Solar Panel For Camper - *General Questions*

[Greggl]

I'm wanting to run a small fishtank pump off of a battery connected to a solar panel, do I need a special water pump to do this?

Is it possible that the solar panel could fry a deep cycle battery if it is constantly plugged in? How do I prevent this, and how do I wire it up?


How do home appliances run off of a solar battery, there must be an inverter right?

Im looking for a battery and solar pannel combination that would enable me to run a small fishtank as much as possible, preferably in addition to lights and what not, what would be the best?

How would I go about charging my cellphone off of the battery?

I'm a total beginner, and I dont even know where to begin to look to find the answers that I'm looking for

Thanks
I greatly appreciate it!

[lkruper]

Greggl:
I'm wanting to run a small fishtank pump off of a battery connected to a solar panel, do I need a special water pump to do this?

lkruper:
No

Greggl:
Is it possible that the solar panel could fry a deep cycle battery if it is constantly plugged in? How do I prevent this, and how do I wire it up?

lkruper:
You need a charge controller.

Greggl:
How do home appliances run off of a solar battery, there must be an inverter right?

lkruper:
Yes

Greggl:
Im looking for a battery and solar pannel combination that would enable me to run a small fishtank as much as possible, preferably in addition to lights and what not, what would be the best?

lkruper:
It depends on your goals and circumstances. Is utility power available? What do you mean by as much as possible?

Greggl:
How would I go about charging my cellphone off of the battery?

lkruper:
It depends on what your charger needs. I just bought a 12v outlet and 12v charger for my iphone. Some chargers need 110v.

Greggl:
I'm a total beginner, and I dont even know where to begin to look to find the answers that I'm looking for

lkruper:
I understand.

[Rainwulf]

Gregl, look at the questions that have been answered, then go from there.

You need to look at:
do you want mains power equivalent? or just devices that run of 12 volts.

You need to look at the absolute amount of power in watt hours.

To get watt hours multiple the devices current by 12 volts, then multiple by the number of hours its on.


Step 1:
For example, if a pump required 1 amp, thats 12 watts, over 24 hours is 288 watthours.

Step 2:
Your battery needs to be able to provide that power for a whole day to 50 percent Depth of Discharge (worst case) so you need a battery capable of providing double that so, 576 watt hours. If you need it to provide power for 2 days, multiple by 2. Etc.

Step 3:
Divide your watt hours by 12 volts to get your approximate AH for your battery. so 576/12 is 48ah, so a 48 ah will safely provide 1 amp for 24 hours until it gets half flat.

Step 4:
Now, you have to recharge this battery. That means replace the AH you lost, plus account for charging inefficiencies. I use 0.7 but Sunking could probably correct me.
So you are using half of your battery, so 24ah. You need to replace 24/0.7 which is 34.3ah.

Step 5:
Now, you need to look at how much sun you do get. That depends on where you are. Lets use for example 6 hours. So you need to replace at LEAST 34.3ah over 6 hours.

Step 6:
divide 34.4ah by 6 hours. That gives you 5.73 amps. Then add your load! So you need to provide at least 6.73 amps for 6 hours BEST CASE SCENARIO. A solar panel, using a PWM controller thats capable of 10 amps, you would need 6.73amps times 12 volts panel so 80.76watt. So, a 120 watt panel for a safety margin, and for the fact that PWM controller cant use the full voltage of the panel. For a sanity check, multiple your panel wattage by 6 hours to get a value that should be higher than your usage. 120*6 is 720, so 720wh to replace 288wh from stage 1. Gives you the ability to charge on cloudy or slightly overcast days.


Step 7: Go back and then look at any other possible things you could be using this power system for, add them to the watt hours at the start. Adjust again.

Step 8. My personal step here is then to double the panel wattage again. This gives you a large safety margin. If you NEED this to run 24/7 with absolutely no interruptions, and if you know in your area you can go weeks with cloudy weather, either organise an AC backup, or keep adding panels and batteries.

Unless you buy a fairly complex system that can switch back to mains, or can handle interruptions to your 12 volts, dont do this.

A cheaper system, panel+regulator+battery cant guarantee you power, so your load has to handle interruptions.
Also make sure you include low battery cut off, most cheap PWM controllers do this. Otherwise you run the risk of killing your battery.


I could be wrong in so many places here, so i accept all corrections.

[Sunking]

I'm wanting to run a small fishtank pump off of a battery connected to a solar panel, do I need a special water pump to do this?

Is it possible that the solar panel could fry a deep cycle battery if it is constantly plugged in? How do I prevent this, and how do I wire it up?

The only thing you need to know is: Anything you take off grid will be many times more expensive than buying the power from the electric company for the rest of your life. Additionally makes you an extremely heavy polluter. Now that you know that you have to ask yourself a question.

"Why in the hell do I want to pay many times more to go off grid and be a dirty filthy polluter?"

Once you have done that, then you will know exactly what to do.