New from western PA - question regarding ultracapacitors for gas-hybrid


New Member
Mar 12, 2010
I'm putting together a bike with a hub motor and was interested in using a small inverter generator to eliminate the battery.

This was discussed at length in this thread, Gas powered electric- a measure of success,

From reading many threads here, the problem seems to have been well summarized on the thread linked above:

The idea behind hybrid gas/electrics is to drive the electrical system from batteries, which are being recharged by the generator. The battery has the capacity to provide the high amerage for takeoffs and hills. The generator just needs to provide enough amperage to maintain speed once attained, and recharge the battery with the power needed to get the bike up to speed.

Thus, the gas engine can be smaller than would otherwise be needed, as it can run in it's maximum efficiency RPM range. The battery stores the small excess power until it's needed. A regenerating controller can also convert some of the kinetic energy back into electrical energy when slowing down or going downhill and push it baqck into the battery, so that it's not all lost to heat.
I know of at least one industrial application using a small diesel generator and large ultracapacitors in a full size city trolly, without batteries.

Is there any way this could be scaled down to ebike gas hybrid applications, to use a small gas generator and ultracaps to replace a battery bank?


Active Member
Sep 18, 2009
Hi Brian, I just saw this after replying somewhat to the mentioned post.
Here is the problem-most small generators are quite heavy, the HF job is around 50# (one of my buddies gave me one that was defunct with a good engine- the engine itself is real heavy for a 2 stroke!) and you still need to convert that juice to your voltage of choice. The cheap generators are also very loud.
My solution was a harbor Freight (HF) 2.5 hp engine that is quiet and a torque monster compared to any 2 stroke, linked to a car alternator. The downside to this, is the engine and alt. weigh 30 #.
I am sure, you could do what you propose, but your biggest issue is obtaining a small generator and how much noise you are willing to tolerate. I heard the Honda generators are very quiet but they cost a grand. That is almost tripple what I have in 2 bikes.


If you use an 8 pound wind generator 24 volt 450, hey wait it is the same motor as the 8 pound 24 volt 450 watt scooter motor...,jack shaft that with the China girl, use 2 different controllers to same motor/generator one a wind/solar charge controller the other an ebike/scooter controller we would get what we are looking for only takes .5 horsepower to produce the 450 watts that's not that much off the middle and top rpm horsepower band right we also only put a 250 watt front hub motor so in electric mode it uses 700 watts the 'jackshafted' electric mode, then you flip the switch to recharge mode after ulyou fire up the engine all the components are out on the internet except a 'double clutched jackshaft' aka a shift kit that would allow us to freepedal, pedal with the generator/motor, and finally pedal with the generator, and ICE.