Forgive my ignorance. I have a 2021 iV PHEV Octavia and wasn't sure what battery powers the 12v socket in the boot? Want to know what the chances are of accidentally flattening the petrol engine starter battery if I leave something plugging in overnight.

 

Second question, does anyone know a way of switching the socket so it's not powered when the vehicle isn't running?

 

Thank you!

B

my son superb had a flat battery,he was told if you used the boot plug in and left it plugged in ,it would run the battery down.hence this what happened on his car.

@Joss1733 Just being nosy but what was plugged in and drawing power to flatten the cars battery?

a mini water cooler that held a couple bottles 330ml of water for his dogs

It doesn't take much to drain the battery. I had a work safety GPS tracker plugged in to the 12v. Just a little thing that doesn't seem to use much, but after a week over Christmas not driving the battery was nearly flat. 

22 hours ago, Joss1733 said:

a mini water cooler that held a couple bottles 330ml of water for his dogs

Yep same for me with my old 2018 diesel Octavia... and trying to jump it wasn't easy only because with no power getting the bonnet open is very tricky. I assume this only applies to UK models which have the bonnet catch inside the nearside door. Being a passenger door in the UK, there is no physical key lock to open it - just the electric central lock. Ending up bending the catch lever and forcing it, which damaged the footwell trim 🙄

 

That was a mistake I only made once!

 

Anyway I was wondering what the power arrangement is in the PHEV. Does the high voltage battery charge the 12v battery and therefore the boot socket? Or is the 12v system separate?

The 12 volt system is separate. It charges whilst driving or when the main charger is plugged in: for example today the resting voltage was 11.8v and it rose to 13.1v when I connected the main charger. I had a flat battery (4.8v) on December 30th when the car was parked for five days: the dealer claimed that it was due to the power steering control unit being live and so draining the battery. Not sure wheher that's true, but a software update was applied. I notice that the resting voltage drops by about 0.3 volts overnight, but as I never monitored resting voltage before getting the Octavia iV I don't know whether this is normal behaviour for a 12 volt battery.

Thank you @Jim2015, that was exactly the answer I was after!

 

For others interested, @VAGProf has some very handy info re the 12v and high voltage systems from this thread: 

On 29/07/2021 at 10:02, VAGProf said:

Hello all, I've read all the posts in this topic and found some wrong information.

 

I'll try to explain how the system works in short, if anyone has some questions, I will kindly answer them.

 

To start with, the 12V battery is charged ONLY with the high voltage system, by the power electronics that also drives the motor (the big metal block with the 6 orange wires connected to it next to the ICE) to be more precise.

There is no alternator on the ICE, so if you drive in E-mode or hybrid, it doesn't make a difference in charging the 12V battery. 

 

This means the high voltage system must be active to charge the 12V battery, so only when driving or charging the HV battery.

 

The reason why there is only 13.1 or .2V  is because the 12V battery is monitored by the gateway, it knows the charging state, so if it is above 80%, ther is no need to charge it, purely wasted energy to keep the system at 14V all the time. This is why the converter only supplies 13.2V to the system to just prevent the battery from discharging. 

 

When driving and using the regen while braking, the system will be at 14V, all the modern cars do this, not only the hybrids. Actually most of them only have 12 - 12,5V while accelerating, when coasting or braking the alternator will start to charge the battery. 

 

Why Sir_Ron_Norris' battery died, I haven't got a clue, but it isn't related to driving in E-mode or hybrid. Could be an driver error (leaving a light on, something plugged into the 12V socket,...), bad ground connection or just a faulty battery. 

 

I hope with the new battery the problem has been solved.