[Video] R Martin A100 Electric Bike Review

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Preface


If you live outside the city, petroleum powered vehicles are the transportation mode of choice. But there are a litany of secondary costs associated with cars and trucks; gas, parking, and environmental degradation to name a few. I drive a 1988 Nissan 300zx that I love to death, but its efficiency is starting to wane in its old age. To make matters worse, the roads in southern Kentucky leave quite a bit to be desired, and not so long ago I had to take my car to a mechanic to have parts of its wiring harness re-connected from all the jostling and bumping. All this just to drive to and from campus where finding a parking spot is a dubious affair every morning. So I decided to go green, so to speak, and save myself some in the process.

I decided to invest in an electric bicycle. A road bike would have been nearly as effective given my distance from campus, but wouldn’t have been nearly as fun. When I set out to research electric bicycles, I found that there are quite a few models on the market ranging from $500 to $8000. Bikes above the $1500 mark looked very attractive, but it wasn’t until the $3000 mark that I could find significant improvements on speed, range, and integration with the frame. Another interesting finding was that all of the bikes under the $1500 mark shared very similar components; a chinese brushless hub motor and some off the shelf throttles and very questionable throttle control boxes. Where these bikes diverged was in battery technology, but I’ll get into that later. Conversion kits are available, but at around $260 with $60 shipping, the cost savings were negligible considering I didn’t have an appropriate bike to convert and batteries were, naturally, not included.

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The most important part of an electric vehicle of any kind is the battery that it employs. I found that inexpensive electric bikes sold through Amazon, Target, and Walmart all included lead-acid batteries. This was absolutely unacceptable for me; lead acid batteries are extremely heavy and have a low power density. Those two attributes have negative feedback on each other; the increased weight only exacerbates the low power density. I needed to find a bike with a lithium chemistry battery, which itself posed a problem. Lithium batteries of sufficient size to drive a bicycle are very expensive; a replacement costs over $300. I looked into building a battery myself, but complex lithium battery charge controllers were both difficult to find and prohibitively expensive. To make matters worse, pre-assembled bikes that did include lithium batteries often compromised aspects of the bike frame to accommodate the large battery pack.

Despite all these pitfalls, I was able to find the perfect electric bicycle. I found the R Martin A100 for sale on the rmartinltd.com website for only $599. It was to come partially assembled with a large 36v 10Ah lithium battery, 350 watt motor, all the control accoutrements, and used a standard mountain bike frame. I was excited by the sheer value of this kit, but was slightly put off by the AS-IS disclaimer in the description. I investigated this little impediment by calling customer support at 6:00 in the afternoon, well after business hours. I was greeted by a friendly American sales representative (sorry internation service reps, you’re just difficult for me to communicate with) who was very knowledgeable about the technical aspects of the bikes. I first asked him about the AS-IS moniker, and he explained to me that these bikes were the previous year’s model that had arrived late from China. He was upfront with me about the Chinese electrical components, but assured me that the actual bicycle was chosen and customized by R Martin themselves. He indicated that despite the fact that the bikes were being sold AS-IS, customers could rest assured that the bike would arrive working, it was just that servicing a discontinued model would be cost prohibitive for R Martin, which is a relatively small business. I even delved a little deeper, stating first that I would almost certainly be modding the bike once I received it. He told me the voltages and amperages of the charger itself, the battery, and the connector style used for charging. For a sales representative, I was very impressed by his technical knowledge.

I decided to take the plunge, and ordered right then and there, which leads us to the actual review.

The Complete Package


The R Martin’s technical specifications are as follows:

  • 36v 10Ah lithium polymer battery
  • 350 watt throttle controller
  • 7 speed Shimano gear shifter
  • Aluminum alloy frame and wheels
  • Hybrid tires
  • A 350 watt motor that, supposedly, works up to 700 watts
  • Front and rear lights


I was originally going to include the assembly instructions in my video review (below) but the bike needed so little assembly that I decided not to even bother. An enormous UPS box arrived at my door, and after opening I found that all I had to do was attach the front tire, handle bars, and bike seat. Even the wiring was pre-installed, indicating some very interesting (and effective) packing techniques from the people at R Martin.

After getting everything put together, I called my hipster friends over to help me adjust the bike. This is where my first criticism resides. Any pre-assembled bike you purchased will need some adjustment, but everything was loose on the A100. The brakes were installed completely haphazardly, rubbing profusely on the tires. This complaint is mitigated by the fact that R Martin includes high quality brakes. In fact, all of the mechanical bicycle parts followed this pattern of high quality components with questionable workshop installation. For the duration of the review you will likely notice that I am glowingly happy with the bike itself but, worry not, I have plenty of criticism for the electric components and some of the operational nuances.

Most mechanical elements of the bike hid pleasantly surprising features and considerations. The front fork includes shock absorbers with the ability to adjust stiffness. This is actually very important when riding on streets because shock absorbers that are very soft will waste a large portion of the energy the rider exerts.


What is generally known as "the handle bars", or rather the actual handlebars, neck, and stem were all made of real aluminum alloy, rather than the cheap, soft aluminum alloy with high iron content that cheap bikes are typically made of, and this is true of the entire frame as well. The stem is adjustable via aluminum rings, which is another feature that inexpensive store bikes typically forgo. Disappointingly, a bolt was missing from the neck of the handle bars, which you can see in the picture (and video) below.

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I was pleasantly surprised to find that the tubes comprising the frame are slightly ovoid in shape along the lower and rear portions. This non-circular shape gives the frame strength along the center axis, which is important for keeping the bike frame from twisting when the motor is outputting some serious torque. Of note, the frame includes holes with rubber grommets for the wiring to run through, streamlining the appearance of the bike significantly.

The entire pedal and front crank assembly is made of steel and high strength aluminum, which is nice compared to off-the-self store bikes. The chain itself needed to be shortened by a single link, which is not uncommon but can be frustrating or impossible without the correct tools. The Shimano shifter and gearset are of good quality and were correctly configured out of the box.

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The tires are hybrid, which is to say they lie somewhere between large mountain bike tires and small street tires. This is ideal, because as tired width increases, the amount of energy required to push them increases. However, the actual quality of the rubber tire itself leaves much to be desired. I will almost certainly have to replace them. Despite this, the aluminum wheels are decent.

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We finally arrive at the electric portions of the A100. I will first say that it is all low-rent chinese material, but that doesn’t mean it performs poorly or that it will fail over time, it simply means that lots of corners were cut here and there during manufacturing. Some of these cost saving measures have a big impact and some do not. This is where I was most apprehensive before receiving the bike, so I will try to cover every detail for those of you who might decide to give electric a try.

Starting with the electric motor itself, it is a 36v 350 watt brushless motor. The motor weighs a good bit, pointing towards a healthy portion of copper coiling and magnets. On the A100 product page it states that the motor is capable of handling 700 watts, which I am inclined to believe. However, the motor is engraved with a 350 watt rating right on the center surface giving me some doubt about this 700 watt maximum, but I have some intuitions about why R Martin decided to mention it. Having spent several hours researching these chinese bicycle kits, I found that the difference between the 350 watt kits and the 700-1000 watt kits was almost always the throttle controller itself, and not the motor. 48v kits do seem to have beefier motors. While I do not have hard evidence to back this theory up, if you peruse ebay you will see what I mean. Because of this, and after thoroughly inspecting the internals of the control box, I do genuinely believe that the bottleneck in the system does not reside within the motor itself.

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Speaking of the wimpy throttle controller, you can’t even see it in the pictures. In the video review below you can see that the control box is actually hidden in the battery receptacle. This does add to the appearance of the bike, but it also hides how incredibly weak the box itself is. I opened the control box up to look at the circuitry inside and was mightily disappointed. I regret not taking a picture, but there were only six small, poorly soldered mosfets in charge of voltage regulation. If you don’t already know, this voltage regulating circuitry dictates the amount of electricity flowing to the motor entirely, so speed and torque are dictated by this flimsy component. On the bright side, these controllers are very standardized, and a higher wattage controller could easily be swapped out.

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I want to spend a moment on the battery itself. It weighs only 10 pounds, which isn’t light per-say, but it definitely beats the lead acid equivalent. The battery resides inside an aluminum enclosure that slides into a receptacle inside the battery cage and has a red LED light in the back for safety.

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At the end of the review I’ve included a video about how I’ve modified the bike, and therein you can see the actual lithium battery freed from its aluminum enclosure. I learned some interesting things about large lithium batteries from this endeavor, first and foremost that you DO NOT mess around with these high voltage, high amperage batteries without knowing what you’re doing. This battery literally detonated my multi-meter even when using the 10amp circuit. When modifying the battery I was very lucky not to have shocked or burned myself badly in the process, but I was also wearing protective rubber gloves for most of the process. I did short the battery on a couple of occasions and, let me tell you, if you’ve seen how much a nice new car battery sparks when you connect the terminals, you have no idea how violently a battery can spark until you’ve messed with one of these. My soldering assistant was clipped to the insulation of the positive battery terminal at one point, and after shifting my weight slightly I managed to nudge the outside barrel of the charging port against the metal foot of the soldering assistant and the spark was so violent that it shot nearby screws in every direction. I’m serious people, do not underestimate the power of these things.

The curious aspects of the battery I mentioned earlier were not immediately evident. For example, the A100 product page lists the battery as lithium polymer but neglects to mention exactly which chemistry the battery is. There are several lithium polymer chemistries available, most notably Lithium Iron Phosphate, or LiFePO4. LiFePO4 has some definite advantages over the competition, like a greatly reduced risk of explosion, a longer lifespan (in terms of charge cycles and age), and higher amperage output. Despite this, LiFePO4 batteries are around 14% less energy dense, or 14% heavier depending on how you look at it. I would certainly trade a 14% margin on energy for the greatly reduced risk of an explosion right between my legs. LiFePO4 batteries are also cheaper and more environmentally friendly than other lithium ion chemistries. Logically the battery is likely LiFePO4 simply because the closest analogue on the market are motorcycle lithium batteries which are almost exclusively LiFePO4, but really the biggest tell is that LiFePO4 is the cheapest to manufacture, period. Part of this cost saving advantage is due to LiFePO4’s flexibility when it comes to charging; higher density lithium batteries require very tight tolerances when it comes to charging and cell management (which necessitates a more costly controller), but LiFePO4 isn’t very picky. For example, the charger included with the A100 is 48v, not 36v, which only supports my theory that the battery is LiFePO4 based. In fact, the only thing that makes me doubt that the battery is LiFePO4 is the fact that there weren’t any cylindrical cells inside.

Otherwise, the remaining electronic parts are the on/off/pedal assist controller, the twist throttle, and the electronic brakes. The pedal assist controller has three option for low, medium, and high levels of pedal assistance, and the twist throttle actually has several levels of control. The brakes work as you would expect, but cut off power to the motor the moment you touch them.

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Operation


Using the bike for the first time was surprising! Despite the weak 350 watt controller, the bike has plenty of go to it. Pedal assistance is always on unless you activate the throttle, and engages the motor after about two and a half pedal rotations The difference between low, medium, and high settings are negligible on hilly terrain, but on flat, even streets setting the pedal assist to high yields a considerable speed boost. R Martin recommends not using the throttle for extended periods, but I found that the weakness of the throttle control box prevents both the motor and the control box itself from overheating. The 7 speed shifter works decently, but the mechanism is jerky and feels pretty bad.

I live in an area with remarkable hills, and I found that this bike helps me make it up them without having to work hard. That being said, this is not a scooter. You should really pedal most of the time for the best speed. In terms of range, I live three miles from campus and, despite the hills, riding between my house and campus barely puts a dent in the battery. To put it into perspective, after traveling to and from campus twice in a day, the battery charged up to 100% in less than 20 minutes after returning home. This from a battery that charges for 3-5 hours when fully depleted. I would say that as long as the rider is pedaling, the mileage should actually exceed the 30 mile rating that R Martin lists on the product page.

To sum things up, this was a great project. In the video review below, it’s clear that my friends and I had a great time putting everything together and testing out the A100. After using the bike for a few days, it was evident that the battery mount in the back isn’t ideal, but it is perfectly workable for a short commute. The bike can get to scary speeds when set to "High" and the rider is pedaling at the highest gear ratio. I hope this inspires some people to leave their cars at home once in a while, and if you’ve got any questions please be sure to leave them in the comments!

Good:

  • Nice bicycle components
  • Quick charging
  • 25+ mph with nominal pedaling
  • Modular, lithium battery
  • 30+ mile range

Bad:

  • Jerky shift mechanism
  • Low quality battery cage
  • Top and rear heavy
  • Questionable throttle control box

Video Review + Mod:

Note: I don't want to sound too self-deprecating, but I have noticed the frequency with which I use the sounds "uh" and "um" when I'm on camera. Believe me, I'm working 'round the clock to address the... issues... with my speech. I got an A in my professional speaking class, but then everything is easier with a script, right?

Note 2: I mention in the beginning of the review that the motor is rated to 750 watts, but it is actually 700w.

We had a great time, see for yourself!

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Thanks! My next post will be a comparison between the HTC Nexus One on ICS and the HTC Mozart (WP7.5) and how they perform considering they have identical hardware!