[Foo Gee]

A friend of ours has an electric car and her husband has been abroad for a while and it crossed my mind that their battery won't have been charged. The car is parked on a street and so it's not hugely practical to have a lead across the pavement for a trickle charge and she doesn't drive.

If it was a standard car battery I would be worried about the battery discharging and then requiring replacement. Would this be the case for an electric car battery pack too?

[Colonel Panic]

Depending on what is "left on" in the car - such as dash cams etc - the battery can lose 1-2% a day in "phantom drain". The best advice is to leave the car with enough juice to last for the duration when possible, but if not leave it plugged in.

[Rob P]

Join the RAC

They will send a handy little van to charge it enough to get to the nearest charger.

The saving grace is that unlike an ICE where the starter requires a disproportionate amount of electricity to the size of the battery, the 'starting' load on an EV is virtually the same as normal use.

Rob P

[leifarm]

Depending on car model the 12 V battery may not be recharged by the main pack unless the car is "started", that is for example the case with my Mitsubishi i-Miev. If this is the case and the main battery still has plenty of charge, it might be advisable to power up the car for an hour or so to top up the 12 V?

[Jim Jones]

The power battery ( that drives the car), has huge capacity and should be ok for some time as it disconnects itself usu g relays powered by the 12volt. . The 12 volt battery, as already mentioned, is small as it is not used for churning an set of pistons and valves into action. It can be drained by alarms etc, but should be easy to charge, and can be jump lead ‘started’ so it opens the relays to the power battery, which will then continue to replenish it. Powering up the car at intervals will keep it topped up, but obviously not indefinitely.

[riverrock]

The traction battery (the big one) should be fine - they degrade pretty slowly and are pretty large.
12V battery as said above will depend on the car. Some cars will detect a low voltage and engage the traction battery to charge it (Tesla) while others will allow it to slowly empty till its dead (Renault) so the car might need a traditional jump start (but likely also the 12V battery replacement).
I believe that some (Tesla) also has a "storage" mode which reduces battery use further, and doesn't go through the top-up cycle as often as it degrades the 12V battery.

You could "offer" to take it out for a drive for them... you might be converted to electric!

[malcolmfrost]

Personally I would try and get it on a charger if possible. It won't do either battery any good to completely discharge. The main battery will be happiest between 20-80% so don't be tempted to "fill her up"!

[Flying_john]

For long term lack of use, the traction battery is ideally left at between 50% and 80% charged as the advice is the Lithium batteries degrade more quickly if left at 100% and continually topped up/trickled, something about migration of lithium at high states of charge !

With the Leaf, when the car is switched on the traction battery charges the 12v battery. If I don't drive mine for 2 or more weeks, I just go and turn it on, listen to some music, tinker with the on board electronic wizardry to see if I can find any new options I have yet to discover for 10 minutes. Seems to work.

[Foo Gee]

Thank you for the advice.
Unfortunately, the car has been sat since unused since October and her husband is abroad working in Asia unlikely to be back until after April.
I have told her to get the car on charge up to 80% but I would imagine the 'standard' battery is probably unusable by now and I hope there hasn't been any damage to the main driving cells.
I would think the brakes might even be stiff by now if they're anything like on my car if it sits for too long.
Unfortunately, there is only street parking where she is and I just hope she can get a lead across the pavement to it without some idiot tripping up and trying it on!

[malcolmfrost]

Could you get her husband to put you on his insurance policy?
This might help with running a cable outside!
https://www.tlc-direct.co.uk/Products/CAFC83Y.html?source=adwords&ad_position=&ad_id=415703895078&placement=&kw=&network=u&matchtype=&ad_type=&product_id=CAFC83Y&product_partition_id=934892185560&campaign=shopping_cable_accessories&version=finalurl_v3&gclid=Cj0KCQiAvbiBBhD-ARIsAGM48bxl7f--T5_MyN_ZyBNs87WFdj7UVjnJypX3pkQycqupEiL4m7jkYdAaAi1gEALw_wcB

[Aerials]

How does the husband charge the car when he's at home? Obviously not easily just now, so would it be possible to tow or push the car to a position where an electricity supply is available?

[stevelup]

As others have said, the main traction battery will not have run down. Depending on exactly what car it is, there's a possibility that the 12V battery may have become discharged. Bringing this back to life is no different to 'jump starting' an ICE car.

Personally, I'd just leave it alone. Can't see what benefit plugging it in will bring.

[Paul_Sengupta]

Personally, I'd just leave it alone. Can't see what benefit plugging it in will bring.

I could save the replacement of the 12V lead acid battery.

[stevelup]

Maybe... Might already be shot... Might never get shot... Plugging it in now, then leaving it till April... Might die between now and then. Just too many unknowns.

One thing that might be worth doing is to just measure the 12V battery before anything more radical. Or just get in it and see if everything comes to life as normal without any warnings. If that happens, then there's probably nothing to worry about.

Not all EVs actually have a problem with the 12V batteries anyway - most will top them up occasionally using the traction battery.

A vital piece of information is missing from this thread... What is the car?

This question would be better asked on SpeakEV - there are experts on basically every model on there who will have first hand experience.

[Flyin'Dutch']

What does the owner think?