Trailer build

[postmatic]

Hi everyone,

Been using these forums for information for a while and decided it was about time I posted something.

I've been working on converting an old e-trike into a trailer for my e-bike and had some technical questions. While I was in the middle of my build I was hit by a car on my ebike, I managed to get the exact same ebike to replace my write-off. Which leads me to my dilemma...

I had planned initially to just tape off the old wires on the e-trike motor, but I thought that in theory I could put my controller from the write-off into the trailer and utilize the Regen constantly to send power to my ebike while towing the trailer.

Would I be able to just wire the power wires from the controller to an old computer cable and just plug it into the charge port?
Would I be over loading the Regen on the old controller?
Would I be sending too much power back through the system by running constant Regen?
Would I need to put some sort of resistor in the line from the trailer to limit the amps feeding back to the pack?

Sorry for so many questions, just couldn't really find anything to describe what I'm thinking of building.

 

[SlowCo]

No that won't work.
Even if you'd be able to hook everything up correctly the drag of the "regenerative BRAKING" would cost much more energy than it would generate. It's like strapping a windmill on top of a Tesla car to charge it while driving and thinking that it would gain instead of cost energy...
What motor is in/on the e-trike? A direct drive or a geared hub?

 

[postmatic]

I'm not aiming at having perpetual motion, just looking to extend the range of my bike while towing my trailer. Figured if the electronics are in the trailer I could utilize it for that purpose. I realize that the main purpose of Regen is during braking but it also feeds back power if you cut your throttle on a large hill without applying braking, hence my theory of using it in the trailer to extend my range while towing.

The donor e-trike was a Tao Freedom Plus. The motor is connected to the rear axel and drives both wheels either together or independently. My guess would be via a differential, but I haven't had a reason to open it up and check. (If it ain't broke...) I'm not exactly sure which type that would be but I could post pictures of it if that helps?

 

[SlowCo]

As it can only supply back energy when braking it could be slightly beneficial when braking on a downhill ride. But all the extra weight and friction while riding on flat or uphill will probably cost more energy than it can regenerate. So the best way to save energy would be to remove as much weight and friction from the trailer as possible.

 

[postmatic]

My understanding from the Regen is that if the back wheel is spinning when the throttle is off, then it supplies power back to the pack. That's why if you have no pack installed and you spin the pedals on the ebike you can get the chirps of power being supplied to the alarm system similar to reconnecting the pack. Is this not a common feature? As I know that this occurs with the controllers that I have

 

[SlowCo]

For an electric motor to be able to supply energy it has to become a generator. For a generator to be able to output energy you have to put energy in. Regenerative braking supplies back energy by converting the braking force into heat/friction and some electricity. Only backing off the throttle will thus not result in serious regenerative braking and supply almost no electrical energy. To gain any significant energy to recharge the battery pack you'll need to go downhill and use the regenerative braking at an optimum. But the extra energy it will have cost you to go uphill in the first place will have been greater than the regenerated electrical energy you'll be able to harvest.

 

[postmatic]

That's a different understanding of how the Regen worked than I understood from my research.

My understanding was that when the throttle is not engaged, then the controller receives a signal from the motor that the magnets are still spinning. Takes this information and sends power back through the controller power supply, not just when the brake is applied but also when the wheel is spinning without power applied. I've seen some technical specs that also imply that the controller from those specs would do that which led me to believe it was common place.

Technically, since the motor in the trailer wouldn't be running the trailer I could short the electric brake cable on the donor controller and it would think that I'm always braking if the Regen only works when the brakes are on?

 

[SlowCo]

How do you think the rotational energy from a spinning wheel can be converted to electric energy?
It's not by magic but through the controller that "makes" the electric motor attached to the wheel into a generator. And converting energy always comes with a loss (heat). It's just physics...

 

[postmatic]

I didn't say it was magic. I stated that the controller was needed to convert the AC from the motor to DC for the pack. And I understand that there is always a loss of energy in the process. I'm educated, and know how to research topics of interest.

What I'm asking is....

Would I be able to just wire the power wires from the controller to an old computer cable and just plug it into the charge port?
Would I be over loading the Regen on the old controller?
Would I be sending too much power back through the system by running constant Regen?
Would I need to put some sort of resistor in the line from the trailer to limit the amps feeding back to the pack?

I understand that I won't be achieving perpetual motion or anything close to it. I also understand that any additional voltage that can be supplied to the pack will extend my range, even if only by a few kilometers. Carrying groceries home on a trailer would greatly shorten the range, thus any additional range I could get would be beneficial. Hence my desire to make use of a motor that will be there regardless of whether it is hooked up or not.

 

[SlowCo]

The simple answer is: No, it doesn't work that way.
Although you seem to think that you are educated and can research you don't seem to understand the basics. And yes you are thinking in "perpetuum mobile" circles.
The key is in your last sentence: "hooked up or not". If "hooked up" then it takes energy to make energy. And it'll cost more then you'll gain.

 

[postmatic]

I've seen projects where people took the hub motor and controller from an ebike and converted them into windmills. No added electrical parts, just added fan blades to the rim to catch the wind and make it spin. They successfully generate power for off-grid living using packs and step down converters to run 12v lighting. If I'm thinking improperly, can you explain how these systems are successful?

I say hooked up, as in the motor will be attached to the axel whether or not I connect it to the power system for Regen or not. If it's there why not make use of it?

 

[goatman]

are you thinking about cogging

 

[JackFlorey]

I also understand that any additional voltage that can be supplied to the pack will extend my range, even if only by a few kilometers.

Nope. In your example it will DECREASE your range by a few kilometers.

If I'm thinking improperly, can you explain how these systems are successful?

Those systems pull energy from the wind and turn it into electrical power.

Your system would pull energy from your forward motion and turn it into electrical power. If your goal is to stop, that's a great use. If your goal is to get more range from your vehicle, then it will fail, because when you take energy from your forward motion you slow down.

 

[postmatic]

I had not taken cogging into account. How would that come into play?

Those systems pull energy from the wind and turn it into electrical power.

Your system would pull energy from your forward motion and turn it into electrical power. If your goal is to stop, that's a great use. If your goal is to get more range from your vehicle, then it will fail, because when you take energy from your forward motion you slow down.

Both are rotating the hub motor in the same fashion, just one is using wind and one is using the friction of the trailer tire moving on the ground. It wouldn't be effecting my main motor in anyway, it's a secondary motor that would be hooked to the drivetrain on the trailer and could potentially be utilized.

How is the wind rotating the motor any different from the trailer rolling and rotating the motor?

 

[JackFlorey]

Both are rotating the hub motor in the same fashion, just one is using wind and one is using the friction of the trailer tire moving on the ground. It wouldn't be effecting my main motor in anyway, it's a secondary motor that would be hooked to the drivetrain on the trailer and could potentially be utilized.

Do the following experiment.

Ride your bike with a trailer and see what your range is.
Now add a brake to your trailer wheel. Engage the brake so there is drag on the trailer wheel. Ride the same course again. See if the range is the same.

It will not be; it will be less. That brake will transform your forward motion into heat, and thus decrease your range. Your "secondary motor generating voltage" will do the same thing.

 

[SlowCo]

How is the wind rotating the motor any different from the trailer rolling and rotating the motor?

This question shows you are still thinking in "free energy" terms.
Your ebike and trailer are a "system". And any energy you think of extracting with that system has to be put in first by you pedaling and/or the electrical drive train of your ebike. And energy input will be larger then energy extracted. So you will have to pedal harder/more and/or your battery pack will have to output more energy if you want to extract energy from dragging (regenerative braking) the trailer. In your case there is no outside (wind)energy to be harvested but only the energy you and your ebike put in. And due to losses that input energy will have been more then the energy you can recoup.

 

[SlowCo]

[youtube]gahKxbwUcYw[/youtube]

This video shows very clear that it takes much more energy input than you can recoup. If you watch till the end you'll see him compare the efficiency of this mechanical set up (15%) with his previous electric bike with regenerative braking (15.7%).

 

[LewTwo]

This video shows very clear that it takes much more energy input than you can recoup. If you watch till the end you'll see him compare the efficiency of this mechanical set up (15%) with his previous electric bike with regenerative braking (15.7%).

Interesting video. Thank thee for posting the URL :thumb:

 

[postmatic]

I found his other video on the Regen more informative on the topic.

https://youtu.be/-suxSqrP_X4