Will Caliban start on Monday morning?

[Rolfe]

I still don't see why the 12V battery would need to be topped up anyway within a week.

What is the Ah capacity of the SE's 12V battery? Maybe 50Ah or more? With a 50Ah capacity and, let's say worst case 100mA quiescent draw, then you're looking at it lasting 500 hours without any top up.

That of course is the other good question. Assuming the 12V is OK in itself (no reason to think it isn't) then how long is it likely to be good for if for whatever reason the car isn't topping it up? I don't know but I'd have thought a week would be OK. But I wanted more info, hence this thread.

 

[redwood98]

I've had another thought. What if I simply went and sat in the car for a bit? Wouldn't that let the 12v charge?

So that's two possible plans. Ignore the whole thing until Monday and if the car won't wake up then walk to Halford's and buy a jump starter battery. Or go and sit in the car for a bit, maybe a couple of times, to force the 12v to charge. I wonder how long I should sit for?

I would get in the car for a little bit every other day and check the voltage. As you can check the other battery percentage at the same time and avoid waking the car up remoting.

 

[Coulomb]

As you can check the other battery percentage at the same time and avoid waking the car up remoting.

I would think that sitting in the car would wake up as many or more computers, plus HVAC and displays, as a remote scan. But that would guarantee charging the 12V battery, assuming that the HVAC is on.

But I agree with the idea of sitting in it every 2 days or so. I think that a few minutes should be enough time. The DC-DC can pour a lot of current into the 12V battery. 20x more than a typical 12V car battery charger that you connect with clips or plug in.

 

[T1 Terry]

The concern regarding the 12v battery health stems from post #23
The dashboard was showing 14v before I parked the car and the app said 12.5v after it was parked and locked. Which is fine. The question is, will it stay fine until Monday if it isn't topped up from the traction battery?
If a 12v nom. lead acid battery is holding it's charge, it should have shown 12.8v or higher then the DC to DC stopped charging it. 12vdc is flat with a lead acid battery, 12.4v is 50% capacity remaining .... so the battery is showing clear signs of being far from as new condition ..... if it had dropped to 12.3v or less, I'd be making preparations to avoid getting stuck with a dead 12v battery, 12.5vdc, if there are no added loads to pull the battery down, it should be good sitting for a week or so .......

T1 Terry

 

[MG Clive]

I'm sorry, but getting in the car every day will power up everything that is run by the 12 volt battery, so doing this would further deplete the 12 volt battery. If the main battery did charge up the 12 volt battery during this process, I doubt it would charge up enough to cover any voltage loss from powering it up, it would just drain both batteries.

Just leave it alone, it will be fine when you go back to it.

 

[tsedge]

My battery has always ranged from 12.1V to 12.8V when not being charged since new and around 14.3V when being charged.

I've had zero problems in nearly 3 years and have often left the car for weeks at a time.

What is normal depends on the vehicle, battery and loads / HV charging design. EVs seem to be a bit different to ICE cars in this respect.

Very few people seem to have had battery failures and those reporting multiple ones tend to have had phantom power drains from software bugs that are addressed in updates OR have had something plugged into the OBD2 port causing a drain (or loose battery wires).

As far as I can tell, the perception that we all need a 10mm spanner and booster has been generated by the small number of problem stories reported here.

Edit: Right now my MG4 reports 12.1V, 38% SOC. This is normal.

 

[MGFour]

If you think that it might be an issue connect to car and switch on preheating which will also pop a charge in 12v battery, Just set to the heat to say 15 or whatever the current ambient temp is so it doesn't need to heat/cool much if any.

 

[Everest]

That of course is the other good question. Assuming the 12V is OK in itself (no reason to think it isn't) then how long is it likely to be good for if for whatever reason the car isn't topping it up? I don't know but I'd have thought a week would be OK. But I wanted more info, hence this thread.

Oy! @Rolfe... you've been keeping me awake - there I was at 3am thinking about Caliban, all resplendent in Holborn Blue with a bike in the back!

In the middle of the night I did some more mental maths for you...

Assuming the 12V battery capacity is around 50Ah. Then IF the MG4's battery discharges fully within a week AND it was topped up from the HV battery, then my maths says that the HV battery would be supplying 50Ah x 12V = 600Wh every week. Which for a 52kWh HV battery is just over 1% of its capacity per week. But we know from many other threads on here, including yours, that the SOC of the HV does not deplete at a rate of 1% per week when a vehicle is left idle.

But frankly, a week? Pfui, you'll be totally fine. If you can top it up to above 50% before you go, do it. I noticed a car charger at the entrance to the car park I used at Glasgow, and that was probably the reason it was there. But if you can't, don't fret. If the terminals on your 12v are tight it will be fine, I'm sure. As I said, I left mine for more than two weeks and it didn't drop even 1%.

Oh yes!
I left my car for 7 weeks while in the hospital. And I did not notice any loss of charge

So, my advice is he'll be fine. Just leave Caliban to sleep for the week - give him a rest from his drive down to Brighton and don't keep wake him up until you're ready to go home

 

[tsedge]

I've found the HV SOC to be either the same or 1% less after a typical 2 week holiday with the car left untouched.

 

[Rolfe]

I imagine Caliban is sound asleep by now. I haven't tried the app since Wednesday evening. I'm inclined to go with Everest here. I'm not in the middle of nowhere. I'm not in a desperate rush on Monday either, because I'm going home and the friend who's with me is going to stay over till Tuesday anyway, so it doesn't matter if we get in late.

I think there's a decent chance the car will be fine if I just leave him to sleep. But if not, Halford's is 20 minutes walk away (0.8 miles, so not walking fast). (I guess the bike would have been handy there, but she didn't come on this trip.) I have my emergency physical key. Say an hour altogether to get to Halford's, buy a jump starter pack, walk back and get into the car and start it. Not a dealbreaker.

I lost at least an hour to a closure on the M6 on the way down, then at least 20 minutes more because I stupidly went to Cherwell Valley where there was a scrum at the chargers when I should have had the sense to go straight to Baynard's Green a mile away in the first instance. And still got here by 8.30. Assuming nobody decides to kill themselves on the motorway this time, and I have the sense to avoid honeypot chargers, we're not really that pushed for time.

 

[Rolfe]

I've found the HV SOC to be either the same or 1% less after a typical 2 week holiday with the car left untouched.

That's not really the point though. The question is whether the 12v will be OK if the car is left with the traction battery at such a low SOC that the 12v will not be topped up.

 

[tsedge]

It means:

• 12V batteries don't lose much when the car is off
• Topping up the 12V battery takes almost nothing out of the HV battery
• Therefore it can top up the 12V battery even if it is at a low SOC

You continue to worry, worry and worry about this event that has not even happened.

 

[Rolfe]

But...

From the manual:

View attachment 41000

 

[salty]

I really hope it does start. And I'm pretty sure it will. But it'll be a bit of an anti-climax if it does.

 

[Everest]

I really hope it does start. And I'm pretty sure it will. But it'll be a bit of an anti-climax if it does.

If Caliban starts OK on Monday (as I'm sure he will), then @Rolfe should drive home via the Hardknott Pass a couple of times to keep us all in suspense for a bit longer

 

[tsedge]

But...

I do wonder what you could put this worry energy into instead that would be more productive and enjoyable.

I find it is generally better to worry about things that have already happened. There's enough of those out there, or at least that is my experience. YMMV.