The Amazing Journey of DIY Solar Nodes

If you think DIY is a simple thing, then you must not have heard of Jinan-Buddhist White Cat 's Meshtastic build story.

All joy is accompanied by pain, and all pain gives birth to new joy.

This community activist Copy my homework! My minimalist Meshtastic solar node.Although the result is gratifying, the whole process is definitely a "technical comedy".

Next, let's take a look at his story and find meaning in his struggles. This is also why so many people in the community like DIY.

Basic configuration of Buddhist white cat

Buddha White Cat is similar to the design in the previous guide, and still uses the Heltec T114 and 18650 lithium battery.

He added an MPPT CN3791 control board to the guide, significantly improving solar charging efficiency. Other than that, the other components remained largely the same as the original. It can be said that this was a DIY journey informed by reference but also informed by innovation.

For a detailed list of materials, please refer to the previous article on the T114 solar node .

However, the real highlight of the story lies not in the components, but in his battle of wits with the batteries.

The "protracted war" with batteries

Round 1: Buying the wrong series battery pack

According to the Meshtastic Solar Node Guide , the solar node requires a parallel 18650 battery pack to meet the T114's 3.7V voltage requirement. However, a series battery pack would add up to a 7.4V output voltage, clearly exceeding the T114's safety range. Buddhist White Cat failed to note this difference when purchasing and purchased the wrong series battery pack.

The result was predictable: during testing, he discovered the device wouldn't boot properly and might even have damaged its electronic components. Fortunately, he discovered the problem in time and prevented further failures. This incident delayed his battery box project by a week.

Round 2: Trouble with the protective plate

White Cat carefully checked the parallel battery compartment the second time he purchased. However, this time the problem lay with the batteries. The 18650 batteries he purchased came with a built-in protective plate, which increased the length of the batteries and prevented them from fitting smoothly into the compartment.

Since the protective plate usually adds a few millimeters to the length, which makes it impossible to accommodate these batteries in a standard 18650 battery box, he tried various adjustments, but to no avail.

Round 3: Seller's Mistake

On his third attempt, he thought he had it all figured out. He double-checked that he'd bought a parallel-connected 18650 battery pack, but the seller unexpectedly gave him another "helper." The battery pack he received was still connected in series, nearly leaving him doubting his fate.

This not only wasted time but also left him feeling somewhat frustrated about the reliability of the supply chain. But he didn't give up and continued searching for a solution. Someone in his group couldn't help but joke, "Did you offend the battery god? ��."

Round 4: Saving the country through a roundabout way

Three consecutive failures didn't make him give up. Instead, he opted for a more roundabout solution: abandoning the standard 18650 battery case. He added a plastic sleeve to the 18650 battery with its own protective plate, upgrading it to a 21700 battery, and then used a 21700 battery case.

In this way, he successfully bypassed the size problem caused by the protective board and finally got the node powered on successfully.

DIY is really a love-hate relationship!

A little episode about parallel battery boxes

To further increase the battery capacity of the device, he purchased two battery packs, each capable of holding two batteries, meaning he could eventually connect four 18650 batteries in parallel. He soon realized that connecting the positive and negative terminals of the two battery packs in parallel presented a new challenge.

So, he asked in the community group : "Hey guys, how do you solder one wire to two wires?" (How do you connect the wires from two battery boxes together so that they can be connected to the battery port on the MPPT board?)

Enthusiastic friends shared their experiences:

Generally you cut the wires, bundle the copper wires together
, tin them,
and seal them with heat shrink tubing or tape.

He followed everyone's advice, but cleverly added a little innovation of his own: he placed the soldering work under the kitchen range hood, so that the fumes generated by the soldering could be directly exhausted by the kitchen hood flue, without the need to purchase and install additional fume extraction equipment.

Finally, he successfully connected the two battery boxes in parallel and ensured that the solder joints of each connecting wire were firm and neat.

Upgrade Highlight: MPPT Module

The Foxi White Cat Build also includes the CN3791 MPPT module, which is a big plus. The MPPT (Maximum Power Point Tracking) module optimizes the charging efficiency of solar panels , especially in less-than-ideal lighting conditions.

This coincides with the optimization suggestions in the guide, and can even be said to be an early implementation of the "future improvements" mentioned in the guide.

After adding the MPPT module, the efficiency of the solar panel has increased significantly. Previously, charging efficiency would drop drastically when there was a shadow, but now it can maintain stable charging even on cloudy days.

Final Result

Despite numerous setbacks with the battery, Buddha White Cat 's node was ultimately completed successfully. He deployed the node on his balcony, equipped with a high-gain antenna and solar panels, ensuring stable operation and low power consumption.

I believe that for him, although DIY is tiring, the sense of accomplishment of watching his equipment run steadily is irreplaceable.

His story epitomizes Meshtastic DIY, telling us that DIY isn't just about hands-on practice; it's an adventure full of unknowns. While you may encounter various problems, as long as you persevere, you'll always find solutions.

Author: Hays Chan | Community blogger

Translator:Joe Tan | KEEPTEEN | meshtastic node repeater

Website: https//www.keepteen.com

Article link:https://www.keepteen.com/blog-Solar-Lora-12710/The-Amazing-Journey-of-DIY-Solar-Nodes-11942054.html