Loss of battery power while laid up

[StEvnut]

We recently took a 16 day road trip in our Motor Home so the MG5 was in our garage for approximately 18 days with a 35% charge at the beginning. When I went to get her out she was down to 20% and asking to be charged.
I’ve read about this possibility but never experienced it, last long park up was only a week and no significant loss of juice.
Anyone else had this disappointment?

 

[5teep]

Something draining the 12v battery and the main batt recharging it?

 

[Adee]

There are usually some systems that run even when the car is not working, particularly immobiliser and alarms (maybe other things with electric cars). So I suppose the main battery tops up the 12V battery. But I have to admit that is one hell of a lot of power to have drained - roughly 1kWhr/day!!
Could you have made a mistake with your records??

 

[Kithmo]

It shouldn't lose anything, the HV is isolated when the car is turned off. The only thing I can think of is that the battery was warm when left and cold when restarted, but the amount lost seems a lot even for the battery cooling down. Or maybe it equalised itself ?

 

[AnonymouseDriva]

There are usually some systems that run even when the car is not working, particularly immobiliser and alarms (maybe other things with electric cars). So I suppose the main battery tops up the 12V battery. But I have to admit that is one hell of a lot of power to have drained - roughly 1kWhr/day!!
Could you have made a mistake with your records??

From my browsing of the manuals, I think that only happens on the Long Range, and possibly only the exclusive (as it has a * by it in the long range manual.) They refer to it as ‘intelligent charging’

 

[Cocijo]

It’s commonly known as ‘vampire drain’. The Tesla loses about 2-4miles a night. That car of course has a lot of remote data going on when using the app and updating etc. Your losses look excessive.

 

[StEvnut]

Thanks for your thoughts guys - interesting subject. I’m going to keep a check on it in case it’s an indication of something amiss.
mid we say it lost 10% of real range in 18days then it’s only 1 mile a night. I just wonder how normal it is. Using it everyday you’d struggle to notice.

 

[StEvnut]

Thanks for your thoughts guys - interesting subject. I’m going to keep a check on it in case it’s an indication of something amiss.
mid we say it lost 10% of real range in 18days then it’s only 1 mile a night. I just wonder how normal it is. Using it everyday you’d struggle to notice.

 

[Petriix]

I've not seen any range drop overnight but frequently it seems to be 1% lower than when it was switched off, even if it was just a short while ago. Seems to be more of a rounding error than actual power loss.

I definitely wouldn't want to leave the car under 50% charged for any significant period though. The battery really wants to be as close to or just over 50% when not in use.

 

[StEvnut]

I've not seen any range drop overnight but frequently it seems to be 1% lower than when it was switched off, even if it was just a short while ago. Seems to be more of a rounding error than actual power loss.

I definitely wouldn't want to leave the car under 50% charged for any significant period though. The battery really wants to be as close to or just over 50% when not in use.

Thanks
I did wonder if I should have left more. Most batteries are best left near full, but that was the old lead acid type. Not so sure about the new lithium batteries but it’s a good principle, I must see if it’s mentioned in the hand book.

 

[Stormgrey]

Thanks
I did wonder if I should have left more. Most batteries are best left near full, but that was the old lead acid type. Not so sure about the new lithium batteries but it’s a good principle, I must see if it’s mentioned in the hand book.

Best not left fully charged or nearly fully discharged. 40% to 80% is a good range to leave the car parked up.