V2L warning - also discharges 12v battery!

Some observations on this thread:

1. I also had a flat 12v battery after a long V2L session (about 15 hours). However, after a shorter V2L session, the 12V battery was OK. It looks like the 12v battery is being charged during V2L, but maybe this times out after a period of time.

2. The V2L output is pure sine wave, about 220V, 50Hz and can supply 3kW (but I've not tested for how long it can sustain 3kW.

3. When V2L is running, any attempt to check the HV battery SOC (using the app or the car's instrument display) interrupts the V2L power for a fraction of a second. This may explain why appliances behave strangely (like the electric blanket reset).

4. Using a mains socket tester on the V2L output will yield strange results. Live and Neutral are interchangeable from a stand-alone generator, so swapped Live and Neutral is meaningless.
 
Last edited:
Ok, day 2 update:

Yesterday evening, with 100w draw on the V2L, the battery voltage started slowly dropping as the evening went on. We noticed that the car was doing a pulse style charging, every now and again, seemingly at random, the voltage would momentarily spike to 14.3 ish volts then drop back down. That then seemed to stop and the voltage slowly dropped down to below 13v. I decided to put the car in the on position until bedtime, and duly the battery was held at 14.1v until I switched it off again.

This morning, a 2% drop in HV battery level and the main 12v battery showing 12.2v on the app - unfortunately I didn’t get a chance to put the multimeter on the battery to confirm this. Given that the battery spend at least 12 hours on charge yesterday, 12.2v tells me either there was a load on it again overnight and/or the battery is knackered.

More likely the latter, as on putting the car in ready mode, the voltage dropped to 10.2v and the car threw up lots of error messages, intermittently shutting off and reconnecting the HV battery. Eventually it settled itself down and is currently sitting in ready mode with the 12v battery charging as you would expect.

Two things come to mind: quite clearly the 12v battery is not as healthy as you would expect a new battery (as discussed above, we know why that could be). Secondly and in my mind more annoyingly, is that the car doesn’t seem to be able to recognise a discharging 12v battery in off mode (not for an extended period anyhow) and will quite happily let it discharge to the point of not staring the car, even though it has the means to correct it.

In summary, it seems there is a load on the 12v battery with the car off and V2L attached (even with no AC devices attached). The car will pulse charge for a while but will ultimately allow this to discharge the battery to the point of needing a jump start
 
inneseaton said:
Ok, day 2 update:

Yesterday evening, with 100w draw on the V2L, the battery voltage started slowly dropping as the evening went on. We noticed that the car was doing a pulse style charging, every now and again, seemingly at random, the voltage would momentarily spike to 14.3 ish volts then drop back down. That then seemed to stop and the voltage slowly dropped down to below 13v. I decided to put the car in the on position until bedtime, and duly the battery was held at 14.1v until I switched it off again.

This morning, a 2% drop in HV battery level and the main 12v battery showing 12.2v on the app - unfortunately I didn’t get a chance to put the multimeter on the battery to confirm this. Given that the battery spend at least 12 hours on charge yesterday, 12.2v tells me either there was a load on it again overnight and/or the battery is knackered.

More likely the latter, as on putting the car in ready mode, the voltage dropped to 10.2v and the car threw up lots of error messages, intermittently shutting off and reconnecting the HV battery. Eventually it settled itself down and is currently sitting in ready mode with the 12v battery charging as you would expect.

Two things come to mind: quite clearly the 12v battery is not as healthy as you would expect a new battery (as discussed above, we know why that could be). Secondly and in my mind more annoyingly, is that the car doesn’t seem to be able to recognise a discharging 12v battery in off mode (not for an extended period anyhow) and will quite happily let it discharge to the point of not staring the car, even though it has the means to correct it.

In summary, it seems there is a load on the 12v battery with the car off and V2L attached (even with no AC devices attached). The car will pulse charge for a while but will ultimately allow this to discharge the battery to the point of needing a jump start
Click to expand...
When I had the flat 12v battery (after that 15 hour V2L session), the door locks still worked (sounded a bit sluggish) but the Start/Stop button didn't do anything. I now keep a LiFePO4 jump starter in the car as a flat 12v battery completely disables the car. The jump starter was £45 from Lidl.
 
Last edited:
1. Same here, it seems to be after about 3 hours the car stops looking after the 12v battery in off mode. In on mode, it is held at 14.1v (as you would expect).

2
Julian256 said:
Some observations on this thread:

1. I also had a flat 12v battery after a long V2L session (about 15 hours). However, after a shorter V2L session, the 12V battery was OK. It looks like the 12v battery is being charged during V2L, but maybe this times out after a period of time.

2. The V2L output is pure sine wave, about 220V, 50Hz and can supply 3kW (but I've not tested for how long it can sustain 3kW.

3. When V2L is running, any attempt to check the HV battery SOC (using the app or the car's instrument display) interrupts the V2L power for a fraction of a second. This may explain why appliances behave strangely (like the electric blanket reset).

4. Using a mains socket tester on the V2L output will yield strange results. Live and Neutral are interchangeable from a stand-alone generator, so swapped Live and Neutral is meaningless.
Click to expand...
MichaelJHunt said:
I have a question…

Why do you not leave the car in the On state and locked when using the V2L feature?
Click to expand...
 
Further insights:

There is a 0.9A load being applied to the vehicle 12v battery whilst the V2L is plugged in. Quite what this is for I don’t know - I can’t imagine holding the contacts open would account for this.

After about 3 hours the vehicle seems to stop maintaining the 12v battery so it is left with this 0.9A draw for as long as you continue to have the V2L load plugged in (even if no appliances attached). A healthy battery should be able to sustain this overnight but clearly mine is not healthy and the dealer has agreed to replace it.

I am tempted to fit a better brand though so if anyone can recommend a particular battery that would be helpful! I have always ordered Varta batteries in the past for ICE cars.
 
inneseaton said:
Further insights:

There is a 0.9A load being applied to the vehicle 12v battery whilst the V2L is plugged in. Quite what this is for I don’t know - I can’t imagine holding the contacts open would account for this.

After about 3 hours the vehicle seems to stop maintaining the 12v battery so it is left with this 0.9A draw for as long as you continue to have the V2L load plugged in (even if no appliances attached). A healthy battery should be able to sustain this overnight but clearly mine is not healthy and the dealer has agreed to replace it.

I am tempted to fit a better brand though so if anyone can recommend a particular battery that would be helpful! I have always ordered Varta batteries in the past for ICE cars.
Click to expand...
Is it an AGM battery in the ZS EV?
I would go with Varta when replacing mine becomes necessary.
 
Last edited:
Here is one of the battery threads a 096 fits the 2nd battery hole witch is the next size up
sgt4hed said:
I have started this thread because I have seen so many comments about how crappy the 12v battery is so I am looking into viable upgrades ranging from bigger lead acid batteries to Li-Fe or Li-Ion to save a bit of weight in the process. We can also use this thread to discuss options on how to keep the 12v battery in tip top condition whether that be a smart trickle charger if the car isn't going to be used for a while etc.
Click to expand...
 
inneseaton said:
We noticed that the car was doing a pulse style charging, every now and again, seemingly at random, the voltage would momentarily spike to 14.3 ish volts then drop back down. That then seemed to stop and the voltage slowly dropped down to below 13v. I decided to put the car in the on position until bedtime, and duly the battery was held at 14.1v until I switched it off again.
Click to expand...
Wow, that's strange. If your voltage measurement hardware is flaky, that would explain the weird charging on V2L, but not the solid 14.1V when in the ON position.

Maybe during V2L it tries to put a constant current into the battery, but in ON mode it just forces a constant voltage (subject to DC-DC current limit, which is huge on the facelift models). In that case, you might have a flaky current sensor.

But another poster reports a drained auxiliary battery after long V2L use, so more likely there is a bug in the 12V charging under V2L. I'm starting to lose a little faith in SAIC firmware, both quality and responsiveness to problems.
 
I was wondering if the battery terminals on my car were a bit dirty. You could try taking them off and cleaning them & put on petroleum jelly. If they aren't making a good contact the car might think the battery was charged when it wasn't. If this doesn't work could you plug in a 12V trickle charger battery charger into the V2L to keep the 12V battery topped up to give you more reassurance overnight? If the load is 0.9A then a 1 Amp rated charger would compensate. NB. There could possibly be earthing issues if the earths and the 12v negative settle on different voltages but the V2L and/or the charger may not have/need earthing.
 
Last edited:
Ealing Guy said:
If this doesn't work could you plug in a 12V trickle charger battery charger into the V2L to keep the 12V battery topped up to give you more reassurance overnight?
Click to expand...
Heh, good idea. I mean, it's totally sad that we have to come up with workarounds like this, but until this is sorted, no weekends need be ruined!

And if the DC-DC happens to be doing its job for your car one particular night, then the trickle charger will not do much, and its losses will be a negligible drain on the big battery.
 
inneseaton said:
So first time using our new V2L cable on the campsite last night and awoke to a flat 12v battery.

It seems that with the V2L cable attached there is some form of drain on the 12v battery although I cannot work out what or why?!

The process we followed was:
  • car on, discharge screen set to 40% minimum and start discharging
  • car off and locked

Vehicle is a facelift ZS EV Trophy long range registered at the end of May.

Overnight we consumed about 1kwh of mains power (HV battery dropped by 1%) but 12v battery was reading 5.5v this morning.

AA had to be called as we had no way of jump starting but they did it successfully.

If this is a thing then it makes the V2L useless. Any ideas on why it would touch the 12v and how to stop it?
Click to expand...
Great idea to keep a lithium jump starter in the boot. Essential for an EV and cheap, easy and convenient fix for a flat 12 volt battery. I quickly showed mine in a YouTube video on accessories I added on our ZS.
 
Julian256 said:
Some observations on this thread:

1. I also had a flat 12v battery after a long V2L session (about 15 hours). However, after a shorter V2L session, the 12V battery was OK. It looks like the 12v battery is being charged during V2L, but maybe this times out after a period of time.

2. The V2L output is pure sine wave, about 220V, 50Hz and can supply 3kW (but I've not tested for how long it can sustain 3kW.

3. When V2L is running, any attempt to check the HV battery SOC (using the app or the car's instrument display) interrupts the V2L power for a fraction of a second. This may explain why appliances behave strangely (like the electric blanket reset).

4. Using a mains socket tester on the V2L output will yield strange results. Live and Neutral are interchangeable from a stand-alone generator, so swapped Live and Neutral is meaningless.
Click to expand...
Hi. I am looking at running a V2L but cannot find anywhere that backs up your statement of it being pure sine wave. How did you find it out?. Thanks.
 

Similar threads

Jto
Low battery
Replies
6
Views
524
Jto
Jto
A
12V Battery Replacement
Replies
3
Views
498
AYZSEV
A
T
MG ZS EV 12V Battery
2
Replies
33
Views
2K
Tim Green
T
S
Car Lost Power While Driving
Replies
12
Views
474
OriginalBigAl
O
C
Brand new 12V battery discharging
2 3
Replies
54
Views
2K
pollenface
pollenface
Support us by becoming a Premium Member

Latest MG EVs video

MG Hybrid+ EVs OVER-REVVING & more owner feedback
Published
Subscribe to our YouTube channel
Back
Top Bottom