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Quick test for solar range extender

Posted: Jun 02 2021 7:05pm
by JackFlorey
Just did a quick test with the simplest possible solar range extender - a single panel bolted to the rack.

I used a Renogy 100W flexible panel on top of a 1/4" piece of plywood, bolted to the rack of an almost-stock RadCity. A Genasun controller converted the 18V from the panel to the 54.6V the battery wanted, and used the battery charge port to get the power to the battery. An old Powerwerx DC power monitor provided some monitoring.

In 900W/M2 sun (while stationary) I was getting 74 watts, which means the entire setup is ~82% efficient. (Some of that was less than ideal panel performance, some was losses in the charge controller.)

I took a ride at about 2pm to pick up groceries. I was seeing 65 watts traveling any direction but west. Going west my body was shading about 30% of the array and total output was 10 watts or so. Average power over the ride was ~300 watts so I was generating about 1/3 of usage while moving.

The big surprise was handling. I was expecting to feel the big wing back there, but it didn't feel any different than carrying a 2x4 sticking off the back. (i.e. some instability when turning rapidly but otherwise not a big deal.) There was probably some risk of it being blown over when parked, but in the 12mph wind it didn't happen. An unexpected benefit was that the panel shaded the panniers, which meant the groceries weren't in the sun.

After being parked outside for 5 hours (noon to 5pm) I saw 270 watt-hours added to the battery, or about 40% of total battery capacity.

Re: Quick test for solar range extender

Posted: Jun 02 2021 11:38pm
by Hillhater
I can see 1.5 amps being a useful addition for long trips or touring, but i cannot see a practical way of mounting a solar panel on a conventional bike.
Has anyone considered mounting it like a “sunshade”, flat above the riders head ?...minimum windage, max sun.
...not really practical for a daily rider/commuter, but could work and be useful for a touring set up.

Re: Quick test for solar range extender

Posted: Jun 03 2021 3:26pm
by Jordan325ic
It looks a bit funny sticking off a regular bike, but on a longtail cargo it would be more at home. For touring it could be mounted on top of a bicycle trailer cargo box, which you could prop up at the correct angle whenever you get to camp or stop for a lunch break...

Good data!