Battery balancing

[JodyS21]

I’ve heard this as well but not sure where. Do you know where I can get the official information?

You’ll never be given this information officially by MG.
The real battery % data can be obtained via the OBD2 port. From this, with the new BMS it can be seen that when the car tells you it is 100% charged, it is in fact 93-94%. With the old BMS it’s more like 96-97% for real when the car tells you it’s 100%.

 

[Ender]

I just chrged the car and balanced the battery by restarting the charging when ik was already full and connected the ODB2 reader. Attached the results.

Some questions notes:

Unit one shows a battary voltage difference of 0,7 volts.. even though the SOH is 100%

Soc is at 97%

Last maintenance was in july this year.. is the BMS update for all country's?

Max voltage is at 4,23.

 

[Gomev]

I just chrged the car and balanced the battery by restarting the charging when ik was already full and connected the ODB2 reader. Attached the results.

Some questions notes:

Unit one shows a battary voltage difference of 0,7 volts.. even though the SOH is 100%

Soc is at 97%

Last maintenance was in july this year.. is the BMS update for all country's?

Max voltage is at 4,23.

That looks like it was still balancing, not completed, as the EV power is displaying 0.4kW

 

[Ender]

That looks like it was still balancing, not completed, as the EV power is displaying 0.4kW

No it was already finished. Thatvusage is duebto the fact that you have to turn on the car to get the SOH value. Without it being turned on the main relais disconnects the HV battery.

 

[Lovemyev]

No it was already finished. Thatvusage is duebto the fact that you have to turn on the car to get the SOH value. Without it being turned on the main relais disconnects the HV battery.

Did you have your foot “OFF” the footbrake when you booted up the car ?. Just a thought ?.

 

[Coulomb]

That looks like it was still balancing, not completed, as the EV power is displaying 0.4kW

It's positive current (hopefully the sign is displayed correctly) which seems to mean discharging the battery. I would have used the convention that discharging the battery is negative current, but I don't get to decide things like that.

 

[Ender]

Did you have your foot “OFF” the footbrake when you booted up the car ?. Just a thought ?.

No, I started it up with foot on the brake. Left it in parking mode, all ascesoires off.

I guess i should turn it on without my foot on the brake?

 

[Coulomb]

I guess i should turn it on without my foot on the brake?

That's the best way to read the fully charged voltage, yes. That way there is zero load on the traction battery. It should still be possible to read data such as state of health, state of charge, etc.

 

[JodyS21]

I just chrged the car and balanced the battery by restarting the charging when ik was already full and connected the ODB2 reader. Attached the results.

Some questions notes:

Unit one shows a battary voltage difference of 0,7 volts.. even though the SOH is 100%

Soc is at 97%

Last maintenance was in july this year.. is the BMS update for all country's?

Max voltage is at 4,23.

The balance process takes place automatically once the car is fully charged (on AC).
You DO NOT restart the charge process once it is fully charged to initiate the balance process.
The car will not initiate a balance process unless it is when it is plugged in the current state of charge is something like <95%.

When you take the readings, start the car without the brake pedal pressed, then the HV battery is not connected and ensures the car is under no load, then you get a good reading (battery power will not be 0.4kwh)

Your car is not well balanced if your min and max voltages are 0.07 different (4.17 - 4.24). When balanced it’s more like 0.02 difference.

If you can use another app you’ll get more data. There’s 2 SOC - the real & the displayed one, you’ll get the total volts too etc.

 

[Lobogris]

I just chrged the car and balanced the battery by restarting the charging when ik was already full and connected the ODB2 reader. Attached the results.

Some questions notes:

Unit one shows a battary voltage difference of 0,7 volts.. even though the SOH is 100%

Soc is at 97%

Last maintenance was in july this year.. is the BMS update for all country's?

Max voltage is at 4,23.

Which app are you using?

 

[Lobogris]

You’ll never be given this information officially by MG.
The real battery % data can be obtained via the OBD2 port. From this, with the new BMS it can be seen that when the car tells you it is 100% charged, it is in fact 93-94%. With the old BMS it’s more like 96-97% for real when the car tells you it’s 100%.

Mine always shows 92.3% on OBD when the car shows it as 100% charged.

 

[JodyS21]

Mine always shows 92.3% on OBD when the car shows it as 100% charged.

This is the range of real SoC% I've had previously at "100% charged".

 

[rbpasapera]

I’ve heard this as well but not sure where. Do you know where I can get the official information?

If you connect an OBD2 bluetooth scanner to the car port, you can get this kind of information (state of charge, state of health, battery temperature, etc.) using an app like Car Scanner or Torque.

 

[Spinynorman]

I’m sure you’ve all been asked before but as you know not all ODB II units are created equal: which units do you guys recommend?

 

[profdraper]

So, what happens if the battery balancing is interrupted & stopped before it finishes?

Personally, I woould prefer to be able to regularly charge my car to 100% (clearly, like so many other owners do) - but without committing the (~90min) extra time to likely unnecessary balancing. That could be done every six weeks of so as per MG guidelines.

Recently, scheduling charging up overnight regulary (home 7kw) & then the auto battery balance - seems to be reducing my range slightly. Coulld be a coincidence I guess, with slighlty colder weather now in Australia, but still, had not seen this degradation before now.

 

[Lovemyev]

So, what happens if the battery balancing is interrupted & stopped before it finishes?

It’s just viewed as an incomplete balance really.
HV batteries ? that where badly affected by a software bug on some ZS EV’s required the BMS update to correct the problem,
The packs a had suffered badly from being out of balance as a result of this issue.
Owners where advised to use A/C charging until the battery had recovered.
Depending how badly your pack had affected, this could take many many cycles to recover.
My first balance after the update had taken 10 hours !.
And this was a common factor.
Slowly over time the balance cycle would slowly reduce as the battery recovered.
There is a time limit of around 12 hours, if I remember correctly.
If it reaches this point, the balance cycle will just quit and will try again the next time it will be performed.
With the new software, even after many balance cycles, I could never get the balance cycle to complete in less that about 3 hours ( ish ).
Again, this was observed by many owners who had the BMS upgrade.
Charging and balancing on a continuous basis, chasing the figures that MG had put out for the customers after the update ( as a base line figure ) did not sit comfortably with myself.
Charging to 100% every single time, then reducing the range slightly, the putting it back on charge to balance again, went against my own opinions on what is kinder for your battery ? long term.
It is my own belief, that by increasing the space at the top of the pack after the update, this caused the balance cycle to be increased massively.
Until my car received the update after about 12 months, I would alway try to limit my charging to the 80% SOC, in an attempt to protect my battery long term.
Now post update, I found myself charging to 100% every single time, for weeks on end.
When we exchanged the car after two years and nearly 20,000 miles, did I consider we had suffered any degradation and could his be attributed to all this persistent 100% charging ?.
On the first point - YES certainly, do I think this degradation was accelerated by the constant charging to full and balancing ?.
Who knows the real answer to this question !.
But the car did suffer from range loss that is 100% sure.

 

[Kithmo]

So, what happens if the battery balancing is interrupted & stopped before it finishes?

Personally, I woould prefer to be able to regularly charge my car to 100% (clearly, like so many other owners do) - but without committing the (~90min) extra time to likely unnecessary balancing. That could be done every six weeks of so as per MG guidelines.

I assume the more often you balance the battery the less time it takes.
I fully charge and balance about once a month and the balance part rarely takes more than half an hour.

 

[EVready]

Since this thread has been resurrected, I’m going to take the opportunity to ask a question that’s been bothering me. I am waiting on a facelift LR Trophy ZS but know that I am not going to be able to balance regularly. I live in a third floor flat with no private parking, so just park on the street and there aren’t any nearby public 7kW fast chargers that I’m likely to be able to stop at long enough to charge and balance. I may manage it every few months or so.

My question is whether failure to regularly balance the battery can have a permanent negative impact on the battery health, or would the impact be temporary and fixed next time the battery is fully balanced (appreciating that fully balancing the battery may take longer if not done regularly as per the this thread).

Thanks for any advice on this point!

 

[Vince31]

Balancing the battery's 90 (Trophy LR) or so cell modules ensures they are all equalised at 100% charge, this will ensure that each single cell is protected from being overcharged at 100% or below min volts when the pack is very low. Sort of resets everything to make sure all the cells stay within limits.
In your case, if you routinely set the max charge to 80% and never charge to 100% then you'll probably never overcharge any of the cells anyway. Then if you don't let the pack drop below 10% then you'll also probably not drain any one cell too low either. But, again in your case, NEVER try to charge to 100% on a DC Rapid charger as your cells are not balanced and the risk of overcharging one/two out of balance cells is now greater, this can cause pernament damage to those cells. If you ever need to charge to 100% then always do it (or the last 20% anyway) on AC fast or granny charger, and if you can then let it balance as well.

 

[Alb]

I've had my car for a year now and have balanced only once albeit I do fit into that 20-80 mould.
SOH is still 100%.