Build Guide: Hilltop Mesh Repeater S
The Hilltop Mesh Repeater S: 1 W of solar facing vertically south, two 26700 cells as a buffer, antenna directly on the enclosure — with the Inhero MR2.
1. The Concept
The Hilltop Mesh Repeater S is the compact configuration: 1 W of solar in vertical south-facing mounting, two 26700 cells as a buffer, an N bulkhead jack for the direct antenna connection and a clamp for 30 mm masts. An off-grid solar system is dimensioned for the least energetic month, not for the annual yield — in Central Europe that means January. As a rule of thumb, a vertical, unshaded south-facing panel delivers around 1 Wh per day and Wp in January; the MR2 consumes a measured 1 Wh per day. The balance is tight and calculated exactly that way.
The site decides: An unshaded, exposed position and exact south orientation are mandatory for the S — the tightly dimensioned panel depends on every hour of sun. For partially shaded sites or ones that cannot be oriented ideally, the Hilltop Mesh Repeater L with twice the panel area and a larger battery compartment is the right choice. The complete design rationale is on the kit page and in the article Why the MR2 Exists.
The enclosure consists of two main parts: the base carrier with the battery compartment, MR2 mount and lower clamp shell, and the hood, which carries the solar module, the antenna mount and the upper clamp shell. The base carrier is fully populated first, then the hood goes over it — the mast clamping holds both parts on the tube.
Why Na-ion here — and what it costs
The repeater shown is fitted with Na-ion cells, connected directly to the MR2 without a protection module. Nominal capacity is modest as a result. The advantage of this chemistry does not show in a 25 °C datasheet but in winter, and it has two sides:
- Lower cold derating: Na-ion loses considerably less usable capacity at low temperatures than the lithium chemistries. What is little on paper therefore barely shrinks further in frost.
- Full charging even in frost: LiFePO4 and Li-ion throttle around the freezing point and block charging entirely below it by chemistry — exactly when there is hardly any yield to begin with, the little sun available goes unused. Na-ion accepts the full charge current in frost as well. Every hour of winter sun ends up in the battery.
That makes Na-ion the more interesting choice for high-altitude sites with long frost periods — where a nominally larger lithium bank delivers less in January than its number promises.
An honest classification: This configuration — a 1 W panel and roughly 5 Ah of buffer — is cut extremely close to the bone. It is built as a test platform for winter 2026/27 and explicitly not a validated recommendation. Anyone who wants reserve rather than measurement data should fit higher-capacity Li-ion or LiFePO4 cells (then with a protection module and fmax, see section 9) or go straight to the L. Findings from winter operation will be added here.
Not a submarine: Many makers build very tight enclosures, some with a pressure-equalization membrane or a 1 mm drain hole in the bottom. The Inhero enclosures deliberately take the opposite approach: airy by design, with no sealed volume. There is no trapped moisture and no condensation problem, yet the electronics are reliably protected from the weather. This concept has proven itself in the field over years.
2. Parts List
2.1 From the Shop (included in the kit)
| Pos. | Component | Qty |
|---|---|---|
| 1 | MR2 solar mesh repeater board | 1 |
| 2 | U.FL retaining clip, ready-printed (PETG) — included with every MR2 | 1 |
| 3 | Solar panel 6 V / 1 W with pre-soldered cable | 1 |
| 4 | MR2 battery cable — choose variant: LiFePO4 or Li-ion protection module, or without BMS (open ends, for LTO and Na-ion) | 1 |
| 5 | Pigtail N bulkhead jack → U.FL, 15 cm | 1 |
| 6 | BLE adhesive antenna 2.4 GHz, U.FL | 1 |
| 7 | Screw set for MR2 mounting (stainless steel A2, T8) | 1 |
| 8 | Stainless steel bolt set for mast mounting (3 × M6×50 mm TX30 + 3 × M6 nuts) | 1 |
| 9 | ZIISOR 868 MHz fiberglass antenna with N-male connector — depending on the chosen kit variant: 3 dBi (26 cm), 5.5 dBi (40 cm) or 8 dBi (55 cm); not included with the “no antenna” variant | 1 |
2.2 To Source Separately (not in the kit)
| Component | Qty | Note |
|---|---|---|
| 26700 cells — matching the chosen battery cable variant! | 2 | The build shown uses Na-ion (NaFR26/070, 3.0 V, 9.6 Wh ≈ 3200 mAh per cell) with the without-BMS variant. LiFePO4 and Li-ion are operated with their respective protection module and put considerably more energy into the enclosure; LTO needs 2S with an external balancer — details in the battery chemistry guide. |
| Antenna with N-male connector — only with the “no antenna” kit variant | 1 | Omni antenna with N-male connector. Please note: the sealing bushing is dimensioned for the base diameter of the ZIISOR fiberglass antennas; all three ZIISOR models share the same base. Antennas with a different base diameter cannot be sealed properly against it. |
| Filament | — | Weather- and UV-resistant — very well suited: ASA-CF. On color choice, see the note in section 3. |
| Adhesive/sealant: WEICON Flex+bond, 85 ml, transparent | 1 | MS polymer, permanently elastic — bonds the solar module and the antenna-base sealing bushing to the hood |
| Adhesive-lined heat-shrink tubing | — | seals the transition from the sealing bushing to the antenna |
| Small parts | — | Kapton tape, fabric tape, spiral wrap, insulation material for the battery pack |
2.3 Tools
Soldering iron, spot welder (only for bare cells), Torx bits T8 (MR2 screws) and TX30 (mast clamp), side cutters, multimeter for matching cell voltages, hot air for the heat-shrink tubing. No wrench is needed — the M6 nuts sit captive in the hex pockets. For the Na-ion build you also need fine tweezers or a depinning needle to release the NTC wire from the connector housing (section 6).
3. Printed Parts
STL files: free download in the shop. The set consists of three parts: the base carrier (battery compartment, MR2 mount, lower clamp shell), the hood (panel surface, antenna mount, upper clamp shell) and the sealing bushing for the antenna base — the clamp jaws are integrated into base carrier and hood. Everything fits on one build plate. The U.FL retaining clip is not self-printed — it comes ready-printed in PETG with every MR2, because PETG has the elasticity needed for clipping while the brittle ASA-CF is unsuitable for it.
Color choice: The enclosure shown is printed in gray ASA-CF. Gray heats up considerably less in the summer sun and is the thermally more relaxed choice for the battery; black is less conspicuous at the site. The inside temperature can be monitored via the MR2's telemetry.
Arrangement on the build plate: base carrier on the left, hood on the right — each with its integrated clamp shell — and the sealing bushing printed upright in between.
Set painted-on supports along the upper edge of the panel recess: pick the fill tool and click the edge — the smart fill angle (here whatever Bambu Studio preset) governs how far the marking spreads. It should catch exactly the narrow strip; if it runs too far or stops short, adjust the angle accordingly. The automatic detection does not reliably catch this small overhang — and without a clean upper edge the solar module will not sit flush in the recess later.
A look at the slicing result pays off before printing: supports should stand at the painted edge and in the recesses — and nowhere else.
4. Mounting the N Bulkhead Jack and Antenna
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Insert the pigtail's N bulkhead jack into the antenna mount of the hood from the inside and counter it from the outside. The jack sits on the flat top face, right next to the mast clamp.
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Check from the inside: the thin U.FL pigtail hangs freely inside the hood and is pushed onto the MR2's LoRa connector later, when the hood is fitted.
5. Gluing the Sealing Bushing and Solar Module
Gluing is done with WEICON Flex+bond: the sealing bushing at the antenna base and the solar module. By this point the antenna is already screwed onto the N jack and the sealing bushing slid over it.
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Apply an adhesive bead all around the seat of the sealing bushing.
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Slide the bushing down onto the hood, rotating it several times while doing so — the rotation spreads the adhesive evenly across the entire seat. Do not press too hard: a sufficient layer thickness must remain; the permanently elastic layer seals and absorbs movement and thermal expansion.
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Apply a perimeter adhesive bead to the back of the solar module and thread the cable through the pass-through in the panel surface.
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Insert the module, press gently, leave the adhesive layer standing. Finished, the hood looks like this — panel flush, antenna base sealed.
6. Building the Battery Pack — Na-ion Without BMS
Use only undamaged brand-name cells. Mind the polarity. Never solder directly onto the cell can. The cell chemistry must match the ordered battery cable variant — for LiFePO4 and Li-ion the protection module is a mandatory component, not an accessory.
Why Na-ion works here without a BMS: The build shown uses two Na-ion cells (26700, 3.0 V) in parallel, directly on the MR2, with the without-BMS battery cable variant. The two jobs a protection module otherwise performs do not apply to this chemistry: deep discharge is uncritical for Na-ion, and the charge-termination voltage is limited by the MR2 itself once the cell chemistry is set with set board.bat naion1s (section 9). For lithium chemistries this explicitly does not apply — there the protection module remains mandatory.
And why Na-ion at all: not for the capacity — that is modest — but for the winter behaviour: low cold derating and full charge acceptance in frost (section 1). For high-altitude sites with heavy frost that is the decisive difference; for mild locations, Li-ion or LiFePO4 with considerably more capacity are the more sober choice.
Important — balance before connecting in parallel: both cells must be brought to the same voltage before connecting, maximum 10 mV difference (multimeter!). If cells at different voltages are connected in parallel, high equalizing currents flow instantly — quite literally: sparks fly.
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Connect the two cells in parallel and attach the lead of the battery cable.
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Depin the NTC wire (yellow) from the connector housing. Na-ion needs no JEITA temperature monitoring and therefore no battery temperature sensor — the third wire is simply dropped. Plus and minus remain in the connector. Release the contact's latch with fine tweezers or a depinning needle and withdraw the wire completely from the housing; do not yank on the cable, or the crimp will tear off and leave the contact stuck in its chamber.
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Insert the battery pack into the base carrier and secure it. The cells sit in the recesses in the upper part of the base carrier; the lead is routed down towards the MR2 mount.
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Check: cells firmly strapped down, cable neatly routed, nothing chafing.
7. Mounting the MR2
Caution: switch off the MR2 with the DIP switch before connecting the battery, and never power it on without the LoRa antenna connected — otherwise risk of damage to the LoRa TX. Mind the inverted switch logic: switch position “On” activates “3.3V off” (as printed on the silkscreen) — the board is then off. The LoRa pigtail is connected only when the hood is fitted.
Mount the MR2 on the base carrier with the supplied T8 screws, stick the BLE adhesive antenna below the board and connect it, plug in the battery cable.
8. Fitting the Hood and Wiring
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Fit the hood, plug the solar module into the MR2's solar input and push the antenna pigtail onto the LoRa U.FL connector of the RAK module. Then snap on the U.FL retaining clip (included with the MR2).
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The clip is no gimmick: when sliding hood and base carrier together, the LoRa antenna's U.FL connector can pop off unnoticed — for a repeater on a mast, the worst case there is. The clip mechanically secures the connection; the reset button remains accessible.
9. Configuring the MR2
Firmware: The MR2 ships without application firmware (OTAFIX bootloader only). Flashing is most convenient before enclosure assembly (section 7), while USB-C is freely accessible. Two prerequisites: the LoRa antenna must be connected — after flashing, depending on the firmware version, transmission by the repeater cannot be ruled out — and the board must be switched on, otherwise flashing does not work. Mind the inverted switch logic: switch position “On” activates “3.3V off” (silkscreen label), the board is then off — so for flashing and operation the switch is set to “Off”. Then: press the reset button twice in quick succession (double reset), the board mounts as a USB drive, copy the .uf2 file via drag and drop. Ready-made, tested MeshCore builds for the MR2 are available in the firmware releases on GitHub.
To configure, switch the MR2 on — both antennas have been connected since section 8 — and connect via the MeshCore app using the admin access. The values for this build (two Na-ion 26700 cells, 1 W of solar):
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set board.bat naion1s— cell chemistry 1S Na-ion; defines the charge-termination, sleep and protection thresholds. In a BMS-less build this command is the cell protection — it must not be forgotten. -
set board.batcap 5000— battery capacity. Nominal capacity is 2 × 3200 mAh = 6400 mAh; less than that is usable, because Na-ion delivers its nominal capacity down to well below 2 V while the MR2 cuts off considerably earlier by design. The deduction is therefore larger than the 90% rule used for LiFePO4 (FAQ #4) — in exchange, the SOC display and runtime prediction are honest. -
set board.imax 300— maximum charge current following the rule of thumb panel power ÷ battery voltage: 1 W ÷ 3.0 V ≈ 330 mA, rounded down conservatively to 300 mA. A value set too high makes the panel voltage collapse in weak light and the charger stops (FAQ #5). -
set board.mppt 1— enable MPPT. -
set board.leds 0— board LEDs off: they save power and are invisible inside the closed enclosure anyway.
No fmax with Na-ion — and that is the point: Limiting the charge current around freezing is a lithium property; with LiFePO4 and Li-ion, charging is throttled near the freezing point and blocked entirely below it by chemistry. Na-ion accepts the full charge current in frost as well, which is why the command is absent from this configuration — that is exactly what this pack is for. With a lithium pack, set board.fmax 20% belongs in the list (FAQ #6).
Check: get board.conf shows all configured values at a glance, get board.selftest probes the onboard components. Then fully charge the battery once (e.g. via USB-C): the coulomb counter needs one full charge as its 100% reference — until then, the SOC shows “N/A”. For a different configuration (Li-ion, LiFePO4), adjust board.bat and board.batcap accordingly; all commands are explained in the CLI reference.
10. Final Assembly and Sealing
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Insert the three M6×50 screws (TX30) into the clamp shells and pre-assemble them loosely. The M6 nuts sit captive in the hex pockets — no wrench needed. Hand-tight only; final tightening happens at the mast, following the procedure in section 11.
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Seal the transition to the antenna with adhesive-lined heat-shrink tubing. The tubing covers sealing bushing and antenna base; the hot-melt adhesive inside seals permanently. That completes the repeater.
11. Location & Mast Mounting
- Orientation: solar surface vertical and facing exactly south, unshaded. With the S this is not a recommendation but a prerequisite — the design has no reserve for partial shading. Where that cannot be achieved, the L belongs there instead.
- Mounting — clamp for a 30 mm mast, tighten the screws (TX30) carefully: two screws pull in parallel on the upper clamp shell. Tightening one loosens the other — anyone who then forcefully alternates adds up the tensile forces and cracks the ASA-CF. So tighten alternately and in very small increments until the clamp sits firmly on the tube. No tighter than necessary. Then set the lower clamp shell with its single screw just as carefully.
- Radio: every meter of height adds range — and short antenna paths remain the principle: the antenna sits directly on the enclosure, 15 cm of pigtail, no cable losses.
- Frost locations: this is exactly where the Na-ion pack plays to its strength — full charge acceptance in frost and little cold derating. For high-altitude sites with long frost periods it is therefore more interesting than a nominally larger lithium bank that throttles or blocks in January.
- Energy — and the caveat: 1 W vertical south covers the MR2's daily consumption in Central Europe even in January, on paper. With roughly 5 Ah of buffer, however, hardly any safety margin remains: this combination is the test platform for winter 2026/27 described at the start, not a validated setup for unattended long-term operation. Anyone who cannot keep an eye on the site via telemetry should build considerably larger with Li-ion or LiFePO4. And should the battery ever run empty after all, the MR2 goes into deep sleep and wakes up on its own once the sun has recharged the battery — so an empty repeater means a gap in coverage, not a total loss.
12. Legal & Safety
- The kit contains tested, compliant individual components (MR2: CE/RED). Final assembly is carried out by the buyer at their own responsibility for personal use.
- This guide was written to the best of our knowledge but does not replace expertise. Handling battery cells requires care: the instructions in section 6 — matching cell voltages before connecting in parallel, the correct battery cable variant, a protection module for lithium chemistries, insulation, short-circuit risk — are mandatory. Building this project is at your own risk; no liability is accepted for damage resulting from improper assembly or unsuitable components, to the extent permitted by law.
- Operation in the 868 MHz band in accordance with the applicable regulations (duty cycle); the MR2 enforces these in firmware.
© Inhero GmbH · shop.inhero.de · Enclosure design (STL/3MF files) licensed under CC BY-NC-SA 4.0 — private reprinting and further development expressly welcome · Version 1.4