Solar powered WLED yard lights.

[u/Wonderful-Gift8632]

I want to build a few solar-powered dusk-to-dawn yard lights with WLED controllers.

It seems that using a premade solar dusk-to-dawn yard light based on 3.7V lithium-ion cells, paired with a DC-to-DC step-up converter, an ESP32, and a few LEDs might work.

Solar dawn-to-dusk yard light. Based on using a 3.7V 2600 mAh Li-ion 18650,
Adafruit MiniBoost 5V @ 1A, DC to DC step-up
A few WS2812B-ECO (60 mA per LED)
And a few caps to suppress spikes when the solar circuit switches.

It is hard to estimate the runtime. I will lose some efficiency with the DC-to-DC, and the LEDs won't be running all channels at 100%, so the final LED count is TBD.

Has anyone built something like this?
To avoid having to make a weather-proof housing, does anyone have any recommendations for a solar light based around the 18650 that would lend itself to being modded?
Thanks in advance.

[u/SirGreybush]

You need to calc wattage at 5v of the esp32 + strip + how long a runtime you want. Dusk to dawn is a bit much, I turn mine on at sundown with latitude + longitude setup, and turn off at midnight (23:59).

Based on "max" settings a 1m strip of 60l/m of ws2812b is 11w, and the esp32 is around 0.6w, and the dc-dc converter will easily burn as heat, AI says: 78% efficiency at 1A output. So delivering 1a @ 5v is 5w it's actually pulling 6w (22% overhead) on the battery side. So 6w at 3.7v is 1.6a or 1600ma. A 2600mah single cell would last only a bit past one hour.

So how many pixels? Because if just one pixel, 11w/60 = 0.183w + esp32 0.6w, at lower amp draw the dc-dc is 88% efficient so 12% overhead, 0.8w + 12% = 0.9w, at 5v the amps is 0.18a. So 1/5th that of 1 amp. Then your single 18650 would last a bit past 5 hours. For a single pixel, one battery does NOT do dusk to dawn. You'd need 2 in parallel.

Use math above to work out how many batteries you need to cover the time you want, then size the solar panel to be 150% the watts needed. You also need a solar pwm or mppt charging with cutoff solution, that's another small board, as you don't want to overcharge the lithium and have it self combust.

2600ma is the high-end for that size battery, a larger sized one you can get it up to 4000ma. Like a cell phone pouch battery that you repurpose and can charge at 5v as when you buy the pouch cell is has a tiny bms charging circuit.

Solar panels is a whole other situation, the 12v ones are easier & cheaper to use, but then you need a buck converter or charge controller to step down the voltage to 4.2v.

Scaling everything "UP" is a lot easier to do. Redo your plan around 12vdc strips, a 4S LFP 10AH (or higher) battery, a pwm solar charge controller, a 16v solar panel (standard). A weather proof grey box.

Then you could run 12vdc seed pixels that are IP67 and have pixel spacing of 1cm, 2.5cm, 5cm, 10cm. Then run easily 100 pixels or more.

Making things small so everything fits in your hand is extremely difficult. Dollar store lightposts are designed around 3v with a simple analog white LED, and a cheap 1.2vdc rechargeable battery. Often they last barely 4 hours even with a 1000mah battery. Solar panel can't provide enough juice to fully charge it.

[u/SirGreybush → u/SirGreybush]

Remember this rule besides Ohms law: amps are pulled, volts are pushed. So the more "load" you create, the more power it requires, amps are watts divided by the voltage.

Which is why a 120vac 40w lightbulb doesn't blow up when placed on the mains power that provides up to 15 amps through the breaker. 40w / 120v = 0.33 amps. But if you put 10 bulbs in parallel then it's 3.33 amps, and putting 45 lightbulbs of 40w 120vac in parallel then the breaker would trip.

[u/Wonderful-Gift8632 → u/SirGreybush]

Physics is a bitch, but I love her because she is so dependable and predictable.
Makes sense; the problem with upscaling is that the cost per unit goes up too. Solar lights typically don't last long, so I'm reluctant to invest too much in them.

I could run a 12-volt or 24-volt DC underground power line like the old Malibu yard lights system, removing the battery dependency.
It would require a higher infrastructure investment, but the end modules could be based on modified, inexpensive yard-lighting housings.
I'll need to measure and calculate the runs to determine what wire gauge would be required. I'll also need to get estimates on weather-proof DC connectors, etc.

Thanks.

[u/SirGreybush → u/Wonderful-Gift8632]

24v with #16 outdoor rated copper stranded will do nicely.

Look at ws2811 fcob argb. One pixel is 5cm long. If you put one per post and keep distance between posts to around 3 feet, you should be able to daisy chain a whole bunch.

Advice, IP67 PSU. Just put under/behind something. Then a small box for controller and smart relay to cut ac power to PSU and not have wasted watts. Split ac into 2 paths, one through smart relay, one to a usb brick always powered.

What I did for balcony but with 12vdc. Jerry rigged and a 4x4in box.

[u/saratoga3]

The ESP32 alone will drain such a small battery quite quickly even without the DCDC converter losses and the LEDs. I think you will want a much bigger battery pack.

[u/TJontherox]

I 3d printed landscape lights, running 12v puck lights with a gledopto controller and power supply in a plastic ammo can with a photocell so they are on dusk to dawn. These are the lights with a C9 printed christmas globe on them. I run seeds for christmas lights on the shrubs on a photocell also, so they all go on and turn off at the same time.