Building an off grid landscape lighting system

[nerorox]

Hi everybody, I'm hoping somebody can point me in the right direction here, i'm a programmer and i have experience designing embedded circuits but I have 0 experience with solar panels or batteries so this is all new to me.

My goal is to have a fully solar powered landscape lighting system for my backyard, the system I'm building wouldn't need an inverter as it's all DC powered.

Currently I have this setup:

12V50W solar panel
14AWG low voltage landscape lighting wire running from solar panel across yard
6V regulators feeding from the solar panel line
boxes with 18650 batteries with charge controller/battery protection pcb feeding off the 6V regulator
4 spotlights per battery each running at 3.7V each drawing about 40mA average

This system works fine but:

#1 the batteries charge slowly and don't last that long
#2 the batteries charge at different rates depending on how close they are to the panel and lights turn off at different times
#3 the battery charge controllers only provide power to the lights when there's no solar input, this causes the lights to turn on about an hour before sunset when trees start blocking sunlight to the panel

To improve this, I'm considering a centralized 12V LiFePO4 battery in my garage connected to the solar panel. This setup should address charging inconsistencies and synchronize light activation with an ESP32 and a relay. Alternatively, I'm exploring the simplicity of a portable solar generator like the Anker 521.

Does this plan seem effective, or am I overlooking anything?

 

[constantspeed]

I cannot speak to most of this, but depending on how many lights you have, and total power draw and length of time you would like them to stay on, you probably need more or larger solar panels, and yes, a centralized LiFePO4 also sized for capacity. Possibly 12awg or 10awg wire depending on length of runs and total current.

 

[Shimmy]

I think about doing similar, as the big box store solar lights all seem to suck. For me, one challenge is the solar panels are never well situated, so I only get an hour or two of equivalent solar production. That puts all the charging current in a short window which leads to excess voltage drop. If you are going for a central battery 12V might be too low, depending on your run lengths.

Have you measured your "12V" lines at the 6V regulators-- both voltage and current? How many amps of charging can your current battery system accommodate?

 

[SamDeleted]

Currently I have this setup:

12V50W solar panel
14AWG low voltage landscape lighting wire running from solar panel across yard
6V regulators feeding from the solar panel line
boxes with 18650 batteries with charge controller/battery protection pcb feeding off the 6V regulator
4 spotlights per battery each running at 3.7V each drawing about 40mA average

This system works fine but:

So to confirm , you actually have 4 independent micro solar set ups

Each with its own a 50w solar panel, some 18650s , and a spotlight ?

 

[n2aws]

Some thoughts on this (mostly from researching permanent Christmas lighting)

#1). Centralizing power is good. Since you are using regulators, if you can increase the voltage at the source to 24v or 48v, and then use the regulators at the lights, you'll likely see much more voltage consistency at the lights.

#2) To address the problem of some lights turning on/off before others, you'll likely want to centralize the timer functionaility.. potentially along with the power source.

#3) You didn't mention what you are using to set the timers. But, I know Home Assistant is useful for a lot of these types of automations. If using home assistant, you can use their built in timers for "sunrise" and "sunset" to address the issue from tree shading turning the lights on. (Or potentially an offset. maybe an hour after sunset and 20 minutes after sunrise.. as an example.

#4) As you are centralizing everything and re-running wires, I'd consider using conduit. It's relatively inexpensive. But you'll thank yourself for not using direct-bury cable when you eventually hit a wire with a shovel, or string trimmer, or a rodent chews on it.. and need to replace it.

 

[nerorox]

I think about doing similar, as the big box store solar lights all seem to suck. For me, one challenge is the solar panels are never well situated, so I only get an hour or two of equivalent solar production. That puts all the charging current in a short window which leads to excess voltage drop. If you are going for a central battery 12V might be too low, depending on your run lengths.

Have you measured your "12V" lines at the 6V regulators-- both voltage and current? How many amps of charging can your current battery system accommodate?

the power draw is minimal, regulator outputs about 5 volts, current draw is about 1 amp at 5 volts per battery pack, only 4 packs at the moment

 

[nerorox]

So to confirm , you actually have 4 independent micro solar set ups

Each with its own a 50w solar panel, some 18650s , and a spotlight ?

1correct except it's only 1 50w solar panel powering all

 

[SamDeleted]

Its difficult, if close to impossible, to make one solar panel charge 4 separate battery banks I am afraid

Try either one battery bank distributed to the spot lights

Or an individual solar panel for each spot , 5w or 10w would probably keep up

 

[nerorox]

Some thoughts on this (mostly from researching permanent Christmas lighting)

#1). Centralizing power is good. Since you are using regulators, if you can increase the voltage at the source to 24v or 48v, and then use the regulators at the lights, you'll likely see much more voltage consistency at the lights.

#2) To address the problem of some lights turning on/off before others, you'll likely want to centralize the timer functionaility.. potentially along with the power source.

#3) You didn't mention what you are using to set the timers. But, I know Home Assistant is useful for a lot of these types of automations. If using home assistant, you can use their built in timers for "sunrise" and "sunset" to address the issue from tree shading turning the lights on. (Or potentially an offset. maybe an hour after sunset and 20 minutes after sunrise.. as an example.

#4) As you are centralizing everything and re-running wires, I'd consider using conduit. It's relatively inexpensive. But you'll thank yourself for not using direct-bury cable when you eventually hit a wire with a shovel, or string trimmer, or a rodent chews on it.. and need to replace it.

Currently i'm not using anything for timers, my current system turns power to the lights on when there's no solar input, turns power off when there's solar input (tho they drain way before there's solar input again), my goal is to use an esp32 to handle the timers since i have tons of those laying around plus i can easily sync it to my homekit setup to work with my wired lights in the front.

i would consider the idea of conduit as well but the wires area already buried, the goal is mainly to centralize the battery instead of having a bunch of small batteries for the lights

 

[nerorox]

I'm attaching a little sketch of how it's currently done and what my idea for it was, the spotlights use very little power, each spotlight only draws max 50mA at 4V barely 1 amp all together

 

[AntronX]

Victron 75/15 smart solar charge controller ($65 on Amazon) has load output that can be programmed to turn on via schedule and logs solar panel generation and load energy use. Forget about those 6V converters and run 12V direct to lights. Wire 3 LEDs in series to run from 12V direct.

 

[nerorox]

Another question I have now, the panel i have is rated 12V, the open circuit voltage is about 20V, when i wired the panel to it the input at the regulators read 20V and output reads 6V, however, once i connect the load to the regulator (8205/DW01A battery protection/charge controller) then the input at the regulator drops down to 5.5V and the output to a bit over 4V.

This got me wondering because as i mentioned I've designed DC Circuits before with regulators but they work with DC from USB which has constant voltage, i've never seen the output of a DC source match the voltage needed by the load, which is what I'm seeing here.

I did some research and found some posts where people talk of solar panels as constant current sources not voltage sources and that the voltage on the panels is more of a maximum voltage they can deliver and the load determines the output voltage of the panel.

Since the only load are these charge controllers that only needed about 5V, does that mean that a regulator is not needed?

 

[SamDeleted]

This got me wondering because as i mentioned I've designed DC Circuits before with regulators but they work with DC from USB which has constant voltage, i've never seen the output of a DC source match the voltage needed by the load, which is what I'm seeing here.

I did some research and found some posts where people talk of solar panels as constant current sources not voltage sources and that the voltage on the panels is more of a maximum voltage they can deliver and the load determines the output voltage of the panel.

Yes well, I'm not sure on your situation, it's out of my depth,

but that is how it works on a PWM charge controller ,the solar arrays voltage holds the same as the battery voltage

 

[Shimmy]

Do you have a charge controller now, or just straight from the panel?

 

[nerorox]

Do you have a charge controller now, or just straight from the panel?

yes, i use a circuit with DW01 and 8502A chips which are for battery protection (over charge/discharge), these then take the solar panel's output and charge the battery, these are the load on the solar panel output. I have a voltage regulator to drop 12V down to 6V, at the input the regulator reads 20V when there's no load on the regulator, once i plug the charge controller to the output of the regulator the input of the regulator (solar panel output) drops to 5.5V which is what the charge controller is rated for, the output of the regulator then drops to around 4V.

The 8502A circuit is rater for 10V maximum input, my panel is rated for 12V, these charge controllers are the only load on the panel so im assuming that means that the voltage on the panel will drop to match that of the load, therefor if there's no other load on the line that requires a higher voltage, the output of the 12V panel should technically remain at 5.5V since that's all the battery charge is asking for?

Im attaching a drawing showing what im talking about since it's hard for me to explain things sometimes.

 

[SamDeleted]

Its all very complicated!

 

[AntronX]

Why don't you wire 3 LEDs in series for 12V ?

 

[Shimmy]

yes, i use a circuit with DW01 and 8502A chips which are for battery protection (over charge/discharge), these then take the solar panel's output and charge the battery, these are the load on the solar panel output. I have a voltage regulator to drop 12V down to 6V, at the input the regulator reads 20V when there's no load on the regulator, once i plug the charge controller to the output of the regulator the input of the regulator (solar panel output) drops to 5.5V which is what the charge controller is rated for, the output of the regulator then drops to around 4V.

The 8502A circuit is rater for 10V maximum input, my panel is rated for 12V, these charge controllers are the only load on the panel so im assuming that means that the voltage on the panel will drop to match that of the load, therefor if there's no other load on the line that requires a higher voltage, the output of the 12V panel should technically remain at 5.5V since that's all the battery charge is asking for?

Im attaching a drawing showing what im talking about since it's hard for me to explain things sometimes.

What I was getting at is are you doing any solar control-- either PWM or MPPT to regulate the intermediate power. Without that, you end up pulling nowhere near the rating of the panel; your "12V" bus is just a function of the load. You could consider a capacitor bank to stabilize the 12V bus as it currently stands, which for the size of your load likely is the best value.