850 Miles to LA and Back in a Weekend

My wife and I needed to drive to LA to see our daughter graduate so I elected to take our i3 REX instead of the far more logical Honda CR-V. The direct distance is about 350 miles each way, plus dinking around in LA ran the total up to 850 miles. My 2014 i3 has about 53,000 miles on it, and I have had the following coding done:
[*]Expanded gas tank
[*]REX on demand (less than 75% SOC)
[*]Starts in Eco Pro mode
I left Santa Cruz with a full gas tank, full charge, and 4 gallons of gas in two 2-gallon jugs in the trunk. They don't leak, but I sure didn't want to get rear-ended. Rather than go into extensive detail about my trip, I'll highlight a few salient points.
[*]I never charged the battery other than with the REX and regenerative braking. I tried to charge in LA, but could not find an outlet that would pass muster with the 110V charger.
[*]I cruised at 65-72MPH with the REX engine mostly keeping up. I think the max sustained speed is about 70MPH, but a slight headwind (and certainly any inclines) will rapidly drop the SOC.
[*]Going up the Grapevine (either direction) dropped my SOC by about 25% by the time I reached the summit, with the REX at full RPM. By the time I reached the other side of the grade, I had recharged to my starting point.
[*]The gasoline "gas gauge" is very non-linear. Not only does it get tricked by gas in the filler neck, but it overestimates the range by 100% during the last 20 miles. This makes it difficult to pick a place to pull over to refuel, which has to be done with close to zero miles to go so that you maximize the range on each fill-up.
[*]At freeway speeds, I think I got about 65-70 miles per gas tank (two gallons or so). This seems pretty pathetic, especially with the enlarged gas tank, but I don't think the REX is very efficient when charging 100% of the time at full output. I wish that I could monitor the REX engine speed so that I could try to aim for a speed where the engine is turning more slowly, but that's really anal retentive.

My overall impression is that while this was a fun exercise, it just isn't worth it. What's the point if you're going to be burning gas AND not getting very good gas mileage? On the other hand, I still had the fun of good torque and sporty handling.

Finally, if I had one thing that I would do to the i3 to make it better, it would be a setting where I could have the REX turn on at 25% SOC and then have it maintain that level of charge until the car ran out of gas. What concerns me more than anything is to accidentally run the SOC down so that I can't get over a reasonable grade. 6% is dangerous, as others have pointed out.

Cheers,

Chuck Hawley

I've said it before, and I'm saying it again, the car was designed for running around town and short trips. The fact that it can be used on a long trip is a boon to some, but as you noted, it comes with conditions. If you can accept those, fine. The i3 will not be a long-distance tourer, ever. I find it a stellar around town vehicle, and mine gets used nearly 95% of my driving. Your 35mpg seems about typical from what I've heard. TOday, there are a lot of vehicles that can beat that, another reason to not use it as a long-distance tourer. FWIW, while I find mine comfortable for typical commuting and store hopping, on the longer trips (nowhere near as long with my BEV!), I don't find it all that comfortable after an hour or two.

I have a question as a non-REX owner.

So the REX works harder on the grapevine because it's trying to maintain whatever SOC % you clicked it on at? If that's the case, I know there's a CCS charger before the incline, maybe in Gorman? Did you purposely skip on charging? Because I'd think that a full or nearly full battery on the Grapevine and the REX off would save a bunch of gas, noise, and stress, and you'd make a little bit of that up on the way down into LA basin.

The REx tries to match its output to your current use, or, if your SOC is below it's starting point, to return to that point. In stop and go traffic, it can also entirely shut off (the first time it turns on, it will run until warm, though, the main reason why you can't turn it on until the SOC reaches <75% - there has to be someplace for that energy to go while it's still running). As I understand it, it's not a continuously variable speed, but moves in steps. Don't have any experience with a REx, though, so that part may be off.

Somewhere between 70-75mph seems to be about the load that maxes the REx out. Go faster, or add climbing a grade, or at night with all of the lights on and maybe the heater cranking, and that can drop. Nothing 'bad' happens until your SOC starts to get in the range of 6% and less...then, it will disable certain things to try to let you keep going.

Since my 2014 pre-dated the fast DC charging, I get relatively few miles per connected hour on a 220V charger. I haven't exactly figured it out, but assuming 4 miles per kWh, and 6-7 kW charging, we could have connected for an hour and maybe recharged 25 miles' worth. Mostly, we didn't want to stop and I thought I could make it to the top of the Grapevine.

"As I understand it, it's not a continuously variable speed, but moves in steps. Don't have any experience with a REx, though, so that part may be off."

That's exactly what I observe. Perhaps five discrete steps from idle to full power. The changes in RPM are not instantaneous, but it ramps up and ramps down, especially as your speed decreases as you approach a stop sign.

"Somewhere between 70-75mph seems to be about the load that maxes the REx out. Go faster, or add climbing a grade, or at night with all of the lights on and maybe the heater cranking, and that can drop."

I agree. I think I can maintain about 72MPH with low heating loads. Small differences like mild headwinds or slight grades make a difference for certain.

Chuck

chuckhawley said:

...
[*]At freeway speeds, I think I got about 65-70 miles per gas tank (two gallons or so). This seems pretty pathetic, especially with the enlarged gas tank, but I don't think the REX is very efficient when charging 100% of the time at full output. I wish that I could monitor the REX engine speed so that I could try to aim for a speed where the engine is turning more slowly, but that's really anal retentive.

...
Cheers,

Chuck Hawley

Click to expand...

It's too bad REX doesn't have a charge "optimal" mode option to allow for REX charging at a high SOC but with the goal of optimal charge as opposed to holding the state of charge. Wonder how efficient it could be.

First, the conversion from rotational energy to watts-hours on the REx is nowhere near 100%, the basic engine at full power can't refill a dead i3 battery...just not enough time or energy...the power and tank are just too small.

Cars (and trucks) that can refill their own batteries all have significantly larger engines attached, at least those that can also be maintaining speed in the process.