Leaf 30kwh 2017, any opinion on those graphs?

[danelo]

We own the same leaf, 2016. It was still useful in warm weather @ 62% SOH but barely. In cold weather it was useless, turtle mode was instantly on. I successfully replaced the cells I got from VW ID.3.

It's not the SOH that worries me, but Hx. If it was driven hard, it might be overheated and degraded. Balance is only one indicator, but even poor cells can be balanced quite nicely. The problem is, when the cells are under load, their voltage difference rises as they have slightly different internal resistance, because they didn't age the same. (What a sentence 😓) Back pack gets overheated more, because cells are stacked one by another and can't cool as much. This difference in internal resistance is then the reason, that BMS (or LBC as Nissan calls it) limits the amount of power from the battery and eventually shuts it down. SOH shows the remaining capacity, but that capacity can't be used normally because of higher and uneven internal resistance. If you ask me, your state of battery is very poor.

I will give you an example:

This is the state of my first Leaf 30kWh before and after cells swap. You can notice, that the cells are well balanced on bad battery.
Also notice the SOH and Hx. Latter went from 28% to 94%. It could be 100%, but since cells are not original, their configuration is not 96S2P (96 serial with two in parallel) but 96S1P, so only 96 cells and not 192 as original has. I was aware of this and car works fine even in cold weather. Also the voltage difference could be smaller, if I took the effort of charging them within mV range. They will balance eventually...

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Now this is from my other leaf, which has overheated and almost exploded battery.

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This battery still has SOH @ 82%, but Hx is only 49%. Unfortunately this battery is almost dead.

So, how to test it? Plug in LeafSpy and go for a ride. Find a road which goes uphill and drive it there at least some 5 miles up. If your DASH SOC will be dropping quickly and you will get LeafSpy readings of 200mV or more, then this means that the battery is in poor health. By quickly I mean 1% every half mile or so. Then drive downhill and observe the DASH SOC. If it will be rising quickly (of course not as quick as by driving uphill), that is another confirmation of poor battery. See examples below.

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Please, keep in mind, that the SOH doesn't drop linearly and that it is impossible to exactly predict when the battery will die. But when it does, it costs some money or you car is worthless. It is strange with such a low mileage.

If you would pay say 3 or 4k for it and fix the battery for another 4k, then you could have a very nice car which could serve you long time.
But if you pay 7k and then another 8k for battery, then I don't know...

I hope this serves other potential buyers too. Wish you all the best.

So Lucky, how much did it cost you to get the battery in your 2016 back to good condition?

 

[Lucky]

A lot of useful information here.

Thank you 😊.

What I am getting from this thread is that Hx is very important if you live in an area that has a lot hills. Seems like Hx is almost a measure of how much hard work the battery can do. A slightly poor Hx number is probably not so much of an issue if you are in an area that is mostly flat.

So at what percent is Hx considered bad? Looks like around 50% is bad, but is 70% or 85% bad?

My test was carried out from 250m to 410m above sea level, so 160m of roughly 500ft of inclination, which is not very much. I suppose for city driving this would still be a good battery, EV is most efficient there anyway. But my country Slovenia, be it small, is very diverse and sometimes you just have to go uphill a bit. And there the problems start. My wife's Leaf (before repair, Hx 25% and SOH 58%) was still capable of reliably driving her to work and back about 20 miles on a nice sunny day. But that's hardly useful.
Hx in my mind is the percentage of available power for short duration at moderate temperature. I was thinking that real SOH would be multiplication of SOH and Hx, so in my case 82% x 49% would be around 40% of utilization rate, which of course isn't exactly the case, but looks quite realistic.
Anyway, if I would be a buyer of an used Leaf, I wouldn't buy it without LeafSpy and some testing. Anything below 90% SOH and say 80% Hx would raise my doubts. Of course, there are use cases where it can serve you for a long time even with poor battery (commuting and city driving) if you are gentile.

Many people still think, that 80% SOH battery will take you 80% of the initial mileage, but reality is completely different. And these people can benefit the most from this information and save them selves some serious headache and money loss. Previous owner of this car paid 13.500€ for it plus 700€ for opening the battery after he got stranded. Dealer offered new battery for around 17.000€ which he refused. At the end I bought it for 3.500€ + 150€ towing to my house. He lost 10.700€ in two months.

Any comments are welcome.

 

[Lucky]

So Lucky, how much did it cost you to get the battery in your 2016 back to good condition?

Batteries cost me 2,300€, but the amount of labor was huge, mostly because MEB packs are really hard to disassemble safely. It would take less time now but I don't know if I would do it again. The biggest and messiest problem is to detach (de-glue) the cells without damaging them (and causing an explosion). Add about some 200€ for cables, glues and other tiny stuff, so around 2,500€. I managed to sell the used cells for 750€.

 

[shmandi]

So the batteries on photo are from ID3 and you installed them to Nissan Leaf?

 

[Lucky]

Yea, but it was a pain to connect them with those thin tabs.

 

[BlueLectroid]

Here is LeafSpy screenshot from 2016 Leaf with worse parameters but pretty well balanced cells and no difficulties going up 400-800m hills in warmer climate (40°C last week). So how to separate conjecture from science?

 

[chk]

Well the SoH is the estimated maximum capacity of the battery packs.

If the Hx is the conductivity, this means the lower it is the more problems you will get when the battery is stressed by driving uphill or accelerating fast.

Due to a cell swap (one module, #24), our Hx was reduced from about 91 to 88.8, and the SoH decreased from 90.6% to 85.4% from jan 2023 to jan 2024 - thus a bit less range left. But I think there's no way Nissan support will accept that drop as indication to find a better replacement. The replacement service itself took over 5 months until a module was found... Actually, the new module is "too new" and does not fit into the others (https://photos.app.goo.gl/GUubnk7zYnakYREj8 is from jan this year). But there's no noticable problem at the moment, as the car is only used in the city or near surroundings, relatively flat environment.

The higher the resistance is, the more the cell voltage drops (∆U = ∆R * I) and the lost energy heats up the battery.

So if a car with good SoH but bad Hx might be OK in respective conditions, what "bad" means depends on your driving style and environment (hills, temperature)

Edit: sorry, confused current with old values...!

 

[chk]

Want to add the "current" chart of Sep 22 2024: Hx decreased to 79,8%, and SoH to 84.6%. The car is charging at that time, so the new module (with more capacity) is not filled as much as the older ones, resulting in lower voltage.

 

[nlspace]

@chk , Seems to be overcharging the cells--greater than 4.2 and not indicating 100% SoC..? i wouldn't charge that high unless it was necessary for the daily commute.

 

[ACDCPhilip]

Keep an eye on that 12v battery.
Looking at your Leafspy screen shot it's showing only 11.68v.

I would put it on a trickle charge for a day or two, then keep a close eye on the voltage over the next few weeks.

 

[chk]

Good catch - thanks a lot! The lead acid battery is 18 months old only - and the car is charging, so 11.68V ist way too low. I need to keep an eye on that one... I always do PV surplus charging, whatever the PV modules offer from 1.5 to 4.6 kW Nearly no QC any more (once only in the last 2 years). Seems I need to install my 12V watcher box to be notified of problems (small ESP microcontroller waking up every 30 minutes to post the current voltage to my server).

Re overcharging: I intentionally did charge to 100%, although I do that rarely, but I wanted to examine the data with fully charged car. Experimenting. Usually I restrict it to 80% max.

Same 100% procedure yesterday, and look at that chart after having nearly 100% (driving, but with little or no used energy). Perfectly balanced. Unless - the second screenshot was taken 2 minutes earlier - the car is accelerating, and the new module shows itself. But no Hx problem shown, Delta V is acceptable I guess (moderate acceleration).

 

[chk]

@chk , Seems to be overcharging the cells--greater than 4.2 and not indicating 100% SoC..? i wouldn't charge that high unless it was necessary for the daily commute.

Ok, and BTW it was in the region the Leaf itself reduces the charging current asymptotically to find out the 100% mark, so I guess 4.2 is quite normal to find the limit. Due to my "better" module, the BMS might have some problems with the imbalance of qualities, I don't know. Have to rely on Nissan.

 

[nlspace]

the car is accelerating, and the new module shows itself.

That's a nice graph showing how the older cells sag under load whereas the new module holds stiff. Was that at WOT--Do you know the power or current draw during that acceleration?

 

[chk]

Sorry, wot is "WOT"?
But no, it was a little more than 2 segments (I looked at the instrument) but don't know how much that is.

 

[Drew21]

WOT = "full beans," "pedal to the metal," or "Wide Open Throttle" if you're a bit more mature than I am.

 

[chk]

In this case we're STP ("stroking the pedal").

 

[Jerther]

About the low voltage on the 12v battery, IIRC (sorry I really tried my best but I couldn't find the post) it's been suggested somewhere here to remove a fuse to force the car to always maintain full charge on it. Maybe someone can chime in on that, and maybe add some details, pros and cons of doing so?