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Solar lighting - What do the specs really mean, how much light can I actually expect to get and for how long?


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  • Crossy changed the title to Solar lighting - What do the specs really mean, how much light can I actually expect to get and for how long?
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Years ago I bought some solar garden lights.   They were not cheap, they were pretty useless. The panels were tiny, the batteries cheap and the light level would be rivaled by a candle.

I bought this 90w version in a recent purchase a few months back. I liked that it had the panel built in and only one fix and no cables. It has operated very well and I am pleased with its performance

Well Crossy i have similar to the ones you just purchased. My wife switches them on at around 21.30 and they are still working all night, going off at daylight. Have been working fine for ar

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2 hours ago, Crossy said:

Years ago I bought some solar garden lights.

 

They were not cheap, they were pretty useless.

The panels were tiny, the batteries cheap and the light level would be rivaled by a candle.

They worked well enough for marking the edge of the pond but didn't really provide "lighting".

The glimmer lasted about 8 hours when new.

The batteries finally failed after about 18 months.

 

Since then I've shied off solar lights, until now.

 

On the recommendation of another, well respected, member I bought a couple of these:-

 

Light-1.jpg

 

For 660 Baht how badly wrong can it go?

 

In the box:-

  • A 15W solar panel with a decently long lead and a weatherproof connector.
  • The light itself, nicely made plastic moulding, sadly it's a sealed unit so no easy replacing of batteries
  • Remote control with batteries
  • Bolts for the panel and 4 handy expansion wall fittings.

 

The remote has several modes;-

  • Off - Pretty obvious
  • On - On all the time
  • Auto - On when it gets dark, off when the sun wakes up
  • 3H - On 3 hours **
  • 5H - On 5 hours **
  • 8H - On 8 hours **
  • Dim 
  • Bright

** it's currently unclear if this means it will light for X hours every night.

 

So what performance can I expect?

That 15W panel will generate about 50Watt hours in a reasonable day (our 300W panels are doing about 1000Watt hours).

The 20,000mAh battery (likely 3.3V) can store about 66Watt hours.

So the panel and battery are pretty well matched, good start 🙂

 

The main unit being sealed means that I can't actually verify the power of the LEDs (no way they're really "60W") so a spot of estimating.

If our 50Watt hours keeps the light on for the specified 8 hours that makes the LEDs 6.25W.

It's also in the right ball park for a 60W incandescent equivalent (explaining where the "60W" comes from).

 

More as testing proceeds.

 

 

 

Your reasoning on the 60W is correct.

The actual Wattage quoted on Led  is Watt equal. The equivalent luminosity for a standard light.

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JD seems to be a renowned brand for solar lighting.

 

I have a set of these on the way for testing. For me they are intended for ambient light within the perimeter, but strange enough the very same light ( same brand and packaging) goes between 249 and 750 Baht on Lazada

 

https://www.lazada.co.th/products/sh-078-solar-cell-solar-light-led-solar-light-led-78-hvshops-i1419208911-s3656346739.html

 

image.png.10c5f92b87d71f427ca206cff748edae.png

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5 hours ago, Crossy said:
  • 3H - On 3 hours **
  • 5H - On 5 hours **
  • 8H - On 8 hours **
  • Dim 
  • Bright

** it's currently unclear if this means it will light for X hours every night.

 

If that setting would indeed work that way, that would be real positive, especially for my purpose, because who needs light within the perimeter after he went to bed. I haven't seen any other lights with that setting yet.

 

Would it be an option to add such a timer to an existing light?

 

The main requirements of course would be, it has to be small and cheap to build.

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On 11/28/2020 at 11:08 AM, Susco said:

image.png.10c5f92b87d71f427ca206cff748edae.png

 

 

My test light has arrived, so I have a few questions.

 

What direction should I point the solar panel? My idea was to have it horizontal, because the sun is most part of the day high in the sky, but I might be wrong.

 

The solar panel has a very matt surface. Is there a film I need to pull off?

 

It says output 5.5V 2.5W, is that the capacity of the panel?

 

Battery capacity is claimed to be 2000 mAh. Any way to check that, as the battery can be accessed.

 

Last but not least. Is there a way to build a small a miniature sized timer, which would shut down the battery output, on a set time after it get activated at night.

 

Let's say 7 hours after the photocell get activated it shut off and stays shut off for the next 7 hours.

 

 

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7 minutes ago, Susco said:

What direction should I point the solar panel? My idea was to have it horizontal, because the sun is most part of the day high in the sky, but I might be wrong.

 

The solar panel has a very matt surface. Is there a film I need to pull off?

 

It says output 5.5V 2.5W, is that the capacity of the panel?

 

Battery capacity is claimed to be 2000 mAh. Any way to check that, as the battery can be accessed.

 

Last but not least. Is there a way to build a small a miniature sized timer, which would shut down the battery output, on a set time after it get activated at night.

 

Let's say 7 hours after the photocell get activated it shut off and stays shut off for the next 7 hours.

 

 

Point your panel south tilted "slightly" (10-15o).

 

Matt surface is normal, nothing to peel off unless it's obvious (none of mine have had film).

 

5V 2.5W will be the panel output.

 

Unless the battery is marked there's not much you can do to verify the capacity. Perhaps compare the physical size with similar batteries on AliExpress?

 

You should be able to knock up a CMOS 555 (the standard 555 uses way too much power) based timer to do what you want without sucking too much of your valuable battery capacity. How to link it into the existing electronics is another matter entirely.

 

 

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40 minutes ago, Crossy said:

Unless the battery is marked there's not much you can do to verify the capacity. Perhaps compare the physical size with similar batteries on AliExpress

Humm BigClive would disagree.
 

The marking on the battery and literature often have very little to do with the actual capacity of the battery. For the average user actually confirming the capacity is, as you say, not very easy, but with a multi meter checking the load at intervals and run time of the light (and math) will get you to within 20% of the real capacity.
 

The weight of similar chemistry cells of the same size is often a reasonable guide to the gross capacity of a cell, in general the heavier the cell the higher the capacity.

 

Of course all of this requires that you actually have the items. 

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5 minutes ago, sometimewoodworker said:

The marking on the battery and literature often have very little to do with the actual capacity of the battery.

 

I can quite believe that fake batteries are out there just like fake flash cards.

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