Cheap and easy construction of solar-repeater

here is my
Quik and very Cheap Solar Node installation:
It comes with a 18650 battery and the necessary 2,5mm connector for Wisblock. you just need to get an additional solar connector 1,5mm . It even comes with a monopod to fix it somerhere ! It can also be build with internal antenna (comes with wisblock) and used as a solar-powered Mobile node :wink:
if you have the bigger baseboard that came with meshtastic starter kit, that would probably also fit in.

the node has already been running outdoors some rainy days and is charging well.
It is rainproof, the Antenna and Antenna-connection have to be waterproofed some more after assembly .
the solar panel matches the solar input of Rak19003, so it can be connected directly.
Problems: I dont know about UV resistance of the Material, also very hot and very cold weather could damage the battery. I will spray paint the box in bright-grey to keep it a bit cooler in sunlight.

1 solar box:
1 Ipex-SMA Pigtail iPEX to RP-SMA Connector to LoRa® antenna – RAKwireless Store
1 SMA-Antenna for Lora (868 here)
1 1,5mm Solar connector for Rak-Wisblock Solar Panel Connector Cable/5 pcs solar wires
1 Rak 4631 (EU868 here) RAK4631: Nordic nRF52840 Sound Detector IoT Audio BLE Core LoRaWAN Module
1 RAK 19003 RAK19003: WisBlock Mini Base Board - Carrier for WisBlock Core MCU module
for battery Upgrade:
1 18650 2000+mAh +/- wired.

open the solar box (4 screws)
Disconnect battery wires, solar wires and 2,5mm connector from PCB
remove and discard PCB.
remove and discard all stuff, except battery, solar and 2,5mm connector.
maybe keep the battery of remote for later use
solder 2,5mm connector (wire to wire) to battery-wires.
battery can be exchanged for same size, but much higher capacity.
solder 1,5mm solar connector to solar-wires.
install Pigtail connector and atenna (a bit of cutting/adopting required here)
install pre-prepared Wisblock , with 1 screw.
connect BLE and Pigtail to Lora on wisblock.
connect solar and battery. check polarity first !
some cutting and closing holes required on lid
close lid, 4 screws. install monopod.


I checked the mAh of the included 18650 battery .
the Battery inside the solar box delivered 1250mAh down to 3,7V.
so it can be replaced by a 3500mAh if you like, but it is not really necessary.
i should last a good 4 days with no sunshine.
if replaced by a 3500, that should be about 10-12 Days.

so it depends on the situation of installation, if you expect some 3 weeks of darkness, it is also an option to put two 3500mAh inside… if there is not so much darkness in winter, the included battery may do the job.


It isn’t clear whether your battery has embedded voltage cutoff. The solar charge controller on the RAK will stop at 4.2V but there is no low voltage cutoff. The nrf52840 will continue operating down to 2.5V or so which will kill most lithium cells unless there is a low voltage cutoff.

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There is a good thread around here which provides a circuit design to ensure a switch off switch on restart to adress your point… great improvement to a solar powered rak4631

Battery protection circuits can be found on Amazon for less than $2 or you can buy batteries with it built in.

Oh nice… indeed, i found on amazon those lipo 3000mA with integrated protection… ill make try… my only worry is the automatic restart of the rak. It must come when voltage goes higher than 2.2v.
Anyhow thanks for your reply

What range did you get from this?
It looks perfect for my implementations

Agreed, I just wish the lithium batteries with internal cut-offs, would trigger at 3.0V and not 2.5v or 2.4V.

Although I suspect these battery built in cut-offs are just installed as last ditch safety feature in case the normal cut-off built into a device fails.

Anyhow, using a 3 Amp lipo with a solar panel would provide more than 10 days in the dark or under snow to reach a battery low level alarm :

  • I assume I dont use a GPS since the device is not located in a balloon but on top of a pole
  • I also assume the bluetooth is shut off (useless, energy wasting and unsecure)

Sooo battery low level is unlikely to happen.Should it happen, i want the rak to RESTART AUTOMATICALLY (no manual reset or battery unplug /replug) and the Lipo must not die if it happens once (there should be a maintenance check/visit after such an event so then I dont really care about the battery lifetime)…

A builtin battery low voltage protection will not be fine tuned enough for a restart during reloading. This i why ill build an electronic module like described in a thread around here… it will ensure a clean shut off and a restart at power on

In short : Ill analyze the safety requests, do some deeper studies and choose a relevant solution…this thread is a subset of requests which may include periodic pings checks, weather alarms, lightening impacts and so on…
thanks to you all for the discussion… have a nice sunday… and solar eclipse…

yes thank you for that hint. i better install a battery with protection. i will try different batterys soon.
if the node is built the cheapest way ( the included, only one non protected battery) it should not be unadministated , when power is going low, you would have to shut it down by admin channel command or bluetooth to prevent damage… but that way it wont restart either, so actually going low on battery is not an option for this device ! another option would be to reduce power consumption by changing settings, when battery is low… (no open repeating, just local device admin channel for administration… or just use Bluetooth and disable TX, that would save half the energy)
but the solar panel is quite sufficient for powering the device, so that i will see if this is nececesary.
also a good optionwould be to install a bigger 5000 Lipo pack including portiection, or 2 18650 with high Ah, so it wont run empty !

also the batterys have no heat or cold-protection, as it is said … “cheap and easy” will work in many enviroments, but not in arctic or hot-desert… and no superlong Dark-time-runtime…

you have a shopping link !?

i have not seen a empty-rak (of my raks) restart from solar yet… i will try again soon.
maybe if i put it in strong sunlight and cover it and quickly remove cover, to get an voltage burst to start it… have not tried yet.

range primarily depends on antenna and device/antenna position !
not on the device/box it is built on-to.
and on evironmet, specially how much noise… we have some 30km links around here with these devices. but that needs line of sight !
and things are more difficult in eu868 here !

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Nice. Pls keep us informed about your testing

i tested and let the device with “original” 18650 go empty.
it ended at 1,5V battery voltage. the battery is damaged after that an cannot be used any more !!
i discarded the battery and put in a proteced 2500 LIPO battery as seen in picture. below
it still is not an option for these (and other rak devices without additional battery/solar controllers) to go empty since there is no restart, but protection still is a good thing here…the deivce will shut down an is still rechargeable, manual restart required… (needs to open the box !)

going empty can be avoided by using some bigger battery 2000+ mAh… there is alot of room in that box, i think you could also fit 2 pieces (unprotected size) 18650 in there, what can add up to 7000mAh

and many weeks runtime

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