12V battery charging

[Rolfe]

Oh yes, I won't worry about it. Until something happens, of course. But then something can always happen. I've had flat batteries in ICE cars before. When I parked my Golf for 10 weeks at Avonmouth docks, I packed a battery booster pack - even though I didn't need it in the event. The shame of having a five-month-old car not start after a holiday when I was supposed to be taking my friend home would have been a bit much though.

 

[PeteC]

Well, at least if the car had failed to wake up, I'd have had some idea what to do about it. The trouble is, we hear all about the ones that don't wake up and not so much about the ones that behave normally. And how to know if yours is one of the problem ones until you try it? But it seems my battery is good.

I had great confidence in mine after I'd left it for over 6 weeks earlier this year and had no problem when I returned to the car. And then earlier this week I found my car dead after just a day and a half of non-use. Brought back to life with a jump starter pack and behaving as normal since then. So I'll have to see how it goes from now on. Fingers crossed!

 

[Rolfe]

Oh dear! I wonder what influences this?

 

[PeteC]

Oh dear! I wonder what influences this?

I have no idea. We've had the car since last October and no sign of a problem with the 12v battery. Why it drained like that is a mystery to me. I'll be carrying the jump starter with me from now on!

 

[johnb80]

Oh dear! I wonder what influences this?

It all depends if youve been good and have a fairy battery mother whereas if youve been bad you dont

 

[Robf]

It all depends if youve been good and have a fairy battery mother whereas if youve been bad you dont

Thats not right. It actually depends upon a few different factors. As we know the Chinese high hedrons spy on us via the car. If you are for example listening to the BBC or dissing the local Chinese takeaway for a lacklustre sweet and sour (with egg fried rice) they switch on your lights from the secret office and drain your battery. Be carefull out there.

 

[tsedge]

I had great confidence in mine after I'd left it for over 6 weeks earlier this year and had no problem when I returned to the car. And then earlier this week I found my car dead after just a day and a half of non-use. Brought back to life with a jump starter pack and behaving as normal since then. So I'll have to see how it goes from now on. Fingers crossed!

Could have been one of a number of things:

• Parasitic drain from some system that normally is fine but got stuck in a loop.
• The car tops the battery up but not quite enough and these circumstances coincided with it being too low.
• The battery is weak and starting to fail.

With quite a few EVs I hear stories of the 12V battery needing replacement within 2 years of new.

 

[calwoo]

Based on posts here I thought my battery voltage, between 12.2 and 12.5 in the Ismart app might be an issue. So I tested it on a Seely AK500 digital car battery tester and it read 13.8v. Any thoughts?

 

[Alb]

At 13.8V you are measuring charger output.

 

[calwoo]

Thanks. It was measured from the lighter socket. I’ve since used a digital multimeter on the battery terminals and this gave 12.45v

 

[Kithmo]

I've seen voltages on the app from 12.3 to 12.5 and in the car when in ready mode from 13.9 to 14.1
and I've had no problem with mine.
I reckon 14.1v in the car means the battery was low and is receiving a high charge and 13.9v means the battery is just about fully charged.

 

[tsedge]

Mine has ranged from 12.1V to 12.7V on the app when not charging.

 

[PeteC]

Thats not right. It actually depends upon a few different factors. As we know the Chinese high hedrons spy on us via the car. If you are for example listening to the BBC or dissing the local Chinese takeaway for a lacklustre sweet and sour (with egg fried rice) they switch on your lights from the secret office and drain your battery. Be carefull out there.

Ah - I had eaten a Chinese on the last night before the car died! Fish and chips from now on...

 

[Rolfe]

Could have been one of a number of things:

• Parasitic drain from some system that normally is fine but got stuck in a loop.
• The car tops the battery up but not quite enough and these circumstances coincided with it being too low.
• The battery is weak and starting to fail.

With quite a few EVs I hear stories of the 12V battery needing replacement within 2 years of new.

In another thread someone said something about the car not topping up the 12v if the HV battery is at a relatively low state of charge. I can see the logic for this if the HV is really really low, because it will be easier to get a boost for the 12v and get going than to sort out a dead propulsion battery. But the figure mentioned was 50%. Stopping 12v top-up to spare the HV at such a high SoC seems senseless, but if this is true it might explain a few things.

 

[siteguru]

FWIW I got back to my car around 8.45pm last night (after a week in offsite airport parking) and it all started up OK.

 

[Rolfe]

Pleased to hear it!

 

[fnegroni]

In another thread someone said something about the car not topping up the 12v if the HV battery is at a relatively low state of charge. I can see the logic for this if the HV is really really low, because it will be easier to get a boost for the 12v and get going than to sort out a dead propulsion battery. But the figure mentioned was 50%. Stopping 12v top-up to spare the HV at such a high SoC seems senseless, but if this is true it might explain a few things.

50% is probably safeguarding the HV battery sacrificing the cheap 12v battery
50% is mentioned in the manual as the minimum SoC when the battery isn’t being used for some time.

 

[OriginalBigAl]

As an alternative to a battery booster would a smaller 12v motorcycle battery work with some leads and crocodile clips.?

 

[Rolfe]

You can buy lead/acid battery booster packs. I had one for my Peugeot, which had some sort of parasitic drain problem that was never identified. That finally leaked and got dumped, but I bought a new one in 2018 when my Golf was due to be parked up for ten weeks at Avonmouth docks. That's the one I had with me this week in case the MG4 ran into trouble.

Unfortunately I dropped it on the concrete garage floor when I was charging it up and cracked the casing. I have no idea whether it's still serviceable after that.

 

[calwoo]

I haven’t seen battery voltage displayed in the car. Where do I find it?