Rex Maintenance Mode

Had not used Rex since getting the i3 2 months ago. I was wondering if we should purposely run it down to get Rex on to make sure it works. Then very next day it showed message that Rex needs to turn on for maintenance purposes since it had not been used in a long time.

Ran for 10 minutes

I spotted some posts about REx non-usage and that there appears to be a 2k mile cutoff point, by which the REx maintenance is enforced by the vehicle. In order to prevent that, I actually ran it for a few minutes the other day, when vehicle mileage approach the 2k mile mark.

We drove 240 miles this weekend and the REx has been used for about 5 miles during that distance. In hindsight, we could have done without the REx usage, but I'm always a bit cautious when it comes to CCS Rapid charger availability and operability. We're now on over 2.3k miles and I still have around 90% of the delivery petrol in my tank. Despite this, I'm glad happy I went for the REx model, as there will be times when we need it.

one thing I noted was that it is actually charging in this mode because I made a short trip when it first came on and plugged the car in when I got home. It had not completed the 10 minutes and when I got back in it said that maintenance mode could not run because the battery was>75% charged. Later in the day on another trip it came on and completed.

I finally bought the dvdinmotion hack and drained my 5 month old gas in one outing.

getakey said:

Had not used Rex since getting the i3 2 months ago. I was wondering if we should purposely run it down to get Rex on to make sure it works. Then very next day it showed message that Rex needs to turn on for maintenance purposes since it had not been used in a long time. Ran for 10 minutes

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psquare said:

I spotted some posts about REx non-usage and that there appears to be a 2k mile cutoff point, by which the REx maintenance is enforced by the vehicle. In order to prevent that, I actually ran it for a few minutes the other day, when vehicle mileage approach the 2k mile mark

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Went for "second handover" on Friday and when I asked about REx usage I was advised that the car will switch it on automatically when engine needs to be turned on for a while. As expected BMW have thought of everything.

There are benefits of giving engineers a clean sheet of paper and letting them come up with ideas rather than forcing some corporate idea down their throats! While you may not always agree with why something was done on the i3 (or i8), I feel confident that the option was discussed, its merits debated, and there's a rational decision made about it. That you may not agree is not uncommon, but then, you may not have weighed all of the same set of facts, or your priorities are different. Given the set of design parameters, it's a really neat car. LIke anything, though, not everyone's priorities are the same.

I plan to run my tank dry at least every couple of months. This is why. Here in the US, unless one is fortunate enough to live in a place where real gasoline is available (I don't), we have to run gasahol. Alcohol is hygroscopic. The longer it sits, the more water is mixed in. We have to run premium fuel. It doesn't have any more alcohol in it than regular, but, on average, it sits anywhere from 3 to 5 times longer in the gas station storage tanks because there is less demand for it. I have this from several gas station owners I asked about it. Being a motorcycle rider, I have known several people who have had their fuel gum up their fuel lines and injectors if it was allowed to sit too long, especially with premium. You can prevent this by using Stabil or a similar product. Or, you can keep the fuel fresh. I would prefer the latter.

Sparky17 said:

I plan to run my tank dry at least every couple of months. This is why. Here in the US, unless one is fortunate enough to live in a place where real gasoline is available (I don't), we have to run gasahol. Alcohol is hygroscopic. The longer it sits, the more water is mixed in. We have to run premium fuel. It doesn't have any more alcohol in it than regular, but, on average, it sits anywhere from 3 to 5 times longer in the gas station storage tanks because there is less demand for it. I have this from several gas station owners I asked about it. Being a motorcycle rider, I have known several people who have had their fuel gum up their fuel lines and injectors if it was allowed to sit too long, especially with premium. You can prevent this by using Stabil or a similar product. Or, you can keep the fuel fresh. I would prefer the latter.

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Wouldn't you decrease the rate of this if you kept close to a full tank? Less air/water vapor for mixing.

The tank is sealed and pressurized. All modern gas tanks are not vented to the outside. Not sure it makes a lot of difference.

PDXelectric said:

Wouldn't you decrease the rate of this if you kept close to a full tank? Less air/water vapor for mixing.

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I would imagine so, yes. But bear in mind that, since the fuel has been sitting in a gas station tank for who knows how long, some water is going to be absorbed by the alcohol. If it's enough, and if it sits long enough in the car's fuel system, it can turn gummy and clog things up.

Motorcyclists are always advised to fill their gas tanks at the end of the season with gas mixed with fuel stabilizer, and run their bikes long enough to get the stabilized fuel all the way through the system. I have always done this, and never had a problem. I did have a small bike for a while that I hardly ever rode. The gas sat in that for a month or so once during riding season, and seriously clogged the carburetor and the fuel valve. I've also had problems with other small engines (lawn/yard equipment) when I haven't done this before putting things away for the Winter.

Remember, the range extender is a small motor scooter engine, subject to the same limitations as it would be if installed in a scooter.

If you plan to use the range extender as it is sold to be used in the United States, as in hardly ever, I would suggest running it close to dry, putting in some fuel mixed with stabilizer (like Stabil), and running it long enough to get the stabilized fuel through the system. You want to put the Stabil in first, then refuel. That way it will be mixed right away.

Or, you can just run it down under a quarter tank once in a while and put fresh fuel in.

If the tank is pressurized and you fill it to the brim, how would any more moisture get absorbed? If the pressure remains in the tank after the car is shut off there would be no further entry of humid air until the REx is used and some fuel is burned lowering the tank pressure. As long as the fuel that you buy is usable as far as water content when you pump it, it will still have the same water content months later. Where would any extra moisture enter the closed system?
There is a huge difference between a carbureted motorcycle engine fuel system from the past and a fuel injected emissions compliant scooter engine fuel system from 2015..... I don't think lacquering of the float valves and jets is a real concern in an i3.

WoodlandHills said:

If the tank is pressurized and you fill it to the brim, how would any more moisture get absorbed? If the pressure remains in the tank after the car is shut off there would be no further entry of humid air until the REx is used and some fuel is burned lowering the tank pressure. As long as the fuel that you buy is usable as far as water content when you pump it, it will still have the same water content months later. Where would any extra moisture enter the closed system?
There is a huge difference between a carbureted motorcycle engine fuel system from the past and a fuel injected emissions compliant scooter engine fuel system from 2015..... I don't think lacquering of the float valves and jets is a real concern in an i3.

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As I have already explained, it's not that more water will enter the car's tank. It probably won't if the tank is full, pressurized or not. Actually, as long as it's full, I don't see how it would matter if it was pressurized.

The point is that the water already in the fuel, that got there while it was sitting in the gas station tank, sometimes for extended periods, can cause gummy deposits over time. If it happened as soon as the water got into the fuel, it would probably float or settle, and it wouldn't get pumped into the car. But, unfortunately, that's not how it works. The partial solidifying happens over time. This isn't something I made up. Ask any small engine technician. They'll tell you, with gasahol, if it's a month or two you probably won't have a problem. If it's more than that, you easily could. Cleaning out the mess isn't easy or cheap. And it can gum up injectors just as easily as nozzles in a carburetor.

Will it do the maintenance mode before 2k is up? Had last run the REX on Easter (quite a bit), but not since then. When I parked the i3 tonight and plugged the charging cable in, both the fan and what sounded like the REX (never been outside the car with REX running) started up for about two minutes. I only have 3800 miles, so I doubt I am anywhere close to the 2k since running it.

I think it comes on after 6 weeks of no use.

tom10422 said:

When I parked the i3 tonight and plugged the charging cable in, both the fan and what sounded like the REX (never been outside the car with REX running) started up for about two minutes. I only have 3800 miles, so I doubt I am anywhere close to the 2k since running it.

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The sound was NOT the REX running - it was the cooling system pump. The REX is louder than that. The REX will not run unless the car is in READY status.

The cooling pump makes more sense, only five weeks since last running Rex and it was the first 90 degree F day since I got the i3.

I think the maintenance mode is more on time than miles driven.