Replacing the 12v battery and warranty limitations - what would you do?

[thingaby]

During the breakdown in which my car was bricked by fault codes triggered by the Eurotunnel rapid charger my car 12v battery 'failed' and dropped to 3v charge. The car was recovered to the local dealer where (after 2 days) the fault codes were cleared, the 12v battery re-charged and a replacement 12v battery ordered under warranty. It was a few days until the replacement battery would be available and I decided to use the original battery until the replacement could be fitted. When I arrived back at the dealers some days later they told me the replacement 12v battery had cost £120 but MG would only cover £100 of that cost because the battery was a wear and tear item. There would also be a small fitting charge. I was disappointed by supposed wear and tear issues on a battery after less than 1500 miles - low mileage because the car had been off the road for other repairs! I chose to decline the replacement which on reflection was a daft decision unless I now decide not to replace the original 12v battery.
What should I do? Stick with the original battery which has been fine in the 10 days/380 miles since it was recharged or take the dealer's option that when a battery has been discharged down to 3v it should be replaced? If I do replace it what battery make and size should I choose?

 

[REDLeader]

There is no right or wrong .... I would try a few rapids again to see if same problem occurs. Did garage update software when car was in.

 

[Lovemyev]

I know it’s only £20 they wanted you to pay, but to be totally honest, I think that was a bit spiteful on their part.
I mean, £20 come on !!!!.
You just wouldn’t bother really.
Is it worth pissing somebody off for the sake of asking for £20 - I mean, really ????.
Are they that short of £20 that they could not have covered the cost OMG !.
And then a “small fitting charge” - come on people, it take less than five minutes to fit a new battery !.
I think you did right to tell them to stuff it !.
Principle plays a big factor here.
If the car had covered 12,000 miles and was 1 year old then fair enough, but 1,500 miles is absolutely ridiculous.
Another excellent example of how to lose a customers faith in the brand, for the sake of £20.
Well done ( not ) .

 

[thingaby]

I have done two successful rapid charges since the Eurotunnel debacle but they were both on the same Ecotricity/Gridserve charger. When I unhooked the car from my domestic charger this morning the traction battery was on 80% and the LV battery was at 14v. When I switched the car on again after 90 mins the LV battery had fallen to 13.4v. Hopefully the fall is due to the act of switching on rather than a battery drain. Within a minute in the ready mode the HV battery topped the LV back up to 14v.
I have not yet had the software update done. The dealer to which I was recovered (Caffyns) could not find the update bulletin and was sceptical about its existance on my say so. My own dealer (Stoneacre) can't get me in for the software fix until 15 June.

 

[Alb]

I'd take the new battery for £20 and leave the original fitted.
Sell it for a profit or fit it yourself later if you find it's required.

 

[Ozzie1989]

If they say it's a wear and tear (consumable) item then there is no issue in you changing it yourself. Same as wiper blades, brake pads, tyres imo and changing those wouldn't invalidate your warranty.

Personally I'd buy a 12v boost pack to keep in the car and stick with the original battery as it seems to be behaving now.

I do wonder however with these cars having sat around for a long time before getting to the UK whether we'll see lots more 12v battery issues.

 

[N2STY]

£20 sounds OK is covered for 12 months under the warranty but in small print is says to a max of £100

I have a trade account and can get it for less then £100 with 4 years warranty shame on MG
but I definitely can't get one for £20 so I would get it

 

[Bluecar1]

I am always sceptical of dealers saying parts need replacing because of x without being able to back it up by saying "we did this test and it failed", have had this several time and declined the charge, then checked myself when I get home and most of the time no action required, it does make you more wary of the dealer service department

may be take it to an independent garage who can do a drop test etc on the battery to see how it holds up under load etc ? but may charge for it and if so likely to be more than the £20 MG want to change it under warranty

also most dealers also have the option to wave small charges under a "goodwill" option

discharge to a low voltage for a short period tends not to be terminal, but leaving it in that state is

my previous car a Hyundai Ioniq suffered a flat battery several times over covid lockdowns, most occasions going to 6v ish, recharged and all ok

the other thing to note is many cars when the 12v goes that low you tend get all sorts of weird and wonderful fault codes appear, which then disappear when the 12v is recharged (the joys of driving computers on wheels)

 

[AbuG]

Why do they want a fitting charge if it is covered under warranty??
I would contact MG motors for the fitting charge.
The excess (£20) is in writing so would pay that.

 

[Lovemyev]

Because they are only asking for a £20 contribution towards the price of the brand new battery, does that imply that the original battery is then subject to a warranty claim ?.
Are they prepared to hand you the original battery as well as fit a new battery as well ??.
My guess would be not !.

 

[thingaby]

You are right. Again. They ruled out letting me have the original battery back after the replacement.

 

[Lovemyev]

You are right. Again. They ruled out letting me have the original battery back after the replacement.

Just as I expected !.
It’s been a LONG time since I have worked in a large dealership, but somethings never change.
Still at it ! .

 

[Coulomb]

When I unhooked the car from my domestic charger this morning the traction battery was on 80% and the LV battery was at 14v.

14 V on a nominally 12 V battery is a kind of "surface charge"; it won't stay that high very long.

When I switched the car on again after 90 mins the LV battery had fallen to 13.4v.

Even 13.4 V is not sustainable, and it was only that high because it was being charged heavily.

Hopefully the fall is due to the act of switching on rather than a battery drain.

Most of that fall is because it was no longer being heavily charged by the car's DC-DC converter. After being fully charged, a typical 12 V lead-acid battery will fall to between 12.8 and about 13.1 V with no or very little load, but still be fully charged.

Within a minute in the ready mode the HV battery topped the LV back up to 14v.

Ironically, a battery that shoots up to 14 V very quickly could be nearly dead, with high internal resistance. A light charge can pull it high in voltage quickly, but equally a light discharge can see it plummet in voltage just as quickly. But since your battery was presumably nearly full already and took a minute to get to 14 V, that's a good sign.

As others have said, spending a little time at low voltage (granted, 3 V is quite extreme!), is often not fatal. Spending more than a day or two at that voltage, however, is really bad for a lead-acid battery.

Edit: re-reading your first post, I see that it probably did spend about two days at very low voltage. I'd watch it pretty carefully for a while.

 

[thingaby]

14 V on a nominally 12 V battery is a kind of "surface charge"; it won't stay that high very long.

Even 13.4 V is not sustainable, and it was only that high because it was being charged heavily.


Most of that fall is because it was no longer being heavily charged by the car's DC-DC converter. After being fully charged, a typical 12 V lead-acid battery will fall to between 12.8 and about 13.1 V with no or very little load, but still be fully charged.


Ironically, a battery that shoots up to 14 V very quickly could be nearly dead, with high internal resistance. A light charge can pull it high in voltage quickly, but equally a light discharge can see it plummet in voltage just as quickly. But since your battery was presumably nearly full already and took a minute to get to 14 V, that's a good sign.

As others have said, spending a little time at low voltage (granted, 3 V is quite extreme!), is often not fatal. Spending more than a day or two at that voltage, however, is really bad for a lead-acid battery.

Edit: re-reading your first post, I see that it probably did spend about two days at very low voltage. I'd watch it pretty carefully for a while.

Thank you for your very helpful and expert reply. I will watch the 12v carefully for a while.

 

[tonko]

They keep changing what’s covered by warranty all the time. Once you changed your 12v battery to a new one, they don’t renew your warranty on your new battery. Warranty on the 12V battery is only for 12 months from your purchase date

 

[N2STY]

They keep changing what’s covered by warranty all the time. Once you changed your 12v battery to a new one, they don’t renew your warranty on your new battery. Warranty on the 12V battery is only for 12 months from your purchase date

This is because the new battery will have its own warranty nothing to do with the car

 

[Bluecar1]

I do find the "1 year battery warranty" a little strange as most batteries you buy from car parts depots like Halford in the UK carry a 3 or even 5 year warranty or a reasonable branded battery in the £120 price bracket so why are MG only honouring the first year?