Battery degradation question
Discussion
Hi all, wonder if anyone might know the answer to this please…
Old Nissan leafs are known for having poor batteries, but lots for sale quite cheap now.
My question (numbers are illustrative to make the point):
Let’s say a brand new leaf back in the day would run for 100 miles, and cost £10 to charge.
That same car now has a max capacity of 30 miles. Will it still cost £10 to charge, or will it now only cost £3?
I’m trying to work out if battery degradation means simply less miles, or if it also means less cost efficient as well as less miles.
Thanks!
Old Nissan leafs are known for having poor batteries, but lots for sale quite cheap now.
My question (numbers are illustrative to make the point):
Let’s say a brand new leaf back in the day would run for 100 miles, and cost £10 to charge.
That same car now has a max capacity of 30 miles. Will it still cost £10 to charge, or will it now only cost £3?
I’m trying to work out if battery degradation means simply less miles, or if it also means less cost efficient as well as less miles.
Thanks!
Battery pack degradation essentially comes from two separate sources. 1) The cells going out of balance - the battery pack can only continue charging as long as the most charged cell isn't being over-charged charged and can only discharge until the least charged cell can't safely be discharged any further. Thus as the cells drift further out of balance form each other, the less the overall pack capacity becomes. Not sure which, if any, EVs are capable of actively rebalancing their cells. It requires a separate charging circuit per cell (and there's thousands of them so that's not simple or cheap).
2) The Cells themselves change chemically in two different ways, both of which reduce capacity. Firstly the crystaline structure of the electrodes can degrade, allowing them to store fewer Lithium Ions; and secondly the electrolyte can chemically bond to the Lithium, reducing the number of Lithium ions available to be moved between the electrodes.
Neither of these significantly reduces the efficiency of charging or discharging.
Thought i'd chip in since I just bought a 2015 Leaf last week. My first EV.
Mines is a 24kwh battery, with 11/12 bars health. 66k miles, full Nissan service history. £2,900. At that price, it was worth a punt.
Generally speaking, from the very quick research i did online, it seems that the 24kwh battery might be the better one to have. Smaller capacity yes, however it seems the later 30kwh battery can suffer higher degradation. Perhaps too much crammed in? Certainly seemed to be the case when looking at different 24kwh and 30kwh for sale locally and looking at their state of health bars. But obviously degradation is a risk no matter the battery size.
If you can find one with decent health in the first place and be sensible with your charging habits, you should be able to maintain a decent health. And for the low price of some of them currently, it's a good time to try it with relatively low financial risk. I'd personally not buy one with a low state of health unless it was very cheap to buy, given there are ones with good health at low prices.
As for your question, as already stated then the more the battery has degraded just means less energy can be stored - your cost per mile will be unaffected. It'll just be cheaper to charge, albeit with proportionally less range.
My experience to date (if it's of interest):
I had to do a 65 mile journey home when I bought it, with 89% charge. It was showing 67 miles of range at that point. Was convinced I would need to charge on the way, but made it home with 12 miles remaining averaging a calculated 5 miles per kwh.
Fully charged shows between 78 and 83 miles (depending on recent driving economy). I do town driving (between 30 and 60 miles a day in the evenings), so it makes sense for me. I use the 3 pin granny charger in my garage to charge it, no issues so far. Estimated mileage is fairly accurate so far, will see if/how that drops in the winter. I'm just using my standard electricity unit rate of about 20.8 pence per unit and at a town average of 4miles/kwh that theoretically comes in at about 5p/mile. Some evenings i've had up to 4.7 miles/kwh average, down to about 3.8 when being less efficient with the throttle (and with the climate control on, lights, wipers etc). By no means am I thrashing it though. If I couldn't charge at home then there are several public chargers dotted round my town at 40p/kwh (Chargeplace Scotland) which you can just pay and start/stop charging on their app easily. Up that to 70p/kwh if in need of a quick rapid charge (which I hope not to use).
It's been great so far. A real pleasure to drive, and so simple to operate. That instantaneous torque is great, although i'm happy just wafting about in silence. But while it suits me and my circumstances, that won't be the case for everyone.
Mines is a 24kwh battery, with 11/12 bars health. 66k miles, full Nissan service history. £2,900. At that price, it was worth a punt.
Generally speaking, from the very quick research i did online, it seems that the 24kwh battery might be the better one to have. Smaller capacity yes, however it seems the later 30kwh battery can suffer higher degradation. Perhaps too much crammed in? Certainly seemed to be the case when looking at different 24kwh and 30kwh for sale locally and looking at their state of health bars. But obviously degradation is a risk no matter the battery size.
If you can find one with decent health in the first place and be sensible with your charging habits, you should be able to maintain a decent health. And for the low price of some of them currently, it's a good time to try it with relatively low financial risk. I'd personally not buy one with a low state of health unless it was very cheap to buy, given there are ones with good health at low prices.
As for your question, as already stated then the more the battery has degraded just means less energy can be stored - your cost per mile will be unaffected. It'll just be cheaper to charge, albeit with proportionally less range.
My experience to date (if it's of interest):
I had to do a 65 mile journey home when I bought it, with 89% charge. It was showing 67 miles of range at that point. Was convinced I would need to charge on the way, but made it home with 12 miles remaining averaging a calculated 5 miles per kwh.
Fully charged shows between 78 and 83 miles (depending on recent driving economy). I do town driving (between 30 and 60 miles a day in the evenings), so it makes sense for me. I use the 3 pin granny charger in my garage to charge it, no issues so far. Estimated mileage is fairly accurate so far, will see if/how that drops in the winter. I'm just using my standard electricity unit rate of about 20.8 pence per unit and at a town average of 4miles/kwh that theoretically comes in at about 5p/mile. Some evenings i've had up to 4.7 miles/kwh average, down to about 3.8 when being less efficient with the throttle (and with the climate control on, lights, wipers etc). By no means am I thrashing it though. If I couldn't charge at home then there are several public chargers dotted round my town at 40p/kwh (Chargeplace Scotland) which you can just pay and start/stop charging on their app easily. Up that to 70p/kwh if in need of a quick rapid charge (which I hope not to use).
It's been great so far. A real pleasure to drive, and so simple to operate. That instantaneous torque is great, although i'm happy just wafting about in silence. But while it suits me and my circumstances, that won't be the case for everyone.
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