Mk1 ZS EV Excite Cold Weather Death

I own a 70 plate Mk1 ZS EV Excite that as soon as sub zero temperatures hit a few days ago it began to have issues. Mainly the 12V battery clearly lost charge and it wouldn't start. I managed to get the 12V battery charged back up on the 1st day and got it to go again.
The next day I needed the car, which was Monday, again it was dead as a dodo. This time called out the AA who came and tried to start it with a booster battery but although it was showing over 12V across the terminals when you pressed the Start button it wouldn't go into ready mode and lots of failure warnings like HV battery failure came up on the dashboard display. AA then recovered car to dealer who has yet even with a new 12V battery on the car can't get the faults to clear, so the car is unusable at present and waiting in the dealers for further investigation.

Simple question has anyone else had this happen to them during this cold weather snap?

StattoH said:

I own a 70 plate Mk1 ZS EV Excite that as soon as sub zero temperatures hit a few days ago it began to have issues. Mainly the 12V battery clearly lost charge and it wouldn't start. I managed to get the 12V battery charged back up on the 1st day and got it to go again.
The next day I needed the car, which was Monday, again it was dead as a dodo. This time called out the AA who came and tried to start it with a booster battery but although it was showing over 12V across the terminals when you pressed the Start button it wouldn't go into ready mode and lots of failure warnings like HV battery failure came up on the dashboard display. AA then recovered car to dealer who has yet even with a new 12V battery on the car can't get the faults to clear, so the car is unusable at present and waiting in the dealers for further investigation.

Simple question has anyone else had this happen to them during this cold weather snap?

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I know this may sound like a daft idea, but have you tried offered the 2nd spare key to the car ??.
We had something similar on our ZS EV Gen 1 when it paid a visit to the dealer to have the wiring loom in the door replaced ( MG recall ) the car failed to boot up and the alarm was sounding ( as if the 12 volt was low ) the car was completely dead !.
They replaced the 12 volt battery and it was the same.
MG Tech told them to contact the owner and have the second key delivered.
Straight away the car came to life.
The first key had been scrambled and both keys have to be recoded in pairs.
They had the car for three days !.

MG dealer had my car for three days also, needed a software reboot/upload to get going as its brain was scrambled having had a flat 12v battery. Had the car back a couple of weeks now and was going OK until I didn't use it for a couple of days, at the end of last week, and went to start car and the new 12V battery was flat. Had to get into car using manual key, re charged 12V battery. Then put car on charge from mains, then took car for a 40-50 mile run yesterday. When I got it home the 12V battery was reading 12.4V on my multimeter. So I kept checking voltage every couple of hours and by 10pm last night voltage was down to 10.2V. So clearly 12V battery is being drained by something and relatively rapidly. Will be ringing dealer after new year for them to have a look to find out what is causing problem. Anyone else experienced anything similar?

Hi,

I had a MG ZS EV for over a year (Summer & Winter). On this Forum (and others) the general consensus was never charge the car to 100% (which you can NEVER do anyway as the BMS won't let you, so it is a bit of a mute point anway) unless prior to a long journey.

Anyway with my MG (and the 3 other EVS I have had since) I have always adopted a completely different approach. I charge my cars in EVERY night regardless of the SOC for the following reasons:-


a. As the 12V battery is ONLY charged when driving ( or more correctly whilst in "ready" mode) and charging this has ensured I have NEVER had any 12v battery problems.
b. I never worry about battery balancing as I charge every night and it's never unplugged until I use it, I don't use scheduling, plug it in at night unplug it when ready to go.
c. Don't worry about the main battery, let the BMS and the warranty worry for me.
d. I like to wake up knowing I have a full charge for those unexpected long journeys.

Regards


Frank

StattoH said:

MG dealer had my car for three days also, needed a software reboot/upload to get going as its brain was scrambled having had a flat 12v battery. Had the car back a couple of weeks now and was going OK until I didn't use it for a couple of days, at the end of last week, and went to start car and the new 12V battery was flat. Had to get into car using manual key, re charged 12V battery. Then put car on charge from mains, then took car for a 40-50 mile run yesterday. When I got it home the 12V battery was reading 12.4V on my multimeter. So I kept checking voltage every couple of hours and by 10pm last night voltage was down to 10.2V. So clearly 12V battery is being drained by something and relatively rapidly. Will be ringing dealer after new year for them to have a look to find out what is causing problem. Anyone else experienced anything similar?

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You could well have a parasitic drain, but I would be more inclined to think there could be a problem with your 12 volt battery retaining a charge correctly.
It is not unknown that some EV’s have needed their batteries replacing.
Taking the car for run to help charge the 12 volt battery does help, but the car will charge just the same without moving an inch, as long as you have the car in the READY mode.
But NOT in STANDBY mode.
This will have the opposite affect and will discharge the battery !.
The 12 volt battery will be receiving a charge when you are travelling from the main HV traction battery or via your wall box or Granny cable or when sitting in READY mode.

Lovemyev said:

You could well have a parasitic drain, but I would be more inclined to think there could be a problem with your 12 volt battery retaining a charge correctly.
It is not unknown that some EV’s have needed their batteries replacing.
Taking the car for run to help charge the 12 volt battery does help, but the car will charge just the same without moving an inch, as long as you have the car in the READY mode.
But NOT in STANDBY mode.
This will have the opposite affect and will discharge the battery !.
The 12 volt battery will be receiving a charge when you are travelling from the main HV traction battery or via your wall box or Granny cable or when sitting in READY mode.

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Didn't he say he got a new 12v battery ?

StattoH said:

When I got it home the 12V battery was reading 12.4V on my multimeter. So I kept checking voltage every couple of hours and by 10pm last night voltage was down to 10.2V. So clearly 12V battery is being drained by something and relatively rapidly.

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I don't believe that you necessarily have a drain from that data. When you measured your battery at 10.4 V, it had just been charging it for some time. Lead acid batteries take a while to settle to their resting voltage, and fiercely cold temperatures can play a role as well.

The best test (which might not be practical for your circumstances) would be to keep it at a fairly constant temperature, and measure the voltage about 2 hours after it was last used. Have the bonnet open for testing, as opening doors will wake up all sorts of computers and totally mess up the resting state. It should then hopefully hold its voltage after that.

It sounds to me that the new battery isn't fully charged as yet. We get pretty big batteries in our ZSs, so they can take many hours to fully charge with a moderately small charger (4-6 A). The last 20% of charge can take a bit longer than a simple calculation (such as rated Ah divided by charger rated current) suggests. Plus, they may need longer charging in very cold conditions, or they may not take as much charge.

StattoH said:

MG dealer had my car for three days also, needed a software reboot/upload to get going as its brain was scrambled having had a flat 12v battery. Had the car back a couple of weeks now and was going OK until I didn't use it for a couple of days, at the end of last week, and went to start car and the new 12V battery was flat. Had to get into car using manual key, re charged 12V battery. Then put car on charge from mains, then took car for a 40-50 mile run yesterday. When I got it home the 12V battery was reading 12.4V on my multimeter. So I kept checking voltage every couple of hours and by 10pm last night voltage was down to 10.2V. So clearly 12V battery is being drained by something and relatively rapidly. Will be ringing dealer after new year for them to have a look to find out what is causing problem. Anyone else experienced anything similar?

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Iirc once a 12v battery goes too low (once) it is effectively damaged & a liability that needs replacing.

So the question would appear to be - what's using your 12v batteries up? Dash cam? Obd port adapter? Other?

When 12 volt batteries keep losing their charge and going flat, it is usually only down to a couple of reasons why.
Either one or a couple of the cells / plates in a standard battery have collapsed.
The battery not receiving sufficient charge from the inverter in a EV or the alternator in the case of a ICE.
Some thing left turned on or a boot light not going out when the boot / hatch is closed.
A permanent feed has been left switched on causing a battery drain ( possible OBD port still active or dash camera ).
Or lastly, the car has some type of parasitic drain that will need further investigation.

Lovemyev said:

When 12 volt batteries keep loosing their charge and going flat, it is usually only down to a couple of reasons why.
Either one or a couple of the cells / plates in a standard battery have collapsed.
The battery not receiving sufficient charge from the inverter in a EV or the alternator in the case of a ICE.
Some thing left turned on or a boot light not going out when the boot / hatch is closed.
A permanent feed has been left switched on causing a battery drain ( possible OBD port still active or dash camera ).
Or lastly, the car has some type of parasitic drain that will need further investigation.

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It's like an echo

AK OK said:

It's like an echo

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You must have faster typing FINGER than me @AK OK .

When the batteries goes bad, it's actually not that they can not hold a charge, it's just the internal resistance that reaches a higher value.

See it as a water pipe with calcium in it.

You can have a large tank of water, and if you drain it at a normal pace, you can get all of the water out, but if you want to REALLY get some water out, and open the tap completely, the waterflow will not be enough for you.

This is what happens with a lot of these batteries, and this is the reason you can have a battery that, when measured with a voltmeter, has 13+ volts but if you try to use it for cranking or something high current, the voltage will drop, because the resistance in the battery does not allow the electrons flowing fast enough.

A voltmeter only loads the battery with a few milliamps, to do the mesurement, while a starter motor can draw 100s of amps.

When i worked as an electronic repairman, we usually pranked apprentices, telling them to go to the spare parts guys in the workshop and ask for a new internal resistor for a battery, if it was bad this way

Guys at the spare part department hated us for doing this

[ Edited Coulomb: "internal resistor" → "internal resistance" ]

I once asked an apprentice to ask a stores person to issue him with a tin of tartan paint.
He returned to say, the stores person said that he only had tin's of striped paint and would that do .
A quick load / drop test of the 12 volt battery should relieve any internal faults.

Lovemyev said:

I once asked an apprentice to ask a stores person to issue him with a tin of tartan paint.
He returned to say, the stores person said that he only had tin's of stripped paint and would that do .
A quick load / drop test of the 12 volt battery should relieve any internal faults.

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Itym reveal

Lovemyev said:

I once asked an apprentice to ask a stores person to issue him with a tin of tartan paint.
He returned to say, the stores person said that he only had tin's of striped paint and would that do .
A quick load / drop test of the 12 volt battery should relieve any internal faults.

Click to expand...

Ah, the old apprentice pranks I worked as an auto-electrical/diesel injection engineer, and nearby were several motor dealerships. We were always getting fresh faced lads in for “a box of sparks” etc - we prolonged their agony by asking if they wanted 12v or 24v, and on their return, blue or red sparks - the ones who came in and asked for “a long wait” we let stand five minutes then let them in on the gag

At BSC we asked apprentices to go to the stores and ask for a long stand, they usually came back a couple of hours later.