Long Distance (400 miles) Rex Driving? Do I need to baby it?

[nickp]

I will be making another trip to the bay area from Los Angeles but this time I will not be stopping at too many charging stations. I have 2015 Rex which takes me around 150 miles combined with driving at 70 mph.
So my first stop will be in San Luis Obispo to get it charged after almost 200 miles of driving, majority of which will be on Rex. My next stop will be my destination at Santa Clara driving for 200 miles more which will also be mostly done on Rex.
Now on my first trip I made 4 charging stops and babied the Rex. Do I really need to? I mean it's a 650cc motorcycle engine and last time I checked, BMW motorcycles could take a more severe beating than that.
I mostly drive at an easy speed and will not need to much air etc. so Rex is OK.
Is this doable? Can the Rex take it?

 

[jadnashuanh]

You shouldn't have to baby it, but keep in mind that when you shut it off, the indicated SOC level is the maximum it will try to recover to. If you're pushing the vehicle, your SOC may be dropping wherever you had it set to turn on, and then if you stop, that's the most it will recharge to if you're just refilling the gas tank. You can fool the system by leaving the car in ready and exiting via the passenger side, but if the REx decided to come on while refueling, you could have an issue. It will try to recover only to 6% if your starting point was lower when you shut it off. Otherwise, whether coded or not, you will never get back up to the magic 75% level if it wasn't already there when you shut it off.

 

[theothertom]

You don't have to baby the engine but like Jim said the generator won't keep up. In other words, you will continue to loose charge unless you "baby it" by driving slower. So it's best to code the car and set the REx to come on at 75%. That way you'll have more buffer than if you let it come on naturally around 6%.

 

[CharonPDX]

Agree with the others - don't use default "on at 6%" behavior. Partly for power loss, but also for the lack of flexibility when refueling! With the default behavior, if you need to go further than EV+REx distance in one go, you will have a *VERY* short window to refuel - the last 10-15 miles of driving only. Happen to be in an area with no gas stations for 20 miles when your gas tank drops below 25%? You're screwed.

Definitely use hold-charge at 75%. You won't keep it at the full 75% the whole time, but it gives you a *LOT* of electric range to refill the gas tank. Plus, you can use ICE first, then EV for a bit before refuel, and give the ICE a break during that time.

I'll be doing a ~200 mile (each way) drive in my 2015 REx in a few weeks. There's a 100 mile span with no rapid chargers right in the middle. My plan is to drive the 30 miles to the last rapid charger, top off to 80%, then start the 100 mile span on REx as soon as possible. I'll arrive to that next rapid charger with no gas, and probably 50% battery. I'll refill gas and recharge to 80% there, and should make the rest of the way on battery.

I'll have a level 2 charger at my destination, with plenty of time to charge before I head back. The reverse will be similar - make it to the last rapid charger on battery, top off to 80%, run REx out of gas between there and the next rapid charger, refuel and recharge at the same time.

 

[bwilson4web]

If not coded, get a 2.5 gal, Briggs and Stratton, spare gas can and carry in front. Coded, you can easily avoid the spare can by filling up just as the gas runs out. Hold speed to 70 mph following trucks and it is a piece of cake. Check oil level before leaving.

Bob Wilson

 

[TOEd]

We have driven extensively on REx. Speed is a factor but so is use of heater and driving up a long incline. Although you don't need to baby REx for mechanical reasons imho, it only puts out so much power. So be prepared for reduced power under heavy loads. Also be aware that last 10 km (6 miles) indicated on battery evaporates in very short time. So spare gas is essential imho. We use a 5 litre gas can that we keep in frunk. Have used it 4 times where gas stations are few and far between. Alternative is tow truck.

 

[graememwl]

<snip>
Check oil level before leaving.

^^^^^^^^
This.

I was surprised to find my oil down at the min. Especially as I had only run 1 tank since buying the car as a CPO 3 months earlier.

 

[nickp]

Excellent replies and each suggestion will be heeded.
Also the car is coded so will be holding SOC and yes, the oil suggestion is a very important one. Thanks all!

 

[jadnashuanh]

BOttom line on the hold...the 34Hp may not be enough to hold it, depending on your driving and the terrain. Second point, when you shut it off, unless you recharge the battery, either via an EVSE or a CCS unit, whatever SOC you have becomes your new maximum SOC. IF it's really cold out, and the car is off for a longer time, the cold will lower the SOC, leaving you with a lower maximum than when you initially shut down.

If you understand that, you can run the car and not have problems. if you don't, you might end up in distress. On a long trip, with no chances to plug in, you will tend to continue to eat away at your maximum SOC holding point.

If BMW really intended the car for long-distance travel, they would have installed a larger ICE so it could maintain charge under all normal circumstances, should you decide you want to hold battery capacity for say running through the city center on EV alone. This is a big deal in some cities in Europe, and that may continue to expand in implementation as more and more talk about banning ICE vehicles in their city centers. London was, I think. one of the first to push for this.

 

[arodi3]

If you get into a pinch, you could use the smog test to add SoC to the battery. If you hold your foot on the gas, it charges the battery quicker. Someone posted a charge rate they achieved on here, but I could not find it with a quick search.

This explains how to get the i3 into the emissions test mode: http://www.mybmwi3.com/forum/viewtopic.php?f=13&t=2075 It is very clunky and you have to have the tailgate open the whole time.

I think the HP of the REX would be fine if they let you have full access to it. By that, I mean able to turn it on while parked, that way you could charge up while having lunch, etc. even if you were far from any charging infrastructure.

 

[bwilson4web]

. . . If BMW really intended the car for long-distance travel, they would have installed a larger ICE . . .

It isn't the ICE but the generator and charging circuit. The original engine in the scooter is rated at twice the power.

Bob Wilson

 

[jadnashuanh]

At what RPM does the scooter generate max power? Probably a lot higher than the REx allows. This helps in longevity, ultimate noise levels, and harshness by keeping its output down. So, it is what it is...not optimized for long-distance travel. I'm not saying you can't do it, but there will be a level of understanding and compromise required over a vehicle designed for long-distance travel verses the short-range i3 with the range extender to help in a (primarily) emergency situation for range anxiety.

FWIW, Mazda is planning a similar drivetrain to the REx, in that it's a serial hybrid, but using a rotary engine which should be smoother. They claim to have solved the oil consumption, plus, when driving a generator, it won't be changing rpms that much. Rotary engines are very smooth. It will be interesting to see how that works out.

The ix3, i4, and iNext, all appear to be pure EV's, but most of the other platforms already are available in hybrid or will be within the next few years. For shorter ranges, they can be used as a pure EV, but after the battery is exhausted, will operate as a full-function ICE, and most will have the ability to recharge the battery to full while still doing it because they will have a much larger ICE. They're all parallel hybrids, though.

We're not talking about what could be on the i3, but what it is...the REx engine is too small for unrestricted operation under all conditions, and, the fuel tank is woefully small for any long-distance travel, requiring frequent stops. ANy other vehicle that would only run the engine for about an hour would be laughed out of the marketplace if marketed as a long-distance vehicle. Some people will put up with that, many more, won't. Used as intended, it's sort of a brilliant product given the state of battery tech.

 

[bwilson4web]

Hi Jim,

Just sharing:

. . . For shorter ranges, they can be used as a pure EV, but after the battery is exhausted, will operate as a full-function ICE, and most will have the ability to recharge the battery to full while still doing it because they will have a much larger ICE.

Our Prius Prime only charges to 80%. Up to 80%, the full charge rate can be sustained but as the battery taper region is reached, the ICE has to run at partial power, if parked, and the loss of ICE efficiency makes additional charging impractical. The car turns off the engine.

. . . We're not talking about what could be on the i3, but what it is...the REx engine is too small for unrestricted operation under all conditions, and, the fuel tank is woefully small for any long-distance travel, requiring frequent stops. Any other vehicle that would only run the engine for about an hour would be laughed out of the marketplace if marketed as a long-distance vehicle. Some people will put up with that, many more, won't. Used as intended, it's sort of a brilliant product given the state of battery tech.

Agreed that it was not designed to be a road warrior because the REx can only sustain ~70 mph and doesn't have a 'sticky' option to default ON when doing a cross country. The small tank is an inconvenience but we've done a 700 mi round trip within these limitations.

Bob Wilson

 

[redbarn]

We do a monthly 500 mile each way trip.
I’ve used both our 2015 & now our 2017 I3s for this journey many times.

Mine has been programmed to set the SOC after 75% battery usage.
We start off with a full charge & a full tank of gas.
After the battery reduces to 75%, we immediatly turn on the Battery Hold.
We then run a full tank of gasoline until the gas tank reaches 0.
Cruising on Active Cruise Control at 72 mph, the I3 does use some electric power, circa 10%.
We fill up the gas at the next available gas station & continue on the gas till the tank is empty again.
Repeat the cycle till get near destination.
By now, we know where the stops will be & the whole process is routine.

On both the North bound & South bound journeys, there are Fast Chargers at about 1 Battery range from the destination,
so we recharge the car & occupants and finish on battery.

We’ve done 15+ round trips like this and not had any issues.
I used to carry a small gas can in the frunk but don’t any more.

The I3 may not have been designened specifically for long trips but BMW have engineered the Rex to allow them with ease.

 

[EVMan]

So is the rotatory engine not dirty ?
In today's tough regulations , what is there plan, if not cheating ?
I don't trust these ICE companies any more. , as they have proved it repeatedly with mileage and clean air.

i liked the rex, and thought the noise was not bothersome
But in my last trip, driving at night, the hi rpm humming sound was driving me crazy

 

[i3Houston]

Mazda's shoe box size rotatory engine is something i am looking forward to.

I think it Rex concept(with 150 mile range battery) will be more successful and popular than pure BEVs(lack of charging infrastructure & home charging etc)

 

[jadnashuanh]

FWIW, any ICE used will need to meet the regulations for the country or region of use. An advantage of what amounts to a more stationary application (as in not speed varying like in when driving a transmission and the wheels) is that it's easier to control emissions. The original issue with the Wankel engine was wear and leaks on the seals. Mazda has had since the 1970's to solve that problem.

I don't work for nor receive any compensation from them...I have only the information I've read from other sources, and presented it here as a discussion as to what other companies are planning that are similar to what BMW did with their REx in a serial hybrid configuration. Time will tell long-term whether it works out or not, if it actually makes it into production as they plan.

A purpose built engine optimized for serial hybrid operation may have a better chance than an engine repurposed, like that in the REx.

 

[nickp]

We do a monthly 500 mile each way trip.
I’ve used both our 2015 & now our 2017 I3s for this journey many times.

Mine has been programmed to set the SOC after 75% battery usage.
We start off with a full charge & a full tank of gas.
After the battery reduces to 75%, we immediatly turn on the Battery Hold.
We then run a full tank of gasoline until the gas tank reaches 0.
Cruising on Active Cruise Control at 72 mph, the I3 does use some electric power, circa 10%.
We fill up the gas at the next available gas station & continue on the gas till the tank is empty again.
Repeat the cycle till get near destination.
By now, we know where the stops will be & the whole process is routine.

On both the North bound & South bound journeys, there are Fast Chargers at about 1 Battery range from the destination,
so we recharge the car & occupants and finish on battery.

We’ve done 15+ round trips like this and not had any issues.
I used to carry a small gas can in the frunk but don’t any more.

The I3 may not have been designened specifically for long trips but BMW have engineered the Rex to allow them with ease.

This is exactly what I want to do on my 400+ mile trips to Berkeley from Los Angeles. So far I have made 2 trips but have stopped at regular intervals to charge the car. I am perfectly OK going at a steady 70 mph. Also there are stretches where even on Rex, I have put the car in "Comfort" mode and enjoyed the rush.