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Discussion Starter #1
I am buying a Nissan Leaf 30kWh... it is a 2017 but it only has 6000 miles. I understand about the deterioration of the battery if the car is left standing at a low or high charge so to buy a car with such low mileage it seems risky. Of course, if the previous owner didn't leave it at high or low charge it should be fine but with such a low mileage who knows what the previous owner did.

So, what can I do to check out the battery? I have 1 week to approve or decline the car as it was bought from Cazoo so in that week I have to determine whether the battery is in a good condition. It arrives on Wednesday.

What would you do to determine the condition of the battery?

I am hoping to borrow/buy a ELM327 and with LeafSpy Pro I can probably get a reasonable idea but what else should I do? I thought I'd do some long runs dropping the SOC down as low as I dare then rapid charging... this has helped get a battery condition back up in the past and then that might give me a better idea.

Can you think of what else I might do?

Thanks
 

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Don't think of it like you would an ICE car. Low mileage ICE cars are a problem because they've been typically run for many short trips, never getting up to optimal temperature. This means all the miles have been stressful ones on the engine, and might be a sign of heavy wear. In a diesel car, it might cause problems with the DPF.

What are the EV equivalent problems, if any? It seems like you're reasonably experienced with EVs.
 

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LeafSpy is great to find the battery SOH, but be careful. If you are buying an OBD dongle off the inter-web or borrowing one that has not been safely used on a Leaf before, please read and follow the article below BEFORE plugging it into the Leaf. There are some OBD dongles on the market that can damage the Leaf’s CAN bus due to a manufacturing issue. Note this could apply to any dongle, regardless of brand name.

Warning: Defective Konnwei KW-902 on the market - My Nissan Leaf Forum

Apologies if you already knew about this.
 

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I am hoping to borrow/buy a ELM327 and with LeafSpy Pro I can probably get a reasonable idea but what else should I do? I thought I'd do some long runs dropping the SOC down as low as I dare then rapid charging... this has helped get a battery condition back up in the past and then that might give me a better idea.
Just try and measure the SOH before you buy it.

Running the battery down low and then charging fully does nothing for the health of the battery. It’s an old wife’s tale from the days of NiMH batteries that refuses to die.

What hurts Li-ion batteries is too much heat, charging rapidly when cold and too high or too low SOC for extended periods of time.
 

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Discussion Starter #6 (Edited)
Actually, running the battery down very low and then fully charging on a slow charger such as a granny cable or a 7kW charger does help. It allows the battery to properly balance the cells and it is then easier to see bad cells or other potential issues. It can regain some SOH. Occasional rapid charging at 50kW also seems to help although the evidence for this is circumstantial but I have had a spell of not using a rapid charger but a day with 2-3 rapid charges brought the SOH back to new values..

This is my blog post when I discovered this...
Nissan Leaf Battery Seems to Like Rapid Charging

OK, I do agree though that it doesn't help in the way you mean, like with NiMH batteries... Li Ion batteries like these don't really have much of a memory effect :)
 

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Discussion Starter #8
Slight detail. Interesting that Cazoo would provide a deal of comfort for those buying second hand EVs.
I haven't yet had the car delivered but they seem like a good way to buy any car, EV or ICE, but especially EV. They offer a 100% refund if not completely satisfied with the car within 7 days. It will be interesting to see what their attitude is should I reject the car but the claims seem superb. I was given a sensibly trade-in price too so no complaints there.

For buying an EV it does mean I can check out the SOH and reject the car if I am not happy (if I can get hold of a ELM327 dongle before next Friday!).
 

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Discussion Starter #9
Don't think of it like you would an ICE car. Low mileage ICE cars are a problem because they've been typically run for many short trips, never getting up to optimal temperature. This means all the miles have been stressful ones on the engine, and might be a sign of heavy wear. In a diesel car, it might cause problems with the DPF.

What are the EV equivalent problems, if any? It seems like you're reasonably experienced with EVs.
I am experienced but I wanted to put it out there are others have their own views. Mine are not the only valid opinions out there!!!

The main issue for me when buying an EV is the condition of the battery.

When buying new that shouldn't be a problem as you would expect the battery to be in its very best condition when new but as I found out when I bought my first new 30kWh Leaf that isn't always the case. The battery on my new 30kWh Leaf back in 2015 was below spec when it was delivered. After a little bit of a tussle with the dealer they agreed to replace the battery and then all was well.

When buying used the issue becomes more tricky. How the car is used, in particular what state of charge the car is left to sit at, can have a significant impact on the battery condition. If the battery has sat at high or low state of charge for any appreciable periods then there is a chance that the battery capacity could be compromised. The difficulty then is that when buying used you have no idea how the car has been used or treated. As you say, an ICE (particularly a diesel) that is used on short trips all the time can be detrimental. The issues are different but the fear is the same - has the car I am buying been mistreated?

In many ways it is easier with an EV because we have tools and apps that can show us the condition of the battery, or at least give us a strong hint at it. With an ICE there isn't any way to tell short of pulling the engine apart and even then it might be a difficult thing to determine.

So, when buying a used EV, a very low mileage might be a bit of an indicator that the car has not been driven much and that there might have been significant periods of inactivity. This may not be any issue at all if the battery charge was not particularly high or low so it isn't automatically a problem. I am considering a car that has 6000 miles on the clock that is nearly 3 years old - 2000 miles a year. Did the previous owner keep the car at 70% or 100%...? It makes a huge difference.

I am hoping to use a ELM327 dongle and the app LeafSpy Pro to take a peek "under the hood" so to speak and see if I can determine from the numbers the likely condition of the battery. It isn't foolproof but it is better than dismantling an ICE!
 

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I have a Bluetooth obd dongle that worked for my Leaf. Don't have the leaf any more but kept it in case it would work in the Niro but haven't got around to trying it.
You'd be welcome to borrow it. I'm in Suffolk and don't think you live close by but could post it if no one else near by you offers for you to use theirs.
 
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