Electric bike with a small 25-35cc generator?

bakaneko

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Hi. I sold my HS-142F and will sell my motorcycle as soon as possible. I have a 36V 500W ebike and really like the torque and how quiet it is. The top speed is around 22-23 mph before the limiter kicks in and stops the motor. I found a good deal on batteries and will buy in small bulk enough to run the bike at 18-20 mph for 50 miles on one charge. However, 20 mph is pretty damn slow. So... I want to make a powerful ebike hybrid. Initially, I wanted to do a HS-142F reverse gearbox to test this for everyone but after thinking I don't want to deal with a big motor sounds.

So, as of now I am thinking a 48V 1500W fat tire ebike that will have a top speed of about 45 mph for me (light, light rider and in a tuck) and enough batteries for 50 mile range at 30 mph. But, I hate the ideal of just running out of juice so I was thinking about adding a generator. But not the big 1000W DC-AC generators out there but rather a small 25cc motor (should be quiet) into a 200W brushed motor to charge the batteries incase I am running low on juice on a ride. Can this be done? The 25cc motor will turn the brushed 200W motor and that will create a current and with a boost controller I can use that to charge my batteries? Any thoughts. Take a look at my picture below for what I am thinking. This is all preliminary and atm I am just building the 36V ebike battery bank but can transfer that to the new bike.

Also, I like a fat tire bike because I tried to do an aggressive lean on my 2" mountain bike tires and low side causing a sprained wrist for 2 months... :cry:
 

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wheelbender6

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We have discussed your idea a few times on the forum using a 99cc generator from harbor freight. The 99cc gen is heavy and you will still need an inverter to charge batteries.
Easier to add a small friction drive engine to the rear to drive the wheel when the batteries deplete.
 

bakaneko

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We have discussed your idea a few times on the forum using a 99cc generator from harbor freight. The 99cc gen is heavy and you will still need an inverter to charge batteries.
Easier to add a small friction drive engine to the rear to drive the wheel when the batteries deplete.
Yeah, the retail generators even the small ones (750-1000W) are too big to put on bicycle maybe a tricycle and are AC which means you waste like so much space and energy if you plug your AC charger (100W charger wasting 650-900W). I am talking about a simple 25cc motor turning a small 150-200W electric motor and then feeding that current into a bulk converter with a charge regulator into the battery/bike system. This should be all that is needed for a 36V-48V battery to charge at a safe 3-4A. I've seen on YT videos of a gas generator on back of bikes but they use the retail AC ones again being too large and wasting energy in the charger limitations.
 

Will'smotobikes19

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I thought they discontinued the predator 99cc years ago? don't see much use in using an engine onboard to charge an electric motor, double the weight. A gx25 drive setup would probably be just as good. There was a video of a guy using a 25cc weedeater engine for electricity on youtube but you'd have to mount it on a rack or something. better would be a hybrid bike that can use both a small engine and an electric motor. Electric for town/city and engine for commuting. Hub motor in front and a gx25/gx35 with a belt drive setup would be sweet.
 

bakaneko

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I considered that but I kinda just want one drive train to simplify the system and reduce drag. Electric also utilizes energy most efficiently. So, I think when I convert gas to electric and using that energy either as storage or sent directly to the electric hub motor is more efficient than simply running a belt/chain drive from the gas motor. This is done in real life with modern cruise ships where diesel engines generate electricity for electric propeller motors rather than drive the historical shaft propeller systems. I stopped by Menards/Home Depot and looked at some of the 25cc yard work engines. Damn, they are tiny. It would fit on the rear rack on a bike easily.

Also, I am going to have like a huge battery bank capable of about 50 miles at 30 mph or something like 2-2.5kwH. So, the gas generator is only a back up or incase I am at like 20% capacity I will turn it on. I really want to do this on a fat tire bike but those wheels have such high rolling resistance...
 

darwin

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Yea he's talking a hybrid vehicle like a prius or a volt. Look at the engineering that went into building those. We're talking simple bicycles here folks, cheap, simple and functional should be our motto. Won't happen with a hybrid. On just the electric side though the batt tech is now where you can go 100mi on a charge and the price point is fairly reasonable. The bike I'm getting has a 19.5 ah battery and has all the charge I'll ever need. I'll wear out before the battery does. That's why I'm finally going electric.
 

bakaneko

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The bike I'm getting has a 19.5 ah battery and has all the charge I'll ever need. I'll wear out before the battery does. That's why I'm finally going electric.
What bike are you getting? Your battery will be 800 wH? Right now on my 36V 500W ebike, I can get like 1.75-2 mile per aH riding pretty hard. I am getting some cheap batteries to go from 16 ah to 32 ah. If those work out, I might get like 8 more ah to be around 40-45 ah. Yeah, I like electric atm I can listen to my music without having to blast the volume and go deaf to drown out the gas motor.
 

bakaneko

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There was a video of a guy using a 25cc weedeater engine for electricity on youtube but you'd have to mount it on a rack or something.
Good old YouTube. I see it has been done quite a bit by the number of videos. It is right around the ball park of the power I want to produce too about 100-200W. Though one video has it producing 60W and another 100W. This seems pretty crap for a 25cc motor that should be just under 1 HP. I wonder if they are not opening up the motor or something... 100W is okay but ideally you want 200W atleast with medium throttle.
 

bakaneko

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I've seen reviews of that bike and company. Sweet bike; no "modern" marketing nonsense, quality parts, fair price, and good customer service. Red is a nice color too.

Okay, this is just me thinking out loud. But, you guys are right that weedwacker 25cc generator produces around 100W, which for a 25cc motor seems very inefficient to me. And, 100W is nothing into a 1500-3000W bike. Also, I am using 36V packs with a built in BMS; I dont want to disassemble them to make a 48V battery and then have to get a new BMS. So, its either stick with the 36V battery configuration into a boost converter to work with 48V systems or wire the packs in series to make 72V battery. The boost converter have amp limits up 1500W so I wont be able to fully utilize a 1500W rear hub. If I go with a 72V configuration, I can get the SBP 3000W electric shift kit and have no limits on the power other than the amp limits from the battery BMS. But, in any case, if I stick with a fat tire bike and want a gas engine backup, I don't see any friction kits for fat tire bikes...

Nothing concrete yet, I am still building up my 36V mountain bike into a 50 mile range ebike at 20 mph at the moment. Just thinking about my FINAL bike (30-40mph cruise, 50 mile range, gas back up). :cool:
 
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