Legal implicatons of riding dual drive gas electric motorized bike

[Steve Best]

So I guess that "3 x 12v 8ah 'non-leaded' batteries" helps break the OP's $600 budget.

Ouch, I missed that point. 8ah Li batteries are about $130 each locally and down to $25 each on-line.
Gas motor including tank = 20 lbs $120-$220
3 x 12v 8ah batteries = 8 lbs $75-$400
250w geared hub motor = 6 lbs $140-$220
Controller and all wiring = 1 lb $price included in hubmotor kit

So depending on your shopping ability balanced by a demand for name brand quality, we are talking between $335 and $840 with these quickie on-line estimates. I think it is do-able. I am running my 36v bike on $100 worth of Li batteries (about 3 lbs) and a $20 controller and have about 5 mile range.

Now the problems start when you don't know what you are doing, buy poor quality stuff, put it together wrong, burn it up, gotta buy all over again. Nothing like education to push the budget over the mark.

All that said, I really do believe a 50 lbs, 35mph hybrid cycle is possible for about $600.

 

[5-7HEAVEN]

Ouch, I missed that point. 8ah Li batteries are about $130 each locally and down to $25 each on-line.
Gas motor including tank = 20 lbs $120-$220
3 x 12v 8ah batteries = 8 lbs $75-$400
250w geared hub motor = 6 lbs $140-$220
Controller and all wiring = 1 lb $price included in hubmotor kit

So depending on your shopping ability balanced by a demand for name brand quality, we are talking between $335 and $840 with these quickie on-line estimates. I think it is do-able. I am running my 36v bike on $100 worth of Li batteries (about 3 lbs) and a $20 controller and have about 5 mile range.

Now the problems start when you don't know what you are doing, buy poor quality stuff, put it together wrong, burn it up, gotta buy all over again. Nothing like education to push the budget over the mark.

All that said, I really do believe a 50 lbs, 35mph hybrid cycle is possible for about $600.

How heavy would the bike be, before you motorize it?

 

[Wolfshoes]

As for being legal to ride, I suppose Whizzers first went into use and the law later adapted rather than outlaw them. Bikes having both electric and gas would create a similar legal decision one way or the other.

Electric contact clip assemblies can be purchased as a replacement part for Ryobi power tools fitting up to 4 Ah batteries for $1 each.

Three of them in series would create 52 volts @12 Ah total. The batteries are rated at 18V, but test out at a little lower than that. The lithium batteries are sold at Home Depot at $100 each, but I see a ebay vendor selling them at 2 for $100. Therefore making the batteries $150 total for the set, with the batteries available for other uses when not on the bike. The batteries would be charged off the bike with Ryobi equipment. When the batteries are low, they do not brown out and shut down instead.

In order to have a 20 mph electric speed, a typical 250 watt front hub would not be geared fast enough, so a 500 watt geared my be the most suitable. 500 watts / 52 volts = about 10 amps power needed. Does this mean the batteries would be good at this rate for about an hour with a 12 Ah supply? There may be an error making this over optimistic. Also as an assist with the gas motor running, the drain may be half of that. How many amps continuous the battery contact clips are good for without overheating is a concern.

The geared hub motor would go into free wheel over 20 mph with the gas engine providing the power.

Whether this practical even under the best of possible performance compared to simply having a larger gas motor is another question.

 

[Frankenstein]

Your math is wrong, 3 battery packs of equal amp hours in series triples only the voltage, the capacity remains the same. Paralleling 3 bats keeps the voltage but triples the amperage.

 

[Wolfshoes]

That makes more sense. Under electric drive full load, that would provide about 20 minutes of power. As a engine assist, perhaps it would be 40 minutes of power. A push as to whether or not is worth it.

 

[5-7HEAVEN]

Three 18v/4ah batteries wired in series = 54vdc/4ah.

Three 18v/4ah batteries wired in parallel = 18vdc/12ah.

Three 18v/4ah batteries wired in parallel, then wired in series with another set of three 18v/4ah batteries wired in parallel = 36vdc/12ah.

When wired in series with another set of three 18v/4ah batteries wired in parallel, you get 54vdc/12ah.

Orrr, three sets of (three 18v/4ah batteries wired in series) wired in parallel = 54vdc/12ah.

Sooo, there are two ways of wiring 9 batteries to equal 54vdc/12ah power.

 

[Frankenstein]

Three 18v/4ah batteries wired in series = 54vdc/4ah.

Three18v/4ah batteries wired in parallel = 18vdc/12ah.

Three 18v/4ah batteries wired in parallel with three 18v/4ah batteries = 18v/8ah.

When wired in parallel with another set of three 18v/4ah batteries, you get 54vdc/12ah.

Sooo, it takes 9 batteries in series/parallel to equal 54vdc/12ah power.

It shouldn't take that long to charge that many battery packs, seems like a good investment.

 

[Steve Best]

Hmmm, going light on battery and heavy on motor does not seem like a good idea.
I am riding 250w and 500w bikes and find that 250w can meet my (meager 12-15mph) needs.
The 500w (20mph) bike can drain the 12ah batteries in a hurry with heavy load.

I'd suggest keeping your electric top speed requirement lower than 20mph so as to aid hillclimbing.

Think about your purpose with a hybrid.
Electric is for easy starts in city, away from lights, on hills; and stealth in quiet parks and among people.
This does not require great speed.
Gas is for speed (30-35mph?) and distance (3 quarts gets me over 100miles).
So what do you really need out of electric?
I'd suggest 12-15mph and 5 miles unassisted are probably plenty. This is why I suggest 8ah/250w.

I really like KC's idea: "You only need enough electric power to get you going fast enough to start your gas engine"
Think about it, if you can ride 15mph you can probably start up the gas engine.

Now the only question is how to make a good charging system on the ol' China Girl...

 

[KCvale]

How much electricity would you need, and how much would it weigh and cost?

Beats me, my electrics were all center mount shifters, what is needed for this is a hub drive and a 'water bottle' LI battery that can be put on a rack, that leaves the center for the gas engine.

 

[Wolfshoes]

Newer Ryobi lithium batteries have a rated max discharge rate of 72 Wh (older ones were 48 Wh). According to my math (not my strong suit), 500 watt (hub motor @ 36 volts) / 72 watts @ 18 volts = 7 then x 2 to adj voltage = about 14 batteries minimum for full power. 14 batteries x 1.7 lbs each = about 24 lbs. Add in about 10 lbs for motor related =34 lbs. Not real practical due to the low amperage support from each battery.

This product seems to defy all the rules:

https://comingsoon-tech.com/urbanx-smart-electric-bike-wheel/

Apparently just now hitting the U.S. shores for sale after a kickstarter promotion, this hub motor uses a 36 volt battery that my guess weighs about 4 lbs, rated to propel the bike up to 20 mph, for up to 30 miles. Snap in, on the fly replacement batteries, low center of gravity and good weight distribution on the bike. The entire drive including batteries weighs 18 lbs. This drive is also considered to be strong for off road use. Make note of the flat rate $80 domestic shipping charge bringing the 350 watt version to about $520 with fork support hardware.

I seem to remember mention of a electric braking feature, and that would be a cool; but this may may not be on this model (V2). This product could be a candidate as a performance mod to a single speed gas powered bike. Someone buy one, report back and tell me if this thing is for real.