Battery degradation

[D0bbie]

As posted on another thread, using the Thai app has shown that over the last 3 months, the SOH of my ZS EV has worryingly dropped from 99.5% to 96.34%.

Today I also took it out for a drive consisting of 137.5 miles at 3.9 kw which took the battery down to showing as 10% when plugged back in to charge, which I work out as a battery capacity of 39.17kwh (Hopefully someone will confirm or correct the maths on that!).

For info, I've done just over 21k miles.

After a full overnight charge and balance, Car Scanner showed the attached info. To the untrained eye it doesn't look like anything untoward is going on fuel cell wise that would explain the relatively sudden drop in SOH?

I'd be grateful if someone with a more trained eye could take a look. Cheers.

 

[Paulie68]

As posted on another thread, using the Thai app has shown that over the last 3 months, the SOH of my ZS EV has worryingly dropped from 99.5% to 96.34%.

Today I also took it out for a drive consisting of 137.5 miles at 3.9 kw which took the battery down to showing as 10% when plugged back in to charge, which I work out as a battery capacity of 39.17kwh (Hopefully someone will confirm or correct the maths on that!).

For info, I've done just over 21k miles.

After a full overnight charge and balance, Car Scanner showed the attached info. To the untrained eye it doesn't look like anything untoward is going on fuel cell wise that would explain the relatively sudden drop in SOH?

I'd be grateful if someone with a more trained eye could take a look. Cheers.

How often are you rapid charging?

 

[D0bbie]

How often are you rapid charging?

Rarely. Once a month on average, probably.

 

[macd2401]

A fully charged cell should be well over 4.2V. Have you had the updated BMS? 4.16 is a bit lower than I'd expect from a fully charged cell on the original BMS.

 

[D0bbie]

I've got the January BMS update after previously having the October one.

 

[aleks57]

in February there was an update in which all bugs were fixed, this is a different machine compared to the October version.

 

[D0bbie]

I've just put the car in the garage and it's now dropped to 96.07%.

 

[Gomev]

As posted on another thread, using the Thai app has shown that over the last 3 months, the SOH of my ZS EV has worryingly dropped from 99.5% to 96.34%.

Today I also took it out for a drive consisting of 137.5 miles at 3.9 kw which took the battery down to showing as 10% when plugged back in to charge, which I work out as a battery capacity of 39.17kwh (Hopefully someone will confirm or correct the maths on that!).

For info, I've done just over 21k miles.

After a full overnight charge and balance, Car Scanner showed the attached info. To the untrained eye it doesn't look like anything untoward is going on fuel cell wise that would explain the relatively sudden drop in SOH?

I'd be grateful if someone with a more trained eye could take a look. Cheers.

Your figures look remarkably similar to mine across the board, apart from the SOH. Even that cell unit 6 is consistently fractionally lower than the others on mine too.

 

[JodyS21]

As posted on another thread, using the Thai app has shown that over the last 3 months, the SOH of my ZS EV has worryingly dropped from 99.5% to 96.34%.

Today I also took it out for a drive consisting of 137.5 miles at 3.9 kw which took the battery down to showing as 10% when plugged back in to charge, which I work out as a battery capacity of 39.17kwh (Hopefully someone will confirm or correct the maths on that!).

I've not seen that Battery Resistance figure before 3332.5 Ohm, very interesting.

Could it be using this to calculate the SoH????

Your figures look remarkably similar to mine across the board, apart from the SOH. Even that cell unit 6 is consistently fractionally lower than the others on mine too.

Need some other peoples Battery Resistance figures

 

[Deleted member 2439]

Er, what exactly is battery resistance? I’m intrigued - as 3000 ohms is actually quite high in the world of battery (internal) resistance- which I would expect to be in the fractions of an ohm realm. Perhaps it’s micro ohms, that would be more likely.

 

[Kithmo]

Er, what exactly is battery resistance? I’m intrigued - as 3000 ohms is actually quite high in the world of battery (internal) resistance- which I would expect to be in the fractions of an ohm realm. Perhaps it’s micro ohms, that would be more likely.

Not sure on Lithium batteries but on the old 12v wet cells, the resistance went up as the battery charge went up, this is why the ammeter used to go full tilt when you first attached the (flat) battery to the charger (low resistance) then gradually drop off to almost zero when it was fully charged (high resistance).

 

[aleks57]

the internal resistance of the current source is an order of magnitude greater than the resistance of the external circuit. (theoretical foundations of electrical engineering).

 

[Paulie68]

A fully charged cell should be well over 4.2V. Have you had the updated BMS? 4.16 is a bit lower than I'd expect from a fully charged cell on the original BMS.

No! A fully charged cell on the latest BMS software should be at 4.16V. Over 4.2V shortens the life considerably, this is why the pack voltage was dropped to 449V with the latest update.

 

[macd2401]

No! A fully charged cell on the latest BMS software should be at 4.16V. Over 4.2V shortens the life considerably, this is why the pack voltage was dropped to 449V with the latest update.

That's why I asked if the op was running the new BMS.

 

[Kithmo]

No! A fully charged cell on the latest BMS software should be at 4.16V. Over 4.2V shortens the life considerably, this is why the pack voltage was dropped to 449V with the latest update.

On the old BMS, fully charged and balanced, mine reads:
min cell voltage 14.196V, max cell voltage 14.232V.
HV battery voltage is 456.25V. SOC says 97% on the app.
The variation in cell voltage has always been around, or just over, 30mV.

 

[Gomev]

On the old BMS, fully charged and balanced, mine reads:
min cell voltage 14.196V, max cell voltage 14.232V.
HV battery voltage is 456.25V. SOC says 97% on the app.
The variation in cell voltage has always been around, or just over, 30mV.

On the new BMS, fully charged and balanced, mine reads:
min cell voltage 4.15/4.16, max cell voltage 4.17.
HV battery voltage is 449.5V. SOC says 93.1% on the app.
The variation in cell voltage has always been around 20mV (well at least since I got it back to full fighting fitness).

 

[JodyS21]

No! A fully charged cell on the latest BMS software should be at 4.16V. Over 4.2V shortens the life considerably, this is why the pack voltage was dropped to 449V with the latest update.

450V divided by 108 cells = 4.1667v

4.2V X 108 cells would give a total of 453.6V

So previous BMS with a total voltage of 459V would average 4.25V per cell.

I think the exact ideal max voltage depends slightly on the chemistry/make up of the lithium based cell, it's not always 4.2V (I initially thought it was before reading lots).

 

[D0bbie]

That's why I asked if the op was running the new BMS.

Yes, I'm on the new BMS.

 

[D0bbie]

Yes, I'm on the new BMS.

Now down to 95.84% overnight.

 

[Gomev]

Now down to 95.84% overnight.

This is most peculiar. From your earlier post all your cell banks appear in good order so why is the SoH going down.
Is it possible this is a faulty sensor as everything else looks so in order ?

Could you try with another app and see what that says ?
I use one called Car Scanner ELM OBD2 on android Play store (developer is 0vZ) I have found this to be much more reliable maintaining connection for me.