12V battery low warning light HS PHEV

[DBS]

I have a 17 month old MG HS PHEV which recently started showing a warning light after turning the engine off.
12V BATTERY LOW AVOID PARKING FOR 3 DAYS.

I have taken it to two different dealers in Norfolk, UK and had diagnostics run but they don’t know why it is happening.

On the first visit, the battery had dropped to 28% so they charged it to 100% and said it was because cold weather and under-use of the car but good battery health.
Three days later it was still showing warning light so garage re-tested and battery was 16%. No explanation offered just blank faces.

I then took it to the garage in Norwich who sold me the vehicle and they ran diagnostics which showed 70% charged, healthy battery but several faults showing when the warning light came on. They don’t know what to do except try replacing the 12V battery even though they think it’s ok.

Here’s the worry - THEY DON’T KNOW WHAT 12V BATTERY TO PUT ON THE CAR. Two separate dealerships are unable to give a price or find one compatible as MG say as they don’t manufacture their own batteries the dealer should use their local battery supplier who are saying don’t know what to use. This has been going on for a week and still no answer.

The first garage are now saying it may be a software update issue anyway and are checking it again on 1st March 2023. There have been no issues with car starting or running so feels possible it’s a faulty sensor but I am not a mechanic.

Has anyone else had a problem with the 12V battery or low battery warning light on a HS PHEV?

 

[Jto]

How did they test the battery?
Do you do short trips only.
I have not looked at the battery I would think it’s stop start battery nothing too special 12v xxAH
on the side of the battery will the AH rating.
you just need one the same dimension.
I did a quick search and found that National tyres came up with 3. There is outlet in Norwich

 

[Lovemyev]

I have a 17 month old MG HS PHEV which recently started showing a warning light after turning the engine off.
12V BATTERY LOW AVOID PARKING FOR 3 DAYS.

I have taken it to two different dealers in Norfolk, UK and had diagnostics run but they don’t know why it is happening.

On the first visit, the battery had dropped to 28% so they charged it to 100% and said it was because cold weather and under-use of the car but good battery health.
Three days later it was still showing warning light so garage re-tested and battery was 16%. No explanation offered just blank faces.

I then took it to the garage in Norwich who sold me the vehicle and they ran diagnostics which showed 70% charged, healthy battery but several faults showing when the warning light came on. They don’t know what to do except try replacing the 12v battery even though they think it’s ok.

Here’s the worry - THEY DON’T KNOW WHAT 12V BATTERY TO PUT ON THE CAR. Two separate dealerships are unable to give a price or find one compatible as MG say as they don’t manufacture their own batteries the dealer should use their local battery supplier who are saying don’t know what to use. This has been going on for a week and still no answer.

The first garage are now saying it may be a software update issue anyway and are checking it again on 1st March 2023. There have been no issues with car starting or running so feels possible it’s a faulty sensor but I am not a mechanic.

Has anyone else had a problem with the 12v battery or low battery warning light on a HS PHEV?

12 volt battery failure is not that uncommon it appears ?.
I don't understand why they are struggling to find a battery, the HS PHEV has been out a while now ?.
Here is link to a battery supplier that a lot of the trade uses.
Put your registration number in the search field and see what it throws up.
If it fails to find your car, don't worry give them a call on Monday and they will check the size and spec's of the battery and give you a choice of suitable units that will fit your car.
I maybe an idea to take the measurements of the battery and make a note of the amp/hour of the battery already installed.
The hand book ( manual ) should give you the capacity of the OEM battery, if you cant locate it on the one fitted to the car.
It's next day delivery from them as well.
Of course the dealer has already checked the charging rate of the car we have to assume AND checked for any parasitic drain from the OEM battery ? .
That could possibly be a NO there then ? .

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[DBS]

How did they test the battery?
Do you do short trips only.
I have not looked at the battery I would think it’s stop start battery nothing too special 12v xxAH
on the side of the battery will the AH rating.
you just need one the same dimension.
I did a quick search and found that National tyres came up with 3. There is outlet in Norwich

Thanks for the advice. I do mainly short journeys as I am early retired by the sea but I do make a few long journeys back to the Midlands still to see family hence having a PHEV not EV.

I am just disappointed that the dealer cannot source a battery.

 

[Jto]

Need to drive more a bit more, they tend to charge more for battery, last time I was there some roads where closed Are they open now.

 

[TWbm]

When I had my HS PHEV delivered, long story short, I found that a connector in the main fuse box on the right under the bonnet hadn't been properly tightened and was shorting. It was the red heavy duty cable on a 200amp fuse that charges the 12v battery from the EV battery, located back right in the box.

Early signs were low 12v battery warnings and every other warning light the car has flashing on and off.

Mine actually go so hot it melted the casing.

 

[sticky99]

If you Google 12v phev problems you will see it is an issue on other makes. We gave up waiting for ZS EV and bought a used Kia Niro PHEV. A month after purchase we had a dead car, all caused by flat 12v. Kia owners are now used to carrying a booster box to start it if necessary! Both times it happened to us we had done long journey the day before, 2nd time was after Kia had fitted a brand new battery a couple of months before (under warranty). So who knows why it’s happening! Very frustrating

 

[Got More EVs]

How did they test the battery?
Do you do short trips only.
I have not looked at the battery I would think it’s stop start battery nothing too special 12v xxAH
on the side of the battery will the AH rating.
you just need one the same dimension.
I did a quick search and found that National tyres came up with 3. There is outlet in Norwich

I also own several EVs & PHEVs.
They don’t use regular cranking battery, they use deep cycle batteries, hence the Ah rating. Take measurements of battery width, length& height. Take a photo showing orientation of posts & termnals, any half decent battery support can match it.
If car can with AGM then replace with AGM.
regular cold crank battery can’t handle deep discharge like deep cycles can.
Hope this helps.

 

[Jto]

I service mobility scooter and deep cycle battery’s are used on them, the best are MK, should the battery fail in the first year they replace both batteries on a mobility scooter after testing.

 

[midician]

In Australia, the 12V battery has a 2 year warranty to that would’ve been free battery replacement .

 

[DBS]

In Australia, the 12V battery has a 2 year warranty to that would’ve been free battery replacement .

It’s annoying only a 12 month guarantee as you can buy one from Halfords with 5 year warranty! Anyway they still don’t think it’s the battery and it is still at the garage today.

How did they test the battery?
Do you do short trips only.
I have not looked at the battery I would think it’s stop start battery nothing too special 12v xxAH
on the side of the battery will the AH rating.
you just need one the same dimension.
I did a quick search and found that National tyres came up with 3. There is outlet in Norwich

Thanks for your advice. They now don’t think it’s a battery issue but fault with warning light. They did a software download last week but that failed to stop it. In fact it was worse because when I switch the engine on or try to charge the lithium battery it say “warning 12v battery low - start engine immediately “. Anyway the car is currently with dealer who hasn’t replaced the battery but running yet more diagnostics today.

If you Google 12v phev problems you will see it is an issue on other makes. We gave up waiting for ZS EV and bought a used Kia Niro PHEV. A month after purchase we had a dead car, all caused by flat 12v. Kia owners are now used to carrying a booster box to start it if necessary! Both times it happened to us we had done long journey the day before, 2nd time was after Kia had fitted a brand new battery a couple of months before (under warranty). So who knows why it’s happening! Very frustrating

Thanks. It looks like the battery is in fact healthy but the warning light keeps coming on. It’s still at the dealer today who did a software update last week which they tried with another PHEV 3 months ago. That failed so they are nagging MG for solution. Watch this space ..

When I had my HS PHEV delivered, long story short, I found that a connector in the main fuse box on the right under the bonnet hadn't been properly tightened and was shorting. It was the red heavy duty cable on a 200amp fuse that charges the 12v battery from the EV battery, located back right in the box.

Early signs were low 12v battery warnings and every other warning light the car has flashing on and off.

Mine actually go so hot it melted the casing.

the dealer did check your suggestion for me but all looked good. The battery readings are good just a constant warning light so they have kept the car and are trying to solve the issue right now.

 

[Cafeg]

isnt the phev 12volt battery covered under the mg warranty ?

 

[DBS]

It is only covered for 12 months. Luckily for me my local dealer had the car for SIX WEEKS and decided to replace it for free as a good will gesture. So far it has cured the warning light issue.

 

[ajw1100]

Just my 2p worth
The info unit can show 12v readings, mine has never shown less than about 13 or 13.5v.
If you charge up to 100% then see what the dash shows, take the car for a run and see if, when or where the voltage dtops. Might give you a clue as to what is going on.

 

[Rayz]

I have a 17 month old MG HS PHEV which recently started showing a warning light after turning the engine off.
12V BATTERY LOW AVOID PARKING FOR 3 DAYS.

I have taken it to two different dealers in Norfolk, UK and had diagnostics run but they don’t know why it is happening.

On the first visit, the battery had dropped to 28% so they charged it to 100% and said it was because cold weather and under-use of the car but good battery health.
Three days later it was still showing warning light so garage re-tested and battery was 16%. No explanation offered just blank faces.

I then took it to the garage in Norwich who sold me the vehicle and they ran diagnostics which showed 70% charged, healthy battery but several faults showing when the warning light came on. They don’t know what to do except try replacing the 12v battery even though they think it’s ok.

Here’s the worry - THEY DON’T KNOW WHAT 12V BATTERY TO PUT ON THE CAR. Two separate dealerships are unable to give a price or find one compatible as MG say as they don’t manufacture their own batteries the dealer should use their local battery supplier who are saying don’t know what to use. This has been going on for a week and still no answer.

The first garage are now saying it may be a software update issue anyway and are checking it again on 1st March 2023. There have been no issues with car starting or running so feels possible it’s a faulty sensor but I am not a mechanic.

Has anyone else had a problem with the 12v battery or low battery warning light on a HS PHEV?

Check this out cos not sure,but I was told it needs a 13vdeep Cycle Gel battery. The type they put on some large Mobility cars. Expect to pay up to £99

Check this out cos not sure,but I was told it needs a 13vdeep Cycle Gel battery. The type they put on some large Mobility cars. Expect to pay up to £99

Sorry Meant 12v battery but when it's fully charged it's 12.9. half charge is 12.5 v 12.2v is 25% charged.

 

[anton]

I have a 17 month old MG HS PHEV which recently started showing a warning light after turning the engine off.
12V BATTERY LOW AVOID PARKING FOR 3 DAYS.

I have taken it to two different dealers in Norfolk, UK and had diagnostics run but they don’t know why it is happening.

On the first visit, the battery had dropped to 28% so they charged it to 100% and said it was because cold weather and under-use of the car but good battery health.
Three days later it was still showing warning light so garage re-tested and battery was 16%. No explanation offered just blank faces.

I then took it to the garage in Norwich who sold me the vehicle and they ran diagnostics which showed 70% charged, healthy battery but several faults showing when the warning light came on. They don’t know what to do except try replacing the 12v battery even though they think it’s ok.

Here’s the worry - THEY DON’T KNOW WHAT 12V BATTERY TO PUT ON THE CAR. Two separate dealerships are unable to give a price or find one compatible as MG say as they don’t manufacture their own batteries the dealer should use their local battery supplier who are saying don’t know what to use. This has been going on for a week and still no answer.

The first garage are now saying it may be a software update issue anyway and are checking it again on 1st March 2023. There have been no issues with car starting or running so feels possible it’s a faulty sensor but I am not a mechanic.

Has anyone else had a problem with the 12v battery or low battery warning light on a HS PHEV?

Hi,
I am an HS PHEV owner living in France and have the same problem over the warning message. It began after I failed to turn off the ignition and the 12V went flat. I used a booster to start but after a run of about 120miles the warning still came on. I recharged the battery yesterday using a trickle charger until the charger indicated the battery was now full. No recurrence of the message this morning. The MG was first regIistered n May 2022; I shall contact the dealer who services the car and ask them to do a check of the charging system. I don't see why it should be a problem to replace the 12V battery but I shall check this. If you have resolved your problem please let me know. If not we can keep in touch and I can, tell you happens here. I do have a concern that the booster may have affected the battery and shall ask the garage,
best wishes

 

[silversilver]

Hi. Today dropped off my mg hs at MG dealer Swansea to have the DAB module update updated - again. Anyway the courtesy car (Europcar hire car) an mg hs phev has the issue your describing here. Spoken to Europcar customer service on another point - alarm keeps going off at random times when parked- locked - windows sun roof shut. When they call back I'll mention battery warning and see what they say. I'll update you on here.

 

[mevvi1]

I have started to get the same low battery message. Still waiting for my dealership to get back to me with regard to the message and the cost of a new battery. Just emailed Tanya’s batteries for availability and price. AA suggested the battery might need occasional trickle charge and conditioning as I am a low mileage daily user. Any thoughts please?

 

[Rayz]

I have a 17 month old MG HS PHEV which recently started showing a warning light after turning the engine off.
12V BATTERY LOW AVOID PARKING FOR 3 DAYS.

I have taken it to two different dealers in Norfolk, UK and had diagnostics run but they don’t know why it is happening.

On the first visit, the battery had dropped to 28% so they charged it to 100% and said it was because cold weather and under-use of the car but good battery health.
Three days later it was still showing warning light so garage re-tested and battery was 16%. No explanation offered just blank faces.

I then took it to the garage in Norwich who sold me the vehicle and they ran diagnostics which showed 70% charged, healthy battery but several faults showing when the warning light came on. They don’t know what to do except try replacing the 12v battery even though they think it’s ok.

Here’s the worry - THEY DON’T KNOW WHAT 12V BATTERY TO PUT ON THE CAR. Two separate dealerships are unable to give a price or find one compatible as MG say as they don’t manufacture their own batteries the dealer should use their local battery supplier who are saying don’t know what to use. This has been going on for a week and still no answer.

The first garage are now saying it may be a software update issue anyway and are checking it again on 1st March 2023. There have been no issues with car starting or running so feels possible it’s a faulty sensor but I am not a mechanic.

Has anyone else had a problem with the 12v battery or low battery warning light on a HS PHEV?

Hi
Sorry to hear your problems with your 12v Battery. I personally don't have a PHEV so don't know where the 12v Battery gets its charge from from an alternator from the fuel engine or from the rectifier on your Electric Battery. You need to go to a PHEV dealer. If you have a MG dealership near you ask them. The answer is why you have a separate 12v battery is it does all the 12v auxiliary circuits on your car and computer. I would personally go to a PHEV dealer and get them supply the new battery. Then if that goes flat take it back to the garage that fitted the battery, it's their problem to find it not yours .

 

[midician]

The fact that there is a voltage reading in the car dashboard means there is a Battery Management system in place . Perhaps it’s a BMS fault ? Practically, though it’s easiest to test by replacing the battery .