Solar power for phone charging?

[simon_brooke]

I'm planning an expedition...

I use Google's MyTracks for route logging, which I find fun. But it puts a high load on my phone; with MyTracks running all the time the standard battery on my phone lasts only five hours. Obviously this isn't going to work if I'm away from mains power for a week.

I'm planning to use a trailer rather than panniers. So lashing a flexible solar panel on the top of the trailer would not be a problem, and it should have ample power output. Has anyone done this? If so what sort of regulator unit did you use and where did you get it?

 

[Will1985]

Cunobelin has experience with a Solar Monkey, and jimboalee with a Power Monkey.
Search for them.

 

[simon_brooke]

Cunobelin has experience with a Solar Monkey, and jimboalee with a Power Monkey.
Search for them.

My thanks.

 

[andym]

Have you thought about getting something like a Garmin Legend HCx? Does the same thing (although the display is not as good as a PDA/smartphone) but consumes a lot less power - a couple of AA batteries last me about a couple of days riding. Doesn't stop you taking the smartphone as well but would take the load off.

 

[simon_brooke]

Have you thought about getting something like a Garmin Legend HCx? Does the same thing (although the display is not as good as a PDA/smartphone) but consumes a lot less power - a couple of AA batteries last me about a couple of days riding. Doesn't stop you taking the smartphone as well but would take the load off.

Thanks, but that doesn't really help. It isn't going to last a fortnight away from mains so I'll need some form of solar or dynamo charger anyway, and it can't transmit the log up to Google maps or wherever so I'd have to lug a computer (and some means of charging that) as well. The object is to carry less, not more!

 

[RedBike]

Those panels do seem a tad expensive / large. Perhaps a small charger that runs off AA batteries, a few spare batteries for the phone and one of those free-loader solar chargers.

The freeloaders aren't great. It wont keep your phone charged for a fortnight unless you're off to somewhere really sunny. However, if you supliment its charging with the AA batter charger i'm sure you'll get through a fortnight. Then there's always the spare batteries for the phone just incase.

 

[CopperBrompton]

Solar panels are still pretty inefficient, so you need a large one and a sunny climate to get a sensible amount of power out of it. Which country are you going to?

 

[andym]

Thanks, but that doesn't really help. It isn't going to last a fortnight away from mains so I'll need some form of solar or dynamo charger anyway, and it can't transmit the log up to Google maps or wherever so I'd have to lug a computer (and some means of charging that) as well. The object is to carry less, not more!

The less power you're consuming the smaller the solar charger you need. Assuming you need one at all - it's easy to recharge devices at campsites.

Why do you need to upload the track en route? Can't you do it when you get back?

 

[nigelnorris]

I wonder if a wind powered charger is technically feasible. Strap a small fan to the front of your bike attached to a tiny generator and take advantage of the headwid to generate a bit of juice?

 

[bike_the_planet]

The less power you're consuming the smaller the solar charger you need.

True, but efficiency is still worth thinking about. I took a Solio to Europe last year for charging just a phone and an MP3 player. Even though the internal battery was rated at 1600mAh, it still took the best part of a full day in uninterupted sunlight to get a good charge. And the amount of energy in the battery was enough to charge a phone or an MP3 from empty.

And this is not suprising; at noon on a sunny, midsummers day in Europe, the irradiance at ground level would be around 600 w/m2. Your average inexpensive solar panel has an efficiency of little more than 15%, giving potentially 90W/m2.

So a panel 20cm by 20 cm would give you about 3.5W peak, and about 1W averaged out on part cloudy days in late summer. That's, say, 6V at 150mA. Which means 10 hours of full charging for a 3.7V LiPo 1600mAh battery.

The Solio was smaller than that, so you can see why you have to consider efficiency!

Next time I'm going to use a front-wheel generator (see separate thread on this forum) such as the SON28 or a cheaper Shimano model and build a universal charger for it.

Cheers