Reduction of stated range from balancing the battery?

[ChrisR]

I've just done a full charge and balance on my Gen1 ZS EV and noticed that when it reached 100% the GOM said 252km but once balancing had finished it was 250km. Has anyone else noticed this or can explain what's happening?

I've balanced the battery every month or two over the year and a half I've had it, charging on my 7kW home charger (I do very seldom rapid charging) and usually notice the GOM has stayed at 263km. I assume some battery degradation and the fact that it's winter here has caused some reduction but I was surprised that the act of balancing seemed to have an effect on the reading

 

[Coulomb]

What might be happening is that the BMS resets to 100% SoC when it reaches a certain overall battery voltage. Balancing requires a small amount of power, and during this time the battery may not be at its very highest voltage. If it was, the lower voltage cells might not be able to catch up as quickly.

I'll agree that's a pretty woolly theory. It might be worth trying another charge after the balancing, to see if it gives you back the last 2 km of estimated range.

My GOM used to always go to 263 km as well, now it's well below that. I'm hoping that I'll get back some of those km when winter is over. Unfortunately, I decided to reset the long term trip meter after not touching it for many months. So now I don't know if that reset triggered the reduction or if it was a combination of winter and a little degradation now bringing the SoH below 100%.

 

[ChrisR]

What might be happening is that the BMS resets to 100% SoC when it reaches a certain overall battery voltage. Balancing requires a small amount of power, and during this time the battery may not be at its very highest voltage. If it was, the lower voltage cells might not be able to catch up as quickly.

I'll agree that's a pretty woolly theory. It might be worth trying another charge after the balancing, to see if it gives you back the last 2 km of estimated range.

My GOM used to always go to 263 km as well, now it's well below that. I'm hoping that I'll get back some of those km when winter is over. Unfortunately, I decided to reset the long term trip meter after not touching it for many months. So now I don't know if that reset triggered the reduction or if it was a combination of winter and a little degradation now bringing the SoH below 100%.

Thanks @Coulomb that makes sense to me. I also reset the accumulated trip meter a little while ago and it's 15.0 kW/100km now when it used to be 14.6 so that would probably be effecting the GOM but I'd be interested to see the actual SoH.

 

[Coulomb]

I'd be interested to see the actual SoH.

The unofficial Thai app or something like Car Scanner will tell you that, if you have a suitable OBD II dongle.

 

[Lovemyev]

If you have covered a lot of miles in better weather and driving at a relaxed pace, then your returning ( predicted ) range on the GOM is reflecting your historical data.
It therefore assumes that you intend to drive in this fashion all of the time and that the conditions will also be similar.
When you then reset your accumulative trip, it has no historical data anymore, so is relearning everything.
If you reset your long term trip just before the start of the colder winter months, that has built up good values over the summer, then you are going to see a big fluctuation it what you where use to seeing.
If you left the accumulative trip untouched, then the slide in efficiency and returning GOM predictions will take longer to be apparent.
When you reset the accumulative trip, the historical data has been lost, so the figures reported are instant.
It really depends on what you consider is best for you in the reporting it’s predictions ?.

 

[Vince31]

I've just done a full charge and balance on my Gen1 ZS EV and noticed that when it reached 100% the GOM said 252km but once balancing had finished it was 250km. Has anyone else noticed this or can explain what's happening?

I've balanced the battery every month or two over the year and a half I've had it, charging on my 7kW home charger (I do very seldom rapid charging) and usually notice the GOM has stayed at 263km. I assume some battery degradation and the fact that it's winter here has caused some reduction but I was surprised that the act of balancing seemed to have an effect on the reading

its temperature. The reading is just an estimated and takes into account temperature as well as a host of other things like your previous driving style and the charge of the battery.

 

[Kithmo]

Let it rest and plug it back in see if that brings it back up.
My gen 1 on the original BMS seems to gain another 1.25v if I plug it in again after a charge and balance.
i.e. I charge and balance it and the voltage (using the ZS EV app and OBDII adapter) is 455v. If I then plug it in again a short while after it proceeds to charge again at a lower rate (or it could be balancing more ?) and when it finishes the voltage has gone up to 456.25v

 

[ChrisR]

Let it rest and plug it back in see if that brings it back up.
My gen 1 on the original BMS seems to gain another 1.25v if I plug it in again after a charge and balance.
i.e. I charge and balance it and the voltage (using the ZS EV app and OBDII adapter) is 455v. If I then plug it in again a short while after it proceeds to charge again at a lower rate (or it could be balancing more ?) and when it finishes the voltage has gone up to 456.25v

I don't have an OBDII but the voltage at full charge shows on the dash panel as 451v since the BMS update. I will give the replug in a go to see if it does bring it back up.

 

[Kithmo]

I don't have an OBDII but the voltage at full charge shows on the dash panel as 451v since the BMS update. I will give the replug in a go to see if it does bring it back up.

If you've had the BMS update (mine hasn't), then 450-451v is about the max you'll see.

 

[MichaelJHunt]

Some interesting reading on why we need to ensure that batteries are regularly balanced:

How Does Cell Balancing Improve Battery Life

Cell balancing is a technique that improves battery life by maximizing the capacity of a battery pack. Know more here.

www.ionenergy.co