# Project question about charging with a solar panel

#### spagettilegs

Dec 4, 2018
5
A friend of mine wants to use point to point Wi-Fi from a router 500m from his house.
There is no power at the router location so I he was thinking of using a solar panel and a 12v battery to run the router and his point to point Wi-Fi from an outdoor box.

The solar panel will need to produce enough power to charge the battery and feed supply to the equipment so it can run 24/7 if needed.

The system he’s looking at would be something like https://kuwfi.com/products/kuwfi-2-...oor-cpe-kit-point-to-point-wireless-bridge-92 (POE 24V/0.5A) a standard 12v router which uses between 6-20 amps depending on the model from what I can see online.

My question is about sizing if the equipment. What size solar panel would he need to generate enough power to keep a 12v battery charged based on the above equipment.

I have a 20W 12v solar panel with controller in my garage. I was just wondering if this is suitable?

Apologies for the lack of technical data but he hasn’t chosen any specific equipment yet.

Thanks

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#### Delta Prime

Jul 29, 2020
1,642
My question is about sizing if the equipment. What size solar panel would he need to generate enough power to keep a 12v battery charged based on the above equipment.

I have a 20W 12v solar panel with controller in my garage. I was just wondering if this is suitable?
For the cost of your solar power system I can put it down payment on a house. Solar panels specifications are given in Watts.
Look at wattage is by comparing it to the speed of a car. If a car travels 50 miles in an hour, you would say it is traveling at 50 mph. The same logic applies to wattage.
You multiply the watts by the number of hours a device is running to figure out how much power is generated over a period of time. That's how many watts your solar panel is going to be capable of.
From your information 12 volts battery and your system takes 20 amps.
12 volts times 20 amps equals 240 Watts that's for one hour!
Now the following example is an exaggeration worthy of(woo woo) place in the Twilight zone.
you want that to run 24 hours . So 240watts times 24 equals 5,760watts. Now 5,760watts devided by 12 Volts equals 480Amps.
Your going to need a 12 volt battery with a current capacity of 480 amps and a solar panel
capable of 5,760 Watts. And this all depends on the solar panel itself.The angle of your solar panel, you have to track the Sun. your geographical location

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#### kellys_eye

Jun 25, 2010
6,230
a standard 12v router which uses between 6-20 amps depending on the model from what I can see online.
What models are these? I know of no 'normal' router that uses 240W - please give a link to these routers.

#### spagettilegs

Dec 4, 2018
5
What models are these? I know of no 'normal' router that uses 240W - please give a link to these routers.
Sorry…. I meant watts.

#### spagettilegs

Dec 4, 2018
5
For the cost of your solar power system I can put it down payment on a house. Solar panels specifications are given in Watts.
Look at wattage is by comparing it to the speed of a car. If a car travels 50 miles in an hour, you would say it is traveling at 50 mph. The same logic applies to wattage.
You multiply the watts by the number of hours a device is running to figure out how much power is generated over a period of time. That's how many watts your solar panel is going to be capable of.
From your information 12 volts battery and your system takes 20 amps.
12 volts times 20 amps equals 240 Watts that's for one hour!
Now the following example is an exaggeration worthy of(woo woo) place in the Twilight zone.
you want that to run 24 hours . So 240watts times 24 equals 5,760watts. Now 5,760watts devided by 12 Volts equals 480Amps.
Your going to need a 12 volt battery with a current capacity of 480 amps and a solar panel
capable of 5,760 Watts. And this all depends on the solar panel itself.The angle of your solar panel, you have to track the Sun. your geographical location

View attachment 61304
Wow…. Thanks for the detailed answer.

#### Delta Prime

Jul 29, 2020
1,642
Wow…. Thanks for the detailed answer.
I'm just a youngster. Like a centrifugal governor on a hit and miss steam engine .
I go balls out! Or balls to the wall!
a standard 12v router which uses between 6-20 amps
Would you happen to have ment 6 to 20 watts instead of 6 to 20 amps?

#### kellys_eye

Jun 25, 2010
6,230
Worst case (24V/0.5A and 20W router) your requirement is 32W - to be safe I'd bump this to 50W. A solar PV panel rated at 50W could - theoretically - keep it going during sunlight hours (12 hours) and the other 12 hours from a battery rated at ~50Ahr. With your latitude (whatever that is) this ratio may vary.

It's always wise to factor in 'reality' and add a percentage for inefficiencies (losses) etc and, for solar - which is a crap source anyway - a minimum of 100% would be wise. Accordingly a 100W panel and a battery with 100Ahr would be more like it. If you consider a less-than-24hrs use of the system you could degrade this requirement accordingly.

That the spec of the POE and router, in terms of power consumption, is already quoted worst-case the margins that are shown above will be improved upon and the system should operate effectively.

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