25W of solar panel question

[lsy388]

Hi, i am a beginner of solar maker, i just need some advice about my new 25w solar panel project. May i know if i use 25W of solar panel, what is the capacity of solar controller, storage battery, or even inverter am i suppose to use? As i need to support 5 led light and 1 fan. Please kindly advice, thanks.

[Mike90250]

If you ever think you may want to expand your plans, I would suggest using a charge controller that would handle your expanded ideas.
Generally, the most cost effective is the "Deep cycle, marine battery" sold at big box stores, around $90. Amps per $, it can't be beat.
With only a 25W panel, it will be real easy to drain your battery below what your panel can recharge in 2 days.
I would get a good volt meter, it can be a very usefull tool.
Also, read and print the battery FAQ http://www.windsun.com/Batteries/Battery_FAQ.htm
It has a nice voltage chart, and you really don't want to go below 70%, with only a 25W charge controller.
Also, at a boating store, get a plastic battery box. only about $10, and will contain acid if any leak develops. having 1 battery in a house is not bad, but it could make a mess.
At a autoparts store, get a inline fuse holder, with about a 10A fuse, and attach to the + terminal. Nice to have something inline for safety, if a whire shorts out.

[lsy388]

Thanks for your advice, would you pls kindly also advice base on my 25W solar panel, how many volt of controller and inverter will suit to it? Also what is the capacity of deep cycle battery should i use? Thanks.

[Mike90250]

Thanks for your advice, would you pls kindly also advice base on my 25W solar panel, how many volt of controller and inverter will suit to it? Also what is the capacity of deep cycle battery should i use? Thanks.

I'll assume a 25V panel designed for 12V.
I'd look at the Trace C-12 controller. That can handle up to 12A of power, it's rugged, ready to go out of the box, and simple.

The $90 battery at a big box store will be around 85-100 AH capacity. I'm looking for the best deal for you, not the battery sized to 0.001% of the theory for a 25W panel. A 30AH battery is likely the "optimal size" but it will cost you nearly as much as the "big box store" battery.

Inverter - that depends on what you will power with it. The $45 mod-sine inverters sound like a great deal, till they fry your $200 cordless drill charger.
Read the Inverter FAQ http://www.solar-electric.com/solar_...r_electric.htm
it may help you decide.

[lsy388]

Is it the capacity of solar panel important? As my solar panel only about 25W/10AMP = 2.5volt, can it actually afford to my project?Thank you very much, should any question arises, i will ask for help again, thank you.

[ecusolar]

I dought that your panel has 10Amps, how many cells do you have?

Can you make a picture to post?

Is it the capacity of solar panel important? As my solar panel only about 25W/10AMP = 2.5volt, can it actually afford to my project?Thank you very much, should any question arises, i will ask for help again, thank you.

[lsy388]

Thanks, actually i just don't understand to convert Watt to Volt, on top of that, i also have no idea how many volt of solar panel will take how long of time for charging certain capacity of battery. As my country is in Malaysia, the capacity of sun heat is fantastic, would you pls kindly instruct me about above question? Thank you very much.

[ecusolar]

Need more info

Isy, actually I would start to think about what you want to lightnen, move or use with your panels and for how long in which time of the day and with that we can give a valued opinion.

Only saying I have a 25W panel makes no sense without Volt / Amps values as you can't almost do nothing with it other than move a small water fountain or charge a motocicle battery. You have to know that with any energy you convert you will lose some because of heat.

When you need to go through a charge controller, later a battery and at the end an inverter there is not much left of your 25W.

Thanks, actually i just don't understand to convert Watt to Volt, on top of that, i also have no idea how many volt of solar panel will take how long of time for charging certain capacity of battery. As my country is in Malaysia, the capacity of sun heat is fantastic, would you pls kindly instruct me about above question? Thank you very much.

[lsy388]

Thanks, ok, my specific question about my project as following;
* ? watt of solar panel > ? volt of charge controller > ? volt of battery > 5W
of led light with 8 nos.(10 hour working only night)

That's my project line, would you please kindly design for me, thanks for your help.

[ecusolar]

That's easy if it's right that all LEDs together have 5W.

Get you a cheap new car battery, one of those 3 cil. Suzuki cars, I think they have about 45Amps.
With that load you won't deep circle it as you will only discharge about 10% of the capacity. Why buy a deep circle battery when you can get these for some bucks, in case that it get damaged in 2 years or so, just buy a new one.
Than get you this controller .
Connect your 25W panel, the battery and your load (the LEDs).

5W x 10h= 50W/h, the cheap car battery has 12V x 45Amps = 540W

Your panel has 25W and let's say you have 3 hours of enough light to charge, that's 75W, some power will get lost in the way but you will not lose that much that you don't have enough charge for the night.

Hey Mike, let me know if I'm talking BS but a small thing like this doesn't need to many science I think.

It's almost like triggle charging and discharging.

Thanks, ok, my specific question about my project as following;
* ? watt of solar panel > ? volt of charge controller > ? volt of battery > 5W
of led light with 8 nos.(10 hour working only night)

That's my project line, would you please kindly design for me, thanks for your help.

[lsy388]

Thanks Mike......, i got it now, i am really a SUPER beginner.......,thank you very much.

[Mike90250]

You are forgetting the the 50W LED draw, for 10 hours, that's 500Whours.

This is an impossible situation. You cannot draw 500WH out of any battery, and replace with 25W x 5 hr = 120WH recharge.

The most the 8 LED 's can run, nightly, is .8hr. There are losses recharging the battery, so the solution is larger PV panel or less lighting.

I do agree with the least expensive battery, instead of buying a 40ha battery, get the cheapest battery, which might be a 60ah, but beacuse it's a common auto battery, mass production makes it cheap.

[lsy388]

What about i put 50W of solar panel and reduce led duration working time to 8 hour, is that ok with that? Kindly advice. Thanks.

[greenHouse]

Hey Mike, let me know if I'm talking BS but a small thing like this doesn't need to many science I think.

It's almost like triggle charging and discharging.

You're talking BS.

The OP has yet to say when the open circuit voltage of his solar panel is going to be. And it almost sounds like he's making some non-standard voltage panel -- like 25W at 2.5 volts.

Batteries can't be trickled charged to make them full. The self-discharge of a battery is high enough that a too-small solar panel will never recharge the battery. And if the voltage isn't high enough to begin with, it will never recharge the battery.

[Mike90250]

What about i put 50W of solar panel and reduce led duration working time to 8 hour, is that ok with that? Kindly advice. Thanks.

Still not enough. 250wh can't replace 350Wh

A 25W panel is just not very useful for much more than a couple of LED's.