# Determining Solar panel size:

#### CarltonDranko

Joined Dec 30, 2020
22
Which solar panel is suitable to charge a 12V 7AH battery

#### wayneh

Joined Sep 9, 2010
17,262
In what period of time? From dead to full charge?

#### KeithWalker

Joined Jul 10, 2017
2,804
The choice of which solar panel to use does not just depend on the size of the battery it will charge.You need to consider the following:
1. At what latitude are you located? The angle will determine the amount of atmospheric attenuation of the available sunlight.
2. Will the panel track the sun in both X and Y axes? See above.
3. What is the local daily average amount of sunshine for each season.
4. How much current will the battery be supplying? Is it continuous? If not, how often and how long?
5. How critical is it to keep the battery charged?
There are several other minor considerations but these are the main ones that will affect the size of panel required.
Regards,
Keith

#### wayneh

Joined Sep 9, 2010
17,262
5. How critical is it to keep the battery charged?
That's the one so often overlooked, and yet it's a huge factor.

It's basically an inventory management problem: You have a production schedule and outgoing shipments of power. Your challenge is to size the production level to avoid a stockout, running out and having to interrupt shipments.

Hospitals keeping patients alive by using electrical equipment cannot tolerate a stockout risk of one in a thousand. Maybe one chance in a million is OK, but I doubt it.

Keeping my solar garden lights lit is a completely different scenario. I'd guess they run out of power 90% of nights this time of year. Their little panels would probably need to be 5-10X larger to achieve hospital-grade risk reduction.

#### CarltonDranko

Joined Dec 30, 2020
22

#### Delta Prime

Joined Nov 15, 2019
1,311
Hello there
determine the number of watt-hours that is required to charge a 12v battery
Multiply the voltage of the battery by the amp hours.
Determine the number of sunlight hours that shine on the panels
To figure out the number of solar panel watts you need, divide the number of available sunlight hours with the watt-hours
Bingo! you're done.

#### MrChips

Joined Oct 2, 2009
28,474
All of the above or do a ball-park estimate.

Assume you want to charge a 12V 7Ah battery in 4 hours.
You need about 2A @ 15V = 30W
Double that = 60W

#### CarltonDranko

Joined Dec 30, 2020
22
The choice of which solar panel to use does not just depend on the size of the battery it will charge.You need to consider the following:
1. At what latitude are you located? The angle will determine the amount of atmospheric attenuation of the available sunlight.
2. Will the panel track the sun in both X and Y axes? See above.
3. What is the local daily average amount of sunshine for each season.
4. How much current will the battery be supplying? Is it continuous? If not, how often and how long?
5. How critical is it to keep the battery charged?
There are several other minor considerations but these are the main ones that will affect the size of panel required.
Regards,
Keith
1.-19.0169 Longitude: 29.1528.⁩
2. Using Mppt algorithm(the solar panel will be fixed).
3.6-8hrs
4.juc charging the battery is the main concern
5.

#### KeithWalker

Joined Jul 10, 2017
2,804
1.-19.0169 Longitude: 29.1528.⁩
2. Using Mppt algorithm(the solar panel will be fixed).
3.6-8hrs
4.juc charging the battery is the main concern
5.
I have told you how, so now do a bit of research on Google, get out your calculator and find out what size you need!
Regards,
Keith