Solar panel for indoor system

Hey makers,

I want to make a solar power supply for indoor system. I am looking to charge 36W accumulator, and then distribute the power over the system. I tried to to charge 3W battery indoors succesfully with small panels. Since the accumulator that i want to charge is a bit more massive, i would like to know if it is possible. The purpose: 1. It will be exposed to fluorescent light for about 10-12 hours, and charge the accumulator. 2. When the light goes off at night, a transistor will open the accumulator, and the power that was accumulated for 10-12 hours will be used for about hour and a half.

Before i buy the accumulator and the solar power and the right charger, transistor etc. I would like to know if it is even possible, what restrictions i might have, should i order more that 36W solar panel for 36W accumulator, and there might be questions that i am not even aware of. It will be great if someone can answer some of my questions over here, or ask me questions that i am not aware of.

Thanks in advance!

Start with what kind of battery will you be using?

There are not any good solar/Li battery solutions.

I’d use 12V solar cell(s) with an open/unloaded voltage of 17ish volts.

I’d use a PWM or MPPT Charge controller to charge a lead acid or LiFePo4 battery. I prefer LiFePo4’s for solar over lead acid. I’d opt for a PWM charge controller to keep costs reasonable/down.

The solar panel will provide power to the charge controller, which will charge the battery, which will supply power for the circuit.


Will you be using motors?

The accumulator is np7-12 12V, 7ah. I will be using 2 nema 17 motors. Each 12V 1.5A, but also there is a chance that i will use 1 nema 17 motor, and 4 little dc motors for wheels which will be connected to H-bringe. Basically i am planning to use 36W accumulator, and a charger for the solar panel. I will work on distribute the power over the system in a way that i need. There will be some planning. The question is if it is possible to create power of 36W with solar panel indoors, where the source of light is fluorescent.

Your battery (12V 7Ah) sounds like a Yuasa SLA and it is an 84Wh accumulator. So where does a 36W accumulator come in?

Anyway you can produce plenty of power from solar panels if you have large enough solar panels. But a solar panel which calls itself a nominal 36W panel can probably only produce that amount outdoors at noon on a sunny summer day. It will be a lot less indoors but how much less is not the sort of thing that solar panels normally specify. All you can really do is test it yourself.

Steve

you are right. its 84, i just didnt found 36 yet. I was hoping to see if anybody tried to do it indoors. I would like to test it but before i am trying to do some homework because its not a 10$ modules from aliexpress. Thank you anyway!

It will be exposed to fluorescent light for about 10-12 hours, and charge the accumulator.

Lux is used to measure light intensity (energy) in the visible range. Typical office building fluorescent lighting is around 400 lux, while full sun at noon is around 100,000 lux.

So, a 36W solar panel might produce (400/100000)*36 W = 0.144 W (144 mW) indoors.

Consider using the wall AC socket instead.

valerig: 1. It will be exposed to fluorescent light for about 10-12 hours, and charge the accumulator.

It would be much more economical to charge the batteries from the mains electricity that is powering the lights.

Compared to sunlight any electric lighting is trivial. Bright sunlight in a clear summer sky produces about 1kW per square metre and that is the light intensity against which solar panel output is reported. In other words an 80W panel can produce 80W if the light intensity falling on it is 1kW per square metre.

I have no idea what the intensity from a fluorescent light is but I doubt if it is even 10% of what the sun produces. 1% would be my guess.

...R

And most solar panels, to get those watts, use multiple frequencies of light energy to generate electricity. A indoor light would produce a limited number of optical frequencies, which will diminish a solar cells output.

I have no idea what the intensity from a fluorescent light

Read post #5 to learn.

jremington: Read post #5 to learn.

Sorry. I missed that. But I was not too far wrong with my 1% guess. Your figures suggest 0.4%

...R

PV cells absorb mostly in the far red and near IR, where fluorescent lights emit little radiation.

So, under fluorescent lights, expect maybe 0.1 to 0.2% of full sun output. Perhaps 50-100 mW.

0.1W doesnt sound promissing, the question is how long will it take to reach 0.1W. I charged 3W battery indoors with 2 tiny solar panels which produces around 5W in 5 hours. But there where lamps which are not fluorescent lights (about 10W ).

Don't confuse power (Watts = Volts*Amperes, the rate at which energy is delivered), with energy (Wh = Watt hours = Volts*Amperes*time in hours), or battery capacity (Ah = Ampere hours = Amperes*time in hours).

Use your multimeter to measure the current in Amperes that the solar panel delivers to the battery. That will tell you the charge time in hours to reach a certain number of Ampere hours.

If you don't have a multimeter, now is the time to buy one!

valerig: 0.1W doesnt sound promissing,

Sorry to be blunt. But this is a completely impractical idea. Just give it up.

...R

valerig: Hey makers,

I want to make a solar power supply for indoor system. I am looking to charge 36W accumulator, and then distribute the power over the system. I tried to to charge 3W battery indoors succesfully with small panels. Since the accumulator that i want to charge is a bit more massive, i would like to know if it is possible. The purpose: 1. It will be exposed to fluorescent light for about 10-12 hours, and charge the accumulator. 2. When the light goes off at night, a transistor will open the accumulator, and the power that was accumulated for 10-12 hours will be used for about hour and a half.

Really? You have access to building power and want to charge photovoltaically? Why not just plug in a charger?

Batteries are not measured in watts either, not sure what you mean - perhaps provide links to the exact hardware products you are talking about.

An "open" circuit carries no current, the transistor switched on, it definitely didn't "open". The English language is inconsistent with fluid flow analogy here(!)

jremington: PV cells absorb mostly in the far red and near IR, where fluorescent lights emit little radiation.

Depends completely on the type of PV cell...

jremington: Use your multimeter to measure the current in Amperes that the solar panel delivers to the battery. That will tell you the charge time in hours to reach a certain number of Ampere hours.

I charged battery of 3.7V 0.8A so i assumed it to be 3W battery. My application requires maximum of 12V and 1.5A for about 2 hours which means (or meant before your comment) 36W. So by what you are saying i have to look for 3A battery?

Robin2: Sorry to be blunt. But this is a completely impractical idea. Just give it up.

It looks for now impractical. I might give it up, just have to be sure

Buy all the parts put it together and try it, to be sure.

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