Information on the 12V Battery.

[stevegus]

Stevegus, since you have expertise in this area - can you confirm if a leisure battery would be a good choice as a replacement?

Car batteries and leisure batteries have slightly different requirements.

Car batteries generally have a high potential current rating CCA cold cranking amps - to power the starter motor in cold weather- which takes hundreds of amps.

Leisure batteries are usually aimed at a lower overall discharge level and dont have a high CCA rating - which an EV probably doesnt need!

And there is middle ground like the one in my motorhome that can do both…made by Varta.

Personally if I we’re changing mine, i might look at something that fits the space under the bonnet as it seems to be sized for a much larger battery than is actually fitted. A visit to Halfords with a tape measure would help the decision. Id probably stick with the standard car type.

If you are loaded Lithium batteries are a nice option!

 

[Les burrows]

Well according to this chap it’s not only MG cars that are having this issue with 12v batteries I know this is Hyundai but might have some relevance to others including MGs
Les

 

[Ian Key]

Interesting that lithium 12v batteries need different management software especially for cold weather so that option is out.
Also those who are worried about the 12v battery going flat then perhaps replace it with a larger capacity lead acid battery and don't keep quizing the car through the app.

 

[Diggsy]

Interesting that lithium 12v batteries need different management software especially for cold weather so that option is out.
Also those who are worried about the 12v battery going flat then perhaps replace it with a larger capacity lead acid battery and don't keep quizing the car through the app.

I think this could be a big part of the problem - logging into the car from the app too often, or the app automatically contacting the car perhaps.

 

[Pebble]

Having come from leisure boat and caravan/motorhome industries, I've been a supporter of using leisure batteries in lieu of starter batteries since getting our MG5. We all know from the previous posts and other threads that a starter battery with a CCA isn't necessary for EVs. When my 12v battery does give up (only three months old at the moment so doing well ), I'll be dropping in a lead acid or AGM leisure battery. No brainer for me really .

 

[Ian Key]

Another thought. Is the Bluetooth module on a ignition switched supply or permanent live? If on permanent live could that be flattening some batteries as it searches for a connection?

 

[brianharries]

Thanks for the replies. I will continue to monitor the 12v battery but it seems that from the collective experience 12.5V should be a fair average.

I'm curious to know how the 12V battery is charged (and what would discharge it). Lots to learn about my new toy.

I suppose it is easy to get a bit paranoid about battery voltage when you hear of cars being dead for no apperently reason when their owners try to use them first thing in the morning.

My former EV was a Nissan Leaf. 12v battery charging was a well known issue for many on the Leaf, which was why some of the later 30KWH Vehicles had a small solar panel in the rear spoiler in order to keep the 12v battery fully charged. Noticeably, my 12v battery would run to flat during the winter months. So I hard-wired a small 12v trickle charger into my Leaf with a small socket for it next to the Chademo Charger which I kept plugged in and on charge when on the drive.
My New MG4 had a flat 12v battery (therefore locked out) on my second morning after purchase . I thought it was a return of a similar problem to the Leaf. I disconnected the wireless ‘Car Play’ adapter that had been left connected to the USB C port and have had no further issues. I have since assumed that there was a constant draw through the night from this cheap Japanese adapter. When the voltage on the 12v battery got too low, there wasn’t enough current to initiate a charge on the inbuilt charger of the MG4.
The graph attached shows a charge cycle on the Nissan Leaf from 12:30hrs - 03:00hrs (connected to the mains)….. then an unexplained draw for just under 1hr. Then no draw at all until an inexplicable intermittent draw from 16:30hrs until the 12v battery run to flat several hours later. I was led to believe that I had a ‘sticking’ resistor /relay switch or such like, particularly manifest during the colder winter months. Many folk attempted a fix to this problem, spending lots of money in the process, but with no permanent fix. Not much help I’m afraid, just shedding a little light on the intricacies of keeping the 12v battery fully charged!

 

[Purclewan]

My former EV was a Nissan Leaf. 12v battery charging was a well known issue for many on the Leaf, which was why some of the later 30KWH Vehicles had a small solar panel in the rear spoiler in order to keep the 12v battery fully charged. Noticeably, my 12v battery would run to flat during the winter months. So I hard-wired a small 12v trickle charger into my Leaf with a small socket for it next to the Chademo Charger which I kept plugged in and on charge when on the drive.
My New MG4 had a flat 12v battery (therefore locked out) on my second morning after purchase . I thought it was a return of a similar problem to the Leaf. I disconnected the wireless ‘Car Play’ adapter that had been left connected to the USB C port and have had no further issues. I have since assumed that there was a constant draw through the night from this cheap Japanese adapter. When the voltage on the 12v battery got too low, there wasn’t enough current to initiate a charge on the inbuilt charger of the MG4.
The graph attached shows a charge cycle on the Nissan Leaf from 12:30hrs - 03:00hrs (connected to the mains)….. then an unexplained draw for just under 1hr. Then no draw at all until an inexplicable intermittent draw from 16:30hrs until the 12v battery run to flat several hours later. I was led to believe that I had a ‘sticking’ resistor /relay switch or such like, particularly manifest during the colder winter months. Many folk attempted a fix to this problem, spending lots of money in the process, but with no permanent fix. Not much help I’m afraid, just shedding a little light on the intricacies of keeping the 12v battery fully charged!

View attachment 16489

Interesting thoughts and I had wondered about parasitic losses via onboard electronics such as security devices, Bluetooth, wifi etc. From the various answers I have seen, it seems the MG4s 12V battery is kept topped up by the HV battery but since the HV system depends in turn on the 12V battery to power the control electronics it could theoretically turn into a chicken and egg situation if the parasitic drain is too high.

I feel happy now after the advice on this forum that this is unlikely to happen with an EV.

I suppose I was being a bit paranoid. A lot of modern (especially high-performance) ice cars are so loaded with electronics that even when powered down the drain on the battery can be significant. I know from personal experience that leaving my Aston Martin sitting in the garage unused for 7 days and not being trickle charged WILL result in a very flat battery.

 

[TheHypnoToad]

Interesting thoughts and I had wondered about parasitic losses via onboard electronics such as security devices, Bluetooth, wifi etc. From the various answers I have seen, it seems the MG4s 12V battery is kept topped up by the HV battery but since the HV system depends in turn on the 12V battery to power the control electronics it could theoretically turn into a chicken and egg situation if the parasitic drain is too high.

I feel happy now after the advice on this forum that this is unlikely to happen with an EV.

I suppose I was being a bit paranoid. A lot of modern (especially high-performance) ice cars are so loaded with electronics that even when powered down the drain on the battery can be significant. I know from personal experience that leaving my Aston Martin sitting in the garage unused for 7 days and not being trickle charged WILL result in a very flat battery.

If you look on amazon you can get something called a 'bluetooth battery monitor'.

They are around £20 - £30 which isn't cheap, but cheaper than a new battery.

They pair to your phone and log the voltage over time, and you can even make it send alerts if the voltage goes too lower.

I have one and can recommend it, it will also log the history of your 12v battery voltage and it can make a graph showing it over time:

So far I've not seen it go below 12v, or above 15v, so I would say the battery is working as expected.

 

[tsedge]

If you look on amazon you can get something called a 'bluetooth battery monitor'.

They are around £20 - £30 which isn't cheap, but cheaper than a new battery.

They pair to your phone and log the voltage over time, and you can even make it send alerts if the voltage goes too lower.

I have one and can recommend it, it will also log the history of your 12v battery voltage and it can make a graph showing it over time:

So far I've not seen it go below 12v, or above 15v, so I would say the battery is working as expected.

How much of a drain is the bluetooth monitor itself?

 

[TheHypnoToad]

How much of a drain is the bluetooth monitor itself?

Just checked my order history, according to the listing, 1.5ma which is next to nothing really.

If you search 'B08VHMJYXY' on amazon, that is the item I ordered, or here's a link:

Amazon product ASIN B08VHMJYXY

 

[Diggsy]

Does that device have any effect on battery drain?

Edit, just read, already asked, sorry

 

[brianharries]

Just checked my order history, according to the listing, 1.5ma which is next to nothing really.

If you search 'B08VHMJYXY' on amazon, that is the item I ordered, or here's a link:

Amazon product ASIN B08VHMJYXY

I too can vouch for this device. One on my Motorhome leisure battery; and one on the car….. it gives a terrific peace of mind! Well worth the outlay and a super dependable app.

 

[stevegus]

Having come from leisure boat and caravan/motorhome industries, I've been a supporter of using leisure batteries in lieu of starter batteries since getting our MG5. We all know from the previous posts and other threads that a starter battery with a CCA isn't necessary for EVs. When my 12v battery does give up (only three months old at the moment so doing well ), I'll be dropping in a lead acid or AGM leisure battery. No brainer for me really .

Varta do leisure batteries that also support a cold cranking amps rating.

And mentions of Lithium being unsuitable- i dont understand why (as an electronic engineer) as the battery management is built into the battery itself and they are interchangeable in ICE cars.

Some lithium battery technology would have too high a cell voltage? But the Lifepo4 (?) used in this type of cell have a decent compatibility to a lead acid cell.

There seems to be space for a considerable longer battery as the standard fitment is one of the smallest commonly available

 

[stevegus]

How much of a drain is the bluetooth monitor itself?

The MG app tells you the voltage already….

 

[siteguru]

... but only if you open the app and check it. It doesn't record the voltage and trend the history.

 

[tsedge]

Varta do leisure batteries that also support a cold cranking amps rating.

And mentions of Lithium being unsuitable- i dont understand why (as an electronic engineer) as the battery management is built into the battery itself and they are interchangeable in ICE cars.

Some lithium battery technology would have too high a cell voltage? But the Lifepo4 (?) used in this type of cell have a decent compatibility to a lead acid cell.

There seems to be space for a considerable longer battery as the standard fitment is one of the smallest commonly available

I think Lifepo4 would be prohibitively expensive but I agree it would work so long as it contains its own BMS.

 

[stevegus]

... but only if you open the app and check it. It doesn't record the voltage and trend the history.

Hmmm. I dont want to live my life worrying about things like that batteries have just worked in all my other cars. If i had concerns id just put a bigger battery in the considerable free space available

 

[Byrnie]

Interesting thoughts and I had wondered about parasitic losses via onboard electronics such as security devices, Bluetooth, wifi etc. From the various answers I have seen, it seems the MG4s 12V battery is kept topped up by the HV battery but since the HV system depends in turn on the 12V battery to power the control electronics it could theoretically turn into a chicken and egg situation if the parasitic drain is too high.

I feel happy now after the advice on this forum that this is unlikely to happen with an EV.

I suppose I was being a bit paranoid. A lot of modern (especially high-performance) ice cars are so loaded with electronics that even when powered down the drain on the battery can be significant. I know from personal experience that leaving my Aston Martin sitting in the garage unused for 7 days and not being trickle charged WILL result in a very flat battery. i

Interesting that lithium 12v batteries need different management software especially for cold weather so that option is out.
Also those who are worried about the 12v battery going flat then perhaps replace it with a larger capacity lead acid battery and don't keep quizing the car through the app.

Interesting post, i have an 4 month old MG4 and had a flat 12v battery twice (most recently in an airport car park after being away for only 2 weeks). I spoke to MG who told me that’s the way it is with EV’s (not true, we also have a Tesla and never had that issue) and my battery is fine (although it’s down to 11.5v). So should MG not replace the 12v lithium battery with a battery that won’t discharge so easily?

 

[Ian Key]

Interesting post, i have an 4 month old MG4 and had a flat 12v battery twice (most recently in an airport car park after being away for only 2 weeks). I spoke to MG who told me that’s the way it is with EV’s (not true, we also have a Tesla and never had that issue) and my battery is fine (although it’s down to 11.5v). So should MG not replace the 12v lithium battery with a battery that won’t discharge so easily?

I think you meant to say replace the 12v lead acid battery as it's not a lithium battery.
Have you fitted a dashcam or do you reguarly check the car with the iSmart app? Both of which could discharge the battery.