12v led lights directly from mono panels..increasing panel size to add more lights?

[eddykramer]

Hi guys ,

I was wondering if anyone could help me work this out please and any help would be greatly appreciated.

We have a property that has 3 x 12v flat panel LED lights that run directly to a 60 w panel (please see photos of the equipment). We use them (I guess you would say) passively I.E. they work as LED solar skylights in that they run without battery storage and just work when the sun is up and fade down in light like a normal skylight as the sun reduces it's effect on the panel. They work perfectly for our setup in dark areas of the house and at night these panel lights also have a seperate LED strip inside that is wired to a 240v transformer so we can just switch them on and use them as normal lights at night...Hope this makes sense.

The lights are labelled as 18 watt but I think this may just be internal (non 12v) LED strip that runs off the generic transformer that is plugged into mains...is this correct? The panel light has a 2nd internal flexible strip of LED lights that runs a 2nd passive lighting circuit as it is cabled directly to the panel (no battery involved in the setup and hence when the sun fades/so does the LED light). I spoke to somebody who knows a little about 12v solar and they said you can't or shouldn't run a 12v load (LED/motor etc) directly to a mono panel unless there is a buck converter or voltage regulator that limits the output to a suitable voltage. I told him that there didn't seem to be any sort of buck converter in the path and opened up the back of the panel (black plastic box) and looked at the wiring...it seems to have what I think are a pair of diodes soldered across the terminals and I take it the diodes are so the current doesn’t run back the other way to panels.

My second part of the question is can I get a more powerful 12v mono panel (150w or 200w) and run more of these 12v LED panel lights (currently the brightness level is fine with 3 lights running from the 60w panel) but ideally we would like to run another 10 of these lights without having to buy 3 more 60w panels to run 3 lights from each. Thanks!

[bob-n]

Sorry, I can't see your pictures. Can you repost them? Can you get the make and model of the LED lights?

Your friend is right about at least one thing: a 12V panel puts out a voltage that varies wildly with load current and sunlight. For example:

https://www.altestore.com/store/solar-panels/alte-solar-panels-p40768/#ALTS-150W-12P

is a 150 watt, 12V panel, so meets your needs. The specs show 22.32V open circuit, 18.01V at 8.33A maximum.

Some lights allow variable input voltage and contain their own buck converter. Others have a simple series resistor to limit current and it wastes a little power, but not that bad. It's tough to know what's inside the light.

[eddykramer]

Hi Bob-n
thanks very much for your response. I am having trouble uploading the photos..I just keep getting an error message. I think the lights are basically a custom/homemade type thing. I opened them up and there is a 240v led strip around the perimeter which is wired to a 240v Chinese power supply so they can be switched on at night. They also have a seperate discrete 12v flexible led strip inside that are soldered to security / alarm gauge cable that go straight to the 60 watt panel. There is definitely no other voltage regulator or limiter in the circuit or any electrical components to limit the panel output on the way to the 3 flat panel lights. They all work fine and the way they were sold to me but I guess over time they may fail due to the unregulated power that is supplied to the lights. I’ll try and sort out what is happening with the photos but I was able to post them on another forum in a post which is here: https://diysolarforum.com/threads/cu...s-please.6695/

[bob-n]

It seems like the system is self-limiting, just due to the amount of power available from the panel. If you stay with the same concept, and the sun doesn't get 2X brighter tomorrow, you should be fine. By concept, I mean using a 150 watt panel with 160 watts of LEDs.

This is half-joking, but if the sun is providing power and you're using that power to provide light through a system that is less than 15% efficient, wouldn't you be better off with skylights?

[eddykramer]

Ok thanks that makes sense about the self limiting function of the setup. The reason we are not doing it with skylights is because it is a large downstairs area with a couple of rooms (bathroom and laundry) that have no window to the outside world...we don’t want to have to turn on a light every time we enter those spaces...these mock skylights (and they look and feel as if they were a skylight) work great and serve their purpose exactly as we had hoped they would. From further research (and I’m not sure if I know about it all yet) I propose to purchase one of these:

https://www.jaycar.com.au/12-24v-20a-solar-charge-controller-with-usb/p/MP3752

I think they have three pairs of terminals (panel/battery/load) and I think they need the battery part of the equation to operate (ie they are not a passive regulator). So I am thinking of using this type of thing as the battery in the setup:

https://www.jaycar.com.au/12v-7-2ah-sla-battery-nbn-back-up-battery/p/SB2486

Am I correct in assuming that the battery would allow the lights to function for an hour or two after the sun sets as the battery drains and also would this setup work as I think I should based on my limited knowledge of 12v lights and solar? Also I’m not sure what gauge of cable I would be ok to use with a 150w panel..I have read in other forums that people are using 1.5mm2 or even 2.5mm2 fixed (twin positive/neutral domestic AC cable) instead of dedicated 12v cable for cable runs from their panels but clearly labelling the cables as 12v DC to avoid confusion down the track. Hope this all makes sense and thanks very much for your help with this.

[Mike90250]

LED's are current based devices. They require a certain amount of voltage to start conducting, and then current (amps) controls the brightness. If current is not controlled, the LED will overheat and burnout.
You need to discover what your LED's require, and then provide them properly. Some LED bulbs, have built in driver circuits (the one below does)
https://www.wiredco.com/LED-t10-wedg.../t1024led2.htm

Input: AC12V/DC 12-24V Power: 3W

So that bulb would run directly off a "12"v PV panel (usually 17-23V)

[bob-n]

Mike has a good suggestion of looking for LED lights that specify a 12V to 24V range of input voltage. Alternately, you can get a box that accepts the output of the solar panels (14V to 24V) and puts out a controlled 12V. I did a search of ebay for "12V buck regulator" and many good choices came up, such as this 36 watt model:

https://www.ebay.com/itm/Waterproof-DC-Car-Voltage-Converter-Buck-Boost-Regulator-12V24V-To-12V-3A-36W-/302937595643

But if you want to extend operation beyond dark, you need a battery, as you say. You're right that a solar charge controller is the best way to keep the battery charged and interface the panel to the battery. I don't know that specific charge controller, but the words on the website look OK.

Running from a regulated 12V buck regulator or 12V battery is certainly better control for the LEDs than the wildly varying output of the panel. Now you can buy the largest solar panel you can afford and not worry about overdriving the lights.

Now to the hard details. Lead-acid batteries don't like being fully discharged. The deeper you discharge, the shorter the battery life. Bigger batteries will last A LOT more years (or weeks or days). So don't scrimp on the battery.

Assuming that you are driving all 150 watts of lights at the same time and want them on for 30 minutes per day, that's 75 watt-hours between charges. The battery you list is 7.2A*12V=86.4 watt hours. You'll be running it near empty every day. You'll be lucky if it lasts a few weeks at that rate, probably dead in under a month. I know it's not intuitive. If they rate it for 86.4 watt hours, why can't you use it for 86.4 watt hours? You can, just don't do it too often. Once a month, and you're probably OK. Daily, not so good. If you want to understand more, this article is very good:

https://batteryuniversity.com/learn/article/discharge_methods

So pick a battery with at least 4X your daily needs. Again with the above example, if you plan to run 150 watts of lights for 30 minutes every day, you'll be better off with Jaycar's 38Ah battery SB1699.

All of this assumes that you get sun every day to recharge the battery. If you plan to go many days without sun, you need even more battery capacity (gulp).

Unfortunately, the hardest lesson of solar power engineering is that batteries are the most expensive part of the system and have the shortest life of any component in the system. Sometimes, you need them, but if you can do without batteries, you'll have a system that is much cheaper and more trouble-free.

[LeoHard]

If it were that easy, we would all be doing it. It is, in fact, not that easy. The reason someone hasn't already invented LED solar skylights is that nobody has ever asked. Until very recently, LED technology had only one application: light bulbs. The light from an LED bulb is not bright enough to be used for solar skylights. You can try to get a LED strip light. There you will find a very attractive price, and you have what to choose from. I think that with this product you won't have problems.

[EleanorTodahl33]

I don't allow my wife to use any lighting other than the LED strips on the car's dashboard. She says the light seems dim to her. She didn't leave me alone until I bought her xxxx deleted xxxx A special app controls these LEDs, so she doesn't have to worry about anything. The $19.99 was a surprise to me because I did not expect to buy LED lighting for less than $25. I'm not a fan of flashy car panel lighting, but she loves it. I know for sure that with Vont LEDs, you can take gorgeous photos for Instagram. Take note of this.

[bcroe]

If it were that easy, we would all be doing it. It is, in fact, not that easy. The reason someone hasn't already invented LED solar skylights is that nobody has ever asked. Until very recently, LED technology had only one application: light bulbs. The light from an LED bulb is not bright enough to be used for solar skylights. You can try to get a LED strip light. There you will find a very attractive price, and you have what to choose from. I think that with this product you won't have problems.

As Mike said, basic LEDs are current driven. A voltage regulator (such
as those cheap buck regulators) is far from an ideal controlled LED
source. There are current source regulators. However some LEDs
have a built in resistor or other device to allow voltage control.

As for the first application, LEDs have been in use in the electronic
industry for a few decades, first as indicators and DC signal isolation
devices. Then as drivers for fiber optical cables. At the beginning
we only had red. Bruce Roe

[azdave]

As Mike said....

Bruce,
I'll bet you didn't notice that you are replying to a spammer from last fall who tried to sneak a commercial link into this thread. Then yesterday, another spammer tried the same thing which brought the thread back to the top again.

Mods,
Sending a warning to a spammer is a joke and waste of your time. Just ban them and be done with it. If a mod would have banned LeoHard last September he could not have come back and edited his post recently to include a commercial link.

[bcroe]

. Bruce,
I'll bet you didn't notice that you are replying to a spammer from last fall who tried to sneak a commercial link into this thread. Then yesterday, another spammer tried the same thing which brought the thread back to the top again.

I was more interested to point out LEDs were here a very long time
before they were used for lighting. Bruce

[kamaveles]

You’d better turn to professional specialists. I am not particularly good about such replacement issues. However, I would be interested in how you found out about this situation. I became interested in repairing cars two months ago. I even organized something like an auto repair shop in my garage. Firstly I purchased 5 Modes Vont LED Tactical flashlights for additional lighting. Btw, what would you recommend to a novice car mechanic? Maybe I should read some specialized literature at the beginning.

[PNPmacnab]

I've been amazed at the large number of LED failures with LED strips I've had even when these have been driven by regulated supplies. Everyone wants brighter more power in a smaller package. What is really strange it is not everyone and in the oddest place. Search Dubai lights or LED. Philips makes LED lamps that are only sold in Dubai. they have twice as many LED in a string at vastly lower power making them last forever and consume half the power for the same lumens. Every data sheet for LED had this info from the beginning. The cheapest ceiling lights for my camp were 11W 120V flush mounts. I just kicked out the electronics, added a boost converter and ran them at half the current. Plenty bright.