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MG ZS EV MK2 - LFP (standard range) - Battery SOH Theory

So I just had a look at the document that came with my car, "Complete vehicles certificate of conformity" date or manufacturer of the vehicle is 10/30/21.

And I just checked battery today and it is 96.53%
 

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Wow it makes it look like LFP really suck my MNC with 5300 miles (8529km) is still 100%
"Make it look" are the operational words, when if fact it is the opposite. Your software lies to you when it still gives 100%, ours lies to us when it shows SOH drop every day.

I guess we need to bring this issue to MG's attention, so they can fix their software. Any chance you could have a word with them @Miles Roberts CG ?

@lusitano Your car doesn't have a sticker like this on the door frame?

October sounds like very long before you got it. Is that really the date your car rolled off the assembly line, or could that be the date the type was approved?
 

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@lusitano Your car doesn't have a sticker like this on the door frame?

October sounds like very long before you got it. Is that really the date your car rolled off the assembly line, or could that be the date the type was approved?
Mine is not like yours, I've removed my vin and identifier.
 

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Only just saw your attachment. The measured values line up perfectly with my prediction: 22/12/23 to 15/1/23 are 24 days. Calculated decline in SOH: 24 * 0.0104% = 0.25%. Actual decline in SOH: 96.82% - 96.57% = 0.25%.

I assume you set the day you go the car to 100%, but didn't actually check SOH back then?

My calculation would go: 96.57% is a loss of 3.43%, equal to 330 days of linear decline. I'd put the production day of you battery pack at 19/02/2022.

Do you have a sticker on the driver's side door of your car, with year and month on it? That's when it rolled out of the factory. Battery pack would have been made some days or weeks or even months before that.

@MoDolph Edited - took a little to understand that chart. So that's looking at decline in capacity for a battery stored at a given SOC. Great data, certainly supports my argument that even LFP should not be routinely charged to 100%. Surprised to see how well it supposedly worked being stored at very low SOCs, that's contrary to data I had seen before that saw quite some damage caused by SOC below 20%.

I agree, this will be interesting, hoping that a few people have data. @lusitano posted some data, and it seems to align very well with my predictions, despite taking place at a very different SOH, their car is already below 96%, while my analysis was around 99%.
Assuming I have my ZS much longer, being in Aus, what OBD / Software combo are you using?
 
Assuming I have my ZS much longer, being in Aus, what OBD / Software combo are you using?
If you have had yours longer it would be the Mk1, previous model with NMC battery. This discussion thread would not apply.

You can still read out information the same way.
For occasional use: ELM327 OBDII dongle that connects via Bluetooth with the eZS Android app
For constant monitoring: OVMS

Dongles are cheap on eBay, i.e.: Bluetooth OBD2 ELM327 Car Scanner IOS & Android Diagnostic Auto Scan Tool OBDII | eBay
Same at car stores, or from Jaycar will cost multiple times the price.

This is todays update, so far.
View attachment 14727

Like clockwork it ticks down in a straight line. 0.0104% a day. 3.8% a year.
 
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If you have had yours longer it would be the Mk1, previous model with NMC battery. This discussion thread would not apply.

You can still read out information the same way.
For occasional use: ELM327 OBDII dongle that connects via Bluetooth with the eZS Android app
For constant monitoring: OVMS

Dongles are cheap on eBay, i.e.: Bluetooth OBD2 ELM327 Car Scanner IOS & Android Diagnostic Auto Scan Tool OBDII | eBay
Same at car stores, or from Jaycar will cost multiple times the price.
Hi, what I meant is if I kept the ZS much longer - if you look through the menagerie of issues plaguing the ZS I picked up at the beginning of this year, it is looking like the car may become a reject. The car itself was manufactured September 22.
 
J'ai une théorie que j'aimerais tester.

La théorie est la suivante : dans le Mk2 ZS EV avec batterie LFP (gamme standard), l'état de santé de la batterie (SOH) signalé par la voiture est un fudge, qui n'est rien d'autre qu'un compte à rebours, qui a commencé à fonctionner lorsque la batterie pack a été fabriqué, et diminue linéairement avec le temps.

Ce compte à rebours est calibré pour s'assurer qu'il restera supérieur à 70 % pendant toute la durée de la période de garantie de 7 ans. La diminution du SOH déclaré est fixée à environ 3,8 % par an, ce qui, sur 7 ans, équivaudrait à 26,6 %. Soit 0,0104 % par jour.

Voici un tableau du SOH de ma voiture depuis que j'ai fait fonctionner OVMS, environ 1 semaine après avoir reçu la voiture. Les seules bosses sont lorsque les données n'ont pas été mises à jour pendant quelques jours. N'hésitez pas à tenir une règle contre le bas de la ligne pour voir à quel point elle est droite.

View attachment 14552


Jusqu'à présent, je n'ai que des données pour 2 voitures. Le mien et un autre. Pour ma voiture : la date de production de la voiture est connue, selon les informations du contrat : 28/8/2022. Si j'étends le tableau dans le passé, il atteindra 100 % le 18/8/2022 - tout à fait raisonnable d'avoir la batterie assemblée 10 jours avant que le véhicule ne quitte l'usine.

Ce serait formidable si certaines personnes ici pouvaient confirmer (ou réfuter) cette théorie. Veuillez poster SOH et la date de production comme réponses. Uniquement Mk2 ZS EV avec batterie LFP svp (gamme standard). Ou bien, si vous ne connaissez pas la date de production, lisez SOH à quelques jours d'intervalle et vérifiez si la baisse quotidienne est conforme à ce que je prédis.

Bien sûr, j'ai une explication. Je crois que les ingénieurs de MG ont trouvé trop difficile de mesurer le SOH. Et une réunion a eu lieu un peu comme ça (tous les faits ci-dessus, pure fiction ci-dessous):

Chef de produit : Avez-vous finalement réussi à mesurer le SOH des nouvelles batteries LFP ?
Ingénieur : Désolé, nous ne savons pas comment. La courbe de tension est tout simplement trop plate. Peut-être aurons-nous une bonne idée plus tard, ou cela deviendra plus facile à mesurer une fois qu'il y aura une dégradation importante.
Chef de produit : Mais les voitures entreront en production le mois prochain, et SOH fait partie des conditions de garantie. Nous devons remplir ce PID.
Ingénieur : Que diriez-vous de le régler à 100 % et une fois que nous aurons compris comment mesurer, nous appliquerons une mise à jour logicielle ?
Chef de produit : Personne ne croira qu'il reste à 100 %, si nous le faisons, au premier service, les gens découvriront que quelque chose ne va pas.
Ingénieur : Que diriez-vous d'une diminution linéaire dans le temps ?
Chef de produit : Cela ressemble à un plan, assurez-vous simplement qu'il reste au-dessus du seuil de garantie. Et assurez-vous de continuer à travailler dessus, afin que nous puissions faire cette mise à jour logicielle pour le réparer.
Hi, I totally agree with you.

I bought an MG 4 Standard with the 51kw battery recently.

I checked by chance his SOH view ABRP has recently integrated this information, and I am very disappointed I have 2.11% degradation for only two months of use and 4000km for an LFP battery.

I then decided to develop an application to obtain the most accurate information. I managed to extract this info, and like you I noticed that there is a loss of 0.01% every day. if I don't use the car for two days, on the 3rd day when I go to use it I will have -0.03%.

This story is really very strange, unless the formula for calculating the SOH on PID 22B061 is not correct!

The standard formula for calculating the SOH of a battery is (A*256+B)/100.

The 256 is the number of charges and discharges before the battery begins to degrade. I suppose perhaps that for an LFP this figure must be higher. As I have a new car and assuming my SOH is 100%, the formula should probably be (A*261+B)/100 and I get 99.81% SOH.

Since the last time, has the SOH continued to drop gradually 0.01/day for you? Or has it stabilized please?

Have you made any recent updates that stabilized the daily loss?
 
Hi,

the 256 is a fixed constant that comes from the way the numbers are extracted from the return value a query gets on the CAN bus. A and B are successive 8-bit values in a longer number. To look at it as one 16-bit number, (A*256+B) is the formula. Dividing by 100 creates 2 decimal digits.

The 0.01/day has held steady for every day, except that there was one anomaly: a few days after I got software updates applied to my car and had a full charge with balance, I noticed an increase in reported SOH. Since then it has declined again at the same rate.

I now assume the increase was caused by the only actual measurement of SHO that ever happened. And the steady decline is just an approximation in software in between. No idea how long until the next actual measurement.

In good news: the overall decline was slower than the car had projected. In bad news, the decline is still more than I had hoped for after about 7500km at that time.

Here's a chart from about 1 week after I got the car to now.

Cheers,

Peter
1682463241865.png
 
Hi,

the 256 is a fixed constant that comes from the way the numbers are extracted from the return value a query gets on the CAN bus. A and B are successive 8-bit values in a longer number. To look at it as one 16-bit number, (A*256+B) is the formula. Dividing by 100 creates 2 decimal digits.

The 0.01/day has held steady for every day, except that there was one anomaly: a few days after I got software updates applied to my car and had a full charge with balance, I noticed an increase in reported SOH. Since then it has declined again at the same rate.

I now assume the increase was caused by the only actual measurement of SHO that ever happened. And the steady decline is just an approximation in software in between. No idea how long until the next actual measurement.

In good news: the overall decline was slower than the car had projected. In bad news, the decline is still more than I had hoped for after about 7500km at that time.

Here's a chart from about 1 week after I got the car to now.

Cheers,

PeterView attachment 17136
Hi, thanks for your feedback

What updates did you get please?

BMS updates?

Or Infotainment Software Update?

I also had the right to an update of the CCU for the on-board charger in March 2023, the techenciens spotted the presence of another update of the BMS, but it did not succeed in applied.

Thank you very much for your return on especially for the explanation of the figure 256, I searched on the net without answer but it is the ChatGPT which provided me the famous answer that this figure is the number of charge and discharge before the battery begins to lose capacity. Like what we should not trust this artificial intelligence yet!

Now are you still on a loss of 0.01%/day? Or less?


Regards
 
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