08
Mar

About the new look and Electric Moto MX

Written by admin. Posted in Build Diary

The new look, complete with side panels. Also, Electric Moto MX and related topics discussed in detail

Here is a look at the complete Gen 1 package, now with side panels installed that keeps the dirt off the motors/controllers and makes the outside easy to clean-up, with or without a pressure washer. (Gen2 will have nicer side panels)

There are two filtered air inlets in the upper front air scoops that force air through the motor compartment where it exits in the lower rear. A small ducted fan also moves air through the interior on demand based on the motor heat. It will purge the heat from a hard moto while stopped and shut off automatically when the temperature falls below a preset level.

We suppose the new side panels will turn into a display of company logo’s with room for advertisement, or some really cool graphics…

For those of you that are wondering about the motor, here is a photo of the motor side which has not been too visible previously.

This is what the 2 in the old name we were using, Gen1 CRF2eR implies; two motors. This is what was needed to achieve the goal of matching the performance of the gas version until our new custom EVDrive single motor is complete fore Gen2.  

This will reduce the stress and temperature of each motor which will improve reliability and life. The tradeoff however is reduced range.  More on that below…

Details about the electric CRF and other related topics

This update is also intended to answer some of the common questions that are being asked in many different motorcycle forums. Although most readers welcome the idea and see the new possibilities, there are others that appear threatened by it. It is interesting to see the broad range of topics, from effects on global warming to new motor technology to enlightenment of new opportunities that could not be done with gas powered bikes.

Here are a few of the forums:

Some have posted statements or claims that need some debunking, clearly influenced by bias or preconceived notions. There are even claims that this machine is not possible, simply because it has never been done before, with the implication that if the big corporations have not done it, it can’t be done!

Well, the evidence is here with results that can be felt by throwing a leg over the bike, leaning forward and twisting the throttle…. With this instantaneous power on tap, you better be leaning forward when you twist the throttle. This is no longer just a design on paper with numbers that suggest this performance. The biggest remaining question is “how much range?” (see below)

Model name change

First, we need to update you on our change of nomenclature: 

The “eX” was originally intended for Electric eXperimental. We should have used the “R” for the race model and left the “X” for the trail. 

Here is what we meant to say: 

  • CRF250R –> e-CRF2eR Gen 1 (two motors, supercross moto range)
  • CRF250R –> e-motoCRF250R (single motor version with ~2.5 times range – Gen2 – we are hoping to sell these in 2011 in two configurations)
  • CRF250X –> e-CRF2eX (two motors, full performance, with lights for trail use)
  • CRF250X –> e-motoCRF250X (single motor, longer range, with lights for trail use – Gen2 – let us know if this model is desired)

Design

For a “warm up” exercise in battery pack construction (for the sake of the larger BMW project), this CRF design has been very educational and served it’s purpose quite well. Our initial design was never intended or expected to be a long range enduro bike that matches the range of gas powered machines. This project demonstrates the performance of this new generation of Lithium Ion cell technology with the required power/weight ratio for this application.

Before we started building this electric motocrosser, the drive system details were worked out “on paper” based on the published specifications of the motor, controller, and batteries as well as weights etc. The one item that has been missing until recently is the batteries. The performance of these cells is the primary reason for the success of this “experiment”. We can say with no uncertainty that this hard evidence confirms what the numbers originally implied.

The testing so far has been with two 300 amp motor controllers. If you do the basic math, 600 A * 71 V / 746 W/HP = 57 Horsepower (peak) delivered to the motors where most of that power gets delivered to the drive wheel. With the two 300 amp controllers the performance approximately matches the performance of the CRF250R gas powered bike.

We can also drop in the 450 amp motor controllers into the existing design using the same mounting points. That brings the peak power potential up to 68 HP, with similar performance to the CRF450R but is abusive on the motors pushing them that hard. Yes, this uses up the electrons faster,  but what a rush. Even with this extreme current, there is still some margin left in the batteries. This cell arrangement allows for 960 Amps drawn for short intervals which means the batteries are no longer the limitation in the drive system.

Our future model (Gen2 e-CRF250R) will have the equivalent power available with a single “purpose built” motor that allows significant range extension by replacing the upper motor with much more lithium Ion cells for moto length charge range.

Once we have the top down design we will have an even better result. 

Hon/Yam/Kaw/Ktm/Suz take note…. this is your future too, better get started.

Energy Density –  Comparing gasoline with Lithium Ion

Some forums are talking about the comparison of the energy density between batteries and gasoline. It comes down to: how much energy can be carried in a given volume and weight? To help put this in perspective, here are the numbers that show the energy content difference as well as the various losses delivering the energy to the drive wheels.

With these specific cells (A123 Systems),  the difference is 111 times.

However, not all the energy contained in fuel generates is power that gets applied to the rear wheel.  The reality is gas engines are only 30 – 39% efficient, where the majority of energy is lost as heat off the motor and exhaust.

The energy difference is then actually (111 * 0.3 =) 33 times, assuming you get the power from renewable sources like we currently do.

This is very poor efficiency at 30%.  Even worse when you also include the extraction, refining, and distribution costs that significantly contributes to the overall impact. If the same fuel is used in a electric power generation plant, greater efficiencies allow much more power to be made available in the form of electrical current.

The power grid delivers this energy with little loss to all of us end users already. The transmission and distribution losses in the USA is ~7.2%

This brings the energy difference up to (33 / 0.93 =) 35 times

The electric motor efficiency is in the 90 % area, depending on throttle position all the way to the driving of the rear wheel. There is little heat loss in the drive system, especially with motors with high current capability.

This brings the difference up to (35 / 0.9 =) 39 times

Now when you factor in the weight of the gas engine at 2 times the weight of the electric motor for the same output, the difference is made with more cells, meaning a higher ratio of the total bike weight is now holding energy. 

Net result, delta is down to (39 / 2 =) 19.5 times

When you consider the typical ride (or moto) uses half a tank of gas on the average, and this is still considered an “acceptable” ride, this means another half of the difference; 

(19.5 / 2 =) 9.8 times

Now for the speculative part (but probable since A123 has the new recipe): Because of the intense research and development effort being put into this lithium storage technology around the world (for EV use primarily), there is potential for new developments that will help extend the range enough to match or exceed the range of gas powered bikes.

Here is an example of a recent discovery that shows a serious density/range improvement: 
http://news-service.stanford.edu/news/2008/january9/nanowire-010908.html

If/when this becomes available, they would simply drop into the existing CRF2eR motocross machine and allow full length motos, which would bring the difference down to (9.8 / 10 =) 0.98 times!  Basically, on par.

Still speculative for now.

With regenerative braking, the same forces during acceleration can be applied in reverse, turning the motor into a generator.  This braking power returned to the batteries is most effective for trail use, not so much for competitive motocross. These particular lithium Ion cells can collect as much current as the motor can generate because of their very high current capability. This also means there is no significant heat generated inside these aluminum skinned battery boxes. Anyway, this whittles away the difference even further.

When all the benefits of this electric motorcycle relative to the old gas motor are considered in whole, the net result is a win for a large percentage of our riding. Don’t consider electric bikes as a competitor to gas powered bikes, but more as an addition that creates new opportunities. 

Attributes/Benefits of electric bikes that are difficult or impossible with gas powered bikes:

  1. Massive low end torque starting at zero RPM. No clutch needed for a controlled launch. This will excel in trials riding and on tight/technical trails in the woods.
  2. Silence, relatively speaking.
  3. Continuous acceleration from 0 – 55mph (with current gearing and single speed)
  4. Very little vibration.
  5. No warm up period.  Just turn it on and go full on.
  6. Powered from your own solar panel if so inclined. 
  7. Throttle curve customizing with ease, just plug in your laptop.
  8. Little maintenance.
  9. No fluids (other than brakes and shocks)
  10. No exhaust.  The indoor tracks can now retain their heat without the need for massive ventilation fans which still leave lingering exhaust fumes.
  11. No spark arrester needed, there is little heat to begin with. This means significantly less fire danger. These cells have inherently safe chemistry that will not explode or burn, unlike the batteries in cell phones and laptops.  
  12. Simple cleanup. When the complete drive system is enclosed there is much less to clean. A quick shot with the pressure washer and the bike is clean.
  13. Street legal opportunity. These bikes can now be made legal for dual purpose mode. The broad federal sweep of emission control implemented on January 1 2006, banned all bikes with the statement on the title “for off road use only” from street use. This was strictly for emission control reasons. We know this from Bob’s (our founder) personal experience he had with this matter in 2006 with DMV/DEQ. His Oregon DMV department will grant licenses once they see directly there are no emissions involved and has all the normal required equipment.

Range and cell life

The reason we have not stated it’s range yet is because we began testing prior to the installation of our BMS to confirm the performance. Each riding session was cautiously limited to less than 10 minutes to ensure we do get near the bottom charge level while in this “manual” mode. 

The battery management electronics are a strict requirement to prevent over discharging and possible cell damage. With the proper control in place, these cells will last greater than a thousand full depth discharge cycles. If the depth of discharge is limited to the 2/3 of maximum regularly, the cycle life extends to greater than 5000 cycles. These cells could outlive the rest of the bike depending on where the reserve indicator threshold is set.

In case you are wondering, the cells are prevented from over discharging by virtue of the electronic control that begins decreasing the available power while you are in the “reserve” mode as indicated by the display on the handlebars. Once the indicator lights up, you will have a certain amount of time to get back to the charger. Completely ignoring the reserve indicator eventually results in pushing the bike back to the charger.

Here is our plan as soon as we are able to install the BMS:

  1. Test on firm surface,  fairly level terrain for a mileage comparison that compares against the other electric motorcycles on the market.
  2. Test on loamy and loose surface (motocross track) and report time and mileage achieved.

Charge times

We are in the design/construction phase of a fast charger that will achieve a full charge in 20 minutes. A smaller unit will charge the bike in 40 minutes. Just spin off the gas cap, plug the charge cord connector. An LED will show green when the charge is complete.   

Weight

In the case of the CRF2eR, the chassis is filled with motors and controllers, so this prototype currently exceeds our goal of 250 pounds by over 30 pounds. We have plans to put the beefy drive system on a weight reduction diet and get down to the 250 – 260 pound range. Keep in mind this is the first attempt and it will continue to improve. With the proper investment, it could easily end up at the original CRF250R weight of 238 lbs.

The CRF2eR F/R weight distribution nearly matches the original CRF250R’s. Clearly, a top down design, with resources like Honda, the weight can be improved. Imagine a purpose built chassis, integrated motor, 2 speed electric shifter, and a higher proportion of battery weight relative to the total weight. This will give the best of all worlds; range, power and speed.

This is just the beginning…

Competition

This form may eventually lead to a new racing classes in the motocross world. Until our energy density is where it needs to be for full length motos, we may need pack swapping capability for racing, sort of like NASCAR. Smooth lines and techniques (better use of the energy) allow a rider better distance/kW giving a new skill requirement in EMX events. We hope to see SX length charge capacity soon.

Noise-wise, keep in mind, full on aggressive track riding will not be totally silent! You will still feel the landings and ground contact like the gas bikes on a rough/mx track so it isn’t a complete bore for spectators. Now you might hear the riders yelling at each other, as well as the riders having a chance to hear those at track side.

When on trails with hikers, the chain noise alone makes an early announcement so you can’t really sneak up too close on people. Silence is all relative.

Environment

Coal fired power plants thread:  Some claimed an electric motorcycle will worsen the global warming problem as compared to motorcycles using fossil fuels because it will burn more coal! 

Not only is there less net emissions from electric vs gas power (because of the significantly higher efficiencies of electric motors vs gas engines), the percentage of power from coal is very low, especially here in the Pacific NW. The source of this power can come from renewable sources at any time.

In fact, we buy our power from renewable’s already so there is no coal burned for the electrons when charged here. Taken to the next step, the energy can come from your own roof from panels that are now guaranteed for 25 (some even 35 years) and that pay for themselves in 10 to 15 years.

Imagine a day when you pull your electric dirt bikes to the riding area with an electric rig (with a large capacity pack, charged off the AC line during off-peak hours). This allows for very fast charging of the dirt bike packs because of the very high current/power available in a vehicle size pack. 

Water crossings

There are riders wondering about what happens when you cross a creek with the electric bike. Streams are generally low salt content. These motors will actually run under water, not that it would be good for the motor, but the water is not involved if current does not flow in it. Any current that does flow is localized inside the motor compartment and chassis. It would NOT go around and kill fish in the steam, and it would not shock you if you are standing in water hanging onto the metal bars. The currents stay locally inside, positive terminal post to negative terminal post.

This is very unlike the AC power grid where power is relative to earth and wants to find any conductive path to ground, including through a person strongly coupled to the earth standing in water…

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