Rex 2014 not working when battery is about 6% low

[Maria P]

So I was driving the other day and I had pretty low battery about 10% and suddenly I had to accelerate more than I expected, and I think the battery went too low because the vehicle started to move at the lower speed no matter how much I push the accelerator. I tried to use the range extender, but it will just not kick in. I ended up stopped in the middle of the road and I had to take the car to the garage with a truck.

BMW dealer said it was the 12v battery which was never changed in 10 years so I was thrilled … like wow this is great for a 170.000 km / 105.000 miles car

I went to pick up my car and drove with the rain extender to many places combining obviously with the battery but never going that low again until one day a week after I got the car back that I decided I was gonna wait until the range extender kicked in automatically when it reached 6% battery low and to my surprise, I had the exact same issue and I had to get the truck to take the car to the dealer again .

They had it for a week and they were unable to tell me what was going on. I have been using the range extender with about two or 3% battery and never had any issues although I didn’t drive too fast for obvious reasons. it kind of feels to me that after so many kilometres when it says 6% battery, it might be less than that cause when I’m using it with more battery than that it works absolutely perfect. I just wanted to know if anybody had any issue like this before and if you have any clue of what could it be since my dealer had no idea and now I need to look for other options. Thank you

 

[alohart]

Your issue has been experienced by quite a few early i3 owners. The problem is that the battery management system (BMS) has computed an incorrect charge level at low charge levels so that the BMS will reduce the battery pack's maximum power output to protect its battery cells from being discharged too much.

When this happens, you should be able to see propulsive power bars on upper right section of the power gauge disappearing one by one until there are no power bars remaining. At this point, an i3 will not propel itself. It's better to stop in a safe location while some power bars remain. I always pay attention to the power gauge at low charge levels for a warning when our i3 is about out of power.

The BMW Blog describes this problem. BMW's Service Information Bulletin SI B61 20 16 POWER LOSS AT VERY LOW SOC OF HV BATTERY and SI B61 21 16 SERVICE ACTION: PROGRAMMING CONTROL UNITS (RANGE) describe the problem and the fix. However, these SIB's seem to limit this fix to i3's manufactured only in 2014. Maybe there are later updates to these SIB's that would cover later i3's, or maybe this problem is limited to system software versions (a.k.a., integration levels) earlier than I001-16-03-50x (March, 2016). I suggest asking your dealer whether the fix described in these SIB's, a system software or integration level update, would apply to your i3. Unfortunately, a dealer would probably charge a few hundred dollars for a system software update.

 

[Edszhi1]

So I was driving the other day and I had pretty low battery about 10% and suddenly I had to accelerate more than I expected, and I think the battery went too low because the vehicle started to move at the lower speed no matter how much I push the accelerator. I tried to use the range extender, but it will just not kick in. I ended up stopped in the middle of the road and I had to take the car to the garage with a truck.

BMW dealer said it was the 12v battery which was never changed in 10 years so I was thrilled … like wow this is great for a 170.000 km / 105.000 miles car

I went to pick up my car and drove with the rain extender to many places combining obviously with the battery but never going that low again until one day a week after I got the car back that I decided I was gonna wait until the range extender kicked in automatically when it reached 6% battery low and to my surprise, I had the exact same issue and I had to get the truck to take the car to the dealer again .

They had it for a week and they were unable to tell me what was going on. I have been using the range extender with about two or 3% battery and never had any issues although I didn’t drive too fast for obvious reasons. it kind of feels to me that after so many kilometres when it says 6% battery, it might be less than that cause when I’m using it with more battery than that it works absolutely perfect. I just wanted to know if anybody had any issue like this before and if you have any clue of what could it be since my dealer had no idea and now I need to look for other options. Thank you

A related story. I was driving merrily down the freeway this week and saw an i3 on the side of the road with flashers on. So I pulled over and asked the driver if I could help. Well, the 2015 was low on power and REX wouldn't turn on. She had already called for a tow truck. I realized I did not know what to do to help the situation. My i3S is REX-less (my 2014 i3 had a REX that worked fine when i traded it in). I don't have any i3 jumper cables so I wished the frustrated driver good luck. Is there anything I could have done?

 

[alohart]

I suppose you could have tried to start the REx engine in emissions test mode. If it started, you could have pressed the power pedal to increase the REx engine speed enough to charge the battery pack a bit. Maybe that would have been sufficient for her to drive home.

However, if the REx engine wouldn't start, it would need to be repaired, so there wouldn't have been anything that you could have done.

 

[Azure Blue]

Your issue has been experienced by quite a few early i3 owners. The problem is that the battery management system (BMS) has computed an incorrect charge level at low charge levels so that the BMS will reduce the battery pack's maximum power output to protect its battery cells from being discharged too much.

When this happens, you should be able to see propulsive power bars on upper right section of the power gauge disappearing one by one until there are no power bars remaining. At this point, an i3 will not propel itself. It's better to stop in a safe location while some power bars remain. I always pay attention to the power gauge at low charge levels for a warning when our i3 is about out of power.

The BMW Blog describes this problem. BMW's Service Information Bulletin SI B61 20 16 POWER LOSS AT VERY LOW SOC OF HV BATTERY and SI B61 21 16 SERVICE ACTION: PROGRAMMING CONTROL UNITS (RANGE) describe the problem and the fix. However, these SIB's seem to limit this fix to i3's manufactured only in 2014. Maybe there are later updates to these SIB's that would cover later i3's, or maybe this problem is limited to system software versions (a.k.a., integration levels) earlier than I001-16-03-50x (March, 2016). I suggest asking your dealer whether the fix described in these SIB's, a system software or integration level update, would apply to your i3. Unfortunately, a dealer would probably charge a few hundred dollars for a system software update.

@alohart This is great information. I’ve never paid attention to the power bars. I most definitely will now. I try my best to learn as much as possible about Bailey I3. This is super helpful.

 

[John Croker]

I have experienced exactly this problem with my 2015 i3 REx. I have given dealers and BMW Australia the link to the American BMW Blog, but they say that this information "does not apply" to the Australian i3 RExs. The latest suggested "fix" from my local dealer is to replace the pressure sensor in the fuel tank, but I cannot see how this is relevant. They have also said that it is not possible to re-program the REx, so that it turns on at a higher state of charge, which I believe would fix the problem. This is what we do manually, and it has always been successful. There is a rumour that it is possible to get the REx re-programmed outside of the BMW network. Does anyone know if this is possible ?

 

[Pipino]

My 2015 BMW i3 has been reprogrammed back to EU standard. This allows you to “hold state of charge”, which basically means the rex will maintain any battery percentage below 75%. Rex will still kick in automatically when battery is below 6%.
You can also reprogram the volume of the tank which is limited electronically. It allows you to fill up the petrol tank a bit more to extend the additional milage obtained from the rex.
In order to decrease battery consumption the car is also reprogrammed to start in eco-pro mode.

I hardly use the rex and if i do I aim to use it at the highway so no emission will occur in the urban area.
It is not recommendable to use the rex a lot for multiple reasons.

 

[Caymani3]

"My 2015 BMW i3 has been reprogrammed back to EU standard."
Were you able to do this yourself?

 

[PVEVman]

So I was driving the other day and I had pretty low battery about 10% and suddenly I had to accelerate more than I expected, and I think the battery went too low because the vehicle started to move at the lower speed no matter how much I push the accelerator. I tried to use the range extender, but it will just not kick in. I ended up stopped in the middle of the road and I had to take the car to the garage with a truck.

BMW dealer said it was the 12v battery which was never changed in 10 years so I was thrilled … like wow this is great for a 170.000 km / 105.000 miles car

I went to pick up my car and drove with the rain extender to many places combining obviously with the battery but never going that low again until one day a week after I got the car back that I decided I was gonna wait until the range extender kicked in automatically when it reached 6% battery low and to my surprise, I had the exact same issue and I had to get the truck to take the car to the dealer again .

They had it for a week and they were unable to tell me what was going on. I have been using the range extender with about two or 3% battery and never had any issues although I didn’t drive too fast for obvious reasons. it kind of feels to me that after so many kilometres when it says 6% battery, it might be less than that cause when I’m using it with more battery than that it works absolutely perfect. I just wanted to know if anybody had any issue like this before and if you have any clue of what could it be since my dealer had no idea and now I need to look for other options. Thank you

I had exactly the same problem with my 2015 rex. It is indeed an issue with the BMS, so the BMW dealer had to calibrate my battery, cell for cell. That was a $850.- exercise. Unfortunately it did not fix the problem and left my wife stranded again on a very busy highway and she vowed never to drive that thing again. So on advice from forum members I downloaded the Bimmercode app and programmed my car so you can turn the rex on when the battery is below 75%. Instead of waiting for the REX to kick in at 6% battery, I just turn it on well before that. Now at 63k miles I have a broken hvac compressor and the repair is $14k which is well over the value of the car. Even at a non BMW mechanic shop it will cost around 10k. I have driven this car with great pleasure for 70miles a day, charged by solar panels, but It is very frustrating to sell this car for scrap now because it can't maintain the battery temperature and there is no AC, which is a must in Florida. I'm very disappointed in BMW engineering, so close to get it right but yet so far. Above all, not good for the environment.

 

[John Croker]

"My 2015 BMW i3 has been reprogrammed back to EU standard."
Were you able to do this yourself?

As I understand it the point of the reprogramming is to allow you to manually " hold the state of charge" (at battery levels less than 75%). My i3 here in Australia has always been able to do that, and is still able to do it. The problem arises when the battery gets down to 6-7% and the range extender turns on automatically to take over - at this point there is now insufficient power to move the car and it stops. After the range extender has run for a few minutes it is able to move again. The car is just back from its 3rd visit to the BMW dealers to try to fix the problem, but it is not fixed. They are going to "discuss with the technician" and see if they can come up with anything else. !@#$%^&

 

[PVEVman]

Sounds familiar. Skip the hassle. They can't fix it, just turn the rex on at 15% battery. It is poor software design, they can't fix it.

 

[John Croker]

I am reluctantly coming to that conclusion. Still no response from my local dealer about any other suggestions for fixes.

 

[Gonville]

Pretty sure that some time back there was a recall in the USA to do something with the REX kick in parameters as the BMW was over estimating the remaining charge so that as the REX was slowly winding up to power in stages I think it takes 6 minutes or so? That the car could come to a standstill in that time. As depletion exceeded REX output in the first few minutes. Anyone else remember this amendment? So the max output doesn’t happen until it thinks the SOC is less than 2.5% - if that figure isn’t right the power output won’t cover the requirements.

 

[PVEVman]

When you find yourself stalled, just turn the car off and wait 10 minutes. Then turn it back on and with some luck the rex will kick in again. Otherwise repeat. I managed to get it going again every time. I think you have to give the battery some time to recoup itself a bit and that will be just enough to make the switch to the rex.

 

[John Croker]

BMW Australia say that the problem identified in the US is "not relevant to Australian i3s" even though, as far as I can see, it is exactly the same. Turning the range extender on manually at a point above the automatic turn-on point does work, as long as you remember to do it. The simple fact is that this vehicle has become dangerous to drive, and BMW here in Australia are not interested in fixing it.