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Do you unplug the car when it is finished charging?

  • Yes

    Votes: 15 27.8%
  • No

    Votes: 16 29.6%
  • Stop overthinking this

    Votes: 23 42.6%
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Discussion Starter #1
Fully charged up the car (sorry, it's a PHEV) on the cheap rate leccy last night, but I'm not planning on driving anywhere until Tuesday. Does conventional wisdom say leave the car plugged in or unplug it?

Here are my thoughts:
  1. Unplugging is good because the charger has a giant green light on the front of it that is only on when a car is plugged in
  2. Unplugging is good because the charging cable runs across my usual route for putting the bins out on a Sunday night. With the cable plugged in, I'll need to take the long route (#firstworldproblems)
  3. Unplugging is bad because I'll need to plug it back in again to preheat on Tuesday morning
Yes, I'm massively overthinking this. But I'm also curious what everyone else does.

Also, this question only applies to private chargers. I'm not advocating hogging a public charger until Tuesday. That would be rude.
 

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The main reason to leave plugged in is to allow preconditioning to take place on mains electric. Depending on car, you can do this via (one or more of) schedule, app or key.

When I had Ampera, doing two precondition cycles with key (no app sadly) made a huge difference to EV range and meant I cloud do most of my 48 mile roundtrip commute on electric, even in winter. My Zoe ZE50 should do it via app or on a schedule - once I get it fixed...
 

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5. Leaving it plugged in uses the 12v battery which, if the battery maintenance system on the DC : DC charger isn't up to the job, may go flat.
 

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For a few days it just doesn't matter - stop overthinking it.


Long term depends on the car. See your owner's manual. BMW recommned leaving the i3 plugged in. That way it uses mains power to keep the 12V battery topped up.

LEAF 30 should not be stored at full charge, so it shouldn't be left plugged in for extended periods. I'm talking about weeks not a day or two.
 

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Discussion Starter #6
4. Leave in to avoid wear and tear on the plug.
Is type 2 failure from wear and tear a common issue? I'm not an expert on car charger sockets, but I know that USB-C was designed for a minimum of 10000 insertion and removal cycles (manufacturing defects and external damage aside) - which for 1 cycle a day gives a 27 year life expectancy. I wonder what type 2 was designed for...

The main reason to leave plugged in is to allow preconditioning to take place on mains electric. Depending on car, you can do this via (one or more of) schedule, app or key.
Yeah, I would plug the car back in to use preconditioning. The car's preconditioning cycle is 30 minutes, and It isn't very often that I need to drive somewhere with less than 30 minutes notice.

5. Leaving it plugged in uses the 12v battery which, if the battery maintenance system on the DC : DC charger isn't up to the job, may go flat.
Hmm, interesting - hadn't thought of that one, may require some investigation. I have a jump starter pack if it does go flat, but would be nice to not need it. I've only had to jump start cars a few times over my driving years, and every time, it has been at night and raining.

Long term depends on the car. See your owner's manual.
The manual says keep it at least 30% if stationary long term, or at least 40% if it's really cold. Didn't see anything about whether to leave it plugged in or unplugged, but it's a VW manual, the information is scattered in 40 different sections.
 

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Yeah, I would plug the car back in to use preconditioning. The car's preconditioning cycle is 30 minutes, and It isn't very often that I need to drive somewhere with less than 30 minutes notice.
Yeah but I CBA to go outside and do that at 7am when I forgot to plug in ;)
 

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Discussion Starter #8
Yeah but I CBA to go outside and do that at 7am when I forgot to plug in ;)
I'd force myself outside that once and call it a learning experience. Nothing reinforces learning more than being cold, wet and miserable.
 

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5. Leaving it plugged in uses the 12v battery which, if the battery maintenance system on the DC : DC charger isn't up to the job, may go flat.
That is likely to be very vehicle dependent, and the 12v top-up system should take care of it.
There is generally no reason to unplug until you need to drive - the mains supply is disconnected from the car by the EVSE after charging, so for example things like mains spikes can't damage the car's OBC
 

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Is type 2 failure from wear and tear a common issue? I'm not an expert on car charger sockets, but I know that USB-C was designed for a minimum of 10000 insertion and removal cycles (manufacturing defects and external damage aside) - which for 1 cycle a day gives a 27 year life expectancy. I wonder what type 2 was designed for...


Yeah, I would plug the car back in to use preconditioning. The car's preconditioning cycle is 30 minutes, and It isn't very often that I need to drive somewhere with less than 30 minutes notice.


Hmm, interesting - hadn't thought of that one, may require some investigation. I have a jump starter pack if it does go flat, but would be nice to not need it. I've only had to jump start cars a few times over my driving years, and every time, it has been at night and raining.


The manual says keep it at least 30% if stationary long term, or at least 40% if it's really cold. Didn't see anything about whether to leave it plugged in or unplugged, but it's a VW manual, the information is scattered in 40 different sections.
I don't think it is a problem with the GTE (edit: I am referring to the 12v battery), certainly not if you are using the car regularly.

The GTE will warn you if the 12v battery drops, in some circumstances at least. I left mine plugged in for about a month at the start of the first lockdown, and checked it regularly using the We Connect app.

Towards the end of the month I got a warning in the app that I could only connect 3 more times without starting the car, to protect the 12v battery.
 

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Discussion Starter #11
I don't think it is a problem with the GTE (edit: I am referring to the 12v battery), certainly not if you are using the car regularly.
The car gets used at least 4 days out of 7 at the moment, each journey is about an hour and it gets done twice each day, so I'm not hugely concerned about it sitting unused. Wife is a health care worker and I'm on taxi duty so that she doesn't have to take a bus unnecessarily, so even during the height of lockdown, the (previous) car was getting a fair amount of use. Apart from when she wasn't allowed to go to work for 2 weeks...

Towards the end of the month I got a warning in the app that I could only connect 3 more times without starting the car, to protect the 12v battery.
That's very useful information, thanks!
 

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the mains supply is disconnected from the car by the EVSE after charging, so for example things like mains spikes can't damage the car's OBC
Really? How does it reconnect for preheating? :unsure:
 

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The car gets used at least 4 days out of 7 at the moment, each journey is about an hour and it gets done twice each day, so I'm not hugely concerned about it sitting unused. Wife is a health care worker and I'm on taxi duty so that she doesn't have to take a bus unnecessarily, so even during the height of lockdown, the (previous) car was getting a fair amount of use. Apart from when she wasn't allowed to go to work for 2 weeks...


That's very useful information, thanks!
I think it is specifically when you try and force We Connect to get the latest info from the car by swiping down. I assume it tries to wake up the car to read it.
 

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So the EVSE maintains the CP signal despite the contactors opening?
 

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I would hesitate to leave the car plugged in - unless the charging schedule is amended so it cannot apply a charge. If the car has been charged to 100% I understand it is bad for it to charge again until the charge has dropped to say 80%. I think it would not be a good thing for the charger to add a small amount of charge to bring it back to 100%?
 

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Does leaving it plugged in cause any additional vampire drain at all? Ie the charger is uses more power in its standby mode. That's the thing I don't like about all these wifi connected things we fill our houses with, Lot's of things using say 5W 24/7 can add up quite a few % to your overall energy consumption, call me old fashioned but I like to be able to turn most thngs "off off"
 
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