i3 Charge Speed

[SOL111]

Hi all.

Does anyone know what governs the charge speed of an EV?

I did a 1k mile tour of Cornwall recently and used 50kW chargers exclusively during the week away. Charge times were great.

However, since coming back and using my 7kW home charger, it's been taking an age. For instance, yesterday it took around 8 hours to go from 5-100%. My app showed that it was only charging at around 3.5kW.

Any ideas?

[FeelingLucky]

SOL111 said:

Hi all.

Does anyone know what governs the charge speed of an EV?

I did a 1k mile tour of Cornwall recently and used 50kW chargers exclusively during the week away. Charge times were great.

However, since coming back and using my 7kW home charger, it's been taking an age. For instance, yesterday it took around 8 hours to go from 5-100%. My app showed that it was only charging at around 3.5kW.

Any ideas?

At th risk of sounding patronising, 50kW chargers charge at 50kW, a domestic (single phase) supply can't hope to compete with that.

If for instance you had a 50kW/hr battery in your i3, using a 50 kW charger it would charge in an hour, whereas your 7kW charger will charge in just over 7 hours

It's all about flow, like filling a bucket from a hose rather than a straw.

Also the charger has protection against over charging and thermal management, but typically most EVs seem to tail off dramatically as charge reaches 100%

There are comparison graphs available on sites like ElecTrek showing most charging systems go great guns between 10% and 80% once the temprature is ideal, and build up to max, then tail off for the last 20% or so.
I have to add at this point, all EVs currently differ in charge rate, and several claim to be the fastest, but few tell the full story.

Edited by FeelingLucky on Sunday 9th June 09:51

[SOL111]

Thanks and no you're not patronising lol.

However, like I said, my app shows a meter, which was around the 3.5kW mark.

Speaking just now to my wife, she actually plugged in at 19:00 last night and it didn't finish until 04:00 this morning so a bit longer than I thought.

I have a 94aH i3 so usually goes from 0-100% a lot quicker.

[FeelingLucky]

Is your home charging from a 3 pin plug, or a dedicated fitted charge point?

[SOL111]

I have a 7kW Andersen A2 connected to a 40A breaker.

I guess my question is whether the car is limiting the charge speed or if it's the electrical supply. I didn't think it could be the supply so was wondering if it was the car itself.

[FeelingLucky]

I STRONGLY suspect you are correct.
Try checking charge rates at various points, I'm sure it will show a far higher rate at 30% charged than 90%

Hopefully an i3 expert will be along in a mo with some hard facts, in the mean time, check out the i3 chat on SpeakEV, https://www.speakev.com/forums/bmw-i3/

It's an interesting read.

[uknick]

OP, have you accidentally changed the charging rate from the charging menu in the car?

[BishBosh]

uknick said:

OP, have you accidentally changed the charging rate from the charging menu in the car?

Yes, check this. You can change the charge rate from fast charge to reduced rate.

[SOL111]

BishBosh said:

uknick said:

OP, have you accidentally changed the charging rate from the charging menu in the car?

Yes, check this. You can change the charge rate from fast charge to reduced rate.

Seriously WTF

I've just checked and for some reason all of my settings have changed to 'low' and 'reduced'. I have no idea how this has changed as I've not touched it.

Many thanks though guys. Very much appreciated!

[kambites]

It's also worth noting that the 50kw public chargers are DC whereas your 7kw home charger will be AC and use the car's on-board charger/rectifier. The on-board charger will have a fairly low current limit (although I doubt it's less than 7kw). You certainly couldn't use a 50kw AC charger (if such a thing existed) and expect to get 50kw throughput.

[so called]

I have a 22kWh i3 on 7kW charger which takes less than 3.5 hours to charge - (22/7 = 3.14 hours).
Yours should be 33/7 = 4.71 so I'd expect it to be around 5 hours.

[Goatex]

Worth keeping an eye on as I had the same issue on my 94Ah REX...as in it was charging at 3.5kW when it should have been doing 7kW. Ended up getting a KLE control unit replaced under warranty and has been fine ever since. Note that there weren’t any warnings from the car that there was an issue; just me noticing it wasn’t charging as fast I I thought it should.