Marscar
Posts: 4
Joined: Wed Sep 21, 2022 3:23 am

Buying a 2018 REX i3s

Hello!

First post, and I have yet to buy an i3, so my questions will be about that for now ...

I have seen a 2018 i3s REX with 57,000 on the clock, with one previous owner
The positive side of me says this is a good sign ... not low miles and multiple owners suggesting issues, garage time, and standing time.

However, having picked up a little about ev's in general I'd be interested to know if anyone on here thinks I'm being overly cautious about this particular vehicle.

It's being sold by a large-ish independent franchise that works in volume to keep their prices at the low end of the usual range for trade sales.

What I'm guessing has happened with this car is that they took it in at the end of a lease, at "x" miles near the end of July, listed it with those miles, then did the MOT which passed at "x"+4miles and it has sat for two months, showing "x"+5 miles on the clock.

I will try to post a photo of the screen, but in case that fails, I THINK it is showing:

1) the state of charge as being very low with the range left on the battery as 1 mile.

2) the fuel icon has a triangle exclamation mark warning light above it, with 1.5 of the 4 bars showing the fuel level.

I read this as the dealership having had it sat for two months, using petrol to make any small moves ... and therefore the battery has been left at the low end of it's capacity for all that time.

I thought that ev batteries should ideally be left standing for long periods at 50 to 80%.

They haven't yet answered my request for an image of the battery capacity (via the "secret menu") and I suspect they either don't really know how to do that, or are too busy to want to!

The middle ground between avoiding an earlier i3 and our budget means "120"ah batteries are out of reach, and the REX becomes a necessary factor on top of a "94"ah battery.

EDIT:
I appreciate that a 94ah battery will only show about 88ah at the start of it's ownership.
Also this car is not local, so I'm not sure I want to make a 260+ round trip only to find that the capacity has dropped too far.

Thanks for reading this far!

I look forward to boring you with posts from an actual owner before too long :D
alohart
Posts: 2592
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: Buying a 2018 REX i3s

Unlike many 60 Ah battery packs, 94 Ah and 120 Ah battery packs seem to degrade at much slower rates, so it's very likely that the usable battery pack capacity would be high … unless allowing it to remain at a very low charge level for a couple of months has accelerated degradation.

"Petrol", "MOT", and "miles" makes me deduce that you are in the U.K. where ambient temperatures tend to be not so hot … although that might not have been true while this i3 was sitting at a low charge level. I think that the battery cell degradation rate while at a low charge level would be greater at high and low temperatures, so you might be OK. Too bad the dealer didn't just plug in the included charging cable to charge the battery pack.
Aloha,
Art
[22-04-25 to now] 2019 BMW i3 Imperial Blue Metallic, Giga World, Tech + Driving Assist, Heat Pump, 428 Wheels
[14-11-05 to 22-06-15] 2014 BMW i3 Arravani Grey, Giga World, Tech + Driving Assist, Parking Assist, DC Fast Charging
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Marscar
Posts: 4
Joined: Wed Sep 21, 2022 3:23 am

Re: Buying a 2018 REX i3s

alohart wrote: Wed Sep 21, 2022 5:40 am Unlike many 60 Ah battery packs, 94 Ah and 120 Ah battery packs seem to degrade at much slower rates, so it's very likely that the usable battery pack capacity would be high … unless allowing it to remain at a very low charge level for a couple of months has accelerated degradation.

"Petrol", "MOT", and "miles" makes me deduce that you are in the U.K. where ambient temperatures tend to be not so hot … although that might not have been true while this i3 was sitting at a low charge level. I think that the battery cell degradation rate while at a low charge level would be greater at high and low temperatures, so you might be OK. Too bad the dealer didn't just plug in the included charging cable to charge the battery pack.
Hi, and thank you :-)
Yes, "Good old Blighty" I'm afraid :-/

It's this that I'm wondering about:

"unless allowing it to remain at a very low charge level for a couple of months has accelerated degradation".

...and the fact that we did have a pretty HOT time of it for most of that time.

They're not helping themselves as sellers so far, but then maybe they don't have to try that hard?
Thanks again!
Marscar
Posts: 4
Joined: Wed Sep 21, 2022 3:23 am

Re: Buying a 2018 REX i3s

..... so what would be an ok read out for battery capacity on a 94ah after nearly 60,000 miles?
Less than 88ah I guess, but by how much?!
agzand
Posts: 113
Joined: Tue Dec 22, 2020 3:00 pm

Re: Buying a 2018 REX i3s

The betta kappa max starts around 29.5-30, anything in the 28-29 should be ok.
Marscar
Posts: 4
Joined: Wed Sep 21, 2022 3:23 am

Re: Buying a 2018 REX i3s

agzand wrote: Thu Sep 22, 2022 11:10 am The betta kappa max starts around 29.5-30, anything in the 28-29 should be ok.
Hi, and thanks for you reply ...
Those numbers are surprising.
I must have misunderstood!
I thought the Batt Kap number started at around 90% of the nominal capacity, and was into "warranty territory" if it dropped below 70% .......
Do I need to go back to school?!
EDIT:
Ah! .... A 94ah will be a 33kwh, so you're referring to the % of THAT. ... Goddit :-)

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