Phase 2 of project – Solar (PV) Electric “fueling” a.k.a. “free miles from the sun”

Written by admin. Posted in Build Diary, Build Diary, e-CarE46, e-MotoCRF250R, Solar


With a modest solar array, approx. 11×33 feet, mounted on the south facing roof of the house, the net average cost to drive 40 miles daily is $0 annually, in fact, our founder driving the electric BMW325i , is currently achieving a net positive in power generation.  Not only is this electric BMW325i now higher performance in every way, it is also being fueled 100% by sunlight, truly Net-Zero on energy!  On the R&D lab/shop, a 5.6kW rooftop mounted and grid tied solar array delivers 17,000 miles worth of driving energy annually in the Portland Oregon area.  The solar array puts its power onto the grid during on-peak time, where the BMW’s battery pack is charged during off-peak time at almost half the cost. With solar and “Time-Of-Use” power billing, a profit is made in addition to the 17,000 miles of free driving that covers the cost of tire wear, which is the only real service the vehicle has after the conversion.  With a power inverter directly connecting the solar array to the electrical grid, the power meter spins backwards during daylight hours. When you come home, you just plug into the AC outlet and take back the power you generated during the day. This is very beneficial to the power grid by helping reduce the peak load during the day as a side benefit.  You can size the solar array to match the power used in your normal daily drive.


Regarding the amortization of our EVDrive, Oregon shop PV array factored into the cost of driving the EVDrive BMW, we have accounted for it.   In our case, the system cost after state and federal incentives was $4300 out of pocket cost.   To get the $10,000 grant money from the Energy Trust of Oregon, we are required to meet at least 75% solar exposure.  Since we had tall trees reducing the exposure below 60%, we needed to remove enough to get up to around 80%.  The harvest resulted in 3 full log truck loads of straight fir log sections that returned $4600, prior to taxes.  So our out of pocket expenses are already paid for.

We are currently on track to put greater that 5MWhr onto the grid this year (with a few weeks of best solar of the year we are at 4.7MWhr now).   This results in over 17,000 miles of driving the EVDrive BMW per year, calculated by multiplying 3.5 (miles/kWhr) times kWhr (solar onto grid -which includes charging efficiency going into BMW pack.)

Now, to reconsider the emission profile with the solar array just mentioned above, there are no emissions. None. Not even battery cells venting. In fact, there will be little brake dust left behind with most of braking done with regen control now affixed near hand brake.


Gen2 is progressing

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The Gen2 design is progressing at a faster pace now that we have the strategic partners on-board. Therefore, this project will be running in “stealth” mode, relatively speaking, out of respect for the business agreements. There will still be posting when the time comes with all the details, just not all the detail along the way. 

With our own custom brushless motor design with high power/weight ratio, highly efficient drive system with enough charge for a SX moto in its original weight,  it will perhaps set a new standard in e-motos… we will let 3rd party reviewers in the powersports media and you be the judge… stay tuned…


What’s been going on

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The time has come to give up some detail about what has been going on with what we think and have been told is the “worlds fastest and most capable electric motocross bike”: 

State of gen1 CRF2eR electric:

First off, we haven’t yet mentioned that we had an official track test day in late August at the Albany Motocross park. We rode the electric e-MotoCRF250R full on, wheel to wheel with the gas powered CRF250R equivalent. We also traded bikes to each try the complement.  The results: 

1. Whichever of us was on the electric bike was faster, mainly because of how tight this track is. With only one speed on the electric, on a long straight stretch, the gas bike would eventually blow past. It was always the fastest off the line and up to ~30MPH! In the tight woods section, the electric was king roost! Keep in mind that this is simply the first prototype… Gen2 will be much better…. stay tuned…

2. Got 6 laps under full power. Not bad for this small, but potent pack. On the last two laps, Bob tripled the jump heading into the woods with ease, nervous at first, but it felt “normal” on this 60+ foot jump.

The current machine started life as a development/practice design, quite literally, with it’s heavy cast iron motors consuming the space that should hold the batteries. This is what was available at the time, but it certainly has proven without a doubt that the batteries are indeed ready, and thus has generated new incentive for us to design the ultimate motocross bike. 

Just to give you a sense of the capability of the cells that are inside our CRF2eR, check out this plot we received from Radu, the team leader of MIT’s Electric Vehicle Team that recently demonstrated a charge time of under 10 minutes on an electric street bike.

In the background, they set up a stress test on a single cell that was charged in 12 minutes and discharged in 10 minutes, continuously.  They plotted the capacity change over time as seen below. After 1400 cycles, the capacity only drops a few percent under this continuous stress. 

1,400+ cycles, ~30 days (equivalent to 300,000 car miles). Note that at this high charge rate, you can’t get 100% capacity into them, that is why you see ~90%.

At “normal” current demand levels, the charge/discharge cycle count extends much further. 

Now, imagine a bike with a custom brushless motor that doubles the output power of this current 2 motor design! (4x the power density!) Water cooling, 2x the range, 97% motor efficiency, full variable regen braking, and mud riding OK with a fully sealed package (normal pressure washer cleanup), for just some of the highlights….the others you will see posted later.

Because of the significant potential of this machine with good batteries, the design of the ultimate drive system is the focus for performance with the potential to beat 450’s and on a bike that weighs less than the 250R.  It all comes down to power/weight ratio.  Forget about saving gas or reducing emissions (although it does), performance will speak for itself on the track. 

As this generation 2 machine comes together, we are nearing the holy grail of charge capacity with batteries that will meet or exceed the range of a gas bike. This is why the focus on the ultimate drive system. These cells WILL happen, it is just a matter of time now and we will be ready… (for our street e-motos, our smaller REX range extender, will soothe any range anxiety fears)

Today @ Colorado State University – Inexpensive, longer-lasting batteries could revolutionize the military, automobiles, and health care

And yet another new announcement on a breakthrough that will significantly increase the current delivery and cycle life of the standard Lithium Ion Iron Phosphate cells, the same chemistry as is used in our CRF2eR: 

Lithium Ion Batteries Recharged in Seconds

The important detail with both these breakthroughs is the significant reduction of the cells internal resistance.  This allows for very high currents without creating heat, which is a big part of the mechanical stress that limits the charge rate in all batteries.  To decrease the resistance this far adds greatly to the cells cycle life as well as not needing to actively cool the batteries when fast charging. 

For those technically minded, you may wonder where you may get the enormous power for fast charging, especially when away from outlets? Think storage pack sitting in the rig that got you there. With excess capacity there (relative to bike size charge), VERY fast charge can happen without any generation or transportation losses. Even the new plug-in hybrids have enough energy stored in their battery packs that will handle multiple motos worth of charge put into the bikes. There are ways to prevent having generators run in the pits. 

This, by the way, is the principle that will allow 5-10 minute charging with large electric vehicle packs that would otherwise require having a fat grid-tied connection to dump that much current in that short of time. 


Let the fun begin

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OK, now that the BMS (battery management sys) is installed and working, I can finally go full throttle with a sense of confidence in the cell control. We learned early how quickly cells can be destroyed with such high currents involved. These cells are very robust when properly monitored/controlled, however.

So, let the serious fun begin:

Heads up about the noise level in the first video. Because of the auto gain mic input on the camera, it cranks up the gain from the lack of noise when nearby to the volume level that would match a four stroke, for example, in your audio playback.



Data comparison

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Here is the power and speed curve data of the electric e-MotoCRF250R Gen 1:

This is true SAE rear wheel power displayed.

Here is the quick comparison of rear wheel peak horsepower values:

CRF250X = 26 HP
e-MotoCRF250R Gen 1 = 33 HP
e-MotoCRF250R Gen2 = ~50HP (67HP @ engine out) – not dyno’ed yet

The torque is significantly higher in the electric that makes for excellent at off-the-line acceleration, so competing with gas bikes is now possible   

 The final weigh in with Gen1 prototype:  

CRF250X                 = 253 lbs  
e-MotoCRF250R   = 279 lbs
                                         26 lbs over

Well, with these outdated motors, it is more like the weight of the CRF450X … 

Despite this weight, you can clearly see the true acceleration from the dyno data. Considering the peak power from 25 to 30 MPH, this will truly be competitive on a tight track. 

We made a discovery after posting this dyno data and after our day on the track (see below): We later found all the fat copper lugs were getting so hot, it burned off the insulation around them. The thing that caught my eye was some dark color on one battery box cover that turned out to be charred FR4 material inside that was from a terminal bolt that was glowing red hot while full throttle. This is what happens if there is resistance in the current path and large currents flowing; power is dissipated (and wasted). No cells were hurt in the incident, FYI. 

So, because of that, the dyno data shows lower on the plot (above) than it actually is. Now that the resistive losses have been resolved, it will deliver more HP and now may exceed the 250X peak power, we will have to re-dyno to find out. Despite this wasted power, it performed very well on the track. Now it will perform even better and with more range than we reported below.

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