Outdoor Lantern Solar Solution needed

[The Pool Man]

Originally Posted by jjackstone

The light you linked to is a motion sensor light.

You're right! Amazon changed the link to a different product. I went to my order of the previous bulb, clicked the link, and didn't notice they had changed the dusk till dawner to a motion sensor.

The good news for me is there's a new 7 watt Dusk till Dawner closer to my needs. It's here --

https://www.amazon.com/Sensor-Lights-Lighting-Automatic-Outdoor/dp/B07KFML3CH/ref=pd_sim_60_3?_encoding=UTF8&pd_rd_i=B076CN463G& pd_rd_r=708b4f24-1065-11e9-a4fb-b1d8f98b2ea8&pd_rd_w=WnFrk&pd_rd_wg=jXLfp&pf_rd_p= 18bb0b78-4200-49b9-ac91-f141d61a1780&pf_rd_r=XP9K00YH4MRRENJKQ6X2&refRID=X P9K00YH4MRRENJKQ6X2&th=1

So this conversation has changed slightly in that I'll be using a 7 Watt Dusk till Dawn light instead of 5 watt.

[The Pool Man]

Originally Posted by NeilBlanchard

Typical solar panels are 200-300 watts. The light you linked to is 5W... with a motion detector built into the bulb... The expensive parts are the solar panel, the battery, it's charger, and the inverter - and the labor to install it all.

Hi Neil,

So I goofed you guys up with my bulb link. (Amazon had changed the product at that link and I hadn't noticed.) I altered the link to a 7 Watt Dusk till Dawner which keeps most of your science math similar.

So I'm getting ready to shop for parts but must ask re-ask a basic question -- do the battery, charger, and inverter require a cool space? Or are they designed to sit in hot California sun? If not --

-- would an enclosure help if it was sitting in that same sun? That is: am I water protecting the battery and charger and inverter or thermal protecting them too?

Here is the actual location and scenario I'm contemplating.

https://photos.app.goo.gl/tqTKWRXrDgYZq9N46

So that lantern would have a 7 watt dusk till dawn with almost the same lumens of the real lights throughout our complex. The red lines indicating wiring, which would likely be inside of think pipes. The battery/charger/inverter would be 'boxed' in plain site.

If this sounds about right is there a kit you recommend? I've been looking and it's kind of shocking that batteries for this purpose do not exist with inverters and chargers attached.

[jjackstone]

Yes, the box is more for weather/rain protection than heat. The best thing you can do for heat(or cold) is to run the wires from the solar panel into the house and connect all your electronics there. If that is not feasible then place some sort of cover above the box to keep it out of direct sunlight.
I don't know if there is a direct kit that would work for you. But if you are using a 7 watt bulb lets say for 10 hours a night then that would be a minimum of 70 watt hours per day. I would increase the battery capacity to at least 200 watt hours. You could probably get by with using two 12 volt 10 amp hour AGM batteries wired in parallel. You could use a 50 watt solar panel for charging. You have to be sure the panel is located so that it can get full sun for at least four hours per day even in the winter. JJ

[castlusion]

If you just want it usable system and do not want to know or learn all the ins and outs get a harborfreight.com/100-watt-solar-panel-kit-63585.html you will need to use both lights in my opinion and can get other DC lights latter if that is not enough.. wait till it is on sale and sign up for the coupons it will drop the price. Get one of there batteries if you are close to store but really a deep cycle will do you better and store more. The better the battery the more the cost. For what you want there battery should do the trick with out the hassle and be easy to replace. I used this set up to learn from and have a much more robust set up now. Any RV/camp trailer place sells 12 volt DC lights and bulbs if needed for more light.
It is not a high end system. Some people call it junk, and it is not that either. It is just proprietary connected system. Does not have a lot of ways to upgrade with out buying more of there equipment. At some point that maxes out what can be done. Hope that helps.

[castlusion]

I ran the wires out side A shed and berried "battery box" in the ground with gravel under it and a piece of pvc for gas/pressure release along with the charge controller it was cooler in the summer and stayed warmer in the winter ... do not forget the vent if using acid cell batteries.

[Robaroni]

Hi Poor Man,
I love these kinds of projects, they're so much fun!
OK, if the light is 5 watts that means the current it draws is 5 watts divided by 120 volts or 0.042 amps. BUT LEDs don't run on AC (Alternating current like your mains power). They run on DC (direct current), so this means that inside your bulb there is a circuit to convert AC to DC to run the bulb, also the DC voltage to run the LED is much lower than the 120 volts.

That's a good thing because the LED actually uses less current than the 0.042 amps we just calculated. What makes it better is that the PV module also runs low voltage DC like the LED. So why add an inverter to boost and invert the DC from the module when you can run things without doing most of that?

The trick here for people who don't know electronics is how to disassemble the bulb and tap the output of the bulbs electronics. There are a couple of ways to do this. If you just want a light without the auto off/on then finding the two wires that run the LED is a lot easier but if you want the auto off/on the you will need a meter to test the circuit and find the point where it powers the complete circuit.

Living without, at least at the beginning of your experimenting, isn't a bad idea because you can buy boards on eBay and I guess Amazon to drive LEDs. You can still use your light fixture but what you'll do is remove the standard bulb socket and put the LED driver circuit inside with a plain old LED or a made up unit like this (this is just a suggestion, this light is 18w and is probably a spot light but you get the idea):

https://www.ebay.com/itm/2x-4INCH-36...AV9:rk:13:pf:0

That runs on 12volts DC. So you'll need a battery, a small charger to interface the battery to your PV module like this:

https://www.ebay.com/itm/12V-24V-PV-...frcectupt=true

What I would do is to get the parts I linked or something like them and a PV module.

So, how big a module do you need?
OK, if you're using a 5 watt LED for ten hours you need ~50 watt hours. (5 watts for 10 hours uses 10 times 5 watts for one hour. we use watt hours to calculate our power needs)

Let's say you have an average of 5 hours sunlight for your latitude average daily for one year. ( you can look these up for your area) If you have a 75 watt panel it will put out in 5 hours 75 x 5 or 375 wh. You want some 'overhead' because you'll also need a battery, something like an SLA (sealed lead acid). BUT the battery has something called an amp hour rating. That means how many amps it will put out for an hour but this is misleading. You really don't want to drain your battery more than about 25% to be safe and to have it last. Batteries are rated in cycles, each time you drain it and charge it up is a cylce. The deeper you drain it the fewer cycles it will have in its life. So let's say we have a cheapo 12v - 7aH, SLA battery. It has to run all night (10 hours). a 5 watt LED = 5/12 or ~416 milliamps (milliamps are amps divided by 1000; 416 mA = .416 amps, for example) just so you understand amps and watts. OK, our battery has to supply 50 wH and our battery puts out 7aH x 12v or 84wH. This is not enough because we want to only use 25% of our battery. We need a battery of 50 x 4 (which is 4 times our 25% to make 100%) or 200 wH. 200/12v = 16.6 aH thus we need a battery of this size at 12 volts for our 5 watt LED.

So there you have it. A 5 watt LED, a 75 watt module (60 will probably work), a small charger and a 16 aH 12V SLA battery.
Rob

[BillG]

Pool Man, there are a couple of things to consider regarding sizing of the battery and the panel.

1) How many days do you want the light to operate in the absence of sunlight?
2) How fast do you want the battery to recharge to full capacity?

I think that the first one is the most important, and that determines the battery size. Lets say that you want to turn on the lights at sunset, and leave them on for 12 hours. And you want them to be able to run for 10 days with no good sunlight.

7watts x 12 hours/day x 10 days = 840 Watt hours. Because you don't want to ruin your battery, size it for double that, and don't let it discharge below 50% capacity. So for this example, you might want two 24 series deep cycle batteries, which have about 1000 Watt hours of capacity each.

You will want a charge controller that prevents overcharging and over discharging, the two enemies that destroy batteries. The charge controllers that give the best utilization of your solar panel are called MPPT, or "Maximum Power Point Tracking."

In some cases, you can find a charge controller which also controls the lights. Morningstar makes one, although I don't think it uses MPPT for charge control, rather, the less efficient PWM.

The size of the panel depends on how fast you want to fully charge the battery after being fully discharged. Some also depends on how efficiently the charge controller uses the panel capacity to deliver the charge to the battery.

Figure that the panel can only deliver its full output for 2-3 hours per day on a good day - when the sun is shining directly at it. Before and after that, it is shining at an angle and the capacity is reduced. You will probably want it to deliver in a day, about double what the light bulb draws (84 watts hours in the above example.) If you had an efficient MPPT charge controller, you might want at least 100 Watts of panel. With a less efficient charge controller, you will need a bigger panel, maybe double that.

For what it is worth...

[Robaroni]

Originally Posted by BillG

Pool Man, there are a couple of things to consider regarding sizing of the battery and the panel.

1) How many days do you want the light to operate in the absence of sunlight?
2) How fast do you want the battery to recharge to full capacity?

I think that the first one is the most important, and that determines the battery size. Lets say that you want to turn on the lights at sunset, and leave them on for 12 hours. And you want them to be able to run for 10 days with no good sunlight.

7watts x 12 hours/day x 10 days = 840 Watt hours. Because you don't want to ruin your battery, size it for double that, and don't let it discharge below 50% capacity. So for this example, you might want two 24 series deep cycle batteries, which have about 1000 Watt hours of capacity each.

You will want a charge controller that prevents overcharging and over discharging, the two enemies that destroy batteries. The charge controllers that give the best utilization of your solar panel are called MPPT, or "Maximum Power Point Tracking."

In some cases, you can find a charge controller which also controls the lights. Morningstar makes one, although I don't think it uses MPPT for charge control, rather, the less efficient PWM.

The size of the panel depends on how fast you want to fully charge the battery after being fully discharged. Some also depends on how efficiently the charge controller uses the panel capacity to deliver the charge to the battery.

Figure that the panel can only deliver its full output for 2-3 hours per day on a good day - when the sun is shining directly at it. Before and after that, it is shining at an angle and the capacity is reduced. You will probably want it to deliver in a day, about double what the light bulb draws (84 watts hours in the above example.) If you had an efficient MPPT charge controller, you might want at least 100 Watts of panel. With a less efficient charge controller, you will need a bigger panel, maybe double that.

For what it is worth...

Bill, a 100 watt module for 2.5 hours (this is low, I believe the average for the US is 3 to 4 hours of maximum module output per day), gives 100 x 2.5 = 250 watts. A 5 watt source quadrupling the required power needed for a 10 hour night would be 200 watts, that's at ~25% battery discharge, so while, if you can afford it a bigger module is always better, you can go with a smaller module especially if space is limited.
I don't believe there's any place in the lower 48 that doesn't have sufficient sun for 10 days straight. Also 50% is too low a discharge point it reduces the max battery cycles appreciably. My home system is designed for 75 to 80%.

Two 75 aH group 24 batteries will run about $140 each, he's just lighting a 5 watt LED. His moniker is Poor Man!

[Robaroni]

Poor Man,
Here's a small cheap circuit that should turn off your LED during the day. All the parts are inexpensive and easy to get.

How it works:
The "ts3702" is a comparator, it compares the voltage on pin 2 with the voltage on pin 3. If pin 3 is higher the output pin 1 goes high and turns on the MOSFET "irfz44" which lights the LED lamp. You can change the light when the LED goes off and on by changing "R1". You can even put a variable resistor in its place but make sure to add at least a 10k resistor in series with it or you may damage the "GL5537" which is the photo resistor that senses when it's dark.
Rob

[BillG]

Originally Posted by Robaroni

I don't believe there's any place in the lower 48 that doesn't have sufficient sun for 10 days straight. Also 50% is too low a discharge point it reduces the max battery cycles appreciably. My home system is designed for 75 to 80%.

Two 75 aH group 24 batteries will run about $140 each, he's just lighting a 5 watt LED. His moniker is Poor Man!

Well, a 75% cutoff would then require (4) 24 series batteries. That is too many to safely wire in parallel, in my opinion. I agree that the battery will last longer, but suggest using batteries designed for the job, not car batteries. If he can live with 5 days of autonomy, then he could use two batteries set up for a 75% cutoff. It is my understanding that these are security lights, so it is important that they stay on at night. As I'm sure that you know, a big bird splat will all but shut off the output of a small panel, so that would give him 5 days to find it and squeegee it off before his security lights no longer work.

For what it is worth, my array has not produced more than 8 or 9 Watt Hours per day for the last 11 days according to its monitoring system, and I don't expect the snow to melt off of the array for at least another week, and probably two or three weeks.