Solar relays - best practice?

Hi, I’m looking at the feasibility of using Meshtastic to track rowing boats in use on a secluded river (for both performance and safety reasons). Due to the low elevations, proximity to water and non optimal sealed enclosures, node range is unlikely to be great.

I will therefore need a number of solar powered, ‘idiot proof’ repeater nodes I can deploy permanently along the river to relay back to HQ (and or support staff). Has anyone built such a device - ideally in a weatherproof enclosure with a solar panel attached (and if so - how big a panel for always on relay use?)

Maybe something like this, but ideally not quite so spendy! RAK7205 LPWAN Tracker Node | GPS Tracking IoT Sensor Node | LPWAN BME680 – RAKwireless Store

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Welcome @warwick!

Sorry for the late answer. There are quite a few threads regarding this subject. I did list the first ones that came to my attention:

You might also be interested in the router mode for your stationary nodes: “mesthastic --set-router”. Furthermore, make sure that the hop limit (max TTL) will not be exceeded from the farthest nodes.

Please, share your findings and test results from the field, as real world feedback is valuable for this project.

I hope you luck for the event!


Ok, I am closer to doing some tests. I have 5 Groups of 2, 2.7V 500F super capacitors being charged off a 10watt solar panel. 16V, 0.59A. Goes into an MPPT controller set to output 5.6V 2Ah to charge the capacitors. Each cap has a protection board on it. Each pair is wired in series to make up 5.4V. Then wired parallel to get 5.4V 1250 Farad. From the capacitor it goes into a 5V USB Boost converter, which can provide 5V when the caps are at 1V.

I was hoping for some cold weather. But its 2 degrees C outside this week. Maybe February will bring some -40.

Right now the sun comes up by 0900 and is setting around 1645. I was able to measure 12v 4mA during a very grey overcast and possible snow day.



I’ve had some luck with solar lights.

This kind of stuff is one of those things where it is cheep or reliable, pick one.

If you don’t need them running 24/7, far from the equator (real winter) and don’t care if the batteries don’t keep up when you have several hours or days of cloud cover there are a lot of cheep options.

How many days do these events usually last? Would it be too difficult to pick up and drop off the repeaters and just charge the batteries?

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Well, what I was going for was a repeater you can leave out at a high elevation. Maybe your Ice fishing or sledding. Typically its already -25C and toward February we will go down to -35C to -42C for 2 to 3 weeks before warming back up to -25.

I lost 4 Ridgid 4Ah drill batteries last winter. They get cold and 1 or 2 cells will die. I was able to save 1 pack. I opened up the case and charged just the 1 cell back up to a similar voltage to the others and its been ok. Even your cell phone will suddenly power down on low battery. Bring it in to warm it up and it has %60 battery still.

These super capacitors can be deep discharged and cycle times are high. We will see how it all works when it gets cold and long nights. I missed the shortest day of the year, but theres always next year.

I did consider ‘deployable’ rather than ‘installable’ but part of the justification is 24/7 tracking of lone athletes training as well as the events themselves. I get low temps will be an issue, but its UK so a ‘typical year’ worst case is ‘minus low single figures’ at worst.

Physically mounting equipment for optimal use can be a bit pricey too.

Are you willing to (or have access to) drive some kind of pole in the ground to have somewhere to mount an enclosure, solar panel, and be able to have good antenna and solar panel orientation? Are you worried about theft, or your device being considered unauthorized litter or worse? Some places get very concerned when they find strange electronics left unattended.

All of these can be overcome quite easily in this particular scenario - it’s remote enough that the local pond life on foot are unlikely to get close, and the boating folk in general will keep a look out once they know its safety related. Depending on node range (to be determined in real life tests) it may be that there are enough close buildings / light poles with electric that the power bit ceases to be an issue. I can’t find much online in terms of real life range with non ideal antennae at low river level working to non ‘high building / telecom tower’ gateways… hence the need for tests.


Investing in an antenna tester and tuning your antennas can make a big difference.

Theres not many people out where I go. And now that its built, no sense it sitting in my Garage. Climb a tree and point it south. Maybe check on it once in a while if its not showing up. No cell service where I go.

If someone finds it. So be it. The panel was a spare. Just the cost of the Super Caps, protection circuit, MPPT. Ive lost higher cost items. Lost a car key in the bush once. That was a $600 woops

Hey, I’m wondering if you had a chance to test this solar repeater setup out in the cold? I’m in Alberta also and would like to build something similar to leave out in the elements. Batteries are not really an option for 7 months of the year.

Nothing yet - we are all confined to barracks with wu-flu lockdowns here in UK at present. I have been out on the push bike and some of the home-made onboard gadgets on that stopped working at around 1 degree C (wtih significant wind chill) so I have similar concerns now!

I have it outside right now. I didnt power up the radio. Its burried right now. I will see if I can shovel it out and fire up the radio and monitor it over the weekend.

The MPPT im using wasnt isolating the panel from the caps so they were discharging at night. I got a diode and put it between the Caps and MPPT. With no load Im expecting to find the caps fully charged.

I will bring it in, flash some new firmware and configure it to router, check the voltage of the caps and see how it goes.

Perfect time to test, we are finally getting the expected -35C weather this weekend. And SNOW finally!

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I’m looking forward to hearing more on this.

What capacitors did you use? You mentioned they have individual protection circuits. Is this off AliExpress?

Made me go look at weather forecast, -35DegC on the weekend, overnight. I hate winter.


Protection Boards

USB Boost Converter


Schottky Diodes

Momentary Switch w/ 3v LED

I had the solar panel already and the deep frame allowed me to package everything in behind.
Solar Panel says 15.8V and 0.59A

The solar panel goes right into the MPPT. It is configured to output 5.6V on the output and max 2A, which I think is very close to factory setting. I soldered the wire to one end of the diode and put the other end of the diode under the screw terminal on the Output + of the MPPT. This goes to the capacitors and to the USB. The Capacitors are wired 2 in series, if you are careful when you get the protection circuit, they are attached together. If you dont break them apart they solder to the caps together and then I used a 2 part epoxy to weld the caps together. 5 sets wired in parallel. I removed the USB port from the board and soldered wires in place. I also removed the red LED from the USB power board. I went straight from the USB board right to the battery connector on the Lora32. The USB board can maintain 5v output right down to 1v on the capacitors. The losses on the USB board were very small when it was plugged in and nothing was attached to it after I removed the LED. As for the switch and the LED, I soldered one to the 3v pin on the Lora board and used pin 13 / 15. But I haven’t programmed them to do anything yet. You could maybe even wire the button to the RST on the board to reset it without opening the case. It was more of a future incase I wanted it.


I plan on making my solar repeater look governmental and make a small sticker up that says “Air Quality measuring device” (Please dont disturb)

Im Canadian, so this should make it theft proof. lol


Thanks for taking the time to write this up.

Please let us know how it holds up in the cold.

I forgot to mention, if you plan on charging these capacitors for the first time, just becareful because they want to pull a lot of current. I had to increase my wire size and ended up charging them through the MPPT since it regulated the current. I melted the first set of wires.

I should probably install a 3A fuse between the Caps and MPPT and a 1A fuse between the Caps and USB board.

OK, Up date.

Thursday, I brought the panel in from sitting under a few inches of snow, the voltage was 1.5v and I had the radio powered off. I was little disappointed the voltage was so low with no load, but This is an older panel and it was buried in the snow.

I updated the firmware to the latest release and set router mode. I then placed it outside later that night. I think it was -25c overnight.

Friday was overcast and light flurries, the panel was sitting up a little higher and didn’t get much snow on it. Friday night the temperature continued to drop to -35c.

Saturday was a great day. One upside to extreme cold weather, clear blue skys. The panel was in direct sunlight for most of the day. I had to move the panel from the backyard to the front yard later in the day to keep it from being shaded by my neighbors house. The temperature continued to drop into the night.

Sunday morning when I got up it was -44c, I grabbed some gloves and brought it into my garage to open it up and check the voltage, it was 2.5v and the radio was still powered. So far success. Closed it back up and its still outside.

1 disappointment, and I’m not sure why right now. Since turning on router mode It never shows up in the Metastatic App for a Bluetooth connection. This could just the power saving features of being in router mode. But more importantly, it never appears to be online in the Mesh. When I connect to my T-Beam and send a message, the app only ever shows 1of1 devices. But as far as cold weather charging and keeping it powered throughout the night, I think its doing well.

If anyone is curious what its like to live in an area that gets this cold… this is what happens when your windows don’t seal real well after a few years. All of our windows get condensation on them and they freeze on the inside.


This actually looks promising. The fact that it is able to charge and hold a charge at those temperatures is worth further research.

I’ll order some super capacitors and set something up to do some additional testing and trending.

As for your windows not sealing properly; over the years I tried three different PVC window manufacturers, low E glass and all, they still ice up in -40DegC. Best you can do is reduce humidity for those few extreme cold weeks.