Long haul rexing?

BrianStanier said:

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).

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Does that mean the US does not have the display stating the miles left on electric only? I had it at 35 miles all the time I was doing 76. It only went down when I did some higher speeds I will not discuss. It was a fairly flat motorway with 2 up and the weather was dry. The Rex performed really well, but only gave 35-40 mpg (I did not take details of that, as I just wanted to know I could hold a decent speed). There was very little regen because it was on cruise on a level surface (and I don't slow down unless really necessary).

Thanks all for your feedback. I did ask the sales person if you could run the tank empty but they where not sure. From the comments I get that you can actually do that and that the rex will start after filling the tank without problem. Have you don this ferquent Frank? Any other users done this?

So now that I have pulled the trigger the questions is do I take delivery before my summer holiday or after so that we can still use our petrol car for the holiday. Normally we like to go camping but I do not see the possibility to bring our own tent in a i3. We could rent a fully furbished tent as aleternative however. How easy doe the i3 get full when you are going on holiday with four persons. Is there enough space to bring all our stuff?

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).

Same in Germany. I frequently look into the REx menu ( programmed a button for that ) to look at the SOC, which is updated permanently in 0.5% steps.

Frank

@Second,

I have not emptied my tank at all, so far I only had a 10 minute REx maintainance run in 3.445km.
But others in Germany have emptied the tank repeatedly to the last drop of fuel, and it always started without complaints after filling up. Think there is a reserve for that. So you can really utilize the tank capacity 100% provided you start the REx in time to have some spare electric range.

Frank

Second said:

Thanks all for your feedback. I did ask the sales person if you could run the tank empty but they where not sure. From the comments I get that you can actually do that and that the rex will start after filling the tank without problem. Have you don this ferquent Frank? Any other users done this?

So now that I have pulled the trigger the questions is do I take delivery before my summer holiday or after so that we can still use our petrol car for the holiday. Normally we like to go camping but I do not see the possibility to bring our own tent in a i3. We could rent a fully furbished tent as aleternative however. How easy doe the i3 get full when you are going on holiday with four persons. Is there enough space to bring all our stuff?

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I have asked question to a REX owner and he has on several occasions let petrol run out without any issues battery simply takes over so don't worry about topping up petrol.

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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I would not do that too risky.

We've had our i3 REx two months now. I've taken about four 200-mile one-day trips, each time to the same place and back. I drive the entire trip at 65 miles per hour just for fuel efficiency. As you know, the U.S. model, we're in Arizona, gives the driver no control over the REx. It comes on automatically at 6.5% SOC. So I start with a full charge and gas tank, and carry a Rotopax 2-gallon spare. (The spare isn't really necessary because there's a fuel stop in just about the perfect location, but as there are very few other fuel stops, it provides reassurance.) The REx comes on at 72 to 75 miles, and runs the rest of the trip. The topography is generally flat with some long approximately 2% grades and a few rolling hills. It's been hot lately (around 100 F), but window tinting allows me to be comfortable in Eco Pro mode with the A/C set at 74 F.

The REx engine has no trouble maintaining the charge at 65 MPH. I haven't tested it at higher speeds and am aware of conflicting reports on this forum of whether the REx can maintain the charge at 75 MPH.

Later edit: After writing the above, I once took the same 200-mile trip facing strong headwinds. Without the Rotopax, I would not have made it to the only gas station around for many miles along the sparsely populated route. At the time, I had not yet coded the car to gain control over the REx, so the option of timing gasoline use to allow me to take on some additional fuel at a particular spot wasn't available.

pdurham said:

We've had our i3 REx two months now. I've taken about four 200-mile one-day trips, each time to the same place and back. I drive the entire trip at 65 miles per hour just for fuel efficiency. As you know, the U.S. model, we're in Arizona, gives the driver no control over the REx. It comes on automatically at 6.5% SOC. So I start with a full charge and gas tank, and carry a Rotopax 2-gallon spare. (The spare isn't really necessary because there's a fuel stop in just about the perfect location, but as there are very few other fuel stops, it provides reassurance.) The REx comes on at 72 to 75 miles, and runs the rest of the trip. The topography is generally flat with some long approximately 2% grades and a few rolling hills. It's been hot lately (around 100 F), but window tinting allows me to be comfortable in Eco Pro mode with the A/C set at 74 F.

The REx engine has no trouble maintaining the charge at 65 MPH. I haven't tested it at higher speeds and am aware of conflicting reports on this forum of whether the REx can maintain the charge at 75 MPH.

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For your 200-mile one-day trip, how many times do you need to stop to fill the tank (assuming you start with full charge and full gas tank)? Thanks!

I tested this on level ground at about 70 degrees ambient temps with AC on low in Comfort mode.


Above 70 mph - Rex unable to fully power vehicle (battery range slowly dropped)

Between 64-67mph - Rex able to fully power vehicle

Below 64mph - REX generating surplus power (i.e. could put some charge back into batteries)

Add in hills or more electrical draw, and this would change. I did find that at 70mph, I lost 1 mile of estimated range for every 5-6 miles of travelled distance.

Which means for our European owners, activating REX at 75% battery SoC and driving similarly to what I did would result in the battery going flat after 340 miles (74% battery dip x 5 miles = 340). You would need to refill the gas tank long before that happened and you would have plenty of reserve for hills). But it suggests the max range for an i3 with FULL performance when driven exclusively on the highway is somewhere around 350-375 miles. However, in practice this would be pretty hard to do, and would require a LONG stretch of freeway at 70mph with only the briefest pause to refill the gas tank before resuming. Under 65mph and you could do this indefinitely.

In the USA, however, the story is quite different. At 70mph on the freeway, you would expect to get about 60 miles of range on the battery (93.5% drain) until the REX activated, after which you would have a completely flat battery after only 30 additional miles (6% SoC x 5 miles = 30 miles). At that point, your max speed would likely drop to around 65 mph and would fall far lower on hills. So your trip would be limited to 90-100 miles vs the 350 or so of your European pals.

Thanks CA CARB rules. :-(

Awesome work, bryanmsi. I hadn't considered coding the car, but as I'm considering some longer distance travel, it almost seems essential to get control over the motor.

You can either learn to code, pay a coder, or pay DVDinmotion..... I went with dvdinmotion and I have full control of the REx once the SOC reaches 75%.

Coding to gain the European option of turning the REx on at will at 75% SOC or less as well as the 2.4 gallon gas tank IS very helpful for longer drives. I've coded the car to restore both of these capabilities.

Since doing that, I've adopted the practice of using the REx on freeway stretches of 65 to 75 mph and turning it off for 2-lane, city and suburban driving. The noise and slight vibration of the REx is least noticeable at higher speeds, and battery power is most pleasant and efficient when driving at slow and medium speeds and in stop and go situations. I'll switch back to the battery near the end of a drive to insure that I've used the full available battery capacity by the time I get home. That way, I've driven the maximum number of electric-only miles, and I've used battery power where it's advantages are greatest.

The added control over the REx also allows you to take full advantage of the capacity of the gas tank, whether you have 1.9 gallons or 2.4--you can turn the REx on at 75% SOC, drive until completely out of gas, then use battery power to get to the next gas station. Although my longest trip so far has been only about 250 miles, you could keep this up all day. Compare to the un-coded U.S. car, in which you're forced to exhaust the available battery range before the REx comes on automatically at 6.5% SOC. In that situation, there's no battery backing up the gas tank, so you're forced to refill the tank a bit before it's empty, reducing your usable gas-powered range in proportion to how risk-averse you are.

A not-so-obvious advantage of the 2.4-gallon tank is that I can carry a Rotopax 2-gallon jerry "can" when necessary and there's no risk of overflow when emptying the Rotopax into an empty or nearly empty internal tank. With the 1.9-gallon internal tank, I had to be careful to stop just a bit before the Rotopax emptied all the way or I would end up with a bit of a mess.

Bottom line: control over the REx improves the car's capability and overall enjoyability on drives exceeding the battery range. It probably also improves overall efficiency by using the power source most appropriate for a particular type of driving. And since I'm in a non-CARB state, it's also guilt-free (BMW did not get any ZEV credit for selling me the car, so I'm not even arguably hurting anybody).

I believe that even if I were in a CARB state, I wouldn't be hurting anybody--I'm still using the full battery range of the car. I'm just using it at different times during my drive. If anything, I'm maximizing the efficiency and minimizing the environmental impact of my driving. I believe that the REx is probably most efficient when used on the freeway, and the battery is probably most efficient when used off the freeway. So control over the REx allows the driver to maximize overall efficiency. If the added flexibility gained from having control over the REx means that the i3 can replace an ICE car for a given trip, the environmental benefit is even greater. I believe I understand what California was trying to accomplish with the BEVx category and the rules that define it, but it sure would be nice if they could find a better way.

This is surprising, I knew that their DVD mod was only for the Pro Nav, but it never occurred to me that you needed it for the REx too.