What happens when you run out of charge?

[DerfSdrawd]

So I tested my range to destruction today (BEV). Partly to see what happens although I didn't actually intend to end up calling BMW recovery to get the car home! Starting with a 73 mile range I'd done a 62 mile round trip then decided to do a c12 mile trip but followed a satnav instruction onto a dual carriageway and ended up doing an extra 6 miles.

So on EcoPro+ I managed to get within 3 miles of home after the point where the sat nav said I was 15 miles away with 7 miles of range showing.

The range counts down to 0, and then it went about 5 miles like that. Then the range shows "----" and after that it did about 1.5 miles. When it conks out the right hand side of the drive indicator goes blank so just the regen side is lit up and the car will no longer move. It happens quite suddenly.

The 12V battery kept the hazards going for about 3.5 hours and the car was pretty dead when I got it back home. I had to use the little blue pull tabs to open the charging socket (the blue tabs are inside the offside rear door shut under a polystyrene cover that pulls off). I couldn't switch off the hazards and the park brake no longer operated. The car was in N (to get it onto the tow truck) and I couldn't engage P.

When I plugged it into the wall box it took a little bit of charge at a very low rate then stopped. I pressed the lock button on the remote and although the doors didn't lock, the car started charging. It showed a drivetrain warning on the dash, which then disappeared after a couple of minutes.

After that I could reactivate the P setting on the drive controller and engage the parking brake and it's charging at 7.4kW again.

Did I feel like a tw*t? Yes, but at guess I know the drill now. And BMW/Mondial/Mansfield recovery services were very efficient.

 

[mindmachine]

Why would you do that on purpose when it is detrimental to the life of the lithium battery.

 

[I33t]

Why would you do that on purpose when it is detrimental to the life of the lithium battery.

BMW reserves some capacity to protect against total discharge, the battery is 22kWh and we have 18.8kWh available for traction use.

I doubt it is harmful to occasionally reach towards the bottom of available battery capacity.

 

[woof]

Did I feel like a tw*t?

Thank you for your sacrifice! We appreciate the knowledge.

--Woof!

 

[SanSerif]

The range counts down to 0, and then it went about 5 miles like that. Then the range shows "----" and after that it did about 1.5 miles.

So zero doesn't mean zero?

But does mean "pull over PDQ 'cos I ain't giving you any further warnings!".

Thanks for doing the experiment for the rest of us!

 

[noakey]

The range counts down to 0, and then it went about 5 miles like that. Then the range shows "----" and after that it did about 1.5 miles.

So zero doesn't mean zero?

But does mean "pull over PDQ 'cos I ain't giving you any further warnings!".

Thanks for doing the experiment for the rest of us!

Ditto... This info is valuable too all... great forum

 

[MikeS]

Really glad someone did the test! TVM

 

[Gonville]

that was pretty brave but really really useful to know. Especially the getting it charging again info. Assuming the warranty doesn't say anything about this? Be the same as running out of fuel I guess with any consequences of blocked filters etc.

 

[uktechie]

What a maverick Road Warrior you are.

I would not want to do that myself on public roads.

Interesting to know though.

 

[i3atl]

Thanks for doing this and sharing.

Once the dashes appeared, did the car limit your speed? What speed were you driving for those 1.5 miles?

 

[Houdini]

I too would like to know whether there was any speed limiting or if you could just drive normally for the last 5 miles.

Also do you know approx how many miles you ended up doing, including all the miles after the display went blank?

 

[DerfSdrawd]

Thanks for the various comments - I don't think it was detrimental to the battery, but it certainly was to my evening!

On speed limiting, I was in EcoPro+ and had set the cruise control to 55 mph so I wasn't aware of any additional intervention. I'm pretty sure if I'd put my foot down it would have behaved normally. I was being very careful with the accelerator although not to the extent of crawling along - I ended up with an efficiency rating of 94% that day, with consumption of 4.8ml/kWh vs community average of 3.2ml/kWh if I'm reading the app correctly.

The whole trip on that charge cycle, according to the iRemote, was about 92 miles although bear in mind that when I first set off it wasn't 100% but showed a range of c75 miles. There's no doubt that it really does eek out the range in EcoPro+ if you stick to the speed limit.

The SatNav started searching for charging points as soon as the destination was out of range, although interestingly it didn't list any even though I was only about 3 miles from BMW UK HQ in Bracknell! There are several around there plus several more in Reading.

In the morning the car showed a range of 101 miles and the only thing I had to do was reset the time (it's now set to update automatically) and to do a tyre pressure monitor reset. All my personal settings, profiles, connections etc were retained.

The day after the depletion the car has behaved impeccably, doing around 40 miles on varied roads.

I've covered quite a few of my first 500 miles on the motorway and found that if you go fast 1 motorway mile is about 2 miles of range. But at the legal limit consumption seems to be OK.

Apart from the obvious learnings (esp don't do it again...) it does show that the overall range is quite challenged if something unexpected happens, like getting lost. And because you absolutely must not tow the car, once you're close to zero range it is very important to get to a safe place, not to try and make it home. :idea:

Fred

 

[DerfSdrawd]

I meant to mention that about 2.5 hours after I stopped, I got a text from BMW saying that my SOC was very low and that they recommend recharging the battery(!)

That will no doubt be how they manage the battery warranty - I expect they will have full data on nr of cycles, SOC, depletions etc for each battery pack.
#bigbrother

 

[XXL]

Nice to know you cannot 'brick' an i3

 

[ColaBMWi3]

Okay so my curiosity got the best of me and my stupid side was showing last night. I completely drained my i3. This is what actually happens:

1) Range will drop to 0 or 1 miles and number of epower bars will drop to half and your speed will be limited. It happens suddenly but isn’t very dramatic unless you need to drive over 35 mph. Once the range indicates “- -“ you will have only one epower bar (speed severely limited).

2) At - -% SOC, epower bars will be gone and you will not be able to move the vehicle. You are now operating only on the 12vdc battery.

3) With everything on (AC, lights, butt warmers etc), expect about 20-30 minutes of accessory power. Longer if just hazards.

4) The car will die. A quick warning of brake failure and the check engine light will flash and then total darkness, save for random flickering and the footwell lights holding on for a few minutes. Now both the HV battery and the 12vdc battery are dead.

So, I’ve read that there is an emergency circuit that will charge the 12v battery in situations where both batteries are dead (12v is needed to recognize and accept charging equipment), NOT TRUE. Once both batteries are dead it must be taken to the dealership, because it is too dangerous (or not within the means of the average person) to jump start the 12vdc (since it is not a regular car). To prove this... once the 12vdc battery was dead for sure, I plugged in a Level 1 charger for 24 hours... nothing, dead as a brick.

 

[jadnashuanh]

If you truly ran the 12vdc battery dead, the secondary recharge path may not be able to rejuvenate it. To safely try to fix that battery in that case, you need to disconnect the HV charging with the disconnect switch, then you can do whatever you want to the 12vdc battery. It's only a danger if the HV battery is still attached so you don't damage the DC-DC converter.

 

[gt1]

Okay so my curiosity got the best of me and my stupid side was showing last night. I completely drained my i3. This is what actually happens:

I applaud you spirit of adventure!

1) Range will drop to 0 or 1 miles and number of epower bars will drop to half and your speed will be limited. It happens suddenly but isn’t very dramatic unless you need to drive over 35 mph. Once the range indicates “- -“ you will have only one epower bar (speed severely limited).

2) At - -% SOC, epower bars will be gone and you will not be able to move the vehicle. You are now operating only on the 12vdc battery.

Did the car drove normally at low SOC (1-5%)? How long were you be able to drive on a reduced power with "--%" displayed before the car stopped? How did you manage to set up the test so you were near the charger when the cars stopped?

3) With everything on (AC, lights, butt warmers etc), expect about 20-30 minutes of accessory power. Longer if just hazards.

4) The car will die. A quick warning of brake failure and the check engine light will flash and then total darkness, save for random flickering and the footwell lights holding on for a few minutes. Now both the HV battery and the 12vdc battery are dead.

The only surprise here is that the seat warmers were still working.

So, I’ve read that there is an emergency circuit that will charge the 12v battery in situations where both batteries are dead (12v is needed to recognize and accept charging equipment), NOT TRUE. Once both batteries are dead it must be taken to the dealership, because it is too dangerous (or not within the means of the average person) to jump start the 12vdc (since it is not a regular car). To prove this... once the 12vdc battery was dead for sure, I plugged in a Level 1 charger for 24 hours... nothing, dead as a brick.

I don't see why you couldn't connect the battery to a 12V charger. The DC-DC converter is surely protected against a reverse current flow.

 

[alohart]

I don't see why you couldn't connect the battery to a 12V charger. The DC-DC converter is surely protected against a reverse current flow.

You could certainly connect a charger to the 12 V battery using this BMW procedure. The simple but important step to prevent damage is to disconnect the high-voltage system.

 

[gt1]

Thanks for the link. I didn't know that the HV disconnect was required. I also have a Pacifica Hybrid, which can be charged with the HV battery still connected. They even permit "jump starting" from another car.

 

[jadnashuanh]

A parallel hybrid car is quite different in the connections verses the i3 REx's serial hybrid configuration. In a parallel hybrid, it's essentially two drive motors that can operate semi-independently. In a series hybrid, it ALWAYS is driving electrically, and the REx (in this case) is providing some of the power to make it happen verses the batteries, excess going back into the batteries, while propulsion may come directly from the generator. So, in this case, you don't have the separation of functions like in a parallel hybrid...you can damage things (at least in this design) if you don't follow the directions WRT the 12vdc battery. The i3 REx is closer in configuration to a diesel-electric train...the diesel engine drives generators, while the electric motor drives the train...there's no direct connection between the diesel engine and the wheels...same in the i3.