Why the BMW i3-REx

Started my day at 5:30AM:

• 10 miles to work: -10% SOC
• 10 miles to home (contractor on site, 8AM): -20% SOC
• 10 miles to work: -30% SOC
• 10 miles to home (final inspection, pay bill): -40% SOC
• 10 miles to work: -50% SOC
• 10 miles to home: -60% SOC (end of day)

Thanks to 90F (32C), using AC a lot. No need to fire off REx that was critical to getting car from Charlotte NC to Huntsville, AL.

Bob Wilson

 

Actually I'm in the 'reduce drag' camp. As I drive around town, there are a boat load of similar sized and shaped cars. By no means exhaustive:

	metric	BMW i3-REx	Chevy Spark
1	Pass. ft{3}	84	86
2	Lugg. ft{3}	15	11
3	Hwy	40 MPG(*)	41 MPG

*-measured in two benchmarks and Argonne Labs between seconds 200-275:

Source: 2014 BMW i3-REX | Argonne National Laboratory, embedded in downloadable data files.

It is not clear that adding a mechanical drive path would significantly improve highway performance. However, improving the aerodynamics pays big benefits.

Since highway trips are usually more planned, a removable after body that also serves as storage might be a more cost-effective solution. It might even hold a full-size spare, jack and spare gas container(s).

Bob Wilson

 

They will be visible to following traffic on top of a box with large fireworks markings and next to another box labeled Diamond "Strick Everywhere" matches. Maybe that will get the tailgaters to back off.

Bob Wilson

 

Given recent events, it might attract too much police attention too.

Bob Wilson

 

New data point for REx operation at a constant speed:

	speed	MPG	SOC
1	75	32	loses 20% each cycle
2	65	40	sustained
3	55	44	sustained
4
5	35	45	sustained

• REx runs all the time above 20-25 mph
• REx rpm is constant 2400 rpm
• fuel rate proportional to grade

The REx is holding a constant rpm and varies the throttle proportional to the load. This is identical to a conventional car running on traditional cruise control. Small wonder the REx operating, 40-44 MPG is like an ordinary car.

In contrast, the Prius control laws keep the engine in the peak BSFC, operating line, which varies the rpm as needed. Furthermore, the Prius generates a minimum of ~10kW and banks the excess in the traction battery to be used when the engine is turned off. The REx essentially goes to idle a low power demands.

So let's compare and contrast a BMW i3-REx and Prius 250 mile trip at 65 mph with gas at $2.50/gal:

	metric	BMW i3-REx	Gen-3 Prius
1	block-to-block mph	50	61
2	15 minute fuel/bio breaks	3	1
3	trip duration	5 hrs	4 hr 10 min
4
5	MPG	40	52
6	fuel gal	6.2	4.8
7	fuel $	$15.50	$12.00

Bob Wilson

 

EXECUTIVE SUMMARY

It works but the instructions could be better.

Overview

To install the NEMA 14-50 (aka., RV park socket,) the 48 year old, utility service access service had to be replaced. At the same time, we installed a 16kW, natural gas fueled, automatic switch-over, generator. Then I could mount the JuiceBox wall holder:

Before lacing the wires, I wanted to test it with the car.

The "Quickstart" instructions are pretty lame and important clues are left off like an architecture diagram:

• JuiceBox connects to your WiFi service
• It reaches into the EMotorWerks network to connect to their server
• With your account and a browser, you can see the status the server holds

I honestly thought my connection had failed until pursuing their support links, connected to the server.

The initial status shows the active current, power, temperature, and voltage:

Our NEMA 14-50 has 50A wiring and circuit breakers, one for each hot leg.

The server also shows a graph of the charging:


Summary

The EMotorWerks, JuiceBox Pro (40) works but the instructions leave a lot to be desired. It was actually working when trying to debug the problem, I stumbled on the server and then discovered it was OK. I am not happy that all communications is via their server (one oops and I no longer have data.) But for now, good enough.

I appreciate the irony that in EV mode, my BMW i3-REx is ultimate flex-fuel: nuclear, hydro, coal, PVC, wind, natural gas, e.t.c.

Bob Wilson

 

Nice article that does not apply to my purchase of a used 2014 BMW i3-REx. Taking their outline, point-by-point:

• "Option #1: It’s The Batteries, Stupid!" - has always been the bug-a-boo since the first Prius and Insights hit our shores. It was probably why someone killed the EV-1. The shenanigans and FUD associated with batteries, well we might as well sign-up for "Liars News." Regardless, the serious manufactures are making sure this mission critical part of their business plans are locally managed and controlled. You don't put your future in the hands of those who with a single whim could put you out of business.
• "Option #2: Where Are The Gas Stations?" - absence of rapid, high-rate chargers by 3d parties is not the case in other countries that have to a greater or lessor extent build, non-Tesla, rapid chargers. But obviously Tesla has a business plan that requires such chargers. But the BMW i3-REx short circuits this limitation with a 2 gallon, gasoline tank and engine+generator that can sustain 65 mph (104 kph). Although some dismiss range extenders and the BMW version could be better, it is a 'good enough' solution for 'fly-over' states.
• "Option #3: Dealers Will Be Dealers … Or Not" - or as the Huntsville Toyota dealer accomplished in May, they broke my 'price barrier' on used BMW i3-REx when they offered a Level 3+TSS-P. They insisted I had to test drive it which proved the Level 3 was no match for the Level 2 ECO. But they could not offer a Level 2 ECO+TSS-P, my hard requirement. The existing manufacturers have a 'dealer' problem but Ebay has made that moot.
• "Option #4: BMW Doesn’t Want The Transition To Happen Fast" - Opps too late. I bought my BMW i3-REx May 27. I already have plans for self-maintenance and might have a clue or two about the technology.

After buying my first Prius eleven years ago, there has been over a decade of 'experts' proving the Prius didn't work: it cost too much; it was a 'bad' car; it wouldn't last; it wasn't green. So I used their claims to mitigate how I maintained our 2003 Prius and never looked back. These Prius skeptics reminded me that journalism schools don't teach physical sciences and math.

The path to the future often has ripples and eddies. Sometimes folks have to take one step back needed to take two steps forward in a different direction.

Bob Wilson

 

First day with a 7.3kW Level 2 EVSE over the 1.4kW, Level 1 EVSE and I noticed a new attitude. Ordinarily, I would plan on visiting a high-power, free charging station as part of my ordinary errands. But now, not so much. I can go home and know the car will be fully charged within 2-3 hours. In contrast, the Level 1 charger has been more of a 'sleep over'.

I'll put the Level 1 EVSE in the BMW i3-REx "frunk" with an outlet tester in a baggie (the frunk is not water tight.) The EVSE requires a properly grounded outlet and the tester is a lot easier to use.

Bob Wilson

 

My interest is not just having a charge but the characteristics of BMW i3-REx charging. So the metrics are important:

• first charge - starting around 9:30 AM, the car charged and we see the tapering off as the charge completes.
• periodic wake-ups - very short, low power events, the car is tweaking, perhaps to make up for "OFF" state overhead.
• preconditioning - I had an errand to run and in the +90F (+32C), started cooling off the cabin while getting ready.
  
• hot day charging (after 18:00) - during the tapering down, we see two short spikes which were probably battery cooling cycles. Thermal management of the battery is critical for long life.
  
• requested unplug-plug (about 20:00) - while looking at data, was requested to add a password and prompted to unplug-plugin the car.
• period wake-ups - again short, low power events.
• cooling event - about 3:00 AM, car appears to have initiated a battery cooling.
• 5:00 AM preconditioning - came on as expected with the expected ramp down.
• 5:45 AM manual preconditioning - slow getting into car, triggered it as putting shoes on.

I knew there were more than just traction battery charging going on but had no metrics to understand how much and when. Now I can see the total picture.

EV folks are fond of bragging about how cheap it is to run our electric cars but can easily forget (or don't know) the battery maintenance and other vehicle overhead losses. Compared to driving, these are minor but when the utility bill comes in, the bill will come due.

Bob Wilson

 

I was surprised too. I'm trying to figure out how to make a 'shoe box studio' with a ScanGauge and iPhone to record what is going on. I hate trying to observe and drive at the same time ... too many opportunities to OPPS.

Bob Wilson