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Thread: 2009 sepex GPR-S Owner's Review

              
   
   
  1. #1
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    2009 sepex GPR-S Owner's Review

    The motorcycle that I purchased and have now ridden for 1200 miles, has a large electric motor, rated at 36/48 volts, which (I believe) is sometimes used in golf carts. The motor is a “sepex” type and weighs 58 pounds. It is rated as having a peak of 29 HP, but in practice the batteries can not supply sufficient electrical power to actually generate more than about 6 HP at the rear wheel. Sepex motors are described by EMS as being almost identical to traditional series motors except for the way their field is wired and controlled. Unlike a series-wound motor, whose armature and field windings are wired together in series, the sepex motor’s field and armature windings are excited separately by special sepex controllers that have wire leads to both the armature and the field. Separate control of the armature and field creates distinct advantages over a standard series wound motor, notably adjustable regenerative braking, higher rpm, longer power band, higher efficiency, and easy reversing. All of which sounded good (and new and different) and seemed to be worth a $1200 premium over their standard model, which uses an Etek-type motor and a 72 V/ 40 Ah system, consisting of 24 Thundersky batteries.

    The primary interesting feature of the motorcycle is that when activating the brakes, which were relocated to the handlebars like a motor scooter, the electric motor turns into a generator and pushes electricity back into the batteries, extending the range slightly – to say nothing of reducing brake wear. Just a light touch on either brake lever activates the regenerative feature, which feels like closing the throttle on an internal combustion engine and slowing down under compression. The large size of the motor required cutting a hole in the right side of the fairing to allow the end of the motor to stick out in front of the right foot peg. It all seemed like it would provide an increase in performance and range. And it would have, except that the batteries that were installed in the motorcycle were not the latest “Thunder Sky” batteries, but a set of “Hi Power” batteries that had obviously been sitting around for some time, as the tops of the batteries were pretty dirty and EMS does not currently offer them for sale. These were the same type of 50 amp hour rated batteries that were used on my 2008 bike. (The new “Thunder Sky” batteries have a 50% greater discharge rate, according to their specifications.) As it turned out, the motorcycle, with its sepex motor and 24, 50 Ah “Hi Power” batteries, did not deliver as much of a performance upgrade as I had expected. However, since the batteries still have 3.6 kilowatt-hours (KWH) of storage capacity, it qualified for a 10% rebate from the Federal Government on my income tax return. Any DOT approved electric motorcycle that has a storage capacity of 2.5 KWH or greater qualifies for this rebate. Some states also provide additional rebates or credits toward the purchase price of a “plug-in” electric vehicle.

    Top speed is only about 60 mph, with adequate acceleration from a stop, but not as much pulling power between 30 and 60 mph as had my previous bike. It appears that is because the power to the motor is limited to 7.5 KW (180 amps) peak, and only 6 KW during continuous riding. This is due to either the programming of the Sevcon motor controller, or the inability of the batteries to deliver any more power. When under a load, the voltage of the batteries sag from 76 volts down to 51 volts, at which time the controller cuts the power draw so that the voltage of the batteries will not drop below this value. If they were to do so, it could damage the battery pack. The net result is that it is sort of like having a big V8 engine in your car, fueled with a very small carburetor. Not a good performance combination, but one that is likely to be very under-stressed and reliable. Plus, the motorcycle can be easily upgraded with better batteries in the future (at a substantial cost, of course), with likely a noticeable improvement in performance. Right now the maximum range is 40 miles at a steady 30 mph and about 30 miles in stop-and-go, mostly full-throttle riding, including some up and down hills and riding at top speed on expressways. According to the Cycle Analyst, power usage varies between 70 and 90 watts per mile, depending upon how long full throttle was used.

    Unfortunately, the bike has a drive-ability problem that would be familiar to some BMW riders. It surges under most riding conditions and feels like a 2000-era R1100 model riding around town. You feel constant power pulses at a steady speed and while going up hills. When the bike was new and you would ride over 50 mph for more than a couple of minutes, the power would be cut off without warning until the throttle could be closed and reopened again. This was apparently due to the batteries inability to provide high current for more than a few minutes. After several hundred miles of use, this problem disappeared.

    Charging the batteries takes noticeably longer than it did on my 2008 GPR-S. This is due to the increased energy capacity of the batteries, 3600 KWH vs. the 3000 KWH of the previous vehicle and higher voltage and corresponding lower amperage output of the 6 amp charger, compared with the 8 amp charger that was used in the 2008 version. In any case, it now takes about 8 hours to bulk charge the batteries, at which point the “battery management system”, reduces the charging current and starts cycling the charger off and on for several more hours, until the batteries are fully topped-off. When fully charged, the system will indicate 84 volts (which drops quickly to 76 volts when riding, or after sitting around for a few hours) on the vehicle’s Cycle Analyst computer screen.

    Upon fully charging the batteries from their 40 Ah depleted state, the charger consumes 4.4 KWH of power, according to a “Killawatt” meter. At my current electric power rate of 11.9 cents per kilowatt hour (KWH), the cost of charging the batteries is about 52 cents. I rode 30 miles at the time and this equates to about 1.7 cents per mile for “fuel”. Not too bad, as long as you can accept the restricted range and performance. The other advantage is the lack of motor maintenance and minimal chassis maintenance and its associated cost. Working around the chassis, even without a service manual for a home mechanic, is easy as it is a very basic design.

    Is it worth the money? I would have to say no. But the Electric Motorsport Sepex GPR-S motorcycle is an interesting development that would appeal to hobbyists and electrical engineers, as it is easy to work on and to modify and upgrade (assuming that you know what you are doing). Anyone who wants to just own and ride an electric motorcycle in 2010 would be well advised to look into the Brammo Enertia, as sold by Best Buy or the more expensive Zero S. The cost of the Brammo is $8000, the vehicle is much more refined and if you have a problem, the Geek Squad will come to your house and take care of it for you. The Zero S has better performance than either the GPR-S or the Enertia, but costs over $10,000 and it does not yet have a “track record”.

    I might add that I now have a more complete understanding of the phrase “early adopter” and a much greater appreciation of the value of the established internal combustion motorcycle manufacturers and the resources that they provide to an owner of their vehicles, such as providing a parts supply system, trained mechanics and good customer service – none of which you get with the Electric Motorsport (now Native) GPR-S, unless you have a nearby retail dealer.

    Frankly, I can hardly wait for the Brammo Empulse to arrive next year. I have a 10.0 version on order and when it arrives; my daughter will get my current GPR-S.

  2. #2
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    Here are photos of my 2009 sepex Electric Motorsport GPR-S:
    Attached Images Attached Images

  3. #3
    electrician
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    Good report. Do you think that the AC motor, and 60 ah batteries would help the range and power problems with the GPR-S? Or do you think that is just putting lipstick on a pig?

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    I think the real problem is the Hi Power batteries. I believe that one or more of the batteries in my bike are defective and not holding up their part of the power task, based upon the severe voltage sag observed. Then too, Hi Power batteries are not noted for their high quality. I believe that 60 Ah Thundersky, or similar quality batteries, would likely solve the performance problem. No doubt an AC motor would also be an improvement, but at a much higher cost than the D&D motor.

    Although the bike is not quite as fast and does not have as much pulling power as did the 60V Etek-RT 2008 GPR-S, it does have decent range because of the relatively low power draw. The 2008 bike would draw 11.5 kWh max, while the 2009 bike shows a maximum draw of only 7.5 kWh. Less power output seems to provide a longer range, which makes sense to me. This is actually an advantage when just using the motorcycle for transportation and daily chores.

    Since I have ordered a Brammo Empulse, I plan to coast around with the D&D GPR-S until the new bike arrives. In the meantime, I can live with the reduced performance, which is satisfactory for my local rides within my city and to the three adjacent towns. If I had any really EV skills (which I don't), I would remove the batteries and check them. But doing so would void the "warranty", plus I would likely screw something up and just make matters worse. In the meantime, I am really looking forward to the Empulse.

  5. #5
    electrician
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    I went to the EMS in Oakland and liked like the ride and feel of the GPR-S. The people their were friendly and seem to know their stuff. The Empluse seems like a better bike as far as range and power, but I really do not like the seat height and handlebars. If EMS can get the same performance out of the GPR-S then for sure I will go with them, if not I will have to go with the Empluse.

  6. #6
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    I do like riding the GPR-S because of its small size, light weight and low seat. However, I don't think the small chassis has enough room to pack in enough batteries to keep up with the Empulse - but you never know. Maybe EMS knows something that I don't.

  7. #7
    Senior Member markcycle's Avatar
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    Quote Originally Posted by Richard230 View Post
    I do like riding the GPR-S because of its small size, light weight and low seat. However, I don't think the small chassis has enough room to pack in enough batteries to keep up with the Empulse - but you never know. Maybe EMS knows something that I don't.
    I have three GPR-S rollers in my shop and with the MHM-602 In wheel motor, soon to be set up with the new (not yet released) two speed winding, I plan on having a very competitive bike next year that will hold as much or more battery than the Empluse. How that's going to play out in terms of manufacturing, I don't know yet but I'll be showing technology that will give Bramo serious competition in terms of technology.

    I also hope to be showing next year a chain drive BLDC outrunner motor capable of 20KW continuous and 60KW peak running in a GPR-S. This will be a monster of a motor will be mounted at the swingarm pivot. All this work is being funded by EnerTrac directly no venture capital no government hand outs just dam hard work. Currently none of this work is affiliated with any other company.

    I must say Brammo has motivated EnerTrac (me) to bring technology to the forefront that I thought would take two years. My goal is show bikes that can take huge amounts of batteries and perform as well or better than anything out there.

    With EnerTracs limited capital its hard to know how it will all play out. Next year will be interesting, I doubt Zero is sitting around doing nothing.
    Last edited by markcycle; 02 September 2010 at 1056.
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  8. #8
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    You have to admit that there is some serious EV progress going on right now. The technology is apparently moving along much faster than I would have expected. The odd thing is that it seems to be coming from small start-up companies, while the big billion-dollar guys (such as Honda) seem to be just sitting on their hands. I find that quite disappointing. And if the major car manufacturers are doing anything (other than Nissan and Chevy), they are keeping it real quiet. I would have thought that the big European car companies, such as VW, Fiat, BMW, Porsche, etc. would have jumped on the EV bandwagon - if for no other reason that to get some of those good Euro "green" political brownie points. I wonder what is going on?

  9. #9
    Senior Member harlan's Avatar
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    I have my own personal GPR-S setup with 6kWh of lithium batteries (75V 80Ah), the same size as the base model Empulse. This gets me quite decent range and more power than my 15hp Etek-R can handle. As soon as I get the opportunity I'm going to throw in an Agni motor which should probably net me about twice the power. As is, I can already reach speeds up to 75mph which is plenty fast. Its very capable on the highway and is my primary transportation.

  10. #10
    electrician
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    Agni motor sounds nice, I heard that they are top of the line. But wouldn't an AC motor be better? I don't know, I have always heard that AC is the best motor.

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