Understanding hv battery voltage

[Pebblefeline]

I am trying to understand more about my EV and the battery.

When I look at car scanner I can see cell voltages and max min voltages etc loads of hv battery info.

What should I be looking for in terms of identifying issues?

Just after a little guidance as I want to understand more about the info I can access.

 

[Verdigris]

The cell voltages should be as close to identical as possible. If there is any large variance do a balance charge and check to see if they are closer. Total voltage should be greater than 400V at 100% SOC.

 

[Pebblefeline]

Thanks versigris
So my cells have a standard max voltage of 3.12
And a variance on minimum voltage between 3.1 and 3.12
I am assuming this is a ok

This is taken from car scanner using a Carly obd

 

[Pebblefeline]

I am assuming it is groups of cells marked cmu01 cmu02 etc

 

[Verdigris]

Those variances are fine.

An individual lithium cell will be at 3+ volts and they are usually connected in groups in parallel, so the voltage of that group will still be 3+ volts but the capacity is multiplied by the number of cells. Those parallel groups are then connected in series to make up a pack, typically with a voltage of around 50V (depends on how many groups) and then those packs are further connected in series to give a total voltage of around 400V (or 800V in the case of some Kia/Hyundai/Teslas/Porsche).

 

[5teep]

You're probably overthinking it Pebblefeline (we all do it at first). The individual cells will go 'out of sync' over time especially if you charge on Rapid DC often. All you need to do is charge the car on AC overnight once every couple of weeks or a month and it will balance the cells.
If you tend to plug in to a home charger every day you might not ever notice a balance charge has been done.
The main battery itself is very robust and has a long lifespan, 200k-300k miles easily and even then it will still be perfectly useable (with a bit shorter range).

 

[Pebblefeline]

Thanks guys

I really like to understand how stuff works and ev’s are new to me.

The info is really much appreciated

 

[MickeySw]

Thanks guys

I really like to understand how stuff works and ev’s are new to me.

The info is really much appreciated

More info for the knowledge hungry:
A 61kWh NMC battery as installed in LR versions seems to be 96S1P (all cells are in series, non parallel connections) and are divided into 6 modules. Each of them contains 16 individual cells that are supervised by a CMU (cell monitoring unit)

Complete battery

16 cell module (yellow overlays signify two individual cells)

Courtesy of

MG5 Battery Details anyone?

www.speakev.com

 

[Verdigris]

I saw this video on repairing a ZS battery, the other day:



Gives a good idea of how it all goes together and illustrates how many levels of safety are built in if something does go awry.

 

[Pebblefeline]

Thanks that’s amazing info

 

[myshadows]

I found my old RAV4 hybrid had issues with the battery overheating so I could rarely get a full charge. I found individual modules would be overloaded only during moderate to heavy regen. This was far beyond anything a dealer mechanic was capable of diagnosing.
Every hybrid and ev should have temperature available to drivers like old ICE vehicles

 

[johnb80]

I saw this video on repairing a ZS battery, the other day:



Gives a good idea of how it all goes together and illustrates how many levels of safety are built in if something does go awry.

Clearly one of the more skilled and dedicated technicians. He did a great job there for sure.
Thanks for sharing the video.

 

[Verdigris]

Clearly one of the more skilled and dedicated technicians. He did a great job there for sure.
Thanks for sharing the video.

It almost verged on slow radio/television territory but I think that illustrates that thorough and methodical is the way to go.