[JamesE]

How is the 12v battery charged? Is it from an alternator on the motor a la ICE or is it via a charger from the high voltage battery? I ask this as in these times when my eGolf will not be moving do I have to connect a float charger to the 12v battery or can I simply switch the car on to "ready" for (say) half an hour in order to ensure that the 12v battery does not go flat?

 

[KevinS]

I'm certain that's not necessary. It's been a while since I read the user manual, but I'm pretty sure it charges off the high voltage battery. I travel for work a week or two at a time, so I specifically went to the user manual to read what to do when I leave the car sitting for a couple of weeks at a time. My recollection is it just said to not leave it fully charged - aim for 40 to 60%, so I have it set up to charge to 60% when I'm not driving it for a while.

 

[Carty]

How is the 12v battery charged? Is it from an alternator on the motor a la ICE or is it via a charger from the high voltage battery? I ask this as in these times when my eGolf will not be moving do I have to connect a float charger to the 12v battery or can I simply switch the car on to "ready" for (say) half an hour in order to ensure that the 12v battery does not go flat?

It does not have an alternator, that is certain.
I left my previous VW Golf GTE at the airport for two weeks while on holiday in the USA last year, and everything was fine !.
I am not sure if the 12 Volt battery is charged when the car is left standing for a number of weeks on the e.Golf.
Some EV cars automatically perform this function, some don’t.
Some of the one’s that do, have still reported occasions when the 12 Volt battery has been found to become flat after a period of time !.
It’s not completely flat, it has just fallen below the power required to kick in the HV side of the car.
On my present MG ZS EV your have to boot up the car to allow the HV battery to charge the 12 Volt lead acid battery.
So powering up the car once a week would be a good idea in my case.
Failing that, I could put a little juice back into the 12 Volt battery by using a smart trickle charger once a week ?.
I also have a small booster pack that I could use on the 12 Volt battery if necessary.
If the car is going to left unused for a couple of weeks, try and leave the HV battery at around 50 to 60% SOC.
Leaving the car for long periods of time at 100% SOC or even worse, leaving it at a very low SOC risks “bricking” the pack !.
If your car is now sitting with a high SOC right now, you could lower the SOC by booting up the car and running the heater etc for while.
I guess it helps if you car is fairly new, because the 12 Volt battery SHOULD be in good health.

 

[MrPaulus]

As I posted previously, I left my e-Golf for nearly 6 weeks with the HV battery at 50%. When I got home the 12V battery was dead, and had to be replaced. Lesson learned; I should have disconnected the 12V and/or put it on trickle charge.

 

[JamesE]

I have just ascertained (by measuring the voltage) that as soon as you "switch on" that the 12v battery starts to charge, it does not even need to be "ready". I am thus going to assume that a half hour a week "switched on" should stop it from going flat. This will be easier than hooking up a float charger.

 

[husoi]

By plugging the car and start charging you will be charging the 12v battery.
Play attention to the courtesy light behaviour when you start a charge.

 

[Arianto Nugroho]

Can you 'switch on' when your 12v battery is depleted?

I have just ascertained (by measuring the voltage) that as soon as you "switch on" that the 12v battery starts to charge, it does not even need to be "ready". I am thus going to assume that a half hour a week "switched on" should stop it from going flat. This will be easier than hooking up a float charger.

 

[JamesE]

Can you 'switch on' when your 12v battery is depleted?

I think not, as the instruction book tells you how to use jump leads in such an eventuality.

By plugging the car and start charging you will be charging the 12v battery.
Play attention to the courtesy light behaviour when you start a charge.

That's what I want to avoid as it isn't going to move and I wish to keep the HV battery at around 60% charge. I shall try and experiment with the charge set at 60% and no departure time - I wonder if that will just charge the 12v? I have a feeling not, unless the HV charge is under 60%.

 

[husoi]

For that you will need a trickle charger similar to used on motorbikes.

MOTOPOWER MP00205C 12V 800mA Fully Automatic Battery Charger/Maintainer - Charge, Maintain and Optimize Batteries. UK Plug: Amazon.co.uk: Car & Motorbike

MOTOPOWER MP00205C 12V 800mA Fully Automatic Battery Charger/Maintainer - Charge, Maintain and Optimize Batteries. UK Plug: Amazon.co.uk: Car & Motorbike

www.amazon.co.uk

 

[JamesE]

For that you will need a trickle charger similar to used on motorbikes.

Yes, thanks, I have a float charger, (better than a trickle as it shuts off at full charge). I am trying to avoid doing that as it's a faff, whereas just turning the car on for half an hour a week is easy.

 

[phproxy]

They definitely charge from the HV when the car is 'on'. I might test my GTE today to see if it charges when plugged in/charging the HV battery, as I've not read anything definitive. Assume the behaviour will be the same for e-golf/GTE.

 

[husoi]

Yes, thanks, I have a float charger, (better than a trickle as it shuts off at full charge). I am trying to avoid doing that as it's a faff, whereas just turning the car on for half an hour a week is easy.

Trickle chargers are meant to be plugged for several weeks and they will go on and off as necessary to keep the battery charged. I wouldn't use it if you only leave the car unused for 2 or 3 weeks. This shouldn't affect the battery unless you have a ghost drainer like Tesla.

 

[phproxy]

The Golf GTE looks like it charges the 12V when the HV battery is plugged in.

Key 2nd click, car charging 12v. Not plugged into charge point.

Key turned to first click. Car not charging 12v. Not plugged into charge point.

Key first click with HV battery charging from mains..

 

[gladini]

There used to be something about pressing the button to switch a display to show trip miles or EV range ( on the bit between the 2 dials in front of the driver, non-active display models )
And something about if you did that with the ignition turned on it would given an option to say the 12v battery status ?
I could never get it to show on my car.
I might be talking complete horlicks but this comment may awaken the mind of someone cleverer.

 

[phproxy]

There used to be something about pressing the button to switch a display to show trip miles or EV range ( on the bit between the 2 dials in front of the driver, non-active display models )
And something about if you did that with the ignition turned on it would given an option to say the 12v battery status ?
I could never get it to show on my car.
I might be talking complete horlicks but this comment may awaken the mind of someone cleverer.

?

 

[JamesE]

Trickle chargers are meant to be plugged for several weeks and they will go on and off as necessary to keep the battery charged. I wouldn't use it if you only leave the car unused for 2 or 3 weeks. This shouldn't affect the battery unless you have a ghost drainer like Tesla.

I'm sorry but I must correct your definitions. A trickle charger is what it says - it continuously trickles a small charge in and is quite dumb. A float charger monitors the battery voltage and cuts down the rate of charge until the maximum allowed is reached (around 14v, I forget the precise figure). Should the voltage drop it will start up at an appropriate rate to maintain that voltage.

 

[husoi]

I'm sorry but I must correct your definitions. A trickle charger is what it says - it continuously trickles a small charge in and is quite dumb. A float charger monitors the battery voltage and cuts down the rate of charge until the maximum allowed is reached (around 14v, I forget the precise figure). Should the voltage drop it will start up at an appropriate rate to maintain that voltage.

Well. You call it what you want.
I have a trickle charger for my motorbike that does what you just described.

potatoo Potato...

PS: the correct voltage is 13.8V

 

[MrPaulus]

When my car was left for 6 weeks, I used Car-Net/We Connect to check up on it. Big mistake. I got a message coming up saying something like “If you use Car-Net any more times is may effect the battery”. I think what happens is that when you use Car-Net the car ‘wakes up’ and starts draining the 12V battery. However, as the HV battery only charges the 12V battery when the Start button is pressed, the 12V battery went flat despite there being 60% charge in the HV battery.

 

[Carty]

When my car was left for 6 weeks, I used Car-Net/We Connect to check up on it. Big mistake. I got a message coming up saying something like “If you use Car-Net any more times is may effect the battery”. I think what happens is that when you use Car-Net the car ‘wakes up’ and starts draining the 12V battery. However, as the HV battery only charges the 12V battery when the Start button is pressed, the 12V battery went flat despite there being 60% charge in the HV battery.

Tesla Bjorn has found the same thing with both his model 3 and his ZS EV.
When you open the App to check on the HV battery health, it wakes up the car from a nice sleep.
The Tesla charges the 12 volt battery from the main traction battery I believe, but not in the case of the ZS EV.
A lot of EV’s suffer from this condition.
Checking the car to often with the App can drain the 12 volt.

 

[NellLondon]

I don’t want the faff of getting a battery charger if I can avoid it (and I’m pretty clueless about this stuff these days). From this thread, am I right in thinking my 12v (or whatever) battery will get charged if I switch the car on?

I’ll need to move it out if the drive and back this week to swap bins around so I could possibly take it for a drive if necessary (looks like I can’t get an Ocado delivery this week so I may need to brave the shops anyway).