Helium Hotspot Off Grid Solar Set Up for Nebra Outdoor Miner

This is very much a work in progress.

This instructable covers the build of a base for a Nebra Outdoor Helium Hotspot that contains batteries and a solar panel to allow the hotspot to be deployed remotely.

The Nebra Hotspot is fitted with a 4G Modem connected the the Three network in the UK so should in theory work pretty much anywhere.

These are the parts that I have bought/made for the enclosure for the battery bank and solar charging solution to ensure that my Nebra outdoor hotspot stays powered while located completely off grid!

This was a bit of a lucky find in the garden, it turned out to be EXACTLY the right size for the lead acid batteries that I wanted! You are not going to find one but the dimensions are 400mmx400mmx6mm with a 50mm diameter, 2mm wall, 250mm long tube attached in the middle.

This is the foundation of the build and everything else is constructed around this.

For the batteries I chose lead acid over Lithium simply on a cost basis. I purchased 4 of these 12v 32Ah 063 Powerline specials from Tayna Batteries

https://www.tayna.co.uk/car-batteries/powerline/06...

Each battery is 210mmx175mmx175mm

The batteries didn't come with covers for the terminals and as I planned to place them in a metal enclosure I figured that I ought to have some.

This was the first 3d printing section of the project where I put my resin printer to work. Some simple rectangular covers that are 2mm thick with mounting lugs matched to the batteries.

I bought a solar charge controller to handle the charging tasks, Amazon is my go to

https://www.amazon.co.uk/gp/product/B07PV6MRRY/ref...

I did some modifications as I dont like screw terminals and wanted a plug in solution. I directly soldered on 2 sae connectors for the battery and solar panels to connect to. Note that the plugs for the battery and solar panel are different gender combinations to prevent connection errors.

https://www.amazon.co.uk/gp/product/B09B22SVDX/ref...

As well as a plug suitable for the power input on the Nebra hotspot (although an extension will also be used).

https://www.amazon.co.uk/gp/product/B08LW18D9Y/ref...

I have added an ESP32 LoRa board to monitor the battery voltage. This uses a 30k and 7.5k resistor to provide a potential difference so that the input can be scaled from 0-26.5v to 0-3.3v which will not destroy the input circuit! I also have a 12v to 3.3v converter that is used to power the board itself.

https://www.amazon.co.uk/gp/product/B099ZMYQ4L/ref...

The wiring harness is, as you would expect, very simple. Just 8 brass battery terminals, some ring connectors, wire, and heatshrink required. It is wired as 1 series 4 parallel so I end up with a battery of 12V and 128Ah.

You can see that the connection from the batteries to the charge controller is the sae connector at the bottom and that the ESP32 board is at the top.

The battery enclosure itself is made out of 40mmx40mmx3mm angle iron to clamp down the batteries and 4 406mmx185mmx2mm steel plates to form the sides. This is all combined in to a single piece that slides over the batteries.

You can also see that I have added a ipex to SMA bulkhead mount to connect to the ESP32 board and a bulhead mounted sae connector to connect the solar panel to.

https://www.amazon.co.uk/gp/product/B088W1VNR2/ref...

The panel that covers the top of the batteries is 410mmx410mmx2mm steel plate with a 64mm hole drilled out of the centre for the pole.

I have then employed the 3d printer to create a collar to help take up any tolerance and from a seal around the 50mm tube from the parasol base.

To clamp down and secure the batteries, M10 studding is used between the parasol base plate and the upper angle iron section of the enclosure with stud extenders used to allow countersunk screws to be used to attach the two.

Another 3d printed part is the adapter that converts the 50mm diameter tube on the parasol base to accept the 34mm diameter pole that I am using for the hotspot mount.

I did some calculations, and decided that I would try a 50w Solar Panel. I think I may need another in the winter months but the design is flexible enough that I can add a bigger panel or supplementary panels as required.

https://www.amazon.co.uk/gp/product/B07L92RL58/ref...

As you can see I have added some 40mmx40mmx2mm aluminium profile to accept a u-bolt fitting to attach to the pole.

Some flat aluminium stock is used to create the bottom supports for the panel and has been bent to a z shape to ensure the correct angle is created for the panel.

I have custom made a pole mount that is specifically for the Nebra Outdoor Hotspot. It uses the lower 2 antenna holes that I will not need and the centre grommet fits snugly inside the tube (with another 3d printed bung).

The mount gives a nice clean look with no visible wiring as it all runs down the inside of the pole.

For a true off grid install I have purchased a 4G Modem and I am using the three UK network with an unlimited sim to provide the required connection to the internet.

https://www.amazon.co.uk/gp/product/B08MKL3M8C/ref...

The installation and configuration details can be found on the Nebra website

https://helium.nebra.com/outdoor-hotspot/lte-confi...

I also have 2 LTE antennas from Nebra directly along with the ipex to N-Type bulkhead connectors to ensure that the unit remains watertight.

The batteries are positioned around the parasol base so that the 4 +ve terminals are in a ring close to the centre and the 4 -ve terminals are in a ring around the perimeter. It makes best use of the space that is available and as mentioned before they are a perfect fit. The eagle eyed may see that I have had to 'fettle' the corner of some of the batteries as the tube is not perfectly in the centre.

The studding is installed around the edge of the parasol base, and due to the orientation of the batteries is NOT in the middle of the edge of the base. You can see that the studding connectors are almost flush with the top of the batteries and this allows the angle iron to clamp down tight.

The wiring is very simple and having the terminals aligned as the are gives a nice neat installation. You can see that the terminal covers do their job and that the charge controller is all powered up.

The enclosure simply slips over the batteries and is bolted down with 4 M10 countersunk screws. This will allow the top plate to sit flush.

The top plate is secured with 12 M4x3mm screws around the perimeter in to the angle iron that has been drilled (M3) and tapped to accept them.

You can see the holes in the front of the enclosure that will be used to mount the lower stays for the solar panel.

The solar panel will be mounted on the pole and using the stays will be adjusted to the correct angle. As I dont have the pole on location at the moment I cant do the full mock up! You can see though that the solar panel simply plugs in to the bulkhead connector and can be easily changed if required.

As I dont have my pole, here is a short length of tube showing what it will look like!

Before putting it in the field I have set it up in the garden to test everything is working........

The ESP32 board is programmed to monitor the analogue input on one of the GPIO channels. This, as mentioned before is scaled so that it can read 0-26.5 volts. The voltage is interpreted by the code and split in to 2 bytes that are integers representing the units and decimals. So for example 12.70 would be 12 and 70. This is then sent via the Helium network using the attached hotspot to the helium console.

https://console.helium.com

Here the two integers are recombined in a function and the voltage is passed to Ubidots for monitoring.

function Decoder(bytes, port) {

return { volts: bytes[0] + "." + bytes[1] }; }

Ubidots is quite flexible and you can set up SMS or telegram alerts to notify you when the battery is low etc.

As well as monitoring the voltage with the ESP32 board I have added a hall effect current sensor to see what the Nebra unit is drawing.

https://www.amazon.co.uk/gp/product/B098WP5GPF/ref...

It looks like the average over the last few days it is about 0.69A which at 11.5V (regulated power to the hotspot) is 7.93W. With these numbers the hotspot requires 16.56Ah per day. This, for my 50W panel means 4 hours of PERFECT sunshine per day.

You can see from the Voltage Graph that the trend is downward which means that the solar panel is not providing enough power to recharge the batteries during the daylight hours. There is a deficit in terms of power drawn vs power added which suggests that I need more solar power by way of a larger panel or additional panels and this will only get worse as the winter approaches.

Since the data suggested that the solar panel wasn't big enough to keep up with the lack of UK sunshine I ordered a larger model.

https://www.amazon.co.uk/gp/product/B07TKTQKTS/ref...

This one is 120W which is 2.4 times the capacity of the 50W one. There is a chance that this will be fine for a couple of months but deep in to the winter it may be that I need the 50W panel in parallel as well, and maybe even more capacity. Will have to keep an eye on the data I guess!

Since identifying that the unit is not quite self sustaining, in addition to adding a bigger panel I have also added a charging port so that I dont have to open the box to charge the batteries with a conventional charger if required. This is not really supposed to be there as it should keep itself topped up and the idea is that it will be in a remote location without power. However, it will allow me to charge with a generator or hookup to a vehicle.

Another surplus to requirements feature is the addition of this weatherproof micro USB port that is connected to the ESP32 board inside the box. It will allow me to fiddle with the code if required and I guess it will give me access to live data on site without having to open the box. As mentioned previously data is only passed over the network every 5 minutes where I could get 100Hz plus data via the Arduino Serial Monitor.