Battery isolation fault help

[ManxViking]

Hi all.
Am completely new to here but not MG EVs.
I have read alot of posts about this but it seems my problem might be unique......
I have a 2021 MG ZSEV which I loved bits. I have done 52,000 miles and apart from the usual bits and pieces commonly talked about on here, there have been no real significant issues until now. I had ended up having several occasions where the isolation fault had come up and after the AA had been out to me they had managed to reset the system, and I had carried on my way. However a few weeks ago at home, I came to start the car in the morning to go to work and had notification of the HV isolation fault but not just one icon on the dash on the right hand side, it was like a Christmas tree with several battery icons relevant to the HV system showing faults.
I am lucky enough to have a two post lift so decided to be brave and have a go at removing the battery system underneath the car and having a look as a lot of YouTube videos had shown that the battery fills up with water and causes this fault. So after removal of the battery, I found everything completely soaking and probably about a litre of water in the front two sections of the battery. Following all safety protocols I removed all the batteries, and the main contactor unit at the back of the battery, dried everything out for a couple of days and then reassembled everything and put it back into the car.
In the meantime I bought the Autel maxisys ultra with the EV box so that I could diagnose and hopefully reset the system.
After completing this action there has always been a problem with the BMS showing on the system and despite clearing all faults on the car the isolation fault continues to remain, both on the dash and in the system. As I am not a mechanic and just a very competent DIY car repairer, I am at a loss when it comes to the electrics especially when I've just been 5k on this computer which hopefully was going to clear all the faults.
I am just reaching out to find out if there is something else that is in the electrical system that may have had a problem as I could not find an isolation fault in the battery pack or the connections and all about batteries were within 0.02 of a volt.
The system is low on charge, 6%, but it will not take a charge neither will it go into drive or reverse because of this isolation fault.
Really hope somebody can point me in the right direction as this is a common fault on MG's.
Many thanks,
David

 

[Alb]

The battery is covered by warranty. Why on earth would you choose to invalidate it

 

[fred12345]

The battery is covered by warranty. Why on earth would you choose to invalidate it

agreed

Really hope somebody can point me in the right direction as this is a common fault on MG's.

unless you enjoy doing this kind of work (and I genuinely envy people how know what they are doing on EVs), I would put everything back as it was, call AA to get it to one of MG garages and just ask them to have a look what's wrong.

you got the car from new or bought second hand?

 

[ManxViking]

I bought the car 2nd hand and had decided to get a second for parts, that's arrived this morning and been delivered with the same fault.......
It's odd that this fault is so common on the forums but no one has managed to post what was actually wrong.
I am confident I will find the issue but sometimes just need a point in the right direction, in this instance, if the fault is no longer in the battery then where else in the system could the problem be? The aren't a lot of components from the battery pack to the motor and I have checked all fuses all relays. I'm wondering if there is a pyro fuse or something similar that cuts the power from the battery. There is no fault from the BMS, it only shows fault with the isolation of the battery pack.
I'm just wondering if even with the 5k computer that I've bought it's still needs only an MG dealer too be able to diagnose fully. And that is very frustrating for me, as I can usually work through the issues and come to a conclusion.

David

 

[fred12345]

I bought the car 2nd hand and had decided to get a second for parts, that's arrived this morning and been delivered with the same fault.......
It's odd that this fault is so common on the forums but no one has managed to post what was actually wrong.
I am confident I will find the issue but sometimes just need a point in the right direction, in this instance, if the fault is no longer in the battery then where else in the system could the problem be? The aren't a lot of components from the battery pack to the motor and I have checked all fuses all relays. I'm wondering if there is a pyro fuse or something similar that cuts the power from the battery. There is no fault from the BMS, it only shows fault with the isolation of the battery pack.
I'm just wondering if even with the 5k computer that I've bought it's still needs only an MG dealer too be able to diagnose fully. And that is very frustrating for me, as I can usually work through the issues and come to a conclusion.

David

if one of the cars is still under warranty, I would definitely suggest going to MG; but if it's a project the cars were insurance write offs (flood damage) that's different ... I have seen some sold like that.
yes, from memory, there is a main fuse on the battery itself but can't remember much in detail ...

I'm not sure you will find much technical help from us but I would suggest signing up (with fee) to MG service website where you can download all technical and repair manuals and/or hooking up with some of the people on YouTube that work on EVs

keep us updated on the progress and post some photos ?

 

[fred12345]

must be pyro fuse on both cars ...

something similar was discussed here - hook up with @BRT and @T1 Terry + @chiMol and share everything here please ? (YouTube video is particularly helpful so get recording and share on YouTube step by step)

ZS EV front airbags deployed will not run.

 

[ManxViking]

I thought so too Fred but I can't find any specifics on it. All the repair videos that I've seen reference this isolation problem especially when it's midpack, the batteries and associated parts have just been dried out put back in the car and away you go.
I spent 5k on the Autel maxis ultra EV only to find when I look for the MG battery it's not listed in their system so I have raised that with Autel as I am also unable to link the EV diagnostic to the car.
The thing is that the isolation fault on MG's can be in the motor, the AC pump, the main battery, and a couple of other places which makes life very difficult to diagnose specifically where the issue is. Even more strange that both cars have exactly the same problem and very frustrating that I have not been able to work through to be able to find the problem and fix it.
On a lot of other electric cars there is a specific pyro fuse and that is plenty of information on the web about those but just not MG. I will have a look at paying for the data from MG as it seems it might help me to diagnose.
As I work through the issues I will update here.
Thanks.
David

if one of the cars is still under warranty, I would definitely suggest going to MG; but if it's a project the cars were insurance write offs (flood damage) that's different ... I have seen some sold like that.
yes, from memory, there is a main fuse on the battery itself but can't remember much in detail ...

I'm not sure you will find much technical help from us but I would suggest signing up (with fee) to MG service website where you can download all technical and repair manuals and/or hooking up with some of the people on YouTube that work on EVs

keep us updated on the progress and post some photos ?

Hi Fred. Do you happen to know what the website is called? Trying to get through to customer services is impossible. Thanks. David

 

[fred12345]

Hi Fred. Do you happen to know what the website is called? Trying to get through to customer services is impossible. Thanks. David

MG - Repair & Maintenance Information

rmi.mgmotor.eu

you need to sign up and pay access fee but I think it's worth every penny; if you are thinking of doing some serious DIY stuff on it, best to do it properly...

 

[ManxViking]

Just looking into it now. Thank you. I completely agree with your thinking and will definitely record the work. Not done YouTube before, got a face for radio ? but might try once I've figured it out..... David

 

[Tim Green]

I am not fully conversant with the control electronics and software, but it could be that there is a safety loop in the software that has been tripped and not yet properly reset. In other words, the battery system is ok but the software needs resetting in the proper manner.

 

[ManxViking]

Typically the Autel doesn't have the software yet to cover the battery..... Every other Chinese manufacturers most I've never heard of but not MG! I've looked for pyro fuse information because it could be that it's just tripped it out. On audi's it tends to be in the battery pack but I cannot find it in the MG. I expected to find it easily but not so much.
The other website for MG that allows you to download the information requires me to have a business otherwise it states that it will become null and void and I will not have access, unless I just download everything straight away....

 

[Lovemyev]

There must be a HV fuse in the system somewhere, as I clearly remember MG releasing a software update in the ZS EV Gen1 because some owners had experienced a total shut down on route.
And therefore required a flat bed recovery from the roadside, back to the dealer.
HV fuse replaced and software update was applied.

 

[ManxViking]

Thanks lovemyev.
There's hope yet then ?

 

[Lovemyev]

I guess you have already seen these two videos ?.

 

[fred12345]

the YouTube video that I posted a link to, somewhere on ZS forum, I'm pretty sure it shows the battery fuse? it would give you an idea what to look for and where. But, get those service manuals from MG and that's all you need.

 

[fred12345]

The other website for MG that allows you to download the information requires me to have a business otherwise it states that it will become null and void and I will not have access, unless I just download everything straight away....

I don't think that's correct; it gives you options to join for a different period of time, and you can download everything in one go. I signed up and I'm not a business.
if you are serious about doing work yourself, I don't see how can you do it properly without service manual.

 

[ManxViking]

I guess you have already seen these two videos ?.

Yes. Very informative

 

[MozFromOz]

@ManxViking Looks like you have a big challenge ahead of you.

I don't know about the fuse but there is much more to an isolation fault that that alone. The isolation fault could be present in one or more of your battery modules. A battery immersed in water is a huge issue to recover from.

You will need to test each module, the BMS, and the wiring harnesses for for electrical leakage with a multimeter as a first step. Good modules will show no or very minimal voltage (read a few milivolts) between the electrical connections and the module frame. Any that have leakage will need to be either stripped and/or cleaned of corrosion etc or they will be unusable.

I haven't worked upon MG modules to date but there are similarities between all module based batteries. This video from Dala's EV repair. illustrates some of the steps required to track down an isolation fault in a Leaf battery. You can do a similar procedure with your MG packs.

Now regarding the overall condition of the battery and modules irrespective of having dried them out. Water ingress in a charged battery pack causes corrosion and leaves salty electrically conductive residue everywhere. This residue will likely contribute to further corrosion and risk of ongoing problems with the battery. Ideally you need to wash, brush or clean all of this out of the entire pack and all the modules. Any rusting metalwork needs to be cleaned up and protected from future corrosion to ensure longevity of the pack.

Here I don't know what best advice to give is. Maybe dewatering fluids are a starting point. Even the circuit board in the BMS, and all the fine wires and connectors throughout the pack will need some attention. I will leave it to others with good experience to chip in here.

Once its all cleaned up and all your modules are free from electrical leakage, you will need to manually balance all the individual cells to the same voltage before you return the pack to service in the vehicle.

Finally I advise you to investigate how water can get into the pack and how to prevent a future water ingress problem. Sealing it up is obvious, but you need to consider whether the factory venting to allow for expansion of gasses inside the pack is working as designed as well.

Hope this helps.
Moz

 

[ManxViking]

Hi Moz,
All the parts of the battery pack were removed and like you say, there were a lot of connections which were corroded because of the ingress of the water. The ingress came from the main HV connection plate on the battery and the reason why was that when you remove that unit there is a tiny o-ring type gasket which would not stop anything. I bought some heat resistant gasket sealer when putting everything back together and sealed it properly.
You are right when you talk about the issue being in many different places potentially, as I am not an electrician the way that the power flows through the system is not a straightforward as I originally thought and although I have learnt how to do a lot of testing over the last few weeks but with this sort of thing I have to rely on the diagnostic computer which I'm also learning to use .
The car was not flood damaged, the moisture was ingress only. The car was hit from behind and did not have a lot of damage at all, and that is why I'm struggling to understand what could be wrong. No airbags went off although it does have a notification of the impact on the ECU. The frustrating thing is that both of the MGs that I have have exactly the same problem after small accidents so I would like to think that the issue must be a very small one but similar because they both show the same issues.
I do not know how to do the testing of the electrical system but had no problems with the pack leaking against the housing. I guess it could be that the batteries have gone out of balance very slightly and that might cause a problem but did not think that it would cause an isolation problem.
Will keep working through the issues even if I have to take the battery out again.
Many thanks for your advice.
David

 

[MozFromOz]

Hi @ManxViking
If you have eliminated the electrical leaks in the modules themselves? then it's somewhere else in either the pack wiring or the cable between the pack and the hv system. Dala's video shows the process for testing the modules very well. You need to be absolutely sure.

I doubt battery balance would result in a leakage fault code, or any faults in and of itself as the batteries go out of balance as they age and the system tolerates some drift.

I'd keep looking at the harness if the modules are no longer showing voltage errors to the frames. I'd also dismantle the BMS box and check for corrosion on and around the circuit board.

Moz.