Adding another solar panel

[BobC]

Originally Posted by valsamik

Thanks for the info BobC. I was looking more at TV or coffee maker. I don't use the AC unless on power pole or generator power during the day. I wanted to be able to charge batteries during the day without having to run generator unattended while at the race track.

It all depends on a lot of factors but, fortunately, if you get a controller that has capacity for expansion, adding panels isn't difficult. I'd think that 400w would be more than adequate but you really should do some calculations. Usage is highly personalized. Anything that heats, like a coffee maker is going to be a high consumer of power. A modern, LCD TV, on the other hand, isn't going to be a power hog. Running the generator for a short time to run your microwave or even your coffee maker shouldn't be a problem. That would take a big load off your system. Or, you could always use a French press to make coffee and consume no electricity.

https://gpelectric.com/rv-solar-sizing-guide/

[Koja]

Ohm's law (named after the German physicist Georg Ohm) defines the relationship between Voltage, Current and Resistance.

V = I x R

Where:

V is the electrical potential (voltage), measured in volts (V),
I is the current, measured in Amperes (Amps/A), and
R is the resistance, measured in Ohms (Ω).
Joule's law states that:

P = V x I

where:

P is Power, measured in Watts.
The combination of Ohm's law and Joule's law gives us 12 formulas where 2 of the 4 variables are known. The wheel below is a handy tool and memory jogger. To use it, simply choose the quadrant corresponding to the variable you want to calculate, then select the segment corresponding to the variables that you know the values of.




Web Application Developed by Zero Point Labs

[AJMike]

Originally Posted by Koja

The wheel below is a handy tool and memory jogger.

What "wheel below"? Found no wheel and no link.

[Koja]

http://www.ohmslawcalculator.com/ohms-law-calculator[/IMG]

[BobC]

It pretty much boils down to this:

An appliance that's rated at 1200w is going to draw 1200w/120v = 10a at 120v but will draw 1200w/12v = 100a.

If a 120v appliance is rated in amps, just multiply the rating by 10 to get the 12v amp draw.

None of this takes into account the efficiency of the inverter, which can vary based on type and model. Fortunately, many appliances only draw full wattage for part of the time. For example a coffee maker that cycles on and off will average somewhat less than it's full wattage.

If you're installing everything from scratch, the larger the wire gauge (smaller gauge number) used, the better. If your rig is pre-wired, the wire gauge can be a limiting factor in your installation but you can always re-wire. Here's a calculator FYI:

https://www.renogy.com/calculators#tab_solar-cable

Using larger wiring is cheaper than adding solar panel wattage. A larger gauge will also allow for future expansion.