Gas electric hybrid questions.

Hey guys I'm finishing up some drawings on a gas electric hybrid bike I've been working on for awhile
and was just curious about a few things:

When I will be running the bike off of the gasoline engine, and since both motors will be interlinked by the chain drive,

A: will there be a lot of resistance from the electric motor if the entire electric drive system is turned off causing the gas engine to lose efficency? (its a 10kw bldc motor)

B: Running in petrol mode with the electric motor spinning will it generate enough electricity to be able to charge the batteries and is it as simple as hooking up a voltage regulator/ rectifier to the motor leads?

Thanks for any input!

-Tim T.

Not sure what you are building exactly?
Yes the electric motor will have drag/resistance when rotated without powering it. This can be solved by feeding it enough voltage at very low current to keep it spinning along with the ICE (Internal Combustion Engine).
When you use the electric motor as a generator with the ICE providing the propulsion and spinning the electric motor then it will cost (a lot) more fuel to feed the ICE.

The drag from the electric motor will depend on how well it's made. It won't be a lot, but it will be noticeable. Drag increases with RPM. Roughly a 10% loss from the drag at full speed.

To charge the battery, the motor has to be spinning fast enough to generate more voltage than the battery. This would be a little faster than the electric motor runs by itself. You may also need some kind of limiter to prevent over charging the batteries. What might work better is to use a DC-DC converter between the motor and battery which would allow charging at lower RPM and could also have current and voltage regulation. You would need a way to switch between charging and running the motor so both can't happen at the same time.

fechter said:

What might work better is to use a DC-DC converter between the motor and battery which would allow charging at lower RPM and could also have current and voltage regulation.

Click to expand...

Or you can just use a controller with regen.

Ok this is good food for thought thanks guys. So I assume I can have the ice system separated from the electrical system with two different on/ignition switches, and when using ice I can use the Ice's 12 volt starter battery hooked to an on/off switch connected to the electrical motor to hopefully give it enough juice to simulate -neutral- at 12 volts. The only problem here is that these motors show a minimum voltage of 48v (on the controllers) so not sure if it would work this way. Pulling juice from the ice's stator would work out better I think because it pumps out much higher voltage which i could just throw a regulator on. If i ran both ice and electric motors at same time of course the 12v battery would need the on/off switch to keep it separated from the 100v battery because that would be an instant explosion lol.

As far as the large controllers I've seen go, they all say "braking regen" so it was a bit confusing for me. I don't want a secondary switch that has to be pressed to brake the engine and return some energy to the packs. I was looking for passive regen while in ice mode.

Would running ice and electric system at the same time with zero throttle applied to the electrical system give me a -neutral- feel or would it still drag a lot?

Why don't you tell or show(sketch) what you want to build? Why not electric only? Why the ICE? What riding do you want to do with it? I.e. distance, speed, (steep) hills?

SlowCo said:

Why don't you tell or show(sketch) what you want to build? Why not electric only? Why the ICE? What riding do you want to do with it? I.e. distance, speed, (steep) hills?

Click to expand...

Honestly i wanted to go 50/50 hybrid because full electric builds are still way too pricey.

Having 13hp electric that can take you 50/60 miles coupled with a 10 hp semi auto ice that can take you 150 miles per tank while (hopefully) getting the electric battery charged at least halfway is a win win. You get electric torque for starting off and climbing and for a quieter commute and you get the ice for convenience of filling up faster on long trips.

Also if they are running in tandem at the same time with the semi auto you can leave the bike in top gear without it stalling at red lights so you can just punch off the line using the electric throttle until youre at speed to roll on the ice at top gear.

Did i mention the cool/nerd factor of building it? I think one company in india is the only one doing it hybrid but they are mainly marketing the electric motor as a short lived boost for the bike.

Sorry no pics patents pending lol.

Battery size is going to be one of your main limitations. If you only use the electric for added boost on takeoff, you could get by with a pretty small pack. The energy density of gasoline is still way higher than lithium batteries so if maximum range is your goal, you don't want a huge battery. If you did it right, you could run a little 50cc ICE and get acceleration like a 250cc.

fechter said:

Battery size is going to be one of your main limitations. If you only use the electric for added boost on takeoff, you could get by with a pretty small pack. The energy density of gasoline is still way higher than lithium batteries so if maximum range is your goal, you don't want a huge battery. If you did it right, you could run a little 50cc ICE and get acceleration like a 250cc.

Click to expand...

You get what I'm going for haha. The 50cc and 150cc ice are the same exact dimensions, I wanted it to have the bare minimum for freeway legality at least. The electric motor is 40 lbs plus i think battieries will be 50/60 lbs if i want it to actually be able to hit the freeway for 30/50 miles. Lots of work to do still

I assume you're planning on a hubmotor to save space? Many electric conversions put the battery where the fuel tank was so you'll have to get creative with where you put yours!

Drag of an unpowered electric motor is undesirable on a pedal cycle but are you really going to notice it on a 10+HP ICE bike? Barely, suspect. Feeding it enough power to effectively make it freewheel makes sense when you're using power from the traction battery and the motive force for the bike is your legs. It doesn't make sense to take electrical power from the ICE alternator to do it, as the extra ddrag on the ICE from the alternator will be greater than the drag from the unpowered motor.

Punx0r said:

I assume you're planning on a hubmotor to save space? Many electric conversions put the battery where the fuel tank was so you'll have to get creative with where you put yours!

Drag of an unpowered electric motor is undesirable on a pedal cycle but are you really going to notice it on a 10+HP ICE bike? Barely, suspect. Feeding it enough power to effectively make it freewheel makes sense when you're using power from the traction battery and the motive force for the bike is your legs. It doesn't make sense to take electrical power from the ICE alternator to do it, as the extra ddrag on the ICE from the alternator will be greater than the drag from the unpowered motor.

Click to expand...

I'll have to play around with the numbers but running both systems in tandem turned on at the same time seems like the easiest way to go right now since it will require less wiring and extra parts and cutoff switches.

As far as the alternator goes on the bike it is always pumping out around 100 volts which is capped to 12 volts by the rectifier. I dont think it has enough watts available to power the controller to simulate neutral though, which brings me back to just running both systems in the on position at the same time for neutral gear simulation and passive regen. Thanks for your input i appreciate it.

If it is "just to have a project" then go ahead building this hybrid bike. If you need it as transport/commuter then just buy a bigger cc petrol bike. Because the extra complexity to make it all work (and keep working) together is not worth it financially or time wise. If you just want the "electric/EV acceleration" kick then go all electric with a serious full EV build.

timbodaciois said:

Honestly i wanted to go 50/50 hybrid because full electric builds are still way too pricey.

Click to expand...

This is going to be even more pricey. But if you are OK with that, then -

Ok this is good food for thought thanks guys. So I assume I can have the ice system separated from the electrical system with two different on/ignition switches

Click to expand...

You are going to need more intelligence than that. Spinning the ICE with the ignition off will be sending fuel straight out the exhaust, for example. You'll need a fuel cutoff.

when using ice I can use the Ice's 12 volt starter battery

Click to expand...

Would be sorta nuts to have a traction battery AND a starter battery. Use one.

hooked to an on/off switch connected to the electrical motor to hopefully give it enough juice to simulate -neutral- at 12 volts.

Click to expand...

Are you thinking you can send 12V to the motor and have it just spin freely at high speed? If you do that then the motor will want to run at a very slow speed, and will mightily resist going any faster.

As far as the large controllers I've seen go, they all say "braking regen" so it was a bit confusing for me. I don't want a secondary switch that has to be pressed to brake the engine and return some energy to the packs. I was looking for passive regen while in ice mode.

Click to expand...

For passive regen you have to exceed the motor's base speed. You want active regen. For example, the Phaserunner allows you to set any level of regen you like.

Would running ice and electric system at the same time with zero throttle applied to the electrical system give me a -neutral- feel or would it still drag a lot?

Click to expand...

If you are charging you will feel drag. More charging = more drag. Can't get around that.

Suggestion - build an ebike with a rear hub. Then add a small ICE with a clutch using a left side chain. Use an ethrottle that goes from -100% (regen) to +100% (full power.) Ride in electric mode all the time. When you need extra range, engage the clutch. The ICE will spin up and start running. Set it so that it's always wide open throttle, then use the ethrottle to control your speed.

SlowCo said:

If it is "just to have a project" then go ahead building this hybrid bike. If you need it as transport/commuter then just buy a bigger cc petrol bike. Because the extra complexity to make it all work (and keep working) together is not worth it financially or time wise. If you just want the "electric/EV acceleration" kick then go all electric with a serious full EV build.

Click to expand...

Yeah it's definitely alot of working components and definitely alot of wires haha.

billvon said:

timbodaciois said:

Honestly i wanted to go 50/50 hybrid because full electric builds are still way too pricey.

Click to expand...

This is going to be even more pricey. But if you are OK with that, then -

Ok this is good food for thought thanks guys. So I assume I can have the ice system separated from the electrical system with two different on/ignition switches

Click to expand...

You are going to need more intelligence than that. Spinning the ICE with the ignition off will be sending fuel straight out the exhaust, for example. You'll need a fuel cutoff.

when using ice I can use the Ice's 12 volt starter battery

Click to expand...

Would be sorta nuts to have a traction battery AND a starter battery. Use one.

hooked to an on/off switch connected to the electrical motor to hopefully give it enough juice to simulate -neutral- at 12 volts.

Click to expand...

Are you thinking you can send 12V to the motor and have it just spin freely at high speed? If you do that then the motor will want to run at a very slow speed, and will mightily resist going any faster.

As far as the large controllers I've seen go, they all say "braking regen" so it was a bit confusing for me. I don't want a secondary switch that has to be pressed to brake the engine and return some energy to the packs. I was looking for passive regen while in ice mode.

Click to expand...

For passive regen you have to exceed the motor's base speed. You want active regen. For example, the Phaserunner allows you to set any level of regen you like.

Would running ice and electric system at the same time with zero throttle applied to the electrical system give me a -neutral- feel or would it still drag a lot?

Click to expand...

If you are charging you will feel drag. More charging = more drag. Can't get around that.

Suggestion - build an ebike with a rear hub. Then add a small ICE with a clutch using a left side chain. Use an ethrottle that goes from -100% (regen) to +100% (full power.) Ride in electric mode all the time. When you need extra range, engage the clutch. The ICE will spin up and start running. Set it so that it's always wide open throttle, then use the ethrottle to control your speed.

Click to expand...

Great points you make here. It would be most simple to go full electric and just carry a small generator on the back rack to charge on long trips.

I thought it would be cheaper to go 50/50 but ill run more numbers. On paper the initial upfront cost was way less because i was not spending 3 grand for 720 cells, i was cutting my initial 20kw in half and substituting it with the low upfront cost of an ice system.

As far as the ice spitting fuel out when turned off that should not happen in neutral with the cutoff switch.

I thought about the hub motor but you cant change gearing very much especially when the idea is to run it in tandem with an ice/ on the same gearing as an ice drivetrain so admittedly my imagination has gotten me in over my head.

As far as running the motor off of the 12v at high speed that wasnt supposed to be the intention, my thought process was just thinking it would relieve motor resistance at all speeds and be enough energy to simulate neutral/ coasting.

On your full electric bikes or a zero if you lay off the throttle to coast does the electric motor automatically ruin all of your momentum because youre not feeding it enough to travel at a given speed? These were the initial problems i was having with the design because i feared the drag would be too much to make it worth it and it would simulate me riding around with two flat tires and end up wasting more energy than i could generate with the ice to increase trip range.

I'll think for a bit longer about it and run more numbers. I really do appreciate your replies guys.

timbodaciois said:

As far as the ice spitting fuel out when turned off that should not happen in neutral with the cutoff switch.

Click to expand...

Sure - as long as you have a neutral (or clutch.)

I thought about the hub motor but you cant change gearing very much especially when the idea is to run it in tandem with an ice/ on the same gearing as an ice drivetrain so admittedly my imagination has gotten me in over my head.

Click to expand...

1) With a large DD hubmotor you don't need to change gearing much if at all. You have a lot of power there over a wide RPM band.
2) Regen is VERY hard without a hubmotor.

As far as running the motor off of the 12v at high speed that wasnt supposed to be the intention, my thought process was just thinking it would relieve motor resistance at all speeds and be enough energy to simulate neutral/ coasting.

Click to expand...

Nope. The motor would run at a low RPM, and if you tried to run it at a high RPM it would push hundreds of amps back into the 12V battery.

On your full electric bikes or a zero if you lay off the throttle to coast does the electric motor automatically ruin all of your momentum because youre not feeding it enough to travel at a given speed?

Click to expand...

If the base speed of the motor is higher than the base speed you get from your battery voltage - yes. This can be a problem if you are running with field weakening and you suddenly get off the throttle. Most of the time it's not a problem because battery voltages are usually chosen to be higher than base speed at max RPM.

Thanks bill

There was an old commercial on tv about a prius having more lines of computer code than a fighter jet. Balancing ice vs electric power for max efficiency would likely require a computer. I think you would need full continuous control for rpm and torque of both the gas and electric motor so the percentage of rpm and load can be shared in real time by both motors in any ratio.

I think an ideal setup would be a shared variable coupling between the two motors like a nuvinci hub as a jackshaft. This would allow you to control the electric motor's load and rpm. For instance when cruising on gas power you could have the electric motor rotating as slow as possible. When braking even from low speed you could switch the ratio such that the electric motor is regen-ing at high rpm for your given road speed. You could use one of the electric nuvinci developers kits and a raspberry pi or Arduino for the logic to vary the ratio based on road conditions as well as braking and throttle position.

This would be a cool project but you better be wizard in a few different disciplines.

Easiest thing by far would be a nice electric bike with the most efficient and smallest gas generator you can find. The efficiency hit in that scenario is the weight of the extra copper in the generator that is redundant because you already have copper in the motor.

Thats all just my opinion. Not trying to sound like a know it all.

DanGT86 said:

There was an old commercial on tv about a prius having more lines of computer code than a fighter jet. Balancing ice vs electric power for max efficiency would likely require a computer. I think you would need full continuous control for rpm and torque of both the gas and electric motor so the percentage of rpm and load can be shared in real time by both motors in any ratio.

I think an ideal setup would be a shared variable coupling between the two motors like a nuvinci hub as a jackshaft. This would allow you to control the electric motor's load and rpm. For instance when cruising on gas power you could have the electric motor rotating as slow as possible. When braking even from low speed you could switch the ratio such that the electric motor is regen-ing at high rpm for your given road speed. You could use one of the electric nuvinci developers kits and a raspberry pi or Arduino for the logic to vary the ratio based on road conditions as well as braking and throttle position.

This would be a cool project but you better be wizard in a few different disciplines.

Easiest thing by far would be a nice electric bike with the most efficient and smallest gas generator you can find. The efficiency hit in that scenario is the weight of the extra copper in the generator that is redundant because you already have copper in the motor.

Thats all just my opinion. Not trying to sound like a know it all.

Click to expand...

You're right the easiest way is adding a generator. Ill look into the nuvinci. Some other posters here already stated that if the electric motor is given slow throttle and being forced to move faster it would try to resist the extra speed generated by the ice trying to make it go faster. I had already drawn up a dual electric/ standard ice cable twist throttle so that on the controller i could set different power curves for the electric to die off after a certain ammount of throttle and let the ice take over where electric motors tend to lose efficiency and eat batteries at high speeds.

In other news kawasaki just filed patents extremely similar to mine about a week or two ago so they know there is something in this haha.