Concepts for eBike Propulsion 2

Tweaking and improving...

Added some more height and also filled in the top with a few more cells.

Note how at the peak sunshine of the day power is lower.

When you can produce a constant solar power output of about 350 watts this means when you look at average power consumption where 30 watt hours per mile is pretty typical you can then figure out roughly how much power must be applied to achieve a certain speed in miles per hour.

Based on this you can see how 400 watts will get you all the Green areas.

In a place that is relatively flat it should be possible to travel 50 miles in just over three hours at 15 mph without pedaling.

kingcharles I'll be looking forward to a report.

You ought to create a new thread and then place a link here.

I will go to the new thread to carry on a discussion about your findings.

My hope is to get into the Solar ebike stuff some time next year and am currently still fiddling around with different ideas.

Oh, and be prepared to take lot's of pictures that new Left Side Crank Motor looks really interesting.

Until September.

For a Solar Trailer it would be ideal to have the motor included so that you had everything in one place.

The MY1016Z3 is really cheap ($50) and has a built in 9.78 Reduction so you really don't need any more than that if you run a 20" wheel which would be right for a small trailer.

Direct Drive means no chain... no added friction beyond the geardown.

Weight is about 6 lbs. The only negative on weight is that it's imbalanced which might be enough to steer me back to the use of a chain. If two are used you could drive a larger load much like wheelchairs and that would balance the weight.

The gears are made of very heavy (overbuilt) components and other than the brushes wearing out after about 5,000 miles or so (based on another bike) the motor is durable if less power is used. Actually with a 200 Watt Solar Trailer this motor could last 10,000 miles or more. Motor efficiency is about 78%.

I'm thinking I might start by building something small to get familiar with the issues and then build something like a Travel Trailer later.

There are Step Up Voltage Regulators that run $20 that would convert the Solar Panel voltage to whatever upper voltage I want. They can Step Up a 30 volt input to as high as 80 volts though about 40 volts looks to be the maximum I would actually need. Stepping up the voltage is necessary because input is unpredictable. (you really can't use an ordinary controller)

95% efficiency is possible in one Step Up this way. (pays for the brushes)

This is the easiest way to get power to a drive wheel for a Solar Trailer.

#219 Go Kart chain.

16 tooth motor sprocket and 96 rear sprocket makes a 6-to-1 gear reduction.

MY1016 motor without geardown.

3300 rpm maximum becomes 550 rpm.

Max speed for 20" wheel 32.7 mph.

http://www.advanced-ev.com/Calculators/TireSize/

This is a correction from what I had first posted about rewinding a motor.

It's been a while since I did that (2006-2007) so some of the formulas had been forgotten.

Anyway... the bottom line is that as you reduce the Kv your Resistance grows Exponentially assuming you are using a Constant Copper fill.

So rewinding really only changes the speed the motor is capable of running for a given voltage. Heat is the same, efficiency the same.

It's a rule I have to repeat to myself again and again:

Total Copper Volume defines performance.

You can fiddle with volts and amps in how you feed the motor and you can run at higher rpm if you so choose, but the copper behavior never changes.

There is actually no benefit to different voltages being applied to a motor.

Stepping up the Solar voltage to 80 volts doesn't really get me anything.

That's a MY1016Z3 motor running in a default voltage and current rating.

This is what you can do when you have less power to draw upon (like a small solar panel) but have the ability to Step Up the voltage.

Motors actually "peak" in efficiency only in the perfect combinations.

Notice how at 200 watts of power you never "peak" at 78% but you can extend the above 70% performance across a wider powerband. Peak here is 76%.

This is generically true of all DCPM motors.

The idea then would be to seek a flat powerband that would begin at about 10 mph and go to 20 mph so that the solar power is effective equally all the time.

Keep in mind this is a different mindset... there is no battery so "wasting energy" is not as much of a problem as long as performance is acceptable. The sun is constantly giving you free energy.

I wish there was a brushless MY1016Z3 with the 9.78 gear reduction that was available for $50. The gear reduction is the most difficult part.

A few years ago I bought an RC motor and took it apart to realize the bearings are a joke. The RC motor performance is great, but the bearings are not designed for difficult conditions like on an ebike. So I've given up on the medium sized RC motors... maybe one of the $200 ones might work.

At some point if you continue building performance EVs you will gain awareness there is no replacement for having more copper and iron and magnet. This is ultimately what determines how effectively a vehicle is able to convert the energy in its battery to useful thrust. You are more than welcome to get there the hard way as I also had needed to do myself. Spend enough time on the dyno making pulls with little motors and you quickly learn to appreciate big motors.

https://endless-sphere.com/forums/viewtopic.php?f=30&t=81074&start=50#p1201166

This argument is correct when it comes to efficiency.

In land based industrial situations they often use motors many times larger than necessary in order to increase efficiency. Generators at power plants could be massive and weigh tons, but they are very, very efficient. (95% or better)

Things really only get interesting when you have certain restrictions related to the motor like power limitations (such as solar power) or legal restrictions (like the 250 watt or 750 watt laws) or maybe a desire for something lightweight.

The Tangent Drive:

http://tangentmotors.com

This packs an enormous amount of power into a very low weight and small footprint.

In an absolute sense a hub motor could be more efficient... but are you willing to carry an extra 15 lbs of "sacred copper and iron" just so you can have the better efficiency?

From the rider perspective the lighter weight is more fun to ride.

Again, Luke has a fixation on maximum power in a situation involving ebikes that is normally about very limited power. Electric motorcycles do not have power limitations so that permits a seeking of maximum power.

Solar power is very limited and also variable depending on the sunlight available. I'm still fiddling around with ideas how to solve this one.

Reality

We should note that the mid-drive at 250 watts continues to be the hot product category in ebikes and not the big iron hub motors. You typically see the carbon fiber ebike as a mid-drive... if you want something to perform well on a downhill or cross country race it makes sense to get the weight down and to locate that weight in the center of the bike.

Ultimately I was correct in where ebikes would go... it's the legal power category that will make all the money for the manufacturers.

What was lost was the possibility for an EBRR ("Electric Bicycle Road Racing") sport that would have been like the new BMX and made commonplace maybe even being sold at Walmart. That idea died because of guys like Luke that wanted first a glorified moped and then a lightweight motorcycle. Thanks again for that.

Now the laws are moving towards PAS ebikes and that effectively kills the idea of a sportbike road racer design because you have to pedal to make it go. All the ebikes are becoming more and more like regular upright bicycles.

Anyway... the whole sequence has played out and we are really back to the carbon fiber crowd driving development and actually manipulating the laws to benefit their products. The same companies that are leaders in cycling are becoming the leaders in ebikes.

Solar powered ebikes (without batteries) are still an unchartered territory, so it's the only place investigating at this point.

The point Luke does make is good in some respect.

If you start with a motor that has poor performance generally there is not much you can do to correct it.

There is such a thing as being "too cheap" or "penny wise, pound foolish".

A $50 MY1016 motor will never perform anywhere near a $200 RotoMax 50cc motor.

Let's look at what happens when the high performance motor is given less and less power:

As the voltage and amperage is scaled down the peak efficiency still holds up pretty well.

Let's look closer at the low power result:

The RotoMax 50cc is simply a better motor than the MY1016 as even at low power levels the efficiency is about 20% higher.

Money solves many problems.

The MPH scale at the bottom assumes a 6-to-1 #219 Go Kart chain reduction and a 20" wheel.

Note how this line of reasoning is the reverse of the quest for maximum power. I'm actually taking a high performance motor and getting it to run at a small fraction of it's potential. In this case the RotoMax 50cc is actually lighter than the MY1016 despite having much better performance.

The ideal would be a smaller motor but with oversized bearings. That's the true problem with RC motors because they normally spin props for model airplanes and are not designed for sudden torque situations like the ones you experience on an ebike.

Finally we get to the last tweek:

Now we are flattening out the powerband by increasing the maximum voltage, but we keep the power at under 200 watts which is consistent with solar power input.

Notice that the efficiency drops off because we can't feed the motor what it wants at the higher rpm. But it's still extremely good... above 80% which is better than the MY1016 at any time.

This still assumes a 16 tooth front sprocket and 96 tooth rear sprocket of #219 chain to make a 6-to-1 gear reduction to a 20" wheel.

Wind resistance will typically limit the ebike to 20 mph on flat land so the extra voltage just allows the motor to be useful downhill.

The middle motor is one I own but is in pieces right now and needs rewinding and probably a new bearing design.

$50 - MY1016 Efficiency ~70% - 75%

$100 - Turnigy Efficiency ~70% - 85%

$200 - Rotomax Efficiency ~80% - 90%

The concept is valid in that the bigger and more expensive motor is better which is what we expected.

Weight on each of these motors is less than 5 lbs.

"You get what you pay for."

For a solar powered project efficiency is a very high priority.

But wait...

Can a motor actually be "too big" or demand "too much" power?

It appears you can go too far.

The No Load current on the larger motors can be very high and that's what bends the curve downward as you go up higher in rpm.

So we are seeking a minimal losses scenario.

Since this project will be a solar powered project and the solar racers use CSIRO type Halbach Array motors without iron maybe that's the thing to do here?

That's another thing I've always wanted to do.

Plus, with a trailer you have a blank slate to design on. I'm not trying to adapt to pre-existing bike parts and a DIY motor could be done as a very spread out thing like all those Wind Power DIY jobs you see on youtube. Coils, magnets, fiberglass, epoxy. Make it direct drive, no chain. Of course then you basically have a hub motor which is another option anyway. Weight is a big issue though.

I've got nine months before any work starts on it.

This is another idea I'm considering.

Just make a custom Cargo Bike and add solar to it.

100 watts isn't a huge amount of power, but with the skirts it's there all the time as opposed to flat when it is much lower off peak hours.

It might be possible to get closer to 150 watts and that might be "good enough".

Here the choice would likely be standard ebike motors... hub or mid-drive.

Ideally that area inside the solar is actually usable for cargo.

The advantage here is there is no trailer bouncing around and behaving in ways that work against the bike handling. This should feel solid to ride and nothing weird happens if you go over a bump.

Magnets are expensive.

Steel is heavy.

Those two problems suggest that if there is some way to achieve "good enough" magnetic flux while not needing steel and using less magnet then that design might be worth doing.

Magnetic flux is good and air gap is large, so plenty of room for copper.

I've looked into this before and found that as you increase the separation between Halbach Arrays this increases area for copper... but it's proportional so that adding space and copper equals itself in loss of magnetic flux due to the added space. (if not worse)

A Sparse Halbach Array (if configured correctly) would by it's sparse design grant a lot more space for copper.

The magnets themselves could be built into a carbon fiber disk.

The Sparse layout means you aren't "forcing" the magnets into places they don't want to go. A true Halbach Array is very difficult to build because the magnets resist being placed close together. By giving space between magnets it makes assembly easier. You have to think of practical things when doing DIY projects. (if I even try this)

While we are talking about "fun with magnets" how about a Magnetic Worm Gear?

One wonders if the worm portion could be built as a single magnet since the polarity runs in just one direction. (worm shape, but singlular polarity)

Also... what if the wheel portion were created using a central coil that was placed into the center and that would create a swirling magnetic flux pattern (think of the "Right Hand Rule") and here you could again make a single magnet. If the material is machinable then you cut the gears afterwards. This could be true of the worm too.

If this could be mass produced then a high reduction, zero friction, system would be possible. Imagine 20-to-1 reduction with no friction.

Ideally the material would itself be of a hard steel like substance so that under high loads the steel would just barely touch (increasing torque to a maximum) but under low loads the interaction would be entirely magnetic and frictionless. Neodymium is brittle, so you would need a material more like steel which is not brittle. This becomes a material science problem to find a highly magnetic non-brittle magnet.

At high rpm cruising speed efficiency is optimized.

https://www.kickstarter.com/projects/1568754048/bikee-bike-best-make-your-full-power-ebike-quickly

Another entry in what is becoming a hot new product category.

This one is a Right Side Crank Motor which should reduce any fears associated with the motor torque loosening up the bottom bracket when power is transferred from a Left Side Crank Motor.

They have some high powered versions too, above 750 watts.

I'm "guessing" this is a compound gear reduction along the John Vranish type design but it could be cycloidal or even multiple planetary gears. 10-to-1 is beyond singular planetary gear reduction so it's a mystery at the moment how they did it.

PAS of course.

Kickstarter... it has five days to go...

The performance of a Copper Coil is directly related to it's shape.

Ideally the best coil is hollow.

In other words every time you see a big thick copper coil you can know that it is both heavy and inefficient. It's a bad design.

What this does is open the mind to imagine some use for a more spread out and hollow type of motor design.

Think of the Left or Right Side Crank Motors...

If you could make the doughnut a large empty hollow area and just place the Copper Coil and Silicon Steel as a thin walled external surface layer your efficiency reaches near perfection.

That's a 6" Diameter and 0.25" thick hunk of Silicon Steel "pipe" and it's requiring less than a watt to fully magnetize.

I had noticed this before with the higher frequency issues and they do use hollow copper pipes whenever they need ultra high frequency operation. What is less known is that the conversion from electric current to magnetism experiences a similiar improvement.

Shape matters... a lot.

This is a very rough sketch of the idea, but generally the core of the Copper Coils are completely hollow and that saves a lot of weight and makes everything very efficient.

And I used an excessive depth on the FEMM simulation to make sure I was taking a worst case scenario.

It takes about 30 watts to fully activate the Crank Motor.

Also, I tried up to 500 Hz to see how much loss that creates and it's about 180 watts, so you would design the number of effective steps... not poles since this has no magnets... to fit 500 Hz as a maximum.

We would want about one rotation of the pedals per second (60 rpm)

You could "in theory" make this to have 100 up to 500 steps as a switched reluctance step motor. One hundred steps is still one fifth of the frequency where you begin to notice big hysteresis losses so that would be a good place to start.

The main point of all this is that a Hollow Copper Coil and thin walled Silicon Steel stator function very well together.

The winding would be a Toroidal Shape so the wire runs around and around the outer surface of the "doughnut". So using doughnut terms we never wind through the doughnut hole but instead around the outside. A tricky winding to do.

More on these Toroidal Coils.

Basically the coil is wrapped so that the wire goes in the larger circle direction.

The magnetic field wants to squeeze itself along the boundry on the edge, but the middle is relatively unaffected.

So the tendency is to create something like the "Eye of the Storm" in a hurricane. (typhoon)

If you want to design coils so that they follow natural tendencies then the Hollow Toroidal design makes sense because that is how the magnetic energy wishes to flow.

A large thick bundled Copper Coil creates interference patterns as each strand of wire wishes to act as it's own central vortex. Conflicting vortex patterns create eddy currents which reduce the efficiency of electrical-to-magnetic transfer.

Another product idea.

How about a really narrow thin Crank Motor that effectively removes the hollow center of the vortex? (as described before)

The Pancake Switched Reluctance Crank Motor.

At first the design didn't work so well because the losses from jumping the magnetic flux gap occur right next to each other

By placing the gaps on opposite ends of the pancake coil it evens things out. Then by increasing the central areas it becomes possible to push magnetic flux harder and double the performance.

This type of motor design could fit in an area that is the size of a chainring and could go on either side of the crank.

---> If you wrap the wires along the "long" direction of a Toroid then the magnetic flux will spin outside the "doughnut". (no flux inside)

---> If you wrap the wires along the "in and out" direction of a Toroid then the magnetic flux will spin inside the "doughnut". (like a solenoid)

What happens when you wrap at a 45 degree angle?

Well you get a Rodin Coil that focuses the vortex into the centermost point.

This vortex can actually drive a motor.

http://www.gizmag.com/wendelstein7x-fusion-stellarator-plasma-tests/40014/

To achieve a more stable environment, the stellarator eschews the method of inducing current through the plasma to drive electrons and ions around the inside of the vessel as found in tokamak designs, instead relying entirely on external magnetic fields to move the particles along. In this way, stellarator designs are basically immune to the sudden and unexpected disruptions of plasma and the enormous – and often destructive – magnetic field collapses that sometimes occur in tokamaks.

As such, a stellarator reactor is able to hold the plasma in a containment field that twists through a set of magnetic coils to continuously hold the plasma away from the walls of the device. This is because, in a normal tokamak, with its doughnut-shaped containment vessel and electromagnet windings that loop through the center of the toroid and around the outside, the magnetic field is stronger in the center than it is on the outer side. This means that plasma contained in a tokamak tends to drift to the outer walls where it then collapses.

The stellarator, on the other hand, avoids this situation by twisting the entire containment vessel into a shape that constantly forces the plasma stream into the center of the reactor vessel as it continuously encounters magnetic fields in opposing positions along its entire length.

Why not combine the excellent performance of the Velomobile with solar?

There are some I've seen that have begun to do this but I'm not sure people fully realize that the sun is never directly overhead (rarely) so the sides are ripe for being used to get more performance out of the surface area.

Since solar is all about surface area and so is the Velomobile they could make a great combination.

Will need to run some simulations to see what kind of power is possible.

I'm guessing that 250 watts can be had for pretty much all conditions from Sunrise to Sunset. The front and back sun positions will be the weak areas.

Solar power has some strange quirks.

The performance of a cell has an optimal point where the cell is under some kind of load which makes the voltage sag, but not so much as to sag too much.

This Maximum Power Point Tracking (MPPT) concept is to produce a load on the solar cells that optimizes the actual power output.

These MPPT controllers are typically matched with 12 volt or 24 volt batteries.

PWM as the typical DC-to-DC Voltage Regulator is designed does not make any attempt to optimize the solar cells themselves.

What this means is that when riding a solar ebike with "Direct Drive" solar cells you might happen to hit peak performance if you fiddled with the throttle to find the exact load that the solar cells want to run at, but you would be just guessing.

"Direct Drive" solar cells might be intuitively experienced on the ebike however.

In other words if you fiddle with the throttle you will feel which setting will give the most power.

One might also have a Watt Meter on the bike and just adjust based on that.

Generally the MPPT controllers run over $100 to get a good one. The ones selling for $10 on ebay look to be fakes in most cases. (they say MPPT but are really PWM)

What this says is that having a MPPT and a battery might actually improve energy capture over the "Direct Drive" approach unless you are prepared to throttle fiddle all the time.

This is an idea that is derived from the Mendocino Motor:

https://en.wikipedia.org/wiki/Mendocino_motor

Efficiency in the Mendocino Motor is very low because of a whole list of reasons.

What I'm thinking is that each unit has:

* Solar Cell

* Copper Coil

* Capacitor

* MOSFET

* Hall Effect Sensor

* DC-DC Boost Voltage Regulator

As the unit passes a Halbach-like magnet configuration below where a very strong magnetic field is created so as to circle in just one direction the Hall Effect Sensor reads this magnetic flux and opens the MOSFET and permits the full power saved up in the Capacitor to burst out through the Copper Coil as it passes. Once exhausted the Capacitor can no longer drive any of the circuit and the coils are now "off" as the unit swings past. The Capacitor then begins charging again with energy from the Solar Cell and the DC-DC Boost gets the voltage up high enough so all the parts in the circuit function efficiently. The Capacitor could be charged up to 24 volts if made small enough.

Features:

The best part is that ALL the energy stored up in the Capacitor is spent driving the coils.

Efficiency could actually be as good as the circuitry itself and if designed carefully it could be very good. (80% or better)

This would then drive a fan... probably more of a novelty item, but it might have some value in a kind of Copenhegan Wheel like design. No brushes are required and no controller circuit so it's always on.

Another type of Solar Cargo Bike.

This one is a trike, though in the picture the left front wheel is hidden behind the cube.

The cube is 6 x 6 x 6 so... you know...

The performance looks very consistent both based on time of day and rotation relative to the sun.

150 Watts to 200 Watts all the time.

This is clearly the easiest solar bike to build because this front loading Cargo Bike just has a single pivot. The cube is perfectly flat and square.

Ideally you would use a separate MPPT controller for each of the five sides of the cube that have solar cells. This would then optimize each one to match the ideal load for each surface. You would then pool that voltage and make the DC-DC Boost up from there.

If your Cargo was batteries then range and power could go way up, but you might be forced to add a charger and buy power from the grid if you get used to draining the batteries all the time. Fifty pounds of LifePO4 would be about 2 kWh (2000 Wh) which is a good amount of energy storage. Geez, 100 lbs would be 4 kWh which is a lot.

Funny to remember the "old days" when my SLA batteries weighed 100 lbs but gave "at best" about 500 Wh of true performance. Lipo would be even better, though that introduces some fire danger unless carefully managed.

I kind of like the idea of light weight and no battery so the trike would be okay to ride when not loaded with stuff. This is the perfect grocery store vehicle and a couple bags of groceries wouldn't be much weight so the trike could be made light weight.

This applies more to solar panels that are from the "pre-SunPower" design era, but in the "early days" of solar technology they used to insert diodes into the solar panel system so if one section was shaded or completely dark it was simply bypassed. The SunPower technology appears to eliminate this as an issue if not perfectly then to a large extent.

If there is any question that a cube shaped solar array has a performance hit by differing sun angles then you can always partition each side with it's own diode. These diodes are cheap at less than a buck apiece.

The diodes also can block the entire system from draining the battery at night... assuming you have a battery.

So there are adequate options... MPPT per surface is clearly overkill and too expensive.

One thing I realized is that for a Sleep Trailer that is longer (80") than it is wide (30") you have this excess of area on the left and right panels that just makes for uneven power.

The top area remains constant in rotation, but not in elevation.

What this means is the left and right sides can afford to include good sized windows.

A truly practical travel trailer could provide enough power to get you where you are going and also give you a place to sleep.

By having windows that you can open (with screens to keep bugs out) you give yourself a view of the outside and a better feel of your surroundings. Sound will come into the trailer, so you are more connected to nature. Ideally you camp somewhere with birds chirping in the background. (not the sound of cars driving by)

In the morning sun you cook breakfast on a stove connected to the solar panels.

At 55 years old I was thinking about whether this kind of travel adventure is even interesting for me. Not sure if I'm physically able to enjoy a long trip that this sort of thing could enable. You could literally travel indefinitely with this and if built with foam and carbon fiber (or less expensive fiberglass) you could sleep in sub-zero conditions with no problem as well as air condition yourself in the heat. It's kind of crazy how many places you could survive in with such a system.

But anyway...

By entering the sleeper from the side you make the thing stronger on the ends and this really simplifies everything.

Notice that the Top is 90 cells and each side is 42-45 cells to make things very balanced in all directions of Rotation.

Elevation does drop power but much less so than Flat and even near sunset you are capable of 250 Watts of power.

http://www.forbes.com/sites/greatspeculations/2016/08/12/sunpower-the-latest-victim-in-solar-stock-death-spiral/#2e8e0e184fbb

SunPower’s results contained what one analyst referred to as a “guidance bomb,” but the underlying issue–lower rates being paid by utilities for solar power purchase agreements (PPAs)–is not a new one. SolarCity cut its 2016 guidance for the second time with its results, but, notably stated that even the new, lower guidance assumes “an improvement in residential sales productivity” in the coming months. Utility-scale solar is under severe pricing pressure, retail deployments have been below expectations and the U.S.’ second quarter GDP report showed corporate investments at cycle-low rates, so expecting the commercial market to be solar’s savior is unrealistic.

...

So, in one day, about 13% of the value of the solar ETF was effectively removed, and the pasting the stocks have taken since SunPower’s Tuesday conference call has further lowered the value of the sector. One has to ask oneself: does this mean that remaining solar stocks will be bid up in price as the market sees a scarcity of solar pure-plays or is this in reality a rational response by industry executives to worsening fundamentals and plunging share prices–a throwing in of the towel, if you will? I can’t see how anyone could come up with the former answer instead of the latter, and the market is telling us that solar is dead as an equity play. The death spiral is upon us.

Does this mean we see a brief period of glut and lower prices?

We will see.

http://www.miaminewtimes.com/news/propane-huffing-reid-welch-found-guilty-of-stalking-miami-commissioner-marc-snaroff-6565525

"I inhale propane gas to get high, but I am not the least bit nutty",

Reid Welch once told New Times.

Today a jury found differently. Welch has a had a number bizarre run-ins with the high-profile City of Miami Commissioner Marc Sarnoff. The court found him guilty of 21 separate charges, including one felony charge of stalking.

For four years (2006-2010) I posted often on the website endless-sphere.

Reid Welch overlapped some portion of that time and I do remember reading his posts.

After I was "forced out" (politics you know) after my unfortunate "coup" over there it wasn't too long afterwards that Reid Welch contacted me in the hopes of setting up some alternative website after he was dumped too. I didn't want the bother of managing a website and told him to just find another spot and that was the last I heard from him.

Pretty weird to read about his life this way.

The photo on the lower right is his endless-sphere picture and the background is his mugshot.

And what of my life?

Well... of course it has been "safe"... sort of...

I'm actually going to get a chance to work on my ebike project again after putting it in storage for a few years. Where I left the ebike it was set to only go 30 mph, but it was geared so that the acceleration was decent. The battery is only 12S so roughly 40 volts.

By adding Step Up Boost Voltage Converters I'll be able to increase the voltage to 60 volts.

4 units at 17A is 68A

68A * 40V = 2700W -----> 60V * 45A = 2700W (3.5hp)

This guy had the same idea:

This is an easy way to get more top end without altering the low end climbing ability (which would happen with a different motor winding) and it's relatively cheap at about $75. If I added more battery it would run around $300 at present prices for A123 20ah pouch cells and add weight and be a lot of work.

Anyway... just a way to increase top end from about 30 mph to 45 mph.

This looks to be an easier way.

Using a single Step Up Converter you can get acceptable current with less fuss.

Multiple Step Up Converters require that you get them working together which adds complexity.

These run about $65, so roughly the same price.

And too much current can be bad anyway because of motor overheating issues.

1500 Watts is about right for the motor in question.

Notice that the voltage exceeds the current as far as top speed. This means that the faster you go the "leaner the mixture" so to speak and that means longer range. If you are going downhill your maximum speed can be as high as 48 mph, while on flat land the limit (in a tuck) would be 40-43 mph.

All this is better than the 30 mph absolute maximum before.

Range is based on the assumption you always have the throttle wide open on flat land.

I'm even considering going down further on power to 1200 Watts.

From experience I know the motor can handle 50 Amps of current all day long and not seriously (destructively) overheat, so if I limit the power input it will protect the motor.

Notice how the Step Up (Boost) function does not threaten more heat... you are essentially just making higher speed possible without making any change at low speed.

One last comment... this is a brushed motor, excessive currents tend to destroy the commutator, so it really does make sense to keep the stock windings and operate near the stock current limit. With a brushless motor you can simply rewind the motor without any problem because it comes down to copper fill factor alone. Things are more restricted when using the brushed motors because of brush current limitations.