Okay. I think it's about time to tackle the big questions. Whats the difference between, volts, amps, watts and how much solar power do I need ?
First of all, lets start with a basic foundation to work from. Since you're reading this blog, you must already know that the primary topic and usage for power is on our teardrop trailers. All of our teardrop trailer's are off the grid. We use a deep cycle marine battery to power fans,heating blankets, 12 volt coolers, lights and a whole pile of different accesories.
Since we began our custom teardrop trailer builds, we have come across a handful of people that still want to depend on the "Grid", and some people even want to still use regular kitchen appliances when camping, such as blenders,toasters and yes even coffee makers. I must admit, I am guilty of wanting a good freshly brewed coffee first thing in the morning, no matter where I am camped out. So let's get right to it then. Lets use one item at a time to decide how much power you'll need on your teardrop camping trip.
First we need to understand each definition.
Volts. The volt is a measure of electric potential. Electrical potential is a type of potential energy, and refers to the energy that could be released if electric current is allowed to flow. We use a 12 volt deep cycle marine battery. Sometimes we connect 2 batteries together. Positive with positive and negative with negative. It still maintains 12 volts.
Amps. Amperes are used to express flow rate of electric charge. For any point experiencing a current, if the number of charged particles passing through it — or the charge on the particles passing through it — is increased, the amperes of current at that point will proportionately increase.
Now lets break this down using a basic 12 volt fan as an example; We're using a 12 volt battery as it's source. Almost everything you purchase for a 12 volt system will tell you how many amps it draws, or uses. let's say the fan we choose uses 3 amps. Okay, Let's stop there for a second and now go to the next definition.
Watts. One watt is also defined as the current flow of one ampere with voltage of one volt. How to convert watts to amps The current I in ampers (A) is equal to the power P in watts (W) divided by the voltage V in volts (V): I(A) = P(W) / V(V)
Inverter. A power inverter, or inverter, is an electronic device or circuitry that changes direct current (DC) to alternating current (AC). The input voltage, output voltage and frequency, and overall power handling depend on the design of the specific device or circuitry. The inverter does not produce any power; the power is provided by the DC source. In our case, the deep cycle marine Battery.
Solar. Before you figure out what size solar panel you want, you need to figure out how much power you'll need throughout the day and night. We personally use 100W flexible panel and 2 deep cycle marine batteries. If all you need is a little lighting at night, you'll be fine with a smaller 15W solar panel and a single deep cycle marine battery.
Okay, lets go back to that 12 volt fan. It does not require an inverter to work. It also does not need a solar panel to work. If you want to recharge your battery, you'll need a regular battery charger,solar panel or a 7 pin round trickle charge from your car to trailer battery. If you want to use an appliance like a coffee maker or toaster you'll need an inverter. We use a 3000W inverter. (remember- a coffee maker uses approx 1250W ) A 100W solar panel can produce approx 6 amps per hour on a sunny day. 5 hrs, gives you 30 amps returned back to your battery. That 12 volt fan draws approx 3 amps. Your newly charged deep cycle marine battery should have approx 100 amp hours already in reserve.
A 100ah battery should provide 1 amp for 100 hours, 2 amps for 50 hours, 3 amps for 33 hours etc. It would be nice if this would work all the way up to 100 amps for 1 hour, but there are some limits to the maximum rate of current draw, and how much of that 100amps you can actually use without destroying your battery.
There's a lot more to understanding a 12 volt system but I hope this write up is a begining in helping you to calculate what size system works best for you. Happy trails...