Why the BMW i3-REx

It was a dark and stormy night . . . 42% SOC and charging at 4%/hr it would take 15 hours to reach 100%. So I decided to drive down to the high-speed DC charger. Hindsight, I could have just used the REx around town and stayed at home. Regardless, I met a Tesla model X owner with temp tags getting a charge to go home.

A Leaf owner, he recently added the Tesla X which still had temp tags. He put it under his business so he can rapidly depreciate it. But he needed a charge to reach home and at '100 miles per hour', the 30 minute charge would meet his needs. This suggests since using a 40 kW charger, his typical usage is ~400 wHr/mile. He was using a CHAdeMO to Tesla adapter.

I showed him my BMW i3-REx and how we'd used the engine to do a 700 mile trip to Oklahoma ... using the truck stops for refueling every 80 miles and relief for my wife and her dogs. I had used 'PlugShare' and only found a few 'Tesla NEMA 14-50 outlets along the route' and not enough to handle the EV range. He related taking four days to drive his Leaf from Florida to Huntsville and the growing SuperCharger network that means he can do the Florida drive in one day.

Anyway, new friend met at the charger.

Bob Wilson

 

When driving through the night, solo, or with the wife and her two dogs, not so bad. But I agree it really needs to be 150-160 miles. So happens I have a plan, adding a second tank from a salvage, BUT it would void the warranty. But there is another neat trick that is a lot simpler and accomplishes the same effect.

The filler tube, stainless steel, can have two taps installed, one high above the other, with both leading to a spare tank under the frunk. As gas goes down the filler tube, the gasoline rises up the filler tube and the lower tap, below the empty level of the spare tank. The upper tap, above the top of the spare tank, lets the vapors escape back into the filler tube. The beauty is no extra wiring and mechanically simple. In effect, a 'bulge' in the filler tube.

Bob Wilson

 

Today I have a USB based patch, very simple, that allows 75% SOC REx operation but an equivalent tank patch is not available, yet. The tank patch requires a more complex, windows based, body of software and risks bricking the car. But when I compare it to expanding the amount of gas, even with the spare gallon can, this has lower risk and greater gain.

The way I saw it before the broken motor mount:

	method	gal	range	block mph @65
1	standard	2.0	80	54.0
2	patch	2.5	100	55.9
3	spare can	3.0	120	57.5
4	expand tank	4.0	160	59.0
5	expand+patch tank	4.5	180	59.6

The 2.5 hour cruising range from doubling the tank capacity also matches my expectations for an optimum driving time. Any further and I start looking at taking a biology break to keep the driver refreshed.

Bob Wilson

 

Yes,

The frunk:

So there are options:

• filler-side wall - tall and shrinks the width by the gasoline volume. Air/fume vent at top, easy, and minimal payload stress on the tank wall. Could be done via a removable insert allowing variable, expanded tank sizes. Only a side-impact against the passenger side puts a strain on tank wall which due to dimensions can be internally re-enforced. Rectangular shape means easy fabrication.
• body-side wall - tall so fill and drain would be fairly easy and loss of frunk volume by making it narrower. However, the space is already narrow which restricts contents and in a frontal or rear collision, higher stresses on the tank wall. An insert becomes difficult because of the rear curve.
  
• bottom - also carries load of frunk all the time with higher puncture risk, and problems with air-bubble entrapment limiting fill.

In theory, the whole frunk could become an expanded tank. I'm not headed that way as I need to carry a tire patch kit and a portable, L1/L2 EVSE.

Bob Wilson

 

The one unknown is dealing with the pressurized gas tank. The pressure isn't a lot, gas cap limited to 1/2 bar, but it exists.

 

Another credible review:

Bob Wilson

 

Bob Wilson

ps. Let me know if there is a problem viewing the YouTube

 

Near as we can tell, not in the U.K. or the USA.

Bob Wilson

 

It is the short wheel base that gives excellent city handling but it can couple with an undulating highway pavement. On some roads, changing the speed even a couple of mph can decouple the resonance or shifting right or left a bit in the lane can also moderate the coupling.

Bob Wilson