Greg Grossmeier

Greg Grossmeier at

I bet I know people who know solar power on here...

What should I look for in a solar panel? Portable-ish one as it'll be for my (yet to actually purchase) RV.

SombreKnave, SombreKnave, Douglas Perkins, Douglas Perkins shared this.

Show all 13 replies
Do you already know what you want to power with it? Is it to keep a phone charged, or do you want to power other devices?

In my experience solar powered power banks are basically useless (they aren't able to fully recharge their small battery even in a day of full sun); at a minimum you'll want to look into a panel that is at least a quarter of square meter big (they sell a number of these that are foldable and/or have handles for portability).

If I remember correctly, polycrystalline panels are less efficient overall than monocrystalline ones, *but* they work a bit better under non-ideal conditions such as cloudy weather or wrong orientation, which IMHO is a huge plus for a portable solution. I can't really find a reliable source for this, so it's something that probably requires some research.

As joeyh mentioned, solar panel aging is not a big issue, as long as you keep it in mind and overestimate your requirements a bit; batteries however are a different matter and will require changing every few years,.

Elena ``of Valhalla'' at 2015-02-11T16:13:01Z

Greg Grossmeier likes this.

I built a small 12 volt emergency backup power generator a while ago. You can read the gory details here:

It was more of an experiment than anything else. This provides enough power to charge cell phones and portable LED lamps.

This is what I can tell you of that experience:

Get the largest wattage that you can get. I made this mistake with mine. I purchased a 13 Watt panel. It works well, but the wattage will dictate size of the battery. The rule of thumb is that you cannot use a battery Amp/Hr larger than 1.5 of the amount of watts. In other words, with 13 watts, the battery cannot be more than 25 Amp/Hr. If you get a 100 Watt, then you can have a 150-200 AmpHour battery (this is a boat/camper size battery).

Battery must be deep cycle batteries. Be mindful while buying them. The small ones are the ones used for alarm systems and the large ones are the marine type. There are "solar power" specialized ones. I do not know, but I am using a small deep cycle one for a scooter and it works fine.

Get a controller to make your life easier and do not burn your battery.

Good luck!

Luis at 2015-02-11T19:01:52Z

joeyh, Greg Grossmeier likes this.

For perspective, the old panels here generated 32 amp-hours on this sunny winter day. At noon, 70 watts were being produced. (These panels were originally rated at 256 watts; they might have generated 128 watts 15 years ago.)

The 32 amp-hrs is ample for my laptop for a day. I could stretch this windfall for a week if I needed to. As it is, tomorrow should be fairly sunny too, and the charge controller has nearly topped off the batteries full, so I am running some hard drives on the inverter and blasting hundreds of GB of data around.

joeyh at 2015-02-11T21:55:57Z, Greg Grossmeier likes this.