Long haul rexing?

Considering to buy a i3 with rex as this would be perfect for 90% of our travel and more than perfect for our commuting to work. I do have some questions if this would also be a good car for some of our longer journeys.

We have relatives that require a 200 km single voyage to reach, almost all highway (assume driving at 110 km/h). If you do not mind stopping at the gas stations every 80 km or so, do you think that the i3 will be able to cope with the distance back and forward (so 400 km)? Please assume no recharge for the full 400 km.

For instance leaving with full charge and full battery and turning the rex on when reaching the highway or 75% battery capacity. When stopping for gas whenever needed do you expect the battery to hold the 75%? I joined this forum to get some un-opinionated info. According to the sales person this would not be a problem. I hope that forum members would be able to give me some user experience on this.

I don't see this as an unreachable destination. In fact, it ought to be about as ordinary as any other trip, as long as you can plan to have enough battery capacity available if/when you encounter steep grades or hills. We American's don't have that choice, and will have to, when powered solely by REx, tolerate climbing hills at 35-50 mph (55-80 kph).

The other issue you will have is that you will have to stop for fuel 2-3 times.
Just as you were settiling in.

And don't forget: you may have to plan for a different route (or refueling stops) for the return trip.

-- Ardie

It all comes down to the draw on the battery verses the generator's ability to keep up. Full acceleration, max a/c, or the heaters (especially in the seats) and maybe the rear window defogger, then throw in high beams, the REx cannot keep up while going fast. Depending on the grades on the roads and how you manage your power use, it could be done. Depends on your tolerance for having to stop at what may be hourly intervals to replenish the petrol.

I could live with some drawbacks as long as it could be done. Where I live there are simply no hills and the infrastructure is quite good in terms of petrol stations. I estimate that the range interval is about 25-30 km on the highway. In urban area's the petrol station density is quite large (which is about the whole country, but you would have to get off the highway).

If 100 km/h is the maximum speed at which the rex could keep up that would also be acceptable as there are a lot of roads where this is actually the speed limit. I do not expect the longer journeys to occur more than 20 times a year and we would prefer some drawbacks and travel with the i3 than buying an additional petrol car.

In this case a hourly stop might not be as bad as it sounds. When departing completly full you would have stop somewhere half way. On the return voyage gas up before you leave and perhaps half way again. For us that would preferred above buying a second car.

It is quite possible to do this journey as I recently did 314 miles approx 500 km, having started with a full charge and then a 2 hour top up of approx 60 miles (100 km ) equivalent after 120 mile (200 KM). The rest of the journey being done at 60 mph appprox 100km in ECO PRO mode. The only problem was to remember to re-engage the REX after a refuel otherwise it automatically switched back to battery. SOC remaind at about 20 miles (30 km).

No problem. I've been to Switzerland twice, last time RExing to and fro Geneva, 850 km single (one day), 1700 km roundtrip (two days).
You'll loose some E-range every time you switch of to fill it up since the 'hold' level is reset every time you switch off, but this is a minor niggle.

Regards, Steven

So I've been testing this very issue for the past 2 days with my loaner REx.
Here in Canada, we cannot turn the REx on and off manually. Which really must be addressed by BMW! (Are you listening, BMW?!)

Anyway, at 110km, it appears that the electricity from the REx is being fully consumed to move the car. So you don't want to exceed this speed. This will give you some extra energy to make it up a hill without slowing down.

I am also going to get a custom fuel tank made to keep in the front trunk which will allow you to refuel 3-4x without going to a gas station.

Surge said:

I am also going to get a custom fuel tank made to keep in the front trunk which will allow you to refuel 3-4x without going to a gas station.

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Just never have a front end collision! Taking a bath in flaming gasoline is not good for your overall health!

Well the tank will be professionally made by a co that specializes in this.
I think if you have that kind of front end collision you are in trouble, whether or not there's a tank there or not.

And To be clear, it won't be connected to the i3, so it will not violate the warranty.

You should be able to get 37.5L of fuel in the front. Enough for more than 5 fill ups!
(I think it's a 7L tank in N America, is that right?)

@Second,

easy. You don´t even need that many stops.
You can start the REx at 75% SOC. The advantage is that this makes it possible to run the tank completely empty to the last drop. From there you drive electric to the next gas station. On a 400km trip, I expect you don`t have to stop more often than twice if you keep the speed not too high. Only once if you drive country roads at 80-90 km/h.

Frank

North America's i3s are crippled - you cannot manually start the REx until the battery is down to about 18%. Now, whether that will always be the case, it's hard to tell, but that's the way it is now. So, the functionality of the REx isn't as flexible as it is elsewhere since by the time you can turn it on (or it starts on its own), your battery capacity is already marginal. The way it is implemented here, it is much more of an emergency backup than a viable range extender. But, if you do not need to stress the thing by high speeds or long grades, you may not notice.

I've tested the max speed at which one can drive on the freeway, and it appears to be 110 km/hr (68.75 mph). Note that this is the true speed (as measured by my iPhone 5S). Indicated speed on the i3 was 113 km/hr.

At this speed, the gas generator is providing sufficient power to keep the battery level flat.

Outside temp was 16C, one person in the car (180 lbs),
Eco Pro, hvac set to 20C.

Setting hvac to max heat and full seat heater yielded a 4km reduction in range.

Range on gas alone appears to be 95-100km.

Note that you can of course accelerate and use up that 5% of charge in the batt. But then you have to slow down below 110km/h to recharge the battery, so you have enough charge to accelerate beyond 110 again, or to go up an incline.

You can see when your power is reduced because the bar graph on the speedometer diminishes.

It certainly felt like you could cruise forever at 110 km/h.
This was not the case at 120 km/hr. In a few min, you use up most of the batt and then the car slows to about 100 to recharge. On a slight incline it slowed to 85! Scary.

So keep it to 110 km/hr, or less, for long distance REx driving.

Hope this helps.

I borrowed a dealer Rex and over about 120 miles of motorway (freeway) set the cruise to maintain 76mph (122kph) and had absolutely no loss of electric range. I did tis deliberately as I need to make the trip regularly and was concerned at what speed I may have to limit the vehicle to. It might even be possible to maintain a faster speed, but then that would be very naughty!

My own Rex should be with me in early September and then I can experiment some more.

The apparent difference is due to speedometer calibration. US (and Canada?) ones are usually accurate, UK (and EU) read high, often as much as 10%. 76 indicated is probably 70-72 true.

fdl1409 said:

@Second,

easy. You don´t even need that many stops.
You can start the REx at 75% SOC. The advantage is that this makes it possible to run the tank completely empty to the last drop. From there you drive electric to the next gas station. On a 400km trip, I expect you don`t have to stop more often than twice if you keep the speed not too high. Only once if you drive country roads at 80-90 km/h.

Frank

Click to expand...

Not in North America,,BMW crippled the car in the US and Canada by not allowing you to manually engage the Rex and it does not start automatically until SOC is around 5 or 6%.

BrianStanier said:

The apparent difference is due to speedometer calibration. US (and Canada?) ones are usually accurate, UK (and EU) read high, often as much as 10%. 76 indicated is probably 70-72 true.

Click to expand...

I didn't test that but my BMW R1200RT bike and my 330Ci both read within 1mph of accurate when tested against a satnav, although even that is not accurate.

So my test i3 REx had a speedometer that was off by 2.5%. So 123km displayed = 120km actual
From what I've read, all BMWs exaggerate the speed by this approx. %. Not sure why, but that's what it is.

pastyboy said:

I borrowed a dealer Rex and over about 120 miles of motorway (freeway) set the cruise to maintain 76mph (122kph) and had absolutely no loss of electric range. I did tis deliberately as I need to make the trip regularly and was concerned at what speed I may have to limit the vehicle to. It might even be possible to maintain a faster speed, but then that would be very naughty!

My own Rex should be with me in early September and then I can experiment some more.

Click to expand...

But in Europe you can run the REx anytime. When you say you didn't see a loss in electric range when you drove at 122kph, that doesn't necessarily mean that the battery didn't drain when you were running at that speed. It could have recouped some energy when you slowed down… or perhaps the battery did lose energy but you didn't know, because there is no state of charge display (unless you look at the App, but that's not updated in real time).

In my tests, 110 kph (actual) was about the fastest you could go. Definitely not 120 kph. At 120 kph (123 kph by the dashboard), the car would drive fine for about 10-20 min, then it would slow to about 100 kph (and even 85 kph on a slight uphill grade), as it needed to charge the battery.
So running at 120 kph continuously didn't work for me.

just came back from a weekend trip with my Rex, 300 Km one way, 300 Km back. it was fine, except one time we got the message "milage limited electric only", we think this was that the Rex was running a bit hot. after a call to BMW Munchen (mommy) they told us it was ok to drive the car.

solution was for the rest of the trip to turn the Rex off a few KM before the rest stop, to let the engine air cool better.

Helpful hint! you can assign to a multi-function key "hold constant charge" on or off so you do not have to dive into the menu every time.

Surge said:

or perhaps the battery did lose energy but you didn't know, because there is no state of charge display

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At least on the UK and presumably others with Rex there is a % display of state of charge with 0.5% resolution (on the Rex screen).