Portable Battery Charging Pod for E-Bike Trailer

Greetings All:  I hope I'm in the right place to be asking for suggestions or insight on how to best setup the project I'm about to describe.  I'm not in search of "Free-Energy."  I mention this becasue I know how easy it is for inquiries like mine to go off on various tangents and completely miss the purpose of the original questions.

I'm a self-taught fabricator of sorts.  Some might call me a chronic tinkerer.  I have no problems fabricating out of metal or wood as I have in my home shop a CNC metal mill, a metal lathe among other equipmrnt,   but when it comes to anything having to do with electicity or electornics I'm completely out of my element.

My present project involves building a light weight Cross-Country E-Bike trailer for long distance fighing and hunting trips.  Building the trailer is easy enough but I want to incorportate a removable onboard charging pod onto this bike trailer in order to be able to run off the bike's primary battery while simaltaneously charging my secondary or spare batter as I ride.

As I stated above, I'm not looking for free energy or any other pie in the sky technology.   What I had in mind was to use automobile alternator who's input shaft will be spun by the trailer wheels.  Here's my dilema.

In my mind's eye I already know how it will fit into my trailer but What I DON'T KNOW is how to wire it up.  My only point  of reference is my home made two-panel solar charger which goes from my solar panles to the charge-controller I have mounted on the wall of my shop; then from there to the 12 volt battery.  From the 12 volt battery to a small power inverter with two electrical plugs into which I connect my radio or my fan or other small electical appliances.

With this bike trailer Charging Pod I was wanting to use the spining tires of my trailer as the input power to spin the alternator.   I'm sure I could figure out how to do this through trial and error but I'm also sure it would be less costly if I just ask someone with the experience in electrical work to help me along or at least give me a clue on how to go about this.

The hub motor on my E-Bike is rated at 500 watts and the battery that powers it is a 48 watt 16  amp output. (if I read my manual correctly)   The charger that came with this E-Bike  plugs into a standard wall plug.  The specs on that charger  states the following:

Input: 120 volts-3.0 Amps 60 Hz

Output 54.6 volts    3.0 Amps  Also, I should state that   the symol for alternating currect.  Solid line above with short ------ below the solid line is shown on this Output line.

I've calculated the RPMs on the twenty inch trailer tires I'll be using as they spin a two inch diameter pully on the input shaft of the alternator and I believe that it will produce sufficient RPMs at an average of 15 miles per hour.  I can maintain that average rate of speed while riding my E-Bike for quite a long ride.

I'm aware that there is most likely some critical information that I may be leaving out here so if you can tell me what that might be I'll be happy to find that info and get back to you with it.  For now I'd like to ask any of you who might be inclined give an elctronically-challenged novice what components I would need to connect together to be able to build this E-Bike Charging Pod; and what sequence of components would you go about using?

I have not selected the alternator as of yet but I do want to utilize the charger that came with this E-Bike.  Any help you would be willing to share would be appreciated.

Tim M.


You need to evaluate the circuit flow.
Need basic list first.
1. Your battery has 48v output.
2. You allready evaluated the motor spec.

Break each section and list out the voltage and current rating.

For example -
1. Power source 48v.
2. Motor (single phase, 24v or three phase with current draw)
3. Motor driver ( input voltage - 48V, 3A input).

The above is just an example. List down each individual electrical or electronic components of the vehicle and state down the power requirements. This will evaluate the possibility to connect each of them directly or indirectly by using any other power supply units.

  Joined February 12, 2018      696
Monday at 02:11 PM

Thanks for taking the time to reply and offer suggestions to my initial inquiry.  Even though I understand what you are suggesting, still I can't quite wrap my head around it.   I'm afraid you are offering elecronic insights to an electronics-retard.

Honestly, your reply is the closest thing to a helpful suggestion that I've gotten thus far and still I can't quite fully understand it.  That's not to say that the few other well meaning replies weren't appreciated.

Just to clarify:

Are you suggesting that I get the electrical specs off of each individual component that I intend to use on this project?  If so, doing that is simple enough but then I run into the problem of what to do with all of this information.  My first obsticle in this case would be to figure out exactly what electrical components I'd actually need for such a project.

I'm afraid I keep referring back to my small DIY home solar panel project.  I know exactly what components it took to hook all that up but even then,  if I weren't already bald headed I'm sure I would have pulled all my hair out with all the time I spent figuring out how to wire it all up.  Trying to read the electrical schematics involved in even that simple project was like trying to read Egytian hieroglyphs.  I can't make any sense of those either.  It was only through trial and error that I got it done.

It may be that it's trial and error that I'll have to resort to in order to figure all this electical stuff out as it relates to this portable battery charging pod.  That's how I've had to learn nearly every other project related subjects I've undertaken in life.

If I start backwards and work my way forward regarding components that I'll need, the last component in this list of electrical components will be the OEM battery that came with this E-Bike I've been riding for a while now.  Proceeding backward on that list of components then It would be the OEM battery charger made to recharge this specific battery.   It's at this point that a gap develops in my list of components.

Now: moving forward from the original Alternator component as my source of electrical current generation I don't know if I would be connecting that alternator to a charge controler then a twelve volt battery and then a power inverter or if there's a simpler way to go about it.

I suspect I'm about to go through another one of those trial and error learning curves I alluded to above.  I guess I'll have to just watch a few more tutorial videos to see what my options might be.

Thanks again for taking the time to reply.

Tim M.

  Joined March 11, 2021      1
Thursday at 10:10 AM