Degrading fuel

If you have the Rex tank full with fuel and you manage with pure electric for a long time - months, 6 months etc. Can the fuel in the Rex degrade? Should it be run down occasionally and filled with fresh fuel?

the rex has a regular maintenance cycle

http://www.mybmwi3.com/forum/viewtopic.php?f=13&t=3716

IMHO, I'd probably consider forcing the system to use the REx's gasoline periodically, or I'd put some gas stabilizer in there if I knew I wouldn't be using it for long periods of time. The maintenance cycle runs to make sure it gets oil everywhere on occasion, and to determine if it can actually start when it might be needed...it doesn't use a huge amount of fuel as it only runs for about 10-minutes about every 6-weeks.

I have a related question. I want to run my coded car empty to fill with a fresh fuel and to see how much gas it will take. I will run in the "battery hold" mode. When the tank runs dry, will the car seamlessly switch to the battery power? I assume it will, but want to confirm it to avoid a surprise.

gt1 said:

When the tank runs dry, will the car seamlessly switch to the battery power?

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An i3 REx always runs on battery pack power, even when the REx engine is running. So there is no switching modes from REx generator power to battery pack power.

That said, some REx owners have reported that when the gasoline ran out, the REx engine stopped running as expected, but the car lost all propulsive power despite the battery pack charge level still being sufficient to propel the car, certainly unexpected and not seamless. However, pressing the Start/Stop button to power off the car following by another press to enter Ready state resulted in propulsive power being restored until the battery pack charge level dropped too low to continue propelling the car.

I can think of no reason why an i3 REx should not continue moving without any change in propulsive power when the REx engine's gasoline is depleted. This behavior definitely feels like a bug in the i3's software, so it might have been fixed in recent versions.

Good to know, glad I've asked.

nickthorley said:

If you have the Rex tank full with fuel and you manage with pure electric for a long time - months, 6 months etc. Can the fuel in the Rex degrade? Should it be run down occasionally and filled with fresh fuel?

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I've had times when I drive a month without using the REx but I try to run it before it reaches 6 weeks without running when that happens. Good for the engine to run it occasionally, plus you burn up some gas so it doesn't get too old. There is a maintenance cycle that runs if you don't use the REx for a while, as someone else posted. I've had this cycle run a few times but now I try to plan a long trip if I'm reaching a 4-5 month period that the REx hasn't run.

I've gone 2800 miles and 77 of that was gas...the day I drove it home from Tucson 3 months ago, and haven't used any gas since.
I haven't heard the Rex kick in while driving, perhaps it runs occasionally at night when charging?

engineear said:

I've gone 2800 miles and 77 of that was gas...the day I drove it home from Tucson 3 months ago, and haven't used any gas since.
I haven't heard the Rex kick in while driving, perhaps it runs occasionally at night when charging?

Click to expand...

I hope it doesn't do that! If it's in the garage it'll fill it with exhaust fumes :?

The REx will try to run about every 6-weeks, but there's a condition...you have to get the battery SOC down below (I think) 75% before it can come on. It requires itself to run for awhile to fully warm up and run the oil around, and if the battery level is too high, there'd be no place to put the output of the generator. It won't come on unless the car is also in the READY state (i.e., you're driving it).

What timing! Got this upon start up this morning...



So, around 3000 miles, on mine anyway, the maintenance message comes up.

Then this a little later...



Okay. So I have to travel a little bit...



I didn't feel it engage, but could hear it. This is what the screen looked like with the Rex engaged...



It ran for about 5 minutes.
Hope that helps some of you.

Since the REx is just a generator, you really shouldn't feel any differences in how the car drives! Unlike a parallel hybrid where the ICE and the electric propulsion can both contribute to moving the vehicle, the i3 is a serial hybrid, and the REx only feeds the actual motor that drives the car via its electrical output - excess goes into the batteries, and it can often produce an excess, which is why the SOC must drop some before it can be turned on either manually or automatically.