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HTB releases new high powered motor..

Hanebrink ebike wins hill climbing race at Interbike using Hightekbikes Battery Pack. http://www.youtube.com/watch?v=5Abem0Po194

Custom eBikes made to order. (8 hours ago)

 
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Motor Power Ratings

Motor power ratings are specified in watts. Watts(W) = Volts(V) x Current(A). For example, a motor running at 36V and 21A would about 750W. The thing that most people don’t realize is that motors don’t have an exact value for watts. Consider the specified rating to be a general value as each motor will have a power range. Sometimes motors are purposely under-rated as in the case of electric bikes sold to Europe which by law are limited to 250W. Ever wonder why there are so many motors rated for 250W ? Taking one of these motors as an example, first calculate the current. 250W/36V = about 6.9A That current is too low for 90% of ebikes so it doesn’t add up. The absolute minimum current for an ebike is 10A, and many are 15A. So 36V x15A = 540W, twice what the specified rating is. Of course you can run at a lower voltage, and 24V is still common, especially for smaller bikes. In that case you have 24V x 15A = 360W, and if you lower the current to 12A, you would get 288W which is closer to the specified rating.

Another thing to keep in mind is that hub motors are about 70-80% efficient under load so the power you get to the wheel is the calculated power times efficiency. A 500W motor produces 350W of usable power (70%). The point is that motors can be run at different power levels. They will be most efficient at a specific power level. Below this level ,they will bog down and waste power for example when they are going slow under heavy load. At the higher point of the power range, the motor will start to get hot as it can not dissipate the heat and will waste power. The typical 250W geared motor can usually be run at 450W depending on ambient temp. Our little geared motor is stronger than most and can be run at 500W and even bursts of 700W, but we rate it at 450W.

The Aotema motor is rated at 750W, how did we determine that? The standard way to rate a motor is test it on a sophisticated motor testing apparatus. It puts it under measured loads and plots the various parameters including efficiency and output power. The power rating corresponds to the point of peak efficiency. There’s actually a simpler method anyone can do, while not exact, it gets you in the ballpark. Simply increase the power level supplied to the motor while under load and measure the temperature of the motor. The power level at which point the motor is slightly warm when run continuously (under load) is the maximum power level. The peak power would be another 40% of that value.

You will see motors advertised as 1000W on sites like Ebay and you might think, wow what a great deal on a powerful motor! The problem is any power level can be slapped on a motor. Most of these are actually 500W motors. At 1000W, they are operating beyond the efficient range, will run hot and waste power. So don’t get hung up on power ratings or fooled by exaggerated advertising claims. For more information on your power requirements, contact customer support at Hightekbikes.

 

Range Specification Explained

The expected range for electric bikes depends on several factors, so it is difficult to compare different bikes.  Added to this, the tendency for some sellers to exaggerate makes it even harder for the average consumer to make sense of it all.  This post will attempt to demystify the factors that determine range and allow a potential customer to cut through the BS.  First, lets go over the main factors that determine range for an e-bike.  The weight of the rider, combined with the weight of the bike is a major contributor.  Next in importance is the occurrence and slope of any hills.  It takes allot more power to go up hills which will drain the battery two to three times faster.  Speed is also a major factor, it takes more power to go faster.  Other factors include wind, type of tires and inflation, and riding style.  By riding style, I mean how quick you are starting off and how much you pedal.  Acceleration takes about three times as much current than maintaining the same speed.  So without specifying most of these factors, range specs by themselves are almost meaningless.

There are three general ways to specify range: absolute maximum under ideal conditions, expected under average conditions, and typical what most riders will get.  In the first case, the spec will assume a light rider (>150 lbs), no wind or tail wind, level ground or slight down hill, pedaling the entire time, lowest power setting, speed 15 mph or less.  The average setting will assume a medium rider 150-175 lbs, no wind, level ground, pedaling only sometimes, medium or high power setting, mixed speed.  The typical setting assumes a medium rider, slight or no wind, level ground, maybe a short, slight hill, high power the entire time, full speed the entire time, pedaling only to start off.  So the exaggerating seller will use the ideal conditions for their spec, though while technically possible, will not be typical.  The more honest seller will use the average or typical spec.  At Hightekbikes, we use the typical spec and assume the rider will go full speed the entire time with little pedaling.

This brings us to how range can be calculated given known values.  One general rule of thumb is that you can expect to get 1.5 miles per AH (ampere hours) with a 36V battery.  This assumes average conditions, so varying speed and pedaling some.  So for example, with a common 36V 10AH battery, you would get 10 * 1.5 = 15 mile range.  Going up some hills might decrease that to 1 mile per AH and by the same token, pedaling a lot on level ground and going 15 mph could increase the range to 2 miles per AH.  What it gets down to is how much current will the motor require to move you.  Maybe it take 10-12 amps at full speed (20 mph), 20 amps going up hill and accelerating,  and only 7-8 amps at 15 mph.  First lets clarify ampere hours; AH designates current, measured in amps (A), over time (hours).  Amps * Hours = AH.  So a 10 AH battery can output 1 amp for 10 hours, or 10 amps for one hour.  For example, say it takes 10 amps to go 20 mph and you go full speed until the battery dies.  How far have you gone?  Going back to the formula, you divide 10A into 10AH and get one hour.  So you went 20 mph for one hour.  Multiplying one hour times 20 miles per hour gives you 20 miles.  That’s a bit optimistic, a more common setup would require 15 amps to go 20 mph.  So running the numbers again we get: 10AH/15A = .67 hr,  next 20mph * .67 hr = 13.43 miles.  Lets do one more to illustrate how a slower speed affects the range.  We know slower speed take less current, so at 15 mph, it might only take 7 amps:  10AH/7A = 1.43 hr, 15mph * 1.43hr = 21.45 miles.

The above calculations are based on a 36V battery, the most common with ebikes.  However, what happens if it is a different voltage?  Given the same AH value, a lower voltage will give less range, and a higher voltage will give more range.  To compare batteries of different voltages, we must use watt hours (AH * V) as our measurement.  WHr takes voltage into account and allows us to compare apples to apples.  For example, a 36V 10AH pack is 360 Whrs while a 48V 10AH pack is 480 Whrs.  Clearly, the 48V pack has an additional 120 WHrs of capacity available.  Production e-bikes generally stick to the legal 20 mph limit, so that extra capacity will go towards range.  In contrast, motor kits are designed to reach 20 mph at 36v and when run at 48V, go faster.  So the extra capacity could go towards the higher speed and result in the same range as the equivalent 36V system.  It even might get less range at full speed due to the rate of increased power required to go over 20 mph (due to wind resistance).  However, if the rider maintains the 20 mph speed, he can put the extra capacity to use as extra range.  Some e-bikes are still using 24V, notably smaller foldup bikes.  So you get less WHrs or capacity.  Using the same example of 10AH, the 24V system gives you 240WHrs or 120 less than the 36V system.  Like using the simpler AH rating above, you can use WHrs to determine range.  Instead of miles per AH, it’s miles per WHr.  Based on the typical 15 mile range for a 36V 10AH pack, you are using 26.8 WHrs per mile (360/13.43=26.8).  So with a 24V system (240WHr) you would get 9 mile range, 36V system (360WHR) you would get 13 miles, and with a 48V system you would get 18 mile range.  Note these calculations were for one situation and were for comparative purposes.

Some final points to consider are the efficiency of different motors under different conditions.  For example a gear motor is more efficient at going up hills due to the internal gear ratio.  A direct drive motor is better at high speed cruising.  Also some battery manufacturers spec the AH rating at a lower current than you would typically use in operation.  So the end result is you will not get the full rated amount of ampere hours out of the pack.  Different tires and wheel size can also affect efficiency.   Even so, the general guidelines above, give you a close approximation of what range you can realistically expect.

To summarize, don’t necessarily believe all the claims on range made by some sellers.  Since potential customers use that for comparative purposes, there is a huge incentive to inflate this value.  What you want to do is get the voltage and AH of the battery, make a judgment on the efficiency of the bike and components, factor in riding style and terrain, then plug the values into the formulas.  As a general rule of thumb, you can expect 10-20 mile range from a 36V 10AH pack, with 15 miles being typical.  Contact us at sales@hightekbikes.com for more information.

 

Regen, the Holy Grail of Electric Vehicles.

Based on the clamor for it, you would think regeneration (regen), is the “holy grail” of electric vehicles. There is something inherently appealing to the concept of re-capturing energy. Everyone wants it. The only thing is, it is practically useless for electric bikes. Due to a bicycle’s low mass, there is very little kinetic energy to convert. Then there’s the electrical conversion efficiency. Battery packs require a specific charge voltage and current that must be regulated. Going up and down several hills is the best case scenario, but even then you usually only get 2-3% back. There is a possible downside to regen. Without the proper circuitry, you can damage the battery, especially if it is a lithium pack.

The main problem with using regen on a lithium pack without additional protection is that the BMS will not protect the cells from over-voltage. You might be thinking that the BMS has OV (over-voltage) protection so the cells will be safe. In the case of regen, this is not the case. What happens whenever the BMS detects an OV condition? It turns off the *charger* mosfet, not the discharge mosfets. So when you are zooming down the hill generating 60V+ into a 36V pack, you will cook the cells, because you are pumping current into the output, which is not turned off in an OV condition. The current must be directed into the charger input, so the BMS can interrupt the circuit when a cell reaches maximum voltage. One way to do this is by inserting a blocking diode in the negative discharge path, while connecting the charger’s negative input directly to the controller. You can also use a relay to switch the controller from the discharge path to the charger input, if you don’t want the power loss from the diode. Using the BMS to protect the cells from regen is dicey at best. An external voltage and current regulator circuit would be a lot safer. Some regen controllers are supposed to regulate these, but they are not accurate. Regen is generally not worth the risk, but it can be done with proper design. Contact Hightekbikes for more information before you fry your expensive battery pack.

 

The looming conflict with China over Intellectual Property in the Electric Vehicle Industry.

As countries realize the next big industry involves Green Technology, the scramble is on to position themselves to take advantage of this huge market. In the Electric Vehicle Industry, which includes electric bikes, motorcycles, and cars, China is taking a leading role. There has been great fanfare over the few offerings by American companies such as the Tesla, but few people can afford them so they will have limited market penetration. Meanwhile, Chinese companies have been quietly researching, manufacturing and perfecting electric vehicle technology with the help and encouragement of the government. Not being tied to the petroleum/combustion engine paradigm, their plan is to leapfrog American technology and dominate the EV industry. Having manufactured electric bikes for close to twenty years, they own this sector outright. There are only a handful of companies outside of China (notably Bionx in Canada) manufacturing electric motors for e-bikes. China is also the leader in Lithium Battery production, which power all electric vehicles.

In the coming years, American companies will have to invest huge sums of money to catch up. GM has already invested heavily in the Chevy Volt and other manufacturers will have to follow suit. In the electric bike sector there is new interest in complete e-bikes as well as hub motor conversion kits to retrofit existing bikes. Smaller companies are starting to invest engineering time and funds to develop improved products better suited to the American market. One example is Hightekbikes, an electric bike company who is currently looking for investors to setup a motor design and manufacturing facility in California.

As the market heats up and competition increases, there will be situations where a company takes shortcuts, such as taking a competitors product, have it copied in China, then import and sell it at a discount. They save time and money on development by piggy-backing on another companies investment. Don’t think it would happen? It already has. In this case an American company worked with a Chinese factory to produce an improved motor, investing tens of thousands of dollars. When they released the final revision and it was selling well, another American company went direct to the factory and began importing the same motor kit. Evidently, the concept of Intellectual Property is not well known in China and exclusive contracts may not be honored. Hightekbikes has been fortunate to have good relations with all our partners and vendors. Other companies might not have been as lucky. There will be more conflicts and lawsuits over intellectual property in the future as countries, particularly the U.S. and Chna, battle to dominate the Green Technology industry.

Sites with additional information on IP:
http://en.wikipedia.org/wiki/Intellectual_property_in_the_People’s_Republic_of_China
http://advice.cio.com/intellectual_property_chinas_three_realities
http://www.bnet.com/article/protecting-your-intellectual-property-in-china/204803
http://www.mckinseyquarterly.com/Protecting_intellectual_property_in_China_1643
http://news.wustl.edu/news/Pages/5691.aspx

 

New Direct Drive Motor Released

Hightekbikes has recently released our new Power Cruiser series of Direct Drive Motors. These e-bike kits come in front and rear versions and are disc brake compatible. Direct drive motors are optimized for high speed and high power applications. Designed in the USA, these motors are absolutely the finest quality on the market. They have been copied, but not duplicated. For the ultimate performance and latest design, the Power Cruiser Model 10H stands head and shoulders above the competition.  This hub motor conversion kit includes a high power 22A controller, advanced throttle, brakes with cutoff switch, and power switch that mounts to the handlebars. Typically, direct drive motors can be “over-volted” and this model is no exception.  The controller is 48V compatible and the motor can be run up to 72V with an optional controller. Running at a higher voltage gives you more speed. On a 26″ wheel, the speed will be 20-22mph when powered by a 36V lithium pack.  At 48V, that increases to about 24-26 mph.  With the larger 700C wheel, the speed increases another 2-3mph.  Note that the legal limit in the USA is 20mph without getting a moped license so please consult your local regulations.

 

Lithium Battery Pack Break-In

It’s not widely known that lithium battery packs, especially LiFePO4, have to go through a break-in period. The pack is made up of several cells connected in series, for example a 36V LiFePO4 pack  has 12 cells. When new, the cells do not charge up and discharge at the same rate. One reason may be a chemical inhibitor that is added to slow down self-discharge. At any rate, there is some chemical process going on with new cells that cause them to perform differently when new.  Often the first thing a customer will do when buying a pack is to go out and hammer on it, checking the power and range. Unfortunately that is the worse thing you can do. It is recommended to do 5 to 10 cycles of low discharges followed by charging, preferably over night. A low discharge would be drawing 1-3 AH or riding 1-3 miles, without heavy loads. 

Since the cells will discharge at different rates, the first cell to reach the minimum voltage will trigger the detection circuit in the BMS, which shuts off power. The range will be low and the customer thinks they have a bad pack. By doing short cycles the cells have a chance to equalize and not get far out of balance. The BMS has a balancing circuit but it does not have the ability to bring up a cell that is alot lower than the others. They have to be kept within a certain range of each other. Leaving the battery pack on the charger over night gives the BMS time to equalize the cells. You may see the charge LED on the charger blink on and off during this process.

Once properly broken in, a lithium battery pack will stay in balance if charged after each use and not left for long periods without charging. Ideally the supplier would perform the break-in process before shipping the pack out. That’s currently not posible due to the time involved and equipment required, at best they can do a short cycle. So for now it’s up to the customer to take the time to do it and resist the temptation to “see what the pack can do” when they first get it. So to summarize:  for the first 5-10 times you use a new LiFePO4 battery pack, ride the bike only 1-2 miles followed by extended charging.

 

Geared or Direct Drive Hub Motors?

There are two basic types of motors in wide use today for electric bikes, direct drive and geared. The direct drive has no internal gears or other moving parts except the actual case which rotates around the axle on sealed bearings. The coils are wound around an assembly that is fastened to the axle and remains stationary. The outer ring of the case has a ring of magnets that rotate in close proximity to the electromoagnets formed by the coils. As the coils are energized in a specific pattern by the motor controller, the magnets are attracted and repelled causing the wheel to rotate. The outer case directly drives the wheel of the bike. The geared motor has the same basic configuration, but does not directly drive the case. Instead, there is an intermediate gear assembly driven by the motor. This consists of a freewheel and three planetary gears which transfer the rotation to the outer case and wheel.

Geared motors are smaller and lighter. Due to the gear ratio (typically 4:1), they have good torque, even at low speeds. The gears make a little noise but usually not very noticable. Due to their small size and the physical strength of the gear assembly, there is a limit on the maximum power that they can handle. The internal freewheel isolates the wheel from the motor so there is no resistance when turning the wheel. This prevents the motors from becoming a generator, so can not be used for regen.

Direct drive motors are bigger and heavier but can take more power. Their larger size, bigger magnets and coils, allows them to dissapate more heat. They are totally silent. There are less parts to go bad as they do not have the internal gear assembly. Depending on the motor, there may be some drag due to the magnetic attraction. DD motors turn into generators when rotated so they can be used in regeneration (regen) applications.

Which should you choose?

For riders who want assist but still want a light bike with the least amount of change in how it rides, the geared motor is best. It can get you up most hills with the right power level, but has an upper limit.

For high speed cruising over low to moderate hills, the direct drive works well. It can go faster than the geared motors and can take lots of power. If you can live with a heavier bike, you can load up with batteries and carry a heavy load very far and very fast. If you want regen, you have to use the DD motor.

 

Cold Weather and Battery Capacity

Winter is here and you may have noticed a decrease in your range.  That’s because a battery’s capacity is directly related to ambient temperature.  At freezing temps, the capacity of a lead acid battery (SLA) can decrease up to 60%.  Lithium packs are also affected to a lessor degree, maybe 30-40%.  The recommended charge current also changes.  The best thing you can do is keep the pack as close to room temp as possible.  Don’t leave it outside and keep it insulated when in use.

 

New High Power Motor from Aotema

We have just released a new 1000 watt motor. There are front and rear versions and it is disc brake compatible. The front version fits normal forks, the rear model fits a larger 155mm spacing between dropouts.

We also have a limited supply of ebikes using this motor in stock. The setup uses the rear motor in a full suspension mountain bike frame. A 36V10AH lithium battery in an aluminum case, slides onto the rear rack. Price is $1500.

 

Welcome to my blog!

Greetings, this is Terry Reilly, owner of Hightekbikes.   I’m starting this blog to better communicate with our customers and the public in general.   I’ll be posting the latest information on the electric bike industry and on our products in particular.