MG5 (FL) 12V Battery Drain

[MG5Hyperion]

Good evening all,

We took delivery of our brand new Piccadilly Blue MG5 in March earlier this year (FL model).
We can honestly say that it surpassed a lot of our expectations both in range and charging speed.

However, in May the car developed an issue where the 12V battery drained more than 0.5V in 24 hrs (as shown in the app). MG Poole (where we bought the car) was informed and the car went in at the earliest opportunity (which sadly was 1 month later so around the 30th of May.
At the same time it was also showing the “U Disk identity Failure” Which was also passed on the MG.

They handed the car back the next day and everything seemed fine.

About a week ago, we got the “U disk identity failure” again and consequently the battery drain came back. Thinking the 2 were related I disconnected the 12V battery (as suggested by this forum). This fixed the problem until yesterday.
After an overnight charge and a 160 mile round trip the car was showing 11.9V this morning which has dropped further to 11.6 this evening.
The car will go on charge tonight as we could not charge it last night due to some issue with the charger (Ohme Pro and not related to this regardless whether it’s connected to the charger).

Has any of you come across this issue before? And does anyone know any solution? I will once again inform MG Poole and hope they will be able to offer a more permanent solution.

Thank you for the wealth of information already available on this forum.

Steven

 

[slmorgan42]

Sorry I cannot actually shed light on this but there are many threads saying the battery that comes with the car are not thé greatest.

From experience once a battery has gone totally flat it ends up needing replacing.

 

[MG5Hyperion]

Sorry I cannot actually shed light on this but there are many threads saying the battery that comes with the car are not thé greatest.

From experience once a battery has gone totally flat it ends up needing replacing.

Thank you for your reply.

Yeah I have thought about replacing it, but before I do that I would like to get to the bottom of the draining issue, no use putting a brand new battery in that will then get drained to low voltages within a day or 2.

Also I thought there is a 1 yr warranty on the 12V?

 

[Deep purple]

There are 3 options. Either the battery is faulty which should be very easy to diagnose if it is disconnected and put on test, or the car is draining the 12v battery for some reason, or the car is only intermittently charging the 12v battery.

If the car is draining or not recharging the battery then the more times its voltage goes below about 12 volts and the lower it goes the greater is the shortening of the battery's useful life.

So if the battery is defective MG should replace it as failure after a few months is clearly a warranty issue, or if the car has a fault which drains/fails to charge the 12v battery MG should replace it as it will undoubtedly have suffered some life shortening (but clear the fault before getting the new battery)

 

[MG5Hyperion]

Small update for anyone interested and who might be experiencing similar issues.

Car went into the dealers today and stayed there till the evening.
They reportedly performed a 12V health check, which was passed, and updated the some 12V Battery management software which apparently had crapped out.

Currently it seems to be working but they did ask to keep monitoring it and report it again case it comes back.


Steven

 

[MG5Hyperion]

Another update:

To no one’s surprise the issue returned after about a month. This time it actually died on the driveway and MG assistance got involved.
The car went in again and they performed all sorts of diagnostics and tests in liaison with MG technical. As the 12V battery shows as healthy at the tests they can’t replace this under warranty.

Eventually the car died at the dealership and they were instructed to reprogram everything.

This was done but sadly we needed the car today as we are going on a trip.
Sad to report that nothing changed and now it is continuously giving a 12V low error on the dash.

I have given MG 1-more chance to rectify this (as they didn’t have time to perform all their tests) if they can’t rectify this issue I will be rejecting the car.

 

[MickeySw]

When driving or charging the 12V aux is topped up by the HV battery via the CCU (on board charger), so if you still get 12V low when READY, then MG are looking at the wrong side…

 

[Lovemyev]

Sometimes it’s the obvious that is over looked and gets lost by delving too deep.
When the dealer had the car in for the day and okayed the health of 12 volt battery, there was an opportunity missed here I feel.
The battery should have been fully charged manually and then left overnight at least !.
Then over the following days rechecked for any drop in it’s charge state.
This is a simple way of confirming if the battery is capable of holding onto that charge.
It’s important to establish if it’s a battery problem or a charging problem.
The car should also be checked for a parasitic drain.
While on this subject, you say the car has twice reported a U disc failure.
If the info unit locks up it will keep trying to reconnect.
This could be the source of the parasitic drain ?.
If the dealer is reporting to MG C/S that the 12 volt battery is passing its health checks on the computer, MG will move on to the next step of action.
But there has been insufficient time left before rechecking the state of charge.
The 12 volt battery drain could be slow and therefore needs time to manifest itself.
Given the number of 12 volt battery failures reported here, I still have my suspicions that the obvious is being over looked !.
You have to be 110% sure the battery is capable of retaining a charge over a few days before taking any further steps IMHO.

 

[johnb80]

Good evening all,

We took delivery of our brand new Piccadilly Blue MG5 in March earlier this year (FL model).
We can honestly say that it surpassed a lot of our expectations both in range and charging speed.

However, in May the car developed an issue where the 12V battery drained more than 0.5V in 24 hrs (as shown in the app). MG Poole (where we bought the car) was informed and the car went in at the earliest opportunity (which sadly was 1 month later so around the 30th of May.
At the same time it was also showing the “U Disk identity Failure” Which was also passed on the MG.

They handed the car back the next day and everything seemed fine.

About a week ago, we got the “U disk identity failure” again and consequently the battery drain came back. Thinking the 2 were related I disconnected the 12V battery (as suggested by this forum). This fixed the problem until yesterday.
After an overnight charge and a 160 mile round trip the car was showing 11.9V this morning which has dropped further to 11.6 this evening.
The car will go on charge tonight as we could not charge it last night due to some issue with the charger (Ohme Pro and not related to this regardless whether it’s connected to the charger).

Has any of you come across this issue before? And does anyone know any solution? I will once again inform MG Poole and hope they will be able to offer a more permanent solution.

Thank you for the wealth of information already available on this forum.

Steven

You have a problem either:-
1 A duff battery
2 A duff battery charger
3 A bug / fault module cussing excessive drain.

11.9v = SOC 40% (Way too low, lead acid should never be discharged below 50%)
11.6v = SOC 20%.
The battery is 55a/h therefore to drain overnight 20% = 11 a/h so if we assumed an 11 hour period you have to have drain on there dragging 1 amp constantly for this to happen.

I have obviously made assumptions for the above but I'm sure you'll get the idea.

Good luck, keep us posted.

 

[MG5Hyperion]

Sometimes it’s the obvious that is over looked and gets lost by delving too deep.
When the dealer had the car in for the day and okayed the health of 12 volt battery, there was an opportunity missed here I feel.
The battery should have been fully charged manually and then left overnight at least !.
Then over the following days rechecked for any drop in it’s charge state.
This is a simple way of confirming if the battery is capable of holding onto that charge.
It’s important to establish if it’s a battery problem or a charging problem.
The car should also be checked for a parasitic drain.
While on this subject, you say the car has twice reported a U disc failure.
If the info unit locks up it will keep trying to reconnect.
This could be the source of the parasitic drain ?.
If the dealer is reporting to MG C/S that the 12 volt battery is passing its health checks on the computer, MG will move on to the next step of action.
But there has been insufficient time left before rechecking the state of charge.
The 12 volt battery drain could be slow and therefore needs time to manifest itself.
Given the number of 12 volt battery failures reported here, I still have my suspicions that the obvious is being over looked !.
You have to be 110% sure the battery is capable of retaining a charge over a few days before taking any further steps IMHO.

Thank you for the concern I think at least the last time this was done.
We periodically checked the app as they said they wouldn’t really have availability to take the car and the 12V was charging.


Update after my 2x 3hr drive today: 12V does not charge above 50% as indicated by the car when driving 12V shows between 13.9-14.7V. When switching off the car after a few minutes the 12V warning comes on.

I have informed MG about my intention with regard to rejecting the car. Now I’m just discussing with my partner whether we’re giving them another chance to fix it.

Does anyone have any experience with rejecting a car after +6months?
What value do they usually calculate?

 

[Lovemyev]

when driving 12V shows between 13.9-14.7V. When switching off the car after a few minutes the 12V warning comes on.

Once the car is in ready mode the car should be charging, actually driving the car around makes no huge difference.
Unless you are continually conducting very short trips and running a lot of electrical items.
ICE drivers who witness a low SOC in a 12 volt battery, will often take the car for a drive to help charge the battery.
This will give the alternator an opportunity to recharge the battery.
EV’s have the ability to provide a max charge to the 12 volt battery without moving an inch.
It is also charging the 12 volt when the car is receiving a charge to the traction battery as well of course.
As long as the car is in ready mode, it should be charging the battery.
In ready mode the figures you report above, does suggests that the battery is indeed receiving a charge.
But the battery MUST be able to retain / hold onto that charge it is receiving.
Otherwise it will quickly discharge ( hence the low battery warning ) which could suggest a faulty battery or a huge discharge via a parasitic drain.

 

[AndyX]

Good evening all,

We took delivery of our brand new Piccadilly Blue MG5 in March earlier this year (FL model).
We can honestly say that it surpassed a lot of our expectations both in range and charging speed.

However, in May the car developed an issue where the 12V battery drained more than 0.5V in 24 hrs (as shown in the app). MG Poole (where we bought the car) was informed and the car went in at the earliest opportunity (which sadly was 1 month later so around the 30th of May.
At the same time it was also showing the “U Disk identity Failure” Which was also passed on the MG.

They handed the car back the next day and everything seemed fine.

About a week ago, we got the “U disk identity failure” again and consequently the battery drain came back. Thinking the 2 were related I disconnected the 12V battery (as suggested by this forum). This fixed the problem until yesterday.
After an overnight charge and a 160 mile round trip the car was showing 11.9V this morning which has dropped further to 11.6 this evening.
The car will go on charge tonight as we could not charge it last night due to some issue with the charger (Ohme Pro and not related to this regardless whether it’s connected to the charger).

Has any of you come across this issue before? And does anyone know any solution? I will once again inform MG Poole and hope they will be able to offer a more permanent solution.

Thank you for the wealth of information already available on this forum.

Steven

Hi Steven,

I am having battery drain problem, where the battery was dead after leaving car for 4 days. Almost happened earlier in the year but I took no notice. Spoke to Purbeck MG and it could be related to a radio module fault, where the module continually drains the 12V..I also occasionally get the radio module disconnected fault, which is probably related. Am booking car into Purbeck MG to check if radio module needs to be replaced.

Of course, you may have already handed back the car....

I note you went to Poole MG. Not sure if this was in the UK, ie Hendy. If it is Hendy I would suggest you ditch them and try Purbeck MG in Wareham. They are much more helpful as they are a small family dealer. Hendy are not interested in you other than to make lots of money.

 

[MG5Hyperion]

Hi Steven,

I am having battery drain problem, where the battery was dead after leaving car for 4 days. Almost happened earlier in the year but I took no notice. Spoke to Purbeck MG and it could be related to a radio module fault, where the module continually drains the 12V..I also occasionally get the radio module disconnected fault, which is probably related. Am booking car into Purbeck MG to check if radio module needs to be replaced.

Of course, you may have already handed back the car....

I note you went to Poole MG. Not sure if this was in the UK, ie Hendy. If it is Hendy I would suggest you ditch them and try Purbeck MG in Wareham. They are much more helpful as they are a small family dealer. Hendy are not interested in you other than to make lots of money.

Thanks for letting us know.

We still have the car, currently on a trip to Europe.
Annoyingly (to diagnose the issue) it’s been fine since I did a 12V disconnect, in the UK the error came back in a few days after doing that.


Did Wareham diagnose and correct the issue or just diagnose it?
While Wareham isn’t much further it’s a lot more inconvenient for us as my partner works in Poole.
At the moment we’re actually quite happy with Hendy, I think they also don’t really know what the problem is and have to follow what MG technical advises as it’s a new car.

 

[AndyX]

Thanks for letting us know.

We still have the car, currently on a trip to Europe.
Annoyingly (to diagnose the issue) it’s been fine since I did a 12V disconnect, in the UK the error came back in a few days after doing that.


Did Wareham diagnose and correct the issue or just diagnose it?
While Wareham isn’t much further it’s a lot more inconvenient for us as my partner works in Poole.
At the moment we’re actually quite happy with Hendy, I think they also don’t really know what the problem is and have to follow what MG technical advises as it’s a new car.

I don't know yet as I've only just booked it in. However they were very helpful with a central locking problem I had. Persevered far more than Hendy. But if you are happy with the service then that's fine, of course.

 

[tonyllot]

Hi Steven,

I am having battery drain problem, where the battery was dead after leaving car for 4 days. Almost happened earlier in the year but I took no notice. Spoke to Purbeck MG and it could be related to a radio module fault, where the module continually drains the 12V..I also occasionally get the radio module disconnected fault, which is probably related. Am booking car into Purbeck MG to check if radio module needs to be replaced.

Of course, you may have already handed back the car....

I note you went to Poole MG. Not sure if this was in the UK, ie Hendy. If it is Hendy I would suggest you ditch them and try Purbeck MG in Wareham. They are much more helpful as they are a small family dealer. Hendy are not interested in you other than to make lots of money.

It just happened to me today. 12V battery completely dead even though was normal yesterday afternoon.
I just changed the battery and now, the 'Radio Module Disconnect" is back to normal and all the radios working.

But now, when I switch the car on, it performs all the checks one by one.. fail a few..
I Dont know how to reset that back to normal, anyone has any idea?
the car is reaching 32k miles.., first problem so far..

Many thanks
T.

 

[AndyX]

It just happened to me today. 12v battery completely dead even though was normal yesterday afternoon.
I just changed the battery and now, the 'Radio Module Disconnect" is back to normal and all the radios working.

But now, when I switch the car on, it performs all the checks one by one.. fail a few..
I Dont know how to reset that back to normal, anyone has any idea?
the car is reaching 32k miles.., first problem so far..

Many thanks
T.

The checks you mention will go back to normal once you drive for a while. The radio module error can only be fixed by getting radio unit or a component replaced..you can temporarily fix it by disconnecting and reconnecting the 12V -ve terminal with a 10mm socket. But the error will eventually recur. I tried the update file but that didn't fix it permanently.
Coincidentally, mine is back at the dealers today for them to formally diagnose and log the error with MG. I've only had the fault for over a year.. nothing gets done quicker with MGUK!

 

[tonyllot]

The checks you mention will go back to normal once you drive for a while. The radio module error can only be fixed by getting radio unit or a component replaced..you can temporarily fix it by disconnecting and reconnecting the 12v -ve terminal with a 10mm socket. But the error will eventually recur. I tried the update file but that didn't fix it permanently.
Coincidentally, mine is back at the dealers today for them to formally diagnose and log the error with MG. I've only had the fault for over a year.. nothing gets done quicker with MGUK!

Oh, very usefull insights there Mate, I really appreciate your feedback.
After the issues I had today, I had just book the car for service in 2 weeks time, I might as well ring them tomorrow and talk about this radio module that needs replaced so, maybe, by my appointment they could have in hands to replace.

Thank You so Much.

 

[Jomarkh]

I have had the radio lock up three times, they have done updates on two different occasions but this morning it locked up again and I am stuck on AM...

 

[tonyllot]

The checks you mention will go back to normal once you drive for a while. The radio module error can only be fixed by getting radio unit or a component replaced..you can temporarily fix it by disconnecting and reconnecting the 12v -ve terminal with a 10mm socket. But the error will eventually recur. I tried the update file but that didn't fix it permanently.
Coincidentally, mine is back at the dealers today for them to formally diagnose and log the error with MG. I've only had the fault for over a year.. nothing gets done quicker with MGUK!

One final question, only coz you seem to be very familiar with all these issues, is it the faulty radio module that discharges the 12V battery?

Are these 2 faults related to each other?