[bigwilly312]

Sorry if this has already been discussed. I have a dc motor generator that produces 12v at 150 rpm. I'm hoping to mate this to an Etek style brushed motor that produces 8hp at 48v. This would be in a small lightweight trike for personal transportation. I would set it up almost recumbent bike style except the pedals would turn the generator at about 8 to 1 or 10 to 1 ratio. That would send power to the motor which would then turn the rear wheel. My question is would this generator motor be capable of handling the load placed on it? Would a blocking diode make any difference on this load? If not, I am prepared to accept plan B. Which is to insert four 12v batteries and use the pedal powered generator to simply charge them as I go. I would use some sort of slider throttle on the batteries for speed control. Sorry I don't have all the tech specs but would this work? It's not free energy if I'm pedaling.

 

[bigwilly312]

Each turn of the pedals would turn the generator about 10 times. Depending on how I gear it. I could get as much as 40 to 1 but fear that pedalling would be much to difficult under any load. 60 pedals per minute is a standard leisurely amount I figure. That would be 600 rpms for the generator. That would add up to 48v at just a leisurely pedalling frequency. So the main question is the load capacity. It is a fairly high wind turbine motor that recommends a 75 amp blocking diode. The diode is supposed to prevent current from backing up into the generator. Would this prevent or at least decrease the load factor? Without the batteries, the speed of the pedalling would determine the speed of the tribe. That would make for a much simpler setup obviously. I've watched videos with this motor and 48v appears to give about 50 mph. Not bad for a leisurely cruise.

 

[bigwilly312]

You could be correct. I envision this as a good way to exercise while saving the planet as well. So, at the very least, this is very possible in some configuration. I needed to know that before taking the plunge into the wallet for this Etek motor and whatever else is needed. With an onboard pedal powered generator to charge the batteries, a person could think about using it in a 2 seater trike or maybe even a regular passenger car ev. Have you ever heard the expression "nobody rides for free"? You do your normal driving and your ride along companion does all the pedalling. You could greatly extend your driving range and maybe your wife will shed a few pounds in the process. Sounds like a win win to me I just hope my wife doesn't read this.

 

[bigwilly312]

Ya, my wife might shed a few pounds and your wife may not be happy
with you riding with my wife!
MikeK

Sorry MikeK. I didn't mean to imply that your wife needed to shed a few pounds. That's certainly how it read though. I meant our wives in general. I'm starting to think the parallel suggestion seems like the way to go. I appreciate everyones help but still no answer to the blocking diode factor. Just wandering. If it's job is to block power from draining back into the generator, would it not block the load? Or some of the load?

 

[bigwilly312]

A diode is a semiconductor device that only allows current to flow in one direction. There is a small voltage drop across the diode in the forward direction, between 0.2 and 0.7 volts depending on the type. The 75A rating is the amount of current that can pass through it safely, often this is a maximum rating that requires a suitable heatsink to achieve and it is usually better to stay away from the maximum for reliability. There will also be a reverse voltage rating which is the maximum reverse voltage that the diode can block. IE if the diode was on your generator the diode must block the maximum ripple voltage from the battery/motor system. So the diode will "block" a small portion of the power from the load if you want to look at it that way. There will be power disipated within the diode based on ohms law V=IR where v is voltage, I is current and R is resistance, P=IV is derived from ohms law where P is power, I again is current, and V again is voltage. The power lost/blocked/disipated in the diode can be calculated by the forward voltage drop of the diode times the current through the diode. So a diode with a 0.7 volt drop at 75amps will disipate 52.5watts, if the generator put out 48v as you had hoped the voltage to the battery would be 47.3v.

Sorry if it's a bit confusing and I jumped around too much it's been a long day I know how it works but I might not explain it clearly. Looking up diode in google or wikipedia might help you understand what it does and what it is used for. There are also many types of diodes with many applications and uses.

Well sir, you are the man! I wish my temperal lobes could make out with your cerebellum. I could possibly gain some much needed knowledge perhaps. Thanks to everyone for your help. I will now get on my knees again and pray for alien technology to fall in my lap.

 

[bigwilly312]

I just have two more questions. Is it possible at all to have the pedalling speed activate the batteries to then send power to the motor? Say I pedal up to a 12v to 15v range and then battery #1 is engaged and so on. I'm just trying to avoid using my hands for anything other than steering. I don't know maybe a floating throttle that's based off the voltage sent to the charger. Also all brushed motors just need voltage applied right? This Etek style motor sight keeps suggesting speed controllers.

 

[bigwilly312]

Check out this site. Just follow a similar lead and go for it. It works and maybe you can create something like it.

http://humancar.com/


Watch all the video on this cool concept car that actually works. Human powered electric drive vehicle. No large battery packs needed with this one.

That's what I'm talking about! Thanks for the info. To get past some energy hurdles might require us to do more than set there while talking on a cellphone and drinking a slurpy. Maybe the best untapped power source is us.