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I confirmed a pleasing fact this morning. Since owning the MG and reading about peoples' experiences with EVs and 12v battery issues, I wanted to see whether the MG charged the 12v battery while it was fast charging. I tested it today, using a multimeter to check the 12v battery voltage before and after starting a (fast) charge. Sure enough, before charging (with cable plugged in and car locked, but charger delivering 0 amps) the battery read 12.00v (a bit low - I would have expected 12.4v for a car that was used only yesterday). I then started the charge using the Ohme app, waited for the charge current to rise to 32A, then measured the battery voltage again - 13.25v - Yaaaayyyy - 12v battery is indeed charging along with the HV battery :).
I'm happy now, so have come in for a cup of tea.
 

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I confirmed a pleasing fact this morning. Since owning the MG and reading about peoples' experiences with EVs and 12v battery issues, I wanted to see whether the MG charged the 12v battery while it was fast charging. I tested it today, using a multimeter to check the 12v battery voltage before and after starting a (fast) charge. Sure enough, before charging (with cable plugged in and car locked, but charger delivering 0 amps) the battery read 12.00v (a bit low - I would have expected 12.4v for a car that was used only yesterday). I then started the charge using the Ohme app, waited for the charge current to rise to 32A, then measured the battery voltage again - 13.25v - Yaaaayyyy - 12v battery is indeed charging along with the HV battery :).
I'm happy now, so have come in for a cup of tea.
I thought we already know that it charges the 12V battery when charging on your home charger? Anyway, great to have this confirmed by someone with the hardware to confirm it 馃槃

On a Rapid Charger, it does not charge the 12V battery when charging the HV battery.

Stay Safe and Wash Your Hands. Things are getting worse out there.
 

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I confirmed a pleasing fact this morning. Since owning the MG and reading about peoples' experiences with EVs and 12v battery issues, I wanted to see whether the MG charged the 12v battery while it was fast charging. I tested it today, using a multimeter to check the 12v battery voltage before and after starting a (fast) charge. Sure enough, before charging (with cable plugged in and car locked, but charger delivering 0 amps) the battery read 12.00v (a bit low - I would have expected 12.4v for a car that was used only yesterday). I then started the charge using the Ohme app, waited for the charge current to rise to 32A, then measured the battery voltage again - 13.25v - Yaaaayyyy - 12v battery is indeed charging along with the HV battery :).
I'm happy now, so have come in for a cup of tea.
12.0V is about 50% soc so pretty low if used yesterday.
Make of battery determines actual soc vs voltage chart, but here鈥檚 a useful one...
 
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I thought we already know that it charges the 12V battery when charging on your home charger? Anyway, great to have this confirmed by someone with the hardware to confirm it 馃槃

On a Rapid Charger, it does not charge the 12V battery when charging the HV battery.

Stay Safe and Wash Your Hands. Things are getting worse out there.
Has anybody actually tested it is the case like above?
 

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Discussion Starter #6
Actually, yes, I remember checking this the first time I used a rapid charger (well, actually I didn't test the 12v battery voltage when the car was OFF but charging). The big difference with rapid charging is that the car can be unlocked, so you can sit in it and turn it on (not to "ready" as the car won't go to ready while charging, but will go to "on"). At that point, all the 12v car systems are active (entertainment system etc) and the 12V battery is indeed charging (dashboard LED bar graph shows 14v). I sat there with full heater running for 45 mins, while I dried out (tipping it down with rain that day, back in early feb). What I haven't done is tested the 12V battery voltage while the car is rapid charging, but with the car systems "off" and locked (as if you've wondered off for a coffee or burger). I'll put a multimeter in the car next time I'm allowed out for a long journey...
 

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Actually, yes, I remember checking this the first time I used a rapid charger (well, actually I didn't test the 12v battery voltage when the car was OFF but charging). The big difference with rapid charging is that the car can be unlocked, so you can sit in it and turn it on (not to "ready" as the car won't go to ready while charging, but will go to "on"). At that point, all the 12v car systems are active (entertainment system etc) and the 12V battery is indeed charging (dashboard LED bar graph shows 14v). I sat there with full heater running for 45 mins, while I dried out (tipping it down with rain that day, back in early feb). What I haven't done is tested the 12V battery voltage while the car is rapid charging, but with the car systems "off" and locked (as if you've wondered off for a coffee or burger). I'll put a multimeter in the car next time I'm allowed out for a long journey...
I will check mine because it ran the battery dead :-(

Won't be able to report back for a few weeks though.
 

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Discussion Starter #8
Hmmm... interesting. would be useful to hear the circumstances around that. Maybe this behaviour is subject to a BMS firmware difference....
 

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I confirmed a pleasing fact this morning. Since owning the MG and reading about peoples' experiences with EVs and 12v battery issues, I wanted to see whether the MG charged the 12v battery while it was fast charging. I tested it today, using a multimeter to check the 12v battery voltage before and after starting a (fast) charge. Sure enough, before charging (with cable plugged in and car locked, but charger delivering 0 amps) the battery read 12.00v (a bit low - I would have expected 12.4v for a car that was used only yesterday). I then started the charge using the Ohme app, waited for the charge current to rise to 32A, then measured the battery voltage again - 13.25v - Yaaaayyyy - 12v battery is indeed charging along with the HV battery :).
I'm happy now, so have come in for a cup of tea.
Well the 12volt battery is not the same composition as the 44.5w lithium ion nmc in the MG ZS EV could the charger weaken or destroy the 12volt battery?
 

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Discussion Starter #10
Hi Patrick, as you rightly say, the two batteries are very different indeed. That's why they have very different charging circuits. There is a high voltage AC/DC converter/charger, supplying around 430v DC to charge the main drive battery, from mains input from the charging port (this is the big rectangular silver box on top of the motor assembly under the bonnet). Then there is a DC/DC converter to supply 14v charging voltage for the 12v battery. This circuit does the same job as the alternator/regulator combination in an ICE car, supplying the correct charging voltage for a lead-acid 12v battery. When the car is in "on" or "ready" mode, this DC/DC converter is active and providing charge to the 12v battery (like running the engine in an ICE car). What we've ascertained regarding the MG is that not only does this happen when the car is "on", but also when the car is actively being charged (when off and locked). So the 12v battery get's a boost (at the correct voltage :)) as the drive battery is being charged.
 

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Why does the MG not do what every other EV does which as soon as the car is active the dc to dc converter runs to keep the 12v alive.

it鈥檚 pretty poor that it doesn鈥檛 do this when DC charging or when the car is in use
 

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Discussion Starter #12
Ummmm... I think it does! Whenever the car state is "On" or "Ready" or whenever it's charging (power being supplied by the EVSE) the DC/DC converter is active, maintaining the 12v battery. I'm not sure I understand your comment - can you elaborate?
 

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Why does the MG not do what every other EV does which as soon as the car is active the dc to dc converter runs to keep the 12v alive.

it鈥檚 pretty poor that it doesn鈥檛 do this when DC charging or when the car is in use
What quaint ideas some i3 owners have...
 

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The irony is pre-lockdown we had a number of MG owners sitting in their cars with the car ON but in ACC1 basically (on button with orange light - 1 press) and they overly discharged their 12v. So MG owners are now in the know that 1. you must press button twice to get into ACC2 ON position where DC-DC works on turn car on to drive and sit for 5mins once a week.

Now I'm seeing owners of Zoes, Leafs, Souls posting pics of "I can't get into my car!" "I have got an error message that won't clear" etc. So it seems very much that 12v issues are not limited to just the MG. In fact there was 1 post on the MG facebook group last week where an owner was using their MG to jump start their ICE Juke because it was flat lol
 

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Discussion Starter #15
Let's be clear on terminology here. According to the MG manual, there are three states the car can be in (apart from "off" :) ) - ACC ON and READY. ACC is just the infotainment system active, but NOT the DC/DC converter for 12v battery charging. This is synonomous with having the ignition on in your ICE car but with the engine not running. Then there's ON, which is with all car services active but not enabled for driving (which is necessary when you're plugged into a rapid charger). It's the ON state that you need if you're sitting in your car listening to music with the aircon on full! Ready is, of course, the driving state (which you can't enter if you're plugged into a charger). So as others have said, if you're just sitting in your car, press the "start" button twice (without the brake pedal depressed) to set ACC, then ON. Hope this clarifies things.
 

Zoe Devotee
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Let's be clear on terminology here. According to the MG manual, there are three states the car can be in (apart from "off" :) ) - ACC ON and READY. ACC is just the infotainment system active, but NOT the DC/DC converter for 12v battery charging. This is synonomous with having the ignition on in your ICE car but with the engine not running. Then there's ON, which is with all car services active but not enabled for driving (which is necessary when you're plugged into a rapid charger). It's the ON state that you need if you're sitting in your car listening to music with the aircon on full! Ready is, of course, the driving state (which you can't enter if you're plugged into a charger). So as others have said, if you're just sitting in your car, press the "start" button twice (without the brake pedal depressed) to set ACC, then ON. Hope this clarifies things.
I was keeping it simple. ACC1 and 2 are standard on ALL cars. You turn the key to ACC1 for basics like radio, ACC2 is the same, but if you start the car it returns to ACC too automatically (when you let go of the key) this is on, but in ICE not charging unless you twist key to start car, then ACC is on with 12v charging. ;)

But yeah in EV ACC1 is only fine for radio for a short time (Even though the heater will actually work quite happily). ACC2 (two press of button and green light on button) is good for everything except driving because the DC-DC is energised. (y)
 

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What quaint ideas some i3 owners have...
Helpful comment 馃檮 it was you guys above that said you can run down the 12v by having the infotainment system on when DCFC. Both the Tesla, Zoe and i3 I have activate the 12v charging as soon as you open the door
 

Zoe Devotee
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Helpful comment 馃檮 it was you guys above that said you can run down the 12v by having the infotainment system on when DCFC. Both the Tesla, Zoe and i3 I have activate the 12v charging as soon as you open the door
Zoe is as soon as you unlock the car.
 

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I confirmed a pleasing fact this morning. Since owning the MG and reading about peoples' experiences with EVs and 12v battery issues, I wanted to see whether the MG charged the 12v battery while it was fast charging. I tested it today, using a multimeter to check the 12v battery voltage before and after starting a (fast) charge. Sure enough, before charging (with cable plugged in and car locked, but charger delivering 0 amps) the battery read 12.00v (a bit low - I would have expected 12.4v for a car that was used only yesterday). I then started the charge using the Ohme app, waited for the charge current to rise to 32A, then measured the battery voltage again - 13.25v - Yaaaayyyy - 12v battery is indeed charging along with the HV battery :).
I'm happy now, so have come in for a cup of tea.
It's the
I confirmed a pleasing fact this morning. Since owning the MG and reading about peoples' experiences with EVs and 12v battery issues, I wanted to see whether the MG charged the 12v battery while it was fast charging. I tested it today, using a multimeter to check the 12v battery voltage before and after starting a (fast) charge. Sure enough, before charging (with cable plugged in and car locked, but charger delivering 0 amps) the battery read 12.00v (a bit low - I would have expected 12.4v for a car that was used only yesterday). I then started the charge using the Ohme app, waited for the charge current to rise to 32A, then measured the battery voltage again - 13.25v - Yaaaayyyy - 12v battery is indeed charging along with the HV battery :).
I'm happy now, so have come in for a cup of tea.
Its the HV battery that tops the 12 volt battery up.
 
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