12v Battery Charging

[siteguru]

I could only think this old screen and a up to date one, as the car battery is not charged when charging the HV battery.

Well iSMART must be lying to me every time I charge my car at home and do a scan of the car ... it always shows 13.xV (typically 13.9V) whilst on (HV) charge.

 

[Jto]

Well iSMART must be lying to me every time I charge my car at home and do a scan of the car ... it always shows 13.xV (typically 13.9V) whilst on (HV) charge.

When not on the home charger do you know what the reading is.

 

[tsedge]

Well iSMART must be lying to me every time I charge my car at home and do a scan of the car ... it always shows 13.xV (typically 13.9V) whilst on (HV) charge.

Mine is the same. Definitely charges the 12V when the HV battery is charged. Ought to charge it periodically when it is not being charged.

There have been numerous bugs in the charging system so quite likely updates are needed and also quite possibly a weak 12V battery,

 

[siteguru]

When not on the home charger do you know what the reading is.

I've seen the same when charging on a DC rapid.

Then again, mine is an SE SR so things might be different with Trophies and/or SE LR cars.

 

[Tig170]

the 12v battery is a Varta, so cant really improve on quality - although once in a while things do fail prematurely, likewise the HV system is CATL, again you cant really improve on quality - although once in a while things do fail prematurely

 

[Rolfe]

My 12v is always showing over 14v when the car is charging, and when I got in it yesterday morning to show off its party pieces to the friend I was staying with, again I saw over 14v when I was scrolling through the screens letting him see what information was available. So it probably started charging the 12v when I woke the car up.

 

[Kithmo]

58%... So possibly the main battery needs sufficient capacity (over 30, 40 or 50%) to attempt charging the 12v ?. Mine was under 30% when the 12v went dead. Will be interesting to test

I think you're right, ISTR reading this somewhere, possibly on another make, that 12v smart charging would only occur if the HV battery was over 50%.

 

[Rolfe]

Why would that be, I wonder?

 

[seibegee]

Having had the MG 4 3 months the 12 volt battery has gone flat 4 times. Today it was flat again having been parked for two days with the main traction battery on 40%. The 12v battery voltage is 4.62v which is too low to initiate a charge. Having replaced the battery I am beginning to suspect the MG ismart app may be the cause. I did call the AA on one occasion and he was very familiar with the mg4 issues. One of his theories was going too close to the car with the key in your pocket. Try this, If you stand by the car and open the app you can hear the car wake up with a number of relays being energised. On two occasions I can recall before I found the 12 volt battery flat. The day before I had checked the battery using the app. So to test the theory, if you are not using your car for a few days leave it for a day then do a scan with the app on day 2 to check the 12v battery. Then on Day 3 see if the battery is flat.

 

[jpk]

Having had the MG 4 3 months the 12 volt battery has gone flat 4 times. Today it was flat again having been parked for two days with the main traction battery on 40%. The 12v battery voltage is 4.62v which is too low to initiate a charge. Having replaced the battery I am beginning to suspect the MG ismart app may be the cause. I did call the AA on one occasion and he was very familiar with the mg4 issues. One of his theories was going too close to the car with the key in your pocket. Try this, If you stand by the car and open the app you can here the car wake up with a number of relays being energised. On two occasions I can recall before I found the 12 volt battery flat. The day before I had checked the battery using the app. So to test the theory, if you are not using your car for a few days leave it for a day then do a scan with the app on day 2 to check the 12v battery. Then on Day 3 see if the battery is flat.

If you believe it's the app then force stop it after each use so it doesn't try to connect to your car in the background

 

[Ian Key]

Having had the MG 4 3 months the 12 volt battery has gone flat 4 times. Today it was flat again having been parked for two days with the main traction battery on 40%. The 12v battery voltage is 4.62v which is too low to initiate a charge. Having replaced the battery I am beginning to suspect the MG ismart app may be the cause. I did call the AA on one occasion and he was very familiar with the mg4 issues. One of his theories was going too close to the car with the key in your pocket. Try this, If you stand by the car and open the app you can hear the car wake up with a number of relays being energised. On two occasions I can recall before I found the 12 volt battery flat. The day before I had checked the battery using the app. So to test the theory, if you are not using your car for a few days leave it for a day then do a scan with the app on day 2 to check the 12v battery. Then on Day 3 see if the battery is flat.

Have you had any BMS software updates?

 

[siteguru]

Having had my MG4 for 9 months my 12V battery has never once given me any vibes about running flat.

Then again I've checked the battery connections to make sure they're tight, and when driving I check the tyre pressure screen (at times) to make sure that the HV battery is charging the 12V battery.

 

[seibegee]

Have you had any BMS software updates?

Collected the car from the dealers in May, earliest the dealer can look at it for lack of DC charging, flat 12volt battery, no dab or fm radio issues they tell me is 7th September. When did the BMS update come out?

 

[Ian Key]

Collected the car from the dealers in May, earliest the dealer can look at it for lack of DC charging, flat 12volt battery, no dab or fm radio issues they tell me is 7th September. When did the BMS update come out?

I'm not sure but I know some have had their BMS updated

 

[Kithmo]

My 12v varies between 12.3v and 12.6v when it's not running and sits at 13.9v when it is.
I did condition the battery just after I got it using my Ctek charger and it only took about an hour to cycle through the various stages, so I assume it's ok and not a weak one.

 

[siteguru]

I've never conditioned my battery. I've seen 12.2V to 12.6V as a "resting" range (right now it is 12.4V), and 13.9V (always) when charging.

 

[seibegee]

Sounds good, my 12v battery regularly dips below 11.9v. So when I charged it I did condition the battery using my Ctek MX5 the first time it went flat but at 4.62 volts this time the charger didn't even attempt to charge it so the damage is done. Its possible the car came with a not so good 12v battery. As Siteguru says he checks his connections to make sure they're tight! We've all got to do that .

 

[tsedge]

Sounds good, my 12v battery regularly dips below 11.9v. So when I charged it I did condition the battery using my Ctek MX5 the first time it went flat but at 4.62 volts this time the charger didn't even attempt to charge it so the damage is done. Its possible the car came with a not so good 12v battery. As Siteguru says he checks his connections to make sure they're tight! We've all got to do that .

I would put a decent brand battery in but also check all the necessary updates have been done to make sure it is being charged properly.

 

[seibegee]

I would put a decent brand battery in but also check all the necessary updates have been done to make sure it is being charged properly.

Thanks, good idea. I'll ask the dealer on the 7th September when it goes into be looked at. Hopefully all will be well after. I'm looking forward to being able to fast charge occasionally when needed, not having a flat battery when I need to use the car and perhaps being able to listen to the radio whilst driving, Luxury!

 

[Kithmo]

Sounds good, my 12v battery regularly dips below 11.9v. So when I charged it I did condition the battery using my Ctek MX5 the first time it went flat but at 4.62 volts this time the charger didn't even attempt to charge it so the damage is done. Its possible the car came with a not so good 12v battery. As Siteguru says he checks his connections to make sure they're tight! We've all got to do that .

I had a 12v mobility scooter battery that the Ctek wouldn't revive, I put it on a standard 12v charger (non-smart) to kick start it then on the Ctek after. It brought it back (temporarily) and did last another few months, but finally gave up the ghost eventually, as you say, the damage is done once it's got that low.