Solar Panels: How many watts?
How many watts of solar panels would I need to keep two 12-volt batteries charged? I don’t know the specs on the batteries. I’m looking for a ballpark number. What about portable panels vs those mo...
Forum Discussion
Unless you're actively going to move the portable panels and tilt/position them multiple times a day to see that they produce significantly more than mounted panels, I think Mounted are the way to go. Mounted seem to have better/longer warranties and they are pretty much mount and forget about them. Portables you have to have a decent place to store and then there's the setup, hook up and tear down every time you go camping. Just my two cents.
If your just looking to maintain the batteries between uses, 1-100 watt panel will do that easily. If your looking to keep the batteries charged while camping, an assessment of what you use would be critical to getting that decision right.
Identify what batteries you have so you can figure out how many Amp Hours (AH) they have. Generally, you only want to use 50% of those AH because going below that damages the battery and makes it store less energy upon future recharges.
I'm just going to make up some numbers to illustrate.
So say your batteries are 50AH each. You can take them down to 25AH each without damaging them but then they need a recharge.
So that gives you 25 AH of power to use between fully charged and need to stop and recharge. Now if your your usage is only 10AH a day, you will have 2.5 days of power without solar. If your usage is 25AH a day, you need to recharge daily and more importantly, you need to fully charge your batteries to be able to use your full 25AH again the next day. If they don't get fully charged, your going to be using more than 50% and damaging your batteries if you use your typical 25AH.
Next thing to consider is that solar panels are rated for a specific output but that is is optimal conditions. If you partially shaded because of a tree, or it's a partly cloudy day, or worse yet, it rains all day and you get nothing from the panels. So you want a generator as a backup plan for those days or if you need to assist the panels in getting back to 100% charged batteries. But many people put as many panels as they can which gives a quicker recovery of their batteries but most importantly, gives them a chance to get fully recharged to 100% even if they only get a partial day of sun.
The last consideration is going back to the Batteries. Adding more powerful 12v or (2 or 4-6v in parallel is the favorite configuration for many people) batteries that have higher AH ratings (Stores more power) makes your energy piggy bank much bigger. If you had 2 batteries that gave you a total of 300AH and you could use 150AH a day (Remember the 50% rule), well now your 25AH usage isn't such a big deal. You have 6 days worth of usable energy. A couple cloudy days wouldn't even make you fire up the genny.
Even though the numbers are made up just to make the math easy, I hope this helps you understand the process of deciding what is right for you (and others that may read this). There are a lot of moving pieces to think about but it really boils down to these three things:
* How much energy do you use/need daily
* How much can your batteries store
* How much can the panels reasonably put back in a day
Until you know the first one, it's like asking how much water should I take on my desert hike?
(Usage) How much do you need to drink each day?
(Batteries) How much can you carry?
(Solar Panels) Are there any oasis's to refill along the way?
If your just looking to maintain the batteries between uses, 1-100 watt panel will do that easily. If your looking to keep the batteries charged while camping, an assessment of what you use would be critical to getting that decision right.
Identify what batteries you have so you can figure out how many Amp Hours (AH) they have. Generally, you only want to use 50% of those AH because going below that damages the battery and makes it store less energy upon future recharges.
I'm just going to make up some numbers to illustrate.
So say your batteries are 50AH each. You can take them down to 25AH each without damaging them but then they need a recharge.
So that gives you 25 AH of power to use between fully charged and need to stop and recharge. Now if your your usage is only 10AH a day, you will have 2.5 days of power without solar. If your usage is 25AH a day, you need to recharge daily and more importantly, you need to fully charge your batteries to be able to use your full 25AH again the next day. If they don't get fully charged, your going to be using more than 50% and damaging your batteries if you use your typical 25AH.
Next thing to consider is that solar panels are rated for a specific output but that is is optimal conditions. If you partially shaded because of a tree, or it's a partly cloudy day, or worse yet, it rains all day and you get nothing from the panels. So you want a generator as a backup plan for those days or if you need to assist the panels in getting back to 100% charged batteries. But many people put as many panels as they can which gives a quicker recovery of their batteries but most importantly, gives them a chance to get fully recharged to 100% even if they only get a partial day of sun.
The last consideration is going back to the Batteries. Adding more powerful 12v or (2 or 4-6v in parallel is the favorite configuration for many people) batteries that have higher AH ratings (Stores more power) makes your energy piggy bank much bigger. If you had 2 batteries that gave you a total of 300AH and you could use 150AH a day (Remember the 50% rule), well now your 25AH usage isn't such a big deal. You have 6 days worth of usable energy. A couple cloudy days wouldn't even make you fire up the genny.
Even though the numbers are made up just to make the math easy, I hope this helps you understand the process of deciding what is right for you (and others that may read this). There are a lot of moving pieces to think about but it really boils down to these three things:
* How much energy do you use/need daily
* How much can your batteries store
* How much can the panels reasonably put back in a day
Until you know the first one, it's like asking how much water should I take on my desert hike?
(Usage) How much do you need to drink each day?
(Batteries) How much can you carry?
(Solar Panels) Are there any oasis's to refill along the way?
