Tuesday, August 2, 2016

Trailer for E-trike Phase II, Solar

Phase 1 of this story which includes motivation, requirements and initial progress is located at this link:

This phase will focus on the solarization of the trailer. I will save you any suspense and show you what that looks like after many hours of testing and attaching of the solar panels.

Trailer with about 240 watts of PV panels attached.
Phase 2 began with an inventory of resources. I had designed the trailer to fit some PV panels I've obtained from a salvage operation. The three PV panels are each 35" X 38", about 22 pounds and currently output about 80 watts of power each, 240 watts total. They are old, don't look great, but being a PV expert I know they have some hidden beauty. Looks aren't everything when it comes to PV. Plus they only cost me $4 each.

I set the panels out on the grass and started testing their amperage and voltages in an attempt to figure out the safest, most cost effective way to charge the battery on the e-trike. You see, that battery is very expensive. For me, these days a DC charge controllers' goal is to make sure the battery is charged safely, cost effectively, and doesn't damage the value of the expensive battery.

Initial testing of PV panels and battery charging using a surplus charge controller
Initial testing showed that I needed another charger controller. Searched and searched, and discussed my requirements on Endless-sphere user group. A few weeks later a charge controller from China arrived, and I tested that one.

Testing of DC charge controller suitable for voltages and amps of surplus PV modules.

During this testing, the walls were off the trailer and I noticed that the size of the trike made it perfect for inside the trailer. Don't know the circumstances when I would need such knowledge, but that is one of the features of knowledge, right?
E-Trike inside the trailer.
The next task was to examine all the existing dimensions of the e-trailer, and the specifics of the PV panel, figure out all the clearances, and where the panels would be mounted so that they could grab the most sun and not be shaded, and also hinge at angles to capture the most sun. This took lots of trial and error for this prototyping activity. The wheels came off to attach the panels, or to allow for them to hinge up. The whole PV assembly is removable from the trailer with the removal of a couple brackets and studs. The wiring was put into salvaged plastic conduit, and wired to provide the appropriate voltage for the charge controller and subsequently for the battery charging.

I mounted the charge controller on a permanent wall at the front of the e-trailer.

Charge controller attached to the interior wall of e-trailer.
The positive and negative wires from the PV panels go into the charge controller, the output goes to the battery. This particular charge controller has a USB port for charging phones (only 1 amp), and an output to power appliances. It will turn the appliances off if the battery voltages go too low. I am not using that functionality, but it may prove useful in the future. Guess I should mention that this gizmo only cost $36 including shipping.

Inside of trailer has a carpet.

So now the trike can theoretically travel at 10 miles per hour using just the energy from the sun, converted by the PV panels. More likely, it will charge the battery with the panels deployed pointing directly at the sun while the trike isn't moving, charge the battery for 20 or so miles at a time. Periodically I will plug the batteries into an electrical outlet to give them a full charge and let the battery management system adjust the voltage cells of the battery pack as needed. This is called balancing the battery pack.

E-trike and solar powered trailer.
The trailer doubled in weight by adding the PV panels, originally 75 pounds, now about 144 pounds. But, the PV panels come off. I think I can still achieve my goal of a 100-pound trailer, add PV as desired. Also, PV modules are much lighter weight now than they were when these modules were produced.

The next to phases of this e-trailer build is to make a tiny kitchen front bulb out, make a back fairing with storage (similar to this blog), and make an aerodynamic space rocket that fits the top, all made out of very lightweight materials (possibly coroplast). Stay tuned, and don't hesitate to e-mail me with questions, comments or encouragement. energyideas@gmail.com Thanks for reading.

This update includes a photo from when I exhibited at the tiny house show held at the US Air Force Academy last year.

Trailer and trike at the 2016 tiny house show.

A more recent version puts two of the PV panels permanently onto the top of the trailer.

Trike being charged by PV panels, walls stowed.

48 volts and about 160 watts of power for driving the hub motor on the recumbent trike. PV panels are flat when moving.


  1. Replies
    1. Phase 3 and 4 are planned for a front bulbous kitchen and tail (tear drop shape), respectively. These provide aerodynamics. Also, the PV and walls fold into the trailer so cross wind issues can be minimized.

  2. i like that idea.the post is very informative and I really like it. really interesting.
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    1. Thanks.
      Just found this car size trailer on the internet with a similar light-weight wall design http://www.whatwhyand.how/2017/03/hexayurts-dont-suck-part-ii-my-yurt-has.html?m=1

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