Buying a used EV today - beware.

JKenH

This post was prompted by a post on the Tesla Owners Facebook page about someone whose car had been sitting at a repairers for sometime awaiting parts. Despite requests from the owner to keep the battery charged the repairer let both the HV and 12v batteries with serious implications forcthe long term health of the HV battery. 

That got me thinking about all the Teslas currently sitting on car dealers lots, for months potentially,  with batteries going flat. I wonder how many of them are keeping them charged. The dealer I bought my Golf from had let the 12v battery go flat and had to put a new one and it makes me wonder how EV batteries are being looked after. I don’t know if there is anything in the Tesla warranty about keeping the HV batteries charged. 

Buying  a used Tesla (or any EV) that has been on a dealer’s lot for months would be a worry. 

I have been following prices of 4 Teslas for several months. One was just a random Tesla M3P on the internet, the other 3 were at a local independent car dealer.

The VED on the TM3P expired on 5 August 2022. That’s been 6 months sitting around unused. Can’t be good.
Of the 3 Teslas at my local dealers, one is taxed and the VED on the others expired on 2 September and 6 September. 

I imagine it is a similar story around the country, not just with Teslas but also other EVs. I imagine if you are buying privately or from a specialist EV dealer such as one of the network of OEM main dealers then the battery will have been looked after but if you are looking at one at an independent I would suggest a check on how long it has been in stock and if there is evidence it has been regularly charged. 

Edit: it could be that in a few months time neglected batteries from this era of slow EV sales are showing up as less range and owners seek to move them so again beware. 

Grumpy_chap

Thank you - this is a very pertinent caution for me as I am watching used EV's with a view to acquire should I be able to make it work versus ICE options.

Car_54

12V batteries gradually lose their charge because power is used by alarms etc.

Why does an HV battery go flat?

daveyjp

Depending on vehicle settings from Teslas use HV power when stationary ironically to monitor HV systems, alarm and camera recording system, battery temperatures etc and keep the 12v charged.

I've parked next to one on a hot day and you could hear the HVAC system operating.

JKenH

@Grumpy_chap You’re welcome. I doubt I will get much thanks in some quarters. I must admit I had never considered them going flat until I read the Facebook post about the car at the repairers. I imagine some small independent dealers don’t even have dedicated EV chargers, just use their grannies. With energy costs so high it won’t encourage plugging in. 

I am thinking of getting another EV as a runabout. I can’t justify it financially but I really do like driving EVs. I am looking at Minis but they  are around £20k. 

The problem is everytime I have to go to the shops for something in my petrol car I think that’s costing me £X on top of what I’m buying whereas I used to regard the Leaf (at least in summer) as being virtually free to use. From March when my existing Go Faster tariff ends it will be around 4p/mile in an EV as opposed to the 14-15p in my Golf.  I only did 6-8k miles a year in my Leaf so most I could save in fuel would be £600-800 a year and if I get a Mini it would be less as I went everywhere in my Leaf, not just local trips. 

It’s just how my mind works. Capital costs are sunk costs so I feel happy I’m saving money everytime I go out in an EV so would drive it more.

JKenH

Car_54 said:

12V batteries gradually lose their charge because power is used by alarms etc.

Why does an HV battery go flat?

Have a read of this article 

Will my battery go flat if I leave my EV parked for too long?

https://evcentral.com.au/will-my-battery-go-flat-if-i-leave-my-ev-parked-for-too-long/

One short excerpt 

Here’s what Tesla says in the user manual for the Model 3: “Even when the Model 3 is not being driven, its battery discharges very slowly to power the onboard electronics. The battery can discharge at a rate of approximately 1 percent per day, though the discharge rate may vary depending environmental factors (such as cold weather), vehicle configuration and your selected settings on the touchscreen.”

Grumpy_chap

This seems to be a function of the "vampire drain" materialising again.

I understand that an EV can allow all these electronic circuits to remain powered for the long term while the car is idle, but is there a way to basically shut them all down?
An ICE car can be left at the airport for two weeks and the small 12V battery will hold enough charge, even though the clock / alarm etc are all operating, for the car to start when you get back to the airport.
It would make sense for an EV to have, effectively, an "airport / holiday" setting so when leaving the car for the long term, it uses no more electricity than an ICE car that is just parked.

Krakkkers

Its like driving a petrol car with a hole in the tank.

uknick

Maybe the BMW i3 is different to all other EV, but I left mine unplugged at Southampton Cruise Terminal car park a couple of years ago for 3 weeks and the battery only had a couple of % loss.  Maybe it's a Tesla thing?

JKenH

uknick said:

Maybe the BMW i3 is different to all other EV, but I left mine unplugged at Southampton Cruise Terminal car park a couple of years ago for 3 weeks and the battery only had a couple of % loss.  Maybe it's a Tesla thing?

Maybe it is.

I went away last year on holiday for a week and took battery readings using LeafSpy before and after. My 40kWh Leaf lost 0.4kWh over 8 days or around 50wh per day which equates to a drain of around  4  2 watts per hour. The car had 50% charge and was inside my garage and not plugged in. I believe the car’s HV traction battery tops up the 12v battery so this represents the total electrical drain.

50wh/day in the Leaf against 1000wh/day in a Tesla.

1% a day in a Tesla with a 75 kWh battery equates to 273.75 kWh per annum. If you do 8000 miles pa at 4miles/kWh (mpk) that’s 2000kWh. So vampire drain adds 13.7% to your annual electricity bill for the car. I doubt many people factor that in. That effectively reduces the car’s efficiency from 4 mpk to 3.45 mpk and that’s before charging losses. An indicated 4mpk while driving becomes closer to 3 mpk from the plug. 

Edit: Correction made -  50wh per day is 2 watts per hour not 4.

diystarter7

Hi OP

Many thanks. Just another reason for me not join the gov hyped flow

Thanks