PV1
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Re: Is my battery dying ?

Tue Oct 23, 2018 5:31 am

kiev wrote:i suspect the cell may have been okay since it didn't act like as weak or failed cells as in your case (the quick rise to the top voltage during charging)--my guess was that something on the CMU board failed and was always discharging that cell. Over time the voltage difference kept getting larger until a "full" charge was showing less than 8 bars.

That's what happened to my car a few years ago. The affected cell was consistently lower in voltage than the others (and dropping by the day), but it wasn't showing signs of being weak, as during heavy acceleration or regen, it would drop or rise the same as the other cells. In my case, pack SoC followed the weak cell down. It didn't show any real signs of internal short, either. None of the temperature sensors were reading high and it drove totally fine despite the reduced range.

As for the charge cutoff on level 1 or 2, I forget what the number was. The car ramps down charging as the highest cell(s) reach(es) 4.105 volts to hold them at that voltage. However, if a cell sits at 4.11 volts and doesn't come back down while the charger ramps down, then the car will stop charging. Whatever the SoC is at that moment is what the car considers "full" as far as charging goes. This is what prevents the car from reaching 100% charge.

In my case, with a lower but otherwise apparently healthy cell, the other cells in the pack all reached 4.105 volts, and the charger ramped down to avoid overcharging them. At some point, the cells wanted to go higher in voltage, which the car stopped by ending the charge. Day 1 of the failure, this was at 76% charge. In my case, SoC of the entire pack followed the low cell. Since it couldn't reach 4.105 volts without over-charging the other cells, it never reached 100%. SoC followed the cell down to a total range of about 15 miles by the time I took the car to the dealer.

kiev wrote:i think you do have some truly bad or weak cells, but they are manifesting as reduced range or capacity degradation, and not the "lack of reaching full" on the fuel gauge. But it seems that those 2 cells would be getting over-charged if they were held high while waiting for the others to catch up?

If their internal resistance is high, they would be slower at absorbing the charge. With terminal voltage being held constant, the resistance of the weak cells is limiting charge current for the whole pack. The pack will only charge as fast as the slowest cell can absorb a charge. They would only be over-charged if the car didn't limit per-cell terminal voltage (eg. if the car would ignore the weak cells and try to QC at 361 pack volts).
:idea: :idea: :idea: :!: :!:

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Thanks.

DBMandrake
Posts: 170
Joined: Mon Mar 20, 2017 4:57 am
Location: Scotland

Re: Is my battery dying ?

Tue Oct 23, 2018 7:23 am

Luddite wrote:
DBMandrake wrote:Time for an update on the dying cells situation.



So I've made the decision that I may have to do a cell swap of cells 25, 69 and 70 myself and am currently in the process of sourcing some cells and trying to talk my other half into the idea that I actually need to buy them even though the car is still currently driving! :lol:


I'm planning to get four cells, swap 25, 69 and 70, and keep one "new" one as a spare for the future.


Any luck on the sourcing of cells?

Still working on it.
I have an ion the same age as yours. Mine only has 35k on the clock and I haven't yet read any values from canion but eventually a few cells will need replacing.

Not necessarily.

Individual cells going bad while statistically possible isn't inevitable. If you only get gradual even degradation of all cells then a few spare cells won't do you any good. It's only in the case where most of your cells are OK and there are one or a few bad cells would replacement cells be beneficial. And the replacement cells need to have an equal or higher Ah capacity than the existing cells in the pack to ensure that you regain the full potential capacity of the good cells.

So I'd check the health of your battery with Canion before committing to buying any cells, especially when the actual replacement process is somewhat challenging. (Mainly physically getting the pack out of the car so you can work on it) You also need a special battery charger/discharger/tester to test second hand cells to see that they are OK and confirm their usable capacity, and then discharge them to the correct voltage (about 3.7 volts) for storage until they're needed. If you were to leave them fully charged in storage you would lose significant lifetime of the cells just while they're sitting on the shelf. They're also extremely dangerous in the case of short circuits so you'd need a cool safe place to store them.

In Canion you want to check the Ah figure of the pack as a whole, and to check the capacity balance of the cells Level 2 charge to 100%, ensure all cells are within 10mV then drive the car down to 10-20% then check the voltage balance as I did earlier in the thread. If there are no obvious outliers like the two I see, you have nothing to worry about.
- Simon

EV: 2011 Peugeot Ion
ICE: 1997 Citroen Xantia V6

DBMandrake
Posts: 170
Joined: Mon Mar 20, 2017 4:57 am
Location: Scotland

Re: Is my battery dying ?

Tue Oct 30, 2018 7:27 am

Luddite wrote:Any luck on the sourcing of cells? I have an ion the same age as yours. Mine only has 35k on the clock and I haven't yet read any values from canion but eventually a few cells will need replacing.

A bit of a setback on the cell front.

I have been dealing with a guy in Holland who buys EV packs from scrapped cars and sells them for second life use. He has had a few i-Miev packs through recently. Including a 2013 model with much lower mileage than my car.

Unfortunately when he tested 4 of the cells for me their remaining capacity was only 28Ah. I can only assume that the cells have been poorly treated from the time the car was put off the road until he bought the pack - possibly left at full charge in warm weather. :( At least he tested them for me first rather than me testing them after buying them and finding they were no good.

I now have some doubts about the likely-hood of finding second hand LEV50 cells with sufficient remaining capacity (>39Ah) so I have a question for the experts more experienced with these cars and cells than me.

Would it be acceptable to substitute a few LEV50N cells into an earlier car with LEV50 cells such as mine ? Obviously the cycle life should be dramatically better than the older cells so that as the new hybrid pack continues to degrade those replacement cells would lose capacity much slower than the rest, but I don't think this would cause any problems, in the way that a few weak cells will ?

Of course if other properties like the voltage discharge curve, internal resistance etc are significantly different the BMS may not be happy with the substitute cells... but I don't know enough about the charge/discharge properties of the cells to know how compatible they are in operation and whether they would make the BMS happy or unhappy. Would the BMS just see them as "unusually good" cells among a large number of weaker cells ? Or do the new cells have some disadvantages compared to the older ones ?

Does anyone know or has anyone tried this ? LEV50N cells may be the only ones that will be found second hand still with a useful capacity remaining.
- Simon

EV: 2011 Peugeot Ion
ICE: 1997 Citroen Xantia V6

kiev
Posts: 970
Joined: Sun May 03, 2015 7:15 am
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Re: Is my battery dying ?

Tue Oct 30, 2018 12:29 pm

DBMandrake wrote:...
Would it be acceptable to substitute a few LEV50N cells into an earlier car with LEV50 cells such as mine ?
...
Does anyone know or has anyone tried this ? LEV50N cells may be the only ones that will be found second hand still with a useful capacity remaining.


i haven't done this yet, but i wouldn't hesitate to use LEV50N over the old cells, depending upon the measured available capacity (bench testing). Obviously if the 50N is worn out then there is no benefit, but otherwise newer is better when it comes to batteries and cells. Once the electrolyte gets added and the chemical reactions start, then the life-time clock is ticking and the cell starts to degrade, and there is no stopping it...

With regards to the low capacity of the older cell, i would suggest doing several or 5 charge-discharge cycles to measure the capacity. There are many accounts on other forums of folks getting neglected cells to somewhat revive after several cycles. So it may be worth another look if some 50N's are not available.
kiev = kenny's innovative electric vehicle

DBMandrake
Posts: 170
Joined: Mon Mar 20, 2017 4:57 am
Location: Scotland

Re: Is my battery dying ?

Fri Nov 02, 2018 6:14 am

kiev wrote:i haven't done this yet, but i wouldn't hesitate to use LEV50N over the old cells, depending upon the measured available capacity (bench testing). Obviously if the 50N is worn out then there is no benefit, but otherwise newer is better when it comes to batteries and cells. Once the electrolyte gets added and the chemical reactions start, then the life-time clock is ticking and the cell starts to degrade, and there is no stopping it...

Second hand LEV50N cells are going to be newer than second hand LEV50 cells, since they stopped using the latter in mid 2012. So any second hand LEV50's you get hold of will be at least 6 years old now, which is a lot of calendar age degradation, especially if they have sat at a high SoC.

So LEV50's not only degrade much slower (in theory) they will also be younger. Obviously any replacement cells would need to be equal or greater capacity than the remaining cells in the pack to get any tangible improvement, which is why cells with only 28Ah remaining are no use to me.

Getting LEV50N with plenty of usable capacity left seems quite likely but LEV50 now seems a bit unlikely unless you got a low mileage car that had been cared for. (Not left on 100% charge for example)

LEV50N's having a lower degradation rate than the rest of the pack wouldn't pose a problem I think - the BMS should be OK with a few cells that seem to be degrading slower than the rest as they won't limit the usable capacity of the pack, and the balancing system in this car is fairly strong. (Compared to a Leaf with very weak bleeders)

The question is, how do the LEV50N's perform dynamically under load and rapid charging. If their performance in every parameter is at least as good as the old cells, there shouldn't be a problem. But you also have to consider factors like how fast can they be charged at cold temperatures etc... as these assumptions are all programmed into the BMS to keep the cells in a safe operating area. There would be a risk if any particular parameter was worse than the old cells, such as ability to charge at high/low temperatures.
With regards to the low capacity of the older cell, i would suggest doing several or 5 charge-discharge cycles to measure the capacity. There are many accounts on other forums of folks getting neglected cells to somewhat revive after several cycles. So it may be worth another look if some 50N's are not available.

The guy supplying the cells knows what he's doing, he breaks a lot of packs including Tesla packs and he used a professional high power charger/discharger/tester which did 3 full charge/discharge cycles on the 4 cells that were earmarked for me, and after 3 complete cycles the average capacity of the 4 cells was still only 28Ah.

I suppose it's possible that one weak cell was dragging the other three down, since they were tested in parallel, (testing them individually one at a time would have taken far too long for these size cells) but even if that's the case I'd still be dubious of the long term reliability of the other 3 since they were coming from the same 4 cell group in the pack.

By testing them and letting me know they didn't have the capacity I was looking for he was doing himself out of the sale, so I have no reason to disbelieve the result of the test. (I also have a suitable charger/discharger/capacity tester which I would have done my own testing of the cells individually after getting them to verify their performance then store them at 3.7 volts) He says he gets i-Miev/C-Zero/Ion packs a few times a year so I'll just have to watch his stock and try again when he gets another pack in.
- Simon

EV: 2011 Peugeot Ion
ICE: 1997 Citroen Xantia V6

DBMandrake
Posts: 170
Joined: Mon Mar 20, 2017 4:57 am
Location: Scotland

Re: Is my battery dying ?

Sat Apr 13, 2019 12:41 pm

Thought I'd post an update on the weak cell situation. The car is now up to 51k miles and there has been one further "sudden" drop in Ah capacity, followed by a "normal" steady decline. Ah capacity is now 35.1Ah:

Image

Cell voltage difference at 20% SoC has increased from 80mV to about 125mV, although that may be partly due to cold weather.

Range seems noticeably reduced since before the first big drop in Ah at 38k miles - I now get about 55 miles (mixed cycle) in summer weather without the heater and about 38 miles in winter with the heater. (Near/below freezing conditions) When I first had the car at 39.9Ah I was getting around 63 miles in summer and 43 miles in winter respectively, so I've lost about 8 summer miles and 5 winter miles of range altogether. My 35 mile daily commute in winter is now very tight, with me regularly arriving home with 2 or less bars even turning the heater off the last 5 miles or so.

The range reduction I can cope with as there is a rapid charger on the way home, however another symptom of the weak cells is much slower rapid charging and early tapering of rapid charging due to high internal resistance in two cells - 25 and 70, as shown in my previous cell voltage snapshots.

Even with cell temperatures of around 20C, if I plug the car into a rapid at 20% SoC, it will start at 43kW but start throttling down before 30% SoC. Cells 25 and 70 are reaching 4.105 volts under rapid charging while nearly all the other cells are still at 4.085 volts or less. This causes premature throttling of the charge rate to keep the high resistance cells from going over voltage.

By 50% SoC the charge rate is already down to about 16kW and falling rapidly so getting to 80% takes an eternity. When I first had the car I could charge from nothing to 80% in summer in 20 minutes. Now even charging from 30% to 80% takes about 30 minutes, with the last 20% or so up to 80% being painfully slow. Also quite often the rapid charge will stop at around 73% instead of the normal 82%.

Another possibly related symptom of high cell resistance is that in cold weather the car seems to get confused about the SoC before/after a rapid charge. For example I'll arrive at a rapid charger with 30% SoC reported in Canion, but the moment I plug it in and start a rapid charge session the reported SoC will drop to say 15%. (And the bars drop on the dashboard as well) Then the rapid charge will terminate "early" at say 72%, but if I attempt to re-start another charging session it will suddenly jump to 82%.

It may be my imagination but regenerative braking doesn't seem as strong as it used to be, even in the unlocked B mode - which used to have a very strong action before, now B mode doesn't seem that much stronger than D mode. Since regeneration is just rapid charging, I suspect the same issue of high resistance cells is restricting the amount the car can regen.

So not ideal. :( The car is still perfectly driveable but I think once I've finished paying it off (under 2 years left now) I'll move it on and use the proceeds to buy something a bit better. Demand outstrips supply in the UK so it should be easy to sell, the problem is finding what to replace it with as the EV market in the UK is now a sellers market...

There are other reasons too - for example I've noticed there is a lot of corrosion on the underbody and chassis inside the "engine bay" area, including where the springs attach, on brake lines etc.

I had read that these cars are not rust proofed to UK salt road standards and, well, that seems to be borne out. :( My 21 year old Citroen Xantia V6 which has done 90k miles has far less underbody rust than this 8 year old 51k Ion. :shock:
- Simon

EV: 2011 Peugeot Ion
ICE: 1997 Citroen Xantia V6

DBMandrake
Posts: 170
Joined: Mon Mar 20, 2017 4:57 am
Location: Scotland

Re: Is my battery dying ?

Sun Apr 14, 2019 7:36 am

Argh, spoke too soon. Checked today and I have had another sudden 1Ah drop in capacity. It's now at 34.1Ah at 51724 miles. So I've lost almost 6Ah in two years and under 25k miles. Not very impressed at all as SoH is now at about 74%.
- Simon

EV: 2011 Peugeot Ion
ICE: 1997 Citroen Xantia V6

Gary12345
Posts: 42
Joined: Tue Feb 12, 2019 4:15 am
Location: Essex, UK

Re: Is my battery dying ?

Tue Apr 16, 2019 6:10 am

I wouldn't see any issue using LEV50N as a replacement for LEV50 if that is what you can find. Testing the replacement cells first is a must though as its quite a bit of work taking the pack out. Testing can be done with a fairly high power RC charger, or any decent RC charger and a separate battery discharger.

I'm still waiting for an 8-pack of cells to arrive, most likely will take a couple more weeks. Once they arrive i'll test them to see what the Ah is, if any good i'll keep a few for replacements in my i-miev and sell the rest.

Thanks,

Gary.

DBMandrake
Posts: 170
Joined: Mon Mar 20, 2017 4:57 am
Location: Scotland

Re: Is my battery dying ?

Tue Apr 16, 2019 6:51 am

Gary12345 wrote:I wouldn't see any issue using LEV50N as a replacement for LEV50 if that is what you can find.

I'm on the fence about that. If I was in a situation where a cell had failed and it was the only choice to get the car back on the road, then yes I'd try it. If the cell swap is "elective" to try to improve the usable capacity of a car that is still working mostly OK I'd be a bit more hesitant.
Testing the replacement cells first is a must though as its quite a bit of work taking the pack out. Testing can be done with a fairly high power RC charger, or any decent RC charger and a separate battery discharger.

I have a SkyRC B6AC V2 which can do a discharge capacity test up to 50Ah - however with a maximum discharge power of 5 watts you're looking at a day or two to test a single cell... :mrgreen:
I'm still waiting for an 8-pack of cells to arrive, most likely will take a couple more weeks. Once they arrive i'll test them to see what the Ah is, if any good i'll keep a few for replacements in my i-miev and sell the rest.

Good luck on the cells and I'll be interested to hear what capacity you measure. I approached a seller in Holland for 4 cells last year but when he tested them they only measured 28Ah so the purchase was cancelled. What voltage are you planning to discharge them to when testing their capacity ?

The car charges them up to 4.1 volts and only discharges them to about 3.6 volts - most discharge tests will discharge them much lower (about 3.0 volts) which may inflate the usable Ah capacity figure a bit compared to what you'll really get in the car.

I'd be confident working on the pack once it's out of the car to do a cell swap - I have an electronics background as well as having plenty of experience in fairly substantial car repairs, however for me the issue is I don't have access to a 2 post hoist and trolley to get the pack out of the car safely.

So I'd have to hire access to one from a garage and then have to work in a hurry in someone else's commercial workshop. If I was doing a cell swap I'd rather take my time and work on it at my leisure over 2-3 days.

So while it's tempting I can't see myself doing it unless I end up in a situation where the bad cells get so bad that the car isn't usable. At most replacing the weak cells may get me back up to around 38Ah. Fixing the slow rapid charging it has now would be a worthwhile side effect though.
- Simon

EV: 2011 Peugeot Ion
ICE: 1997 Citroen Xantia V6

Gary12345
Posts: 42
Joined: Tue Feb 12, 2019 4:15 am
Location: Essex, UK

Re: Is my battery dying ?

Thu Apr 18, 2019 2:39 pm

DBMandrake wrote:What voltage are you planning to discharge them to when testing their capacity ?

I will charge to 4.1v and then discharge to 3v. The Yuasa spec sheets show that they test between 2.75-4.1v but there is very little below 3v. That should give me a good idea if the cells are usable in a car.

DBMandrake wrote:I don't have access to a 2 post hoist and trolley to get the pack out of the car safely.

I removed, fixed and replaced my battery pack on the drive without a hoist - its fairly involved but its definitely doable - I had the car up on 3 concrete blocks (the 4" thick ones) under the wheels so the whole car was 12" up, removed the big orange fuse then the thick orange cables, then bolted trolley wheels on a wooden pallet, put this under the car, used 2 trolley jacks with 2x4" on top jacked up underneath the front and back of the pack, then undid the pack bolts and electrical connectors and carefully lowered the jacks with the wood and battery pack on top down onto the wooden pallet, then slid the battery pack out.

I have purposely not described in detail where the fuse and orange cables are, because you need to have researched how to do this part safely - the mitsubishi battery pack removal guide is online and has the relevant safety steps which MUST be followed.

Thanks.

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