Solar system efficiency upgrade

(Andrew) #1

We pulled the trigger on an MPPT solar controller. Hooray for better charging on all days, and even the ominous cloudy ones (sometimes)!


It sure made a huge difference on the system I had in my RV.

An amorphous panel or two would probably be a good upgrade eventually too. Mine made power when it was cloudy and I bought em new for $0.60/watt.

(Andrew) #3

Any recommendations on small panels? I’m looking at getting something in the 20W range to power an isolated WiFi repeater. The general idea is to put together a battery pack with recycled 18650s to smooth out the highs and lows.


I wish I could find a decent deal on small panels but they seem to be a niche market.

The best panels and deal I found were those Kaneka 60 watt amorphous panels for $60 each brand new. They needed an mppt controller though because of the 67Voc.

How much juice does your repeater need? We used to run a hoo too tripmate, which was awesome, off of one of those little cell phone backup batteries with the built in solar panel. It just worked every day. Pretty simple setup for under $50. Pretty easy to hack external antennas into the tripmate too.

(Andrew) #5

I have an RPI3 and 2 WRT54GS routers that aren’t being used. Of course I’d prefer to use what’s already here if possible. They don’t draw a whole lot of power.

I was looking at this, partly because it might have more multi-purpose use than a really small panel. $26-$28 for 20W (nominal).

I also have 2 of these. They work for tiny USB voltages. Even though they claim 7W, I haven’t found them to be very useful for anything other than charging phones.

In practice, solar hasn’t been very efficient here, so collecting more than seems necessary tends to be more effective. Even though we have 24-hour daylight currently, the arc of the sun is so long that most of those hours aren’t actually useful.


That little 20w panel seems like a pretty good deal! I hadn’t seen that one yet. I was never impressed with the goal zero stuff beyond phone charging on sunny days either.

The Rpi and router probably pull ten times what the little tripmate thingy does. I think it goes into some kind of sleep mode when there’s no traffic too.

I really think you’d be better off with amorphous panels up there. I was always blown away when I’d come into the shop truck at 7am, with 4 inches of snow on the panels and a hazy sky, and see my array kicking out 6 amps, or 10% of it’s full sun capacity.

If you do build your own battery pack out of 18650’s, unless they’re all the internally protected ones, you’ll need a lithium specific charge controller like a genasun, or one/some of these

Sorry for all of the amazon links. I can’t stand them, or Bezos. Just using them as examples.

(Andrew) #7

I’ve had those since 2011/2012, and bought them for bike touring. There wasn’t much variety then, but they worked okay. I wouldn’t buy them now though.

What firmware can it run? I’m sure there are lower power WiFi gadgets, but the ability to program for various network topologies and functionality is at play too. There are scenarios where I’d buy something different, but unless something is overwhelmingly awesome, using what we already have sitting around in storage bins will get priority treatment.

I’ve been looking at some BQ24650 modules for [quasi] MPPT lithium charging. The TI chip seems way better than those based on the CN3722 (like in the link you posted).

(Lloyd ) #8

Well since I am usually on the move I keep a goal zero. Charge a tablet and this damn iPhone my mom wanted me to use to keep in touch. Little 20w two panel. I have a couple battery packs and one some kid threw in a trash can in rapid city South Dakota as I was passing through. I’ve had a few goal zeros they work okay to me. But if I acquire a better vehicle for gettting elsewhere I want a little kit for laptops and batteries for sure. We live in a world of mixture. And we all have to admit even rewilders, we like our tech a bit.

(Andrew) #9

Yeah, they’re fine for what they’re designed for (portable USB slow charging at 5V). Most of the stuff around camp is 12V, and the 12V output on the Goal Zero stuff (at least the Nomad series) is “limited” on both voltage and amperage, so it won’t efficiently charge 12V batteries. It’s possible to hack them, and remove their built-in regulator, but then the portability is reduced.

(Andrew) #10

I’m just not seeing any that are even in the ballpark of the prices you paid.

(Andrew) #11

FWIW, there is an OpenWRT build and a option in their online builder for the Tripmate Nano. No stock ROOter build, but that’s probably not as important (and can likely be compiled at some point).

Researching those lead me to the similar products by GL.iNet. What’s interesting to me about those is that the company just uses OpenWRT out of the box. The 300N-V2 is under $20 and uses <2W. The 300M and AR150 are interesting too.


It looks like that company went out of business. Probably why I got my panels so cheap. I looked up manufacturers of amorphous panels and most of them are going thin film.

We ran openWRT on the little tripmate. I wanted to hook up a raspberry pi to it and turn it into a meshnet node/server.

Thanks for turning me on to the BQ24650. I hadn’t looked into them in a while. I just got a friend’s plasma table running, which means that I can finish my cnc machine, which means that I can finally finish my camper trike, so it’s definitely time to finalize the solar plan for it.

The Gl.iNet routers look pretty awesome, and easy to hack too!

(Andrew) #13

Yes, the RPI3 B I have has a USB WiFi dongle with external antenna connector. With 2 wireless interfaces, it can be used as part of a mesh without a 2nd device. So while it does draw more power, it provides other options that can mitigate that. The bus and WiFi on the B+ that just came out have been improved somewhat.


I have a couple b+'s but haven’t even begun to explore their networking potential. I’ve been building CNC controllers out of them and will eventually be setting them up so I can check the camera and remote in over the net. Ever so often, the pi’s will lock up randomly and need to be reset, which is easy. Other than that, I think they’re pretty neat.