Cont: Electric Vehicles II

[Rolfe]

My car is parked up in its own garage for a month, in temperatures hovering around freezing (lowest has been about minus five). It does keep its 12v topped up but there is no other "phantom drain". I left it at 69% so it has plenty to play with, and left the doors unlocked in case the 12v does die (the garage is locked!).

I'm not expecting any trouble, but it's right next to its own charger and there is a jump-start pack (lead-acid) in the garage. I'll probably run a battery heating cycle before I use the car, but we'll be fine.

 

[bruto]

I don't know how fast the 12 volt battery on a EV self-discharges, etc., but I've had some issues in the past with my gasser truck, which sometimes sits for long periods unused, especially these days when I do a lot of travelling, and likewise with my excavator, and have had good luck with a cheap solar trickle charger. On the truck I just stick it on the dashboard, and it keeps the battery topped up enough to start even after a month or so. Just make sure it's either hard-wired in, or if using a 12 volt outlet that it's one that stays live when the ignition is off, because some do and some don't.

 

[Dabop]

I don't know how fast the 12 volt battery on a EV self-discharges, etc., but I've had some issues in the past with my gasser truck, which sometimes sits for long periods unused, especially these days when I do a lot of travelling, and likewise with my excavator, and have had good luck with a cheap solar trickle charger. On the truck I just stick it on the dashboard, and it keeps the battery topped up enough to start even after a month or so. Just make sure it's either hard-wired in, or if using a 12 volt outlet that it's one that stays live when the ignition is off, because some do and some don't.

Many modern cars(especially those with 4 cylinder motors which often have a small battery indeed) can find themselves being too flat to start after only a few days- a combination of high parasitic loads and a small battery can see them effectively dead after only four or five days... diesel cars are often better off as they usually have a larger batter (due to the higher cranking current needed to start a diesel) but that also hurts them too- that higher cranking current means that they are less tolerant of a partially flat battery...

Long gone are the days when you could park a car for months, turn off the key and walk away and expect it to start- there's too much on modern cars that are constantly pulling power from the battery- car alarms, various computers maintaining their 'user settings', audio systems, radio receivers for door unlocking etc etc- these are all small amounts true- but they all add up, and when they are 'running' 24/7 its all added loads that 'ye olden times' care with a points ignition, wind up windows and doors you unlocked by sticking the key in a hole didn't have...

EV's actually have the advantage in that their 12v accessories battery has an onboard charger (running from the EV traction battery) they can (and do) last for several months before 'going flat' (far longer than the few days that most modern cars can last for) but even they have their limits, luckily many airports are starting to provide charging facilities in their long term parking lots- these don't need to be high current fast chargers, in fact they need be nothing more than a powerpoint in each bay that can have the 'granny charger' plugged into- the lighting in most parking bays will draw more than the chargers lol
This is already being done at many airports around the world....



And yes, even the yanks are starting to do it...

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Many airports if they don't provide 'parking chargers' have also got onsite fast chargers in their parking areas like the Gold Coast Airport here

 

[Rolfe]

I left my 2009 petrol Golf in a port-side car park in England for 10 weeks starting at the beginning of January 2019. It thought about it a bit, but it started. Its 12v was only a year or two old though.

 

[novaphile]

I don't know how fast the 12 volt battery on a EV self-discharges, etc., but I've had some issues in the past with my gasser truck, which sometimes sits for long periods unused, especially these days when I do a lot of travelling, and likewise with my excavator, and have had good luck with a cheap solar trickle charger. On the truck I just stick it on the dashboard, and it keeps the battery topped up enough to start even after a month or so. Just make sure it's either hard-wired in, or if using a 12 volt outlet that it's one that stays live when the ignition is off, because some do and some don't.

Mine recharges the 12V from the traction battery for one hour per day, everyday, if required.

After three days of no activity, the car goes into a kind of hibernation mode, where all power using things are turned off, except for the alarm system and door locks.
(The obvious sign of this is that the wifi is turned off after three days.) That reduces the drain on the 12V considerably.

Note that I specifically had the car's cameras wired to a separate power source, which does not recharge until the car is turned on.

The car also has on-board timers, so I could leave it plugged in for extended periods set to charge the traction battery once per week. If I was storing the car in a very cold place, I'd leave it plugged in and set the timers to charge and run the heating once per day. The heating uses more power than the car can draw from its 'granny charger' so I'd set it to charge for a couple of hours after the heating was scheduled to turn off. The combination of the heating and charging would probably be enough to maintain a reasonable ambient temperature in an insulated garage.

IIRC there was a member on the car forum, who left their car standing, unplugged, in an airport car park for six months, and was very pleased to find it ready to go on their return.

I think others have mentioned that the 12V battery doesn't have to do much, it only needs enough power to turn on the electronics and operate the switch that connects the traction battery to the car.

The traction battery supplies power to the generator to start the engine if required. (That plus some trickery with the engine timing.)

 

[xterra]

In 2009, I left my 1999 panel van* in a storage facility for six months, with a small solar panel on the dashboard. The panel was plugged into the cigarette lighter socket. (I already knew that this particular outlet had power even when the car ignition lock was turned off.)

When I returned for the van, it started with no difficulty other than having to pump fuel from the tank to the engine. The gauge on the dash panel showed the battery was fully charged. The clock showed the correct time.

I think I paid about US $12 .00 for the panel.

*ICE, but that's not relevant to the discussion.