A friend of mine was coming out of his local convenience store and what he describes as an Oriental looking gentleman asked him if he happened to have some jump leads as his car wouldn't start. He didn't have any with him (even my wife carries jump leads!) but noticed that the guy was walking back to a Tesla. Anyway he said that he didn't think that jump leads would solve his problem and drove off. Another friend on hearing this tale said that Teslas have a 12v battery which runs all of the car's systems and lights etc separately from the main drive battery and that if this battery runs down or fails then the motor field windings don't get initial power and it won't go. Apparently the 12v batteries don't last more than about 3 years. The battery is normally charged from the drive battery btw. 3 x FL1 2 manual + 1 auto
5 x FL2 4 manual + 1 auto
Now Discovery Sport P250 MHEV SE

They really aren’t the future.

I was surprised as well when I noticed that all the EVs and Phevs I looked at seemed to have an ordinary 12v Lead Acid Battery under the bonnet.

But I was told that apart from running many of the standard in-car electric/electronics, it had an important function of switching the High Voltage Drive Battery on.

https://www.midtronics.com/blog/why-do-ful...y-in-them/ FL2 XS SD4 Auto 2010 2012-2017 (21k - 91k miles) (MY2011)
FL2 Metropolis SD4 Auto 2014 2017- (16k - 77k+ miles) (MY2015)
Metro in its 11th Year of (Extended) LR Warranty / Full LR Service History
(Expensive, but Trouble/Worry free - hopefully?)

ipace had 12v battery issues, no 12v no go, an updated setup in 2021 seems to have cured this At work
At home

"I can't always believe facts I read on the web" - Charles Dickens

winner by default of the tractor vs caravan race

You either have a small (12V) battery that does the alarm, central locking etc or you rely on the main battery.
The temptation is to tap 12V off the main battery, but this discharges to 6 or so cells required at a different rate than the rest, so the battery as a whole has to treat all the cells the same, then you have the nightmare of trying to charge the cells at different rates - no.

Another option is to have a device that acts like a transformer and drops the main battery down to 12V but then the main battery can't go to sleep - leave it for a while (at a dealership?) and the whole battery is flat.

Or have a standard 12V battery that does the standard stuff that is charged from the main battery when the main battery is awake.

12V batteries that go flat while the car is parked is not a new thing, or one that has gone away, thinking about a college who has just spent a kings ransom on a new Alpha Quadrifoglio, don't drive it for more than 2 days and all the lights on the dash illuminate when started as the CANBUS crashes due to low voltage. Tangiers Orange - gone, missing her
Replaced by Ewok what a mistake - now a happy Disco Sport owner

Maybe a solar trickle charge panel will solve most issues like outback/caravan owners have been doing for the last few decades. About as simple as it gets.

Also quite handy if one wants to run a few accessories, like a fridge, & put in a battery for accessories. Hardly difficult stuff. Procrastination, mankind's greatest labour saving device!

Acoustic insulation ARB TPMS 3xARB air compressors After cooler Air tank On-board OCD pressure air/water cleaning Additional 50L fuel Carpet in doors ABE 2x1kg Waeco 28L modified fridge Battery 4x26ah Solar 120w Victron MPPT 100/20 DC-DC 18amps 175amp jumper plug Awning 6x255/60R18

have you been to the UK?

Sunshine is not something that we get often, rain yes, when it's not raining it is overcast Tangiers Orange - gone, missing her
Replaced by Ewok what a mistake - now a happy Disco Sport owner