LoRa SolarNode repeater case for MeshCore / Meshtastic, Xiao nRF / Helltec T114

A compact LoRa SolarNode case that is suitable as MeshCore/Meshtastic® repeater. It offers enough space for up to 4x 18650 cells.

🛠 WORK IN PROGRESS:

• This project is still work in progress. Some dimensions still might change in next iterations. I already printed v1 to v3. Version 1 is running fine for about a month now in cold and wet environment and version 2 for about 3 weeks.

• I tested some new solar panels made of glass instead of epoxy, that are said to be less prune to yellow or get cloudy. They do work fine, so I added another version of the base.

• I tested some BMS boards, which can be mounted under the battery holder. They seem to work fine and be a suitable solution for more safety. I added them to the BOM and instructions.

⚠ ATTENTION: I received a lot of feedback from the community. Most of you like the design, but some were concerned, that a 3D printed case may leak and let moisture inside without proper spray paint or a better gasket made of silicone sealant. I'll leave the decision up to you. So be warned... 😊

✂ NOTE: The base is suitable for different vendors/dimensions of solar panels. Whenever you need a custom size of the case, feel free to reach out to me via direct message.

Features and design specifications:

• Large solar panel, but compact design

• Easy to assemble, only 3 printed parts

• Modular, parametrizable design

• Option for different back covers (either a flat cap or a polemount)

• Enough space for up to 4x 18650 cells

• Integrated BMS on single cell level

• Uses N-type antenna connector

What you need

The solar node can be built in different configurations by selecting the proper back. Currently, either a flat cap or a vertical align polemount is available. The base is required in any configuration. Please print your parts and choose your hardware accordingly.

Please note: All links to Amazon (amzn.to), AliExpress (s.click.aliexpress.com) or marked with * are affiliate links (ads), through which I receive a small commission. Perhaps you would like to support my work by making a purchase.

Parts used (BOM)

Base (required in any configuration)

• 1x solar node base (printed)

• 1x solar node gasket (printed)

• Alternative: some silicone sealant

• 10x M3 heat inserts
  https://amzn.to/4pCMEcw

• 10x M3 stainless washers, standard size (small ones)
  https://amzn.to/4ateL9s

• Seeed studio XIAO nRF52840 & SX1262 Kit (select proper frequency!)
  https://s.click.aliexpress.com/e/_c3FTPBUH

• N-type female antenna connector with u.FL pigtail, 10cm worked fine for me
  https://s.click.aliexpress.com/e/_c4CjWKYD

• CN3791 MPPT solar panel regulator (choose 6V version)
  https://s.click.aliexpress.com/e/_c4naj8yH

• Solar panel 6V 6W 210x165mm (epoxy)
  https://s.click.aliexpress.com/e/_c2zV2wRF

• Alternative: Solar panel 6V 5W 175x175mm (glass)
  https://s.click.aliexpress.com/e/_c4WYcUr5

• Battery holder 4x 18650
  https://s.click.aliexpress.com/e/_c4TLfnuh

• LiIon BMS (1 per cell)
  https://s.click.aliexpress.com/e/_c45VdaP9

• 18650 LiIon cells (known brand)
  https://www.nkon.nl/de/samsung-inr18650-35e-3400mah-8a.html or https://www.nkon.nl/de/samsung-inr18650-35e.html (order 4 identical cells of same type and brand!)

• Alternative: 18650 LiIon cells (unknown brand)
  https://s.click.aliexpress.com/e/_c3SBJkvP (pack of 4 identical cells)

• Outdoor N-type female antenna (select proper frequency)
  e.g. Ziisor 3dBi https://s.click.aliexpress.com/e/_c3pR1c81 or Ziisor 5.5dBi https://s.click.aliexpress.com/e/_c4dqNZ0V

• Some cables

• Some JST plugs (should be JST PH2.0), your CN3791 should contain two cables (mine did)

• Some silicone sealant to glue the panel on the case (or replace the TPU gasket)

• Some tissue paper, to prevent silicone sealant messing all up

• Optional: some spray paint to seal the case and cap

Cap (option 1)

• 1x solar node cap (printed)

• 10x M3x8mm stainless screws, flat head
  e.g. https://amzn.to/3YquoXR or https://amzn.to/4q6tGL8

Polemount (option 2)

• 1x solar node polemount (printed)

• 10x M3x8mm stainless screws, flat head
  e.g. https://amzn.to/4jqeUNh or https://amzn.to/4pijmiF

Tools used

• 3D printer with a large enough print bed (obviously)

• Soldering iron, solder etc.

• Cutter knife and/or chisel

• Optional: fine sandpaper (P180 or higher)

• Silicone sealant to glue the panel on

• A caulking gun

• A silicone spatula or similar

• Hotglue for mounting the pcbs

• Maybe: Heatshrink for insulating some soldered wires

Suggested print settings

• Rafts: No

• Supports: No

• Brim: Yes, 10mm should work to prevent warping (hopefully)

• Resolution: 0.2mm

• Infill: 30% or higher for case and cap, 100% infill for gasket

• Top/bottom layers: 4 or more

• Perimeters: 4 or more to get a sturdy and leakproof case

• Material: ASA/ABS for base and cap/polemount, TPU (95A, maybe softer) for gasket

Instructions

Print base, cap and gasket

Print base (choose correct size depending on your panel) and cap/polemount from a material resistant to heat, UV and weather (e.g. ASA/ABS) and the gasket from TPU (shore hardness 95A worked for me).

Add heat inserts

Use your soldering iron to melt the M3 threaded inserts into the holes on your solar node base. Try to get them as flush as possible, in case of doubt a little bit deeper. Please do yourself a favour and use helical cut inserts. The cheap ones do not withstand the pulling force of proper tightened screws and will get loose over time. Ask me how I know... 🙄

Clean the sealing surface

Remove any excess plastic and smooth out the sealing surface. I used a cutter and chisel, but you might use fine sandpaper on a flat surface. Just try to remove any imperfections to get a smooth surface to prevent any leakages. My first versions had too small holes for the heat inserts I used, therefore a lot of plastic came out. Version 3 has improved the dimensions and should work better.

Spray paint your case and cap (optional)

You might spray a few layers of paint on your case and cap to make it more resistant to water and moisture. I haven't painted/sealed mine. After over a month on my balcony with rain, snow and ice I haven't experienced any problems, yet. Maybe it is needed, maybe not. Time will tell... 🤷

Attach the antenna connector

Insert the antenna connector. Make sure to install the o-ring from the antenna connector to seal the antenna outlet and prevent leakage. Maybe you want to add a little silicone sealant? Tighten down the large hexnut on the outside, but don't overtighten it. You don't want a cracked case.

Solder cables to the solar panel

Use your trusty soldering iron to attach two wires on the solar panel. Be cautious not to heat up the panel too much, or it'll get damaged. Use color-coded wires (red/black) to identify the polarity later.

Glue the solar panel onto the case

Insert the silicone sealant into your caulking gun. Spread a continous but not to thick loop of sealant around the outer perimeter of your solar panel. Add a second loop around the soldering pads your cables are attached to. Fill in the remaining area with some small lines but don't overdo. Feed the cables through the proper inlet and place the panel centered on the case. Press the panel down on a flat clean surface to spread out the sealant. Correct the position again and remove any excess sealant.

Now seal all the edges between solar panel and case to prevent any water from getting in. Use a silicone spatula to remove excess material and a wet finger to flatten it afterwards.

Let the sealant dry for a few hours before you proceed. Otherwise it'll get messy.

Install the electrical components

⚠WARNING: Do NOT insert the 18650 cells before attaching your antenna and checking all polarities twice. It might damage your board!

Solder a JST plug onto the cables from your solar panel. I cut a premade cable from the CN3791 in two parts and attached one side to the solar panel cables. Use some heatshrink if needed. Have attention to get the polarity right. If unsure, you may plug in your JST connector into the CN3791 without the panel attached. Maybe you have to swap the electrical contacts inside the JST connector. A small pin or needle might help removing them from the connector case to switch places.

Solder your second JST connector with a cable to the XIAO nRF board. The solder pads are rather small and located on the bottom of the upper board (the one with the USB-C socket). Check the polarity of your JST connector according the socket on the CN3791 board.

Connect each slot on your battery holder with an own BMS board. Wire all BMS boards in parallel and connect another JST plug. As expected, check your polarity again at this step.

Screw on the antenna to prevent frying your board as soon as it is provided with energy later.

Attach the antenna cable to your SX1262 and place your battery holder and all boards into the case. Attach all cables accordingly (solar panel -> CN3791, CN3791 -> battery holder, CN3791 -> XIAO nRF). Find a suitable configuration and add some hotglue to fix all components. I didn't glue my battery holder into the box so I can remove it and eject all cells more easily.

Check your 18650 cells to have the same voltage! If not, use a proper charger to load all cells. Do not mix different cells! Insert the cells one by one. Be sure to match polarity!

Now flash your board with the firmware of your choice and setup all configuration.

Install gasket, cap/polemount and screws

Have a look at the gasket and remove any blobs and zits to have smooth surface. A lighter might help removing some excess stringing. Lay the gasket onto the sealant surface of your case.

Add the cap or polemount and attach all washers and screws. The cap uses M3x8mm screws, whereas M3x10mm screws are needed for the polemount. Tighten them by hand. Make sure you get a firm fit, but do not overtighten them.

Congratulations

You built your own compact solar node. 👍

Changes

• Version 0.1 (2025-12-07): Initial design

• Version 0.2 (2025-12-09): Changed some dimensions (e.g. cutout for antenna hexnut to small, holes in gasket and cap too large)

• Version 0.3 (2025-12-14): Increased size of holes for heat inserts in housing

• Version 0.4 (2026-01-03): Added polemount and updated BOM/instructions accordingly, v4 parts are compatible to prior v3

• Version 0.4b (2026-02-10): Added new base size for alternative solar panel.