. For instance, this rare sight: the original RAV4 EV was sold from 1997-2003 in California only, but this one made its way to Lawrence, MA. 

Matt and his team have an ongoing waitlist of LEAFs that want battery replacements. Many of the drivers have found him through the Nissan LEAF Battery Replacement Group. Apart from LEAFs, the shop gets a lot of Prius and Volt battery work since they were the only other EVs on the road ten years ago. Although the Model S was on the road starting in 2012, most of them just hit the end of their 8 year warranty so battery work was generally done through Tesla. Matt noted that since newer EVs tend to be under warranty - and rarely have any battery issues - they generally come in for basic maintenance such as brake work and tire changes. 

Since Matt is a known specialist, he can see a wide range of electric cars in his shop on any given day. Below, Leo & Sons has two ends of the EV spectrum: a Porche Taycan and a Smart EQ Electric.

Occasionally, Matt will get calls from a driver of a newer car, like a 2018 LEAF, who wants to swap out a 40 kWh battery with the larger, 62 kWh battery. However, he prioritizes drivers who have very degraded range. If the 40 kWh battery is still healthy, he’ll put the car on the list, but will focus on helping drivers with older, out of warranty cars that are severely range restricted. 

The Steps of an EV Battery Replacement

Matt only has cars in his shop for a few days unless it's a more complicated custom job, such as a recent electric conversion that needs a professional eye. For a typical battery replacement, here is how things happen:

1. Drivers Reach Out

Usually, drivers get in touch when they’re down to six or seven bars, and they are added to the waitlist for a battery. Once new batteries are available, the customer is called and brings in their car. 

2. Diagnostics

Matt starts by running diagnostics with plug in tools like LeafSpy or a proprietary GM tool. The battery is hooked up to a device and information is shared between the Battery Management System (BMS) and the shop and they can see information such as the percentage of capacity remaining, power loss, how many times the car has been AC charged and DC charged, and the temperature of the battery over its lifetime. This data all lives in the battery itself, so Matt can test the battery whether or not it’s still in the car. 

Here are some batteries going through diagnostic testing - one still in the car, and one not.

Matt shows me a current loop that he uses to measure the current running through a LEAF battery while driving or braking.

Diagnostics are run on both the old pack and the new one to ensure that the new one will improve the range of the EV. 

3. The replacement

The swap itself is pretty quick - you need to hoist up the car on the lift (below) so that you can drop the pack out from the bottom of the chassis. With hybrids, the batteries are inside the car, either under the trunk area or rear seat.

Since the battery packs can be dangerous to handle, Matt trains his team on high voltage safety and they use all sorts of safety equipment during the replacement. 

4. Testing and validation

After they swap in the new battery, Matt keeps the car to recalibrate the onboard range estimates and internal computers. This involved running it through a charge cycle and driving the car very conservatively on local roads to see how high the dashboard range can go. Matt tells his drivers that they won’t see ranges that high with normal driving, but he likes to do it as a manual diagnostic of how much range the new battery can get. 

Before returning the car to its owner, Matt also tests other high voltage components, such as the on-board charger, electric motor and heater. Regular safety and maintenance checks are also performed on the brakes, tires, fluids etc.

Below is a special diagnostic tool called a “J1772 Break Out Box” that Matt uses to determine where incoming energy from an AC charger is being directed by the BMS. 

Why do people service or replace their EV batteries? 

Matt’s customers are mostly EV nerds and early adopters. They are the folks who are way into EV tech and who track and monitor their own batteries. They have a good sense of when the battery needs to be replaced because they know all about capacity bars and have Leafspy hooked up. A lot of them are hypermilers and DIYers. 

In many cases, Matt’s customers are the original LEAF owners who have kids that are getting ready to drive. The parents have traded in for a Model Y or something newer and they want to give the kids the old, reliable LEAF. A new battery will ensure that their old car has plenty of life left in it. 

There are also some newer EV drivers who visit the shop. For instance, some customers have found a great deal on a used LEAF and want to get the battery checked out. With the long wait times for new cars, more and more shoppers are investing in an inexpensive older car, replacing the battery, and getting what is essentially a new car at a very affordable price. 

Matt makes sure new EV drivers have reasonable expectations about the battery life and how to take care of it. Matt echoes what we always say: odometer is a poor indicator of battery health. Past charging use and heat are much stronger predictors of how well a battery will hold up.

What is the lowest state of health (SOH) you’ve seen in old LEAF batteries? What about the packs that they are replaced with? 

Matt said the lowest SOH we’ve seen is probably 40-50%, but usually those cars are on the waitlist before they get that low. Most of the replacement battery packs are from salvage titles or junkyards so the SOH starts in the 80% range and goes up to the 90s. Once, he got a salvage car that literally fell off the back of a transport truck. The car was brand new with only a handful of miles, so the state of health was above 99%, but that’s a unique case.  

The other thing to know is that many of the packs that come in have minor damage to the casing or the interconnects. Matt will need to find compatible parts from the graveyard to replace them. In this picture above, the battery in the shipping box came in with a cracked casing. Luckily, there are plenty of old packs to pull one off of, such as the pile of them that the shop is donating to a company that evaluates modules. 

Matt cautions that if you were to try to replace a battery pack at home, the one you receive may not be in pristine condition and to be prepared to have to find parts and connectors to make it work. 

As a fun note, you can tell the earlier LEAF batteries from the newer ones because they are light grey and have a big service disconnect in the center, like in the picture below.

Does the shop get many EVs that aren’t LEAFs?

Matt says that for battery replacements, they see mostly LEAFs, Volts, and Prius, since almost everything else on the road is still under warranty - and rarely needs a battery replacement. He had one driver who wanted to swap out an old Volt battery with a newer one but they couldn’t get the new pack work because the location of the battery management system (BMS) changed from one year to the next. 

But, with a lot of older cars, we can upgrade the battery size when they do the replacement. For instance, you can get a 62 kWh pack into an older LEAF, but the shape and size of the older battery is different, so you have to retrofit the car. It’s do-able, but it takes a lot more work than swapping out a 2012 24 kWh battery pack with a 30 kWh one. Since manufacturers change the shape and connectors with new model years, retrofitting newer batteries into older cars often takes more than a simple swap. It can meet rewiring connections or “translating” a new BMS for an older system. Special parts and pieces help, such as the “Nissan Leaf PTC Power Outlet Delete Cap” made by New Zealand company, EVs Enhanced. 

When they see other vehicles, it can be due to electric issues other than the high voltage battery. For instance, he’s seen problems with a 12 volt battery short circuiting. In the picture below, he’s showing me the battery hold down that was shorted out on the bottom of a 12 volt. Matt’s diagnostic skill means that a lot of tough cases get sent his way. 

What do you do with old batteries?

Matt teaches EV maintenance and battery replacement all around the country through his consulting company, HiVo Group, and donates a lot of the old packs to classes and schools for hands-on experience. He is also approached by startups and organizations that do research into battery aging and second-life storage applications. The picture below is a battery pack from a Peugot van that is not released yet in the US. It is on the same lift that he uses to hoist up a car and remove the battery pack. 

Have you noticed any trends in battery availability or pricing?

Matt says battery availability is always the bottleneck with this business. There are always more people who want replacement packs than can be accommodated. However, prices have gone up. Since most of the battery packs come from used or salvaged cars, price increases in the used car market affect how much the shop has to pay for those cars. 

Batteries are expensive but I’m assuming there’s a lot of labor, too. For a replacement, what ballpark percentage of the price is materials vs labor? 

Very little of the final cost is labor. It’s around 95% material cost, which is the limiting factor in the whole replacement process. 

Do you ever replace modules and not entire packs?

Matt said on the LEAF, and generally with all lithium ion batteries, individual modules degrade very evenly. In the Prius, it’s typical to see more cell level variation. It’s conceivable that if a car was inoperable due to a faulty module, it could be replaced to take it out of failure mode, but they mostly do whole pack replacements.

Final Thoughts

Battery replacements are rare in EVs, especially newer ones. The reason we’re seeing them in the LEAF is because that was the first commercial EV, and it’s been out a while, and it had no thermal management. Even still, those batteries lasted remarkably well. 

You don’t have to worry about the cost of replacing a battery in an EV that’s still under warranty. When a battery is treated well, what we are seeing is that they are holding up for a long time.