Will the MG ZS EV 12v battery discharge if the car is parked for long periods?

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rvh1t

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Hi, my wife took delivery of our brand new MG SV EV exclusive just over a week ago. Of course, we are now in lockdown due to corona virus and will not even be using the car to do essential shopping as she is in the very vulnerable category. So it look s as though the car is going to be garaged for a few weeks. Charging the main battery is no problem, as we have a home charger. However, what should I do about the 12 battery, should I unhook it?
 
Hi,

Reference your question, another member of this forum (Dangerous Doug) carried out a test and concluded that when charging your main battery the 12v car battery is charging at the same time. You can search for his thread. So don't disconnect your car battery at all, in fact I think if you did the car might not charge anyway, just a thought. So plug it in and leave it to do its own thing!!!

PS Dangerous Doug's thread is titled "A piece of good news"
 
But don't charge it to maximum if it not being used. 50-80% is recommended to maintain battery condition and loss of main battery charge is negligible when left unused. A week or two should be fine for the 12v battery but if longer than that maybe fire the car up to ready state which will top up the 12v battery from the main one.
 
I'm pretty sure that the car determines how much the battery can be charged. I dont think you can overcharge one. Mine is ofter left plugged it, but is not taking a charge after a while.

I have also have PHEV which works just the same.....still working quite happily after 6 years ...but with a rather pathetic electric range of only about 28 miles...hence the MG.
 
Hi Guys,

You know something, I don't care, I plug my car back on charge every night no matter what the SOC. The way I look at it is, let the BMS look after the battery. I don't want to change my car driving habits of a lifetime just because I now have a electric motor and not a petrol motor, after all I didn't keep my petrol tank at 50%-80% full, and as far as economy goes I drive the car how I feel, if I feel like a little bit of boy hooligan coming on (where safe) I make use of the gutsy pull of the electric motor and enjoy my driving just as I did when driving my petrol and diesel cars, however on a long trip with the MG I do drive with economy in mind but NOT when I am doing short trips that is well within the return range of the car. Get home, plug it in and off you go in the morning with a full "tank". If my laziness of not monitoring and regulating the cars charging regime (and I do have one, plug it in when home and forget about it until I plug it in again after using it) harms the battery then so be it, I have the 7 year warranty and as my mileage is only about 8000 a year and I will have probably changed the MG ZS EV for the new MG E-Motion or another upgraded MG ZS EV then I don't see the point of worrying about charging regimes. However everyone to their own.

Frank
 
That's fine if you use it on a daily basis and the BMS will indeed stop charging when full and not re-start to keep at 100% - it is just recommended not to leave at full charge for long periods.
 
Frank said:
Hi,

Reference your question, another member of this forum (Dangerous Doug) carried out a test and concluded that when charging your main battery the 12v car battery is charging at the same time. You can search for his thread. So don't disconnect your car battery at all, in fact I think if you did the car might not charge anyway, just a thought. So plug it in and leave it to do its own thing!!!

PS Dangerous Doug's thread is titled "A piece of good news"
Click to expand...
Thanks for that.
 
I would say more than 3-4 days although, as with most things, there is no black and white answer. The possible additional degradation is debatable and likely to be affected by many other factors too. Equally, I wouldn't get overly worried if you can't for any reason but best minimise degradation by getting into good habits where there is little or no downside. Generally recommended to keep charge between 20 and 80% unless you need maximum range for specific trips. Hence choose a vehicle with sufficient range at 80% to cover most of your regular trips.
 
I had problems several times, after only a week of not being used "HV Battery Disconnected" which is caused by the 12v battery being too low. I complained to my dealer and eventually to MG. The first week of lockdown the car failed again, I charged the battery all morning but it still would not start. I was so fed up I called the AA.
After arranging a home visit, I received a call back from the AA Technical Dept and the guy gave me a cure :-
Lock and unlock the car with the KEY FOB.
Push the brake pedal as normal but at the same time apply half throttle
Now press the start button and it will be fine
This has worked everytime
Redpiratepete
 
Very interesting stuff..well worth knowing.

On a COMPLETELY DIFFERENT SUBJECT........but it is related... for me.

Our 2nd Car, a Mitsubishi PHEV, which we have had for several trouble free years, hasn't been used much for the last 3 months. When I moved it yesterday, (despite being fully charged) the engine came on and it announced "engine running to preserve fuel systems"....or something similar. I took it for a spin and the engine stayed on....... It seems OK again now....... New one on me! :oops:
 
Hi Crispydoc.
Very interested to learn your other car is an Outlander PHEV.
I traded one in to buy my MG AS EV. 2016 hs4 in grey.
It was up till now the best car I had ever owned. Roomy and very comfortable, drove beautifully, especially on battery power.
I kept a detailed log on fully.com and it regularly gave 85 + mpg between fill ups with the best over 125 mpg.
Servicing was over £300, but 0 RFL brilliant!
I first saw the MG on a James and Kate YouTube video at the press launch......Exaactly the car for us.
So common ground.
Redpiratepete
 
Thats interesting, it was the James and Kate video that did it for me. I had been looking at other Electric cars, but I'm very keen of the high ride height, which only the MG has. ( at sensible money) .

I regularly do a trip of 155 miles (each way) and on that, the PHEV was only doing about 48 MPG.
The PHEV is fine for just popping around, but at around a 25 mile range in Electric, it just didn't do it for me.

I do love the MG .......if only it did another 30 or 40 miles on a charge, it would be perfect.
 
OFF TOPIC AGAIN.....regarding my PHEV wanting to keep starting its engine, to keep the fuel system working.....I have briefly disconnected the negative terminal on the 12 volt and that has made it forget about it.! ....much safer than faffing around with 15 litres of Petrol! Ive also put the 12 Volt on trickle charge to maintain things during lockdown..... Might have to do that with the MG soon?
 
Hi Chris,
I to had the Mitsubishi Outlander, which I loved, but a £400 bill for servicing a (little used) ice was the last straw. Hence the MG which is loved by all.
Regarding the engine starting on the PHEV I believe it is to use up the fuel in the tank as petrol degrades with time. If stale petrol is left in tank you may have difficulty getting the engine started again.
Love your car collection,
Iain
 
Thanks Iain,

The Mitsubishi always starts when required...it did go through a phase of telling me we needed to run the engine as it had not run for 3 months. But having had old cars for many years I think it was over reacting! If you disconnect the 12 volt for a short while it forgets that stuff. Now its out of warranty, I did the latest full service myself, oil filters etc. Cost me about £45 in parts! I fitted new discs and pads for its last MOT...I doubt it will ever need anymore in my ownership.(cost about £70)

I Waxoyl it every couple of years and it lives in 'slightly' warm dry garage. I've started using best quality petrol and a fuel preservative. (when I do fill it up). But It only get used a few times month, and mostly just on battery. But occasionally I take it on a long trip to Norfolk and back.....usually costs about £40 in fuel!!! Which hurts! It has never gone wrong or failed to start.....saying that, I did fit a new 12 volt about 3 years ago. It costs very little per year and is a useful back up, should it be needed.
 
Why would the 12v go flat so quickly?
Leaving the car at the airport for 2, 3 or 4 weeks and it should still be okay just as an ICE car, that battery is no different.

But would the BIG battery be okay if you parked it with only 20% or less?
 
I have always been anxious when leaving my cars at airports etc. when going on Holidays!

With my classic cars I always fit an isolating switch and occasionally use a smart trickle charger.

When any battery goes flat...it is never quite the same again......and do it a couple of times and it gets even worse. It all down to a tiny bit of 'drain', and lack of frequent use, At least this has been my experience in over 50 years of mucking about with ICE cars...

...I don't pretend to understand EV's, but I do try to use them and plug them in regularly.

HAPPY AND PEACEFUL CHRISTMAS AND NEW YEAR TO ALL.
 
Petrol - on a bike forum I used to frequent, a chemist from Shell posted a long article about keeping petrol in tanks for a long time. Upshot was that there isn't any significant degradation in modern fuels for a period of 2 years. I forget where the 2 years came from, may have been a specific question. I am no longer a paid up member of the forum so can't look up the post, but this goes back several years.

On that note, I have always tried to run ICE vehicles regularly, I hate the thought of them sitting there when they're unused, rusting away...
 
Mine certainly don't 'rust away'.....they are dry and cosseted...:) and only go out on dry days.
 
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