Dead car / flat 12 volt battery 😰

[Kithmo]

No - Is the quick answer.
My CTEK Smart charger has the option to purchase a pair of fly leads, that can be left attached to the positive and negative sides of the battery.
( I will attach a picture is I can )
The charger can then be attached safely onto the car in seconds.
It's a better fit than using the standard crocodile cramps I find.
The also have also purchased the extension lead, that can be used in-line between the fly leads and the smart charger.
Therefore the charger is not left under the bonnet of the car, I can have it plugged into a outlet on the wall and then the charger sit's on a table below.
Just the long extension loom, running from the charger to the fly lead easy connect on the battery.

View attachment 6323

View attachment 6324
View attachment 6325

Same, I think it's called the "comfort" lead IIRC. Mine's still attached to the ZS battery.

 

[Lovemyev]

Same, I think it's called the "comfort" lead IIRC. Mine's still attached to the ZS battery.

Mine also !.
Red eyelet lead on the positive side of the battery, the black negative eyelet lead on the main common body shell earth post's, situated just behind the battery on the inner wing ( if I remember correctly ).
I must remember to remove it, IF we are able to upgrade to the face lift model !.

 

[Hairyfool]

I think the issue is not the lead but the charging device itself charging the battery whilst it is still connected to the vehicle.

There is a threefold problem with this. A lead acid battery needs the charging cycle to take the voltage up to 14.4volts to bulk charge the battery which at least the potential to cause damage. With modern vehicles which can "smart" charge starter batteries this is unlikely.

Then there is the issue of smart charging itself. For the attached device to carry out the process it has to monitor the charge current fairly accurately, however if the vehicle itself is drawing a small current the charger cannot differentiate where this current is going so may not identify the stages of charge. Good "smart" chargers should identify this scenario and drop its mode to static charging at 13.8v.

What is less definable is will the charger even when off have any influence on the cars own battery management and skew the cars view of the status of the battery and I don't think there is one answer for this. It is going to depend on the charger design and the vehicle battery management in conjunction with each other.

I am a little disappointed that vehicles that depend on the battery just to initialise the system and even open the doors will allow the battery to get so flat in the 1st place, not that this is an issue for MG alone.

If this was my problem I would be looking to be able to connect to the battery in some way without needing to unlock and bring the battery voltage up high enough for systems to work. I would not be happy having to do this on a new car.

 

[Ozzie1989]

A lead acid battery needs the charging cycle to take the voltage up to 14.4volts to bulk charge the battery which at least the potential to cause damage.

An alternator on an ICE should be regulated around 14.2v and I would imagine the same for the charger on your EV when in ready mode so any modern smart charger will not cause an issue here.

 

[Biccys]

No - Is the quick answer.
My CTEK Smart charger has the option to purchase a pair of fly leads, that can be left attached to the positive and negative sides of the battery.
( I will attach a picture is I can )
The charger can then be attached safely onto the car in seconds.
It's a better fit than using the standard crocodile cramps I find.
The also have also purchased the extension lead, that can be used in-line between the fly leads and the smart charger.
Therefore the charger is not left under the bonnet of the car, I can have it plugged into a outlet on the wall and then the charger sit's on a table below.
Just the long extension loom, running from the charger to the fly lead easy connect on the battery.

View attachment 6323

View attachment 6324
View attachment 6325

Pretty much like an Optimate charger that many motorcyclists will be aware of!

 

[Hairyfool]

Mine also !.
Red eyelet lead on the positive side of the battery, the black negative eyelet lead on the main common body shell earth post's, situated just behind the battery on the inner wing ( if I remember correctly ).
I must remember to remove it, IF we are able to upgrade to the face lift model !.

I haven't had my cover off yet to know if the MG5 has one but watch out for a battery isolation relay.

Some vehicles have these attached to the negative post and the main chassis earth connected to the other side. When the car goes to "deep" off mode the relay drops just leaving a small lead attached to the negative post as the return for essential services (central locking, alarm etc.) The situations this happens is a bit manufacturer specific but generally for charging I would always recommend both battery terminals. In some cases the relay only disconnects when the G sensor triggers i.e. a crash.

 

[Lovemyev]

I haven't had my cover off yet to know if the MG5 has one but watch out for a battery isolation relay.

Some vehicles have these attached to the negative post and the main chassis earth connected to the other side. When the car goes to "deep" off mode the relay drops just leaving a small lead attached to the negative post as the return for essential services (central locking, alarm etc.) The situations this happens is a bit manufacturer specific but generally for charging I would always recommend both battery terminals. In some cases the relay only disconnects when the G sensor triggers i.e. a crash.

For use with the CTEK units - I recommend that you watch this video.
It gives clear advice on how to connect your charger to your battery, if the battery is still conected to the car or NOT !.
It is in the opening intro of the video.

 

[Spinynorman]

Thanks everyone - very informative. I used a NoCo Genius 2 on my old RAV 4 - yes it was 20 years old and my first car from new. When Covid hit, I was told to Shield and so the car was on the drive for ages with just a drive round the block each week to keep the engine oiled and the tyres from developing flat spots. All I want to do is keep my ZSEV‘s 12 V in good condition until my Zappi is installed in 2 weeks time. It’s been a real pain hanging the granny charger out of a window - which I had to secure with a chain and padlocks! At least with my charger I can just leave it connected and program a charge from the comfort of my sofa…

 

[Elec Car Aust]

Nipped out for a wee jaunt in the 5lr and immediately our nip was nipped in the bud.
The car was dead, the key was doing nothing the doors were locked, the charge flap was locked - no entry.
Used the manual key to pop the lock cover behind the door handle and unlocked the door. Nothing electrical was responding inside the car.
Opened the bonnet and employed the famous 10 mm spanner to disconnect the battery post for half a minute. Reattached everything but still nothing.
Called the AA number and had a patrol van pull up 35 mins later. The battery had 4 volts in it so the patrolman connected his charger for ten minutes then discovered that some twit had left the lights on. Now sadly the finger of blame in these instances points at the most recent driver. There has only ever been one such miscreant so prepare that doghouse- I’m coming in
I’ve now set off for a little run to charge the 12 volt and top up the traction battery.
I’ve offered to take my darling wife out for dinner at the same time.
Is this romantic gallantry or am I just a coward ??
Keep that light switch at automatic folks

Bummer! Yes if 12 volt battery is flat an EV won't start up so you can't even charge from traction battery. Grab a lithium jump starter and keep in the boot. Don't take up any space and have added benefit of a torch and USB charging for devices. We paid approx $150AUD so cheap insurance.

 

[Spinynorman]

Bummer! Yes if 12 volt battery is flat an EV won't start up so you can't even charge from traction battery. Grab a lithium jump starter and keep in the boot. Don't take up any space and have added benefit of a torch and USB charging for devices. We paid approx $150AUD so cheap insurance.

…and of course remember to keep the jump starter charged up…

 

[Kithmo]

…and of course remember to keep the jump starter charged up…

I have one which was left (forgotten) in the boot of my previous car, a Prius, for nearly 4 years without charging it. When I got it out to start the Prius when its 12v battery was flat, it was still showing 3 leds, indicating it was fully charged and it started the car no problem.
I don't know if it would have churned over the starter motor in an ICE at that state but it served its intended purpose for me.

 

[Archev]

I have one which was left (forgotten) in the boot of my previous car, a Prius, for nearly 4 years without charging it. When I got it out to start the Prius when its 12v battery was flat, it was still showing 3 leds, indicating it was fully charged and it started the car no problem.
I don't know if it would have churned over the starter motor in an ICE at that state but it served its intended purpose for me.

I had my 5LR at the dealers today to have the 12 volt battery checked after leaving the lights on - eventually. I’ve bought and used an AA intelligent charger since having the problem last week The car appeared OK since the AA patrol guy attended and we’ve used the car as normal. However the garage had it for four hours today and tested it before and after charging and pronounced it to be correct so that’s a relief (was it really as low as thought originally by the AA??)
As a back up for peace of mind I’ve taken the good advice on here and also bought a NOCO GB40 jump starter to trundle around with the spare wheel and type 2 and Granny and 10 mm spanner and hi-viz and added hat and gloves and flask and bag of mixed nuts.
Many thanks to all for advice and suggestions.

 

[Gomev]

I had my 5LR at the dealers today to have the 12 volt battery checked after leaving the lights on - eventually. I’ve bought and used an AA intelligent charger since having the problem last week The car appeared OK since the AA patrol guy attended and we’ve used the car as normal. However the garage had it for four hours today and tested it before and after charging and pronounced it to be correct so that’s a relief (was it really as low as thought originally by the AA??)
As a back up for peace of mind I’ve taken the good advice on here and also bought a NOCO GB40 jump starter to trundle around with the spare wheel and type 2 and Granny and 10 mm spanner and hi-viz and added hat and gloves and flask and bag of mixed nuts.
Many thanks to all for advice and suggestions.

Don't forget the shovel.

 

[Archev]

Aye, I’ve drilled and filed the 10 mm spanner to save weight but still working on the shovel

 

[biffo]

Treated myself to a Ring RPPL250 High Power Lithium Jump Starter from Halfords (sale item and voucher code so £58.05 delivered), not the highest reviewed item around, general criticism is that it only allows two or three starts but does an EV need a large cranking current or just enough to allow the ancillary systems to connect the HV battery? Either way - I expect to use it on my 1.2 litre Panda more which gets very little driving now.

 

[Lovemyev]

, general criticism is that it only allows two or three starts but does an EV need a large cranking current or just enough to allow the ancillary systems to connect the HV battery?

Two or three starts could be based on a ICE run on derv with a higher compression ratio or a larger 2.0 litre petrol engine ?.
For you Panda it should be fine !.
“Top Tip” - When you are using the jump pack on an ICE car with a manual gearbox, hold the clutch down when you turn the car over !.
Less drag from starter to turn.
You are correct with regards to using it on a EV.
It will need very little to bring the 12 volt up to a level that will allow the car to boot up !.
You probably never run down your jump pack starting EV’s !.

 

[Archev]

Treated myself to a Ring RPPL250 High Power Lithium Jump Starter from Halfords (sale item and voucher code so £58.05 delivered), not the highest reviewed item around, general criticism is that it only allows two or three starts but does an EV need a large cranking current or just enough to allow the ancillary systems to connect the HV battery? Either way - I expect to use it on my 1.2 litre Panda more which gets very little driving now.

Very nice personal pressy and I sincerely hope you never need it
My unit rests under the driver’s seat. I did have it in a side pocket in the boot but that’s the least handy place I reckon. When my 12 volt battery was too low powered to even open the doors I had to flick off the chrome cap on the door handle. This revealed the keyhole for the “flicknife” key blade to unlock the door.
Then I would have had to reveal exactly how unfit I’ve become. Climbing over the seats and faffing about opening the luggage cover would have produced a comedy show of epic nonsenseness.
Additionally, I’ve now had my unit for a couple of months or so. I plugged it in before our three day trip recently, and found that it took half an hour or so to top it up fully. So I’ll now try to plug it in two or three times a year (calendar suitably marked up).
It seems these units can crank up even a diesel a few times and, as you say, EV’s only need a relatively tiny bit of power to get thinks going.
And the Panda should be fine

 

[biffo]

That is an excellent point about where to store it - and something I hadn't considered

 

[Flwul]

You can really see which companies just make cars rather than software when it comes to all these features - admittedly, some are childish and naff, but some are really useful.

Funnily enough, a couple of years ago I saw a video of somebody with exactly the same problem as OP but with his Tesla!! At least then, the Teslas would also still have a "normal" battery for the basic functions, that could die due to lack of use and or accidentall drainage. So, even Tesla did fall foul of this functional design flaw.

 

[Elec Car Aust]

Already considered but thanks

The lithium iron jump starters are a great investment. Fit in palm of hand, weight nothing, and have torch and multiple usb charge ports. Approx $150AUD for a decent one over here. We mention them in this video we done . Cheers from Down under