A lot of questions we receive seem to imply that most sites use difficult math and besides that forget to cover the ground-rules of electronics like Ohm’s law.
To add some extra info, I hope it’s possible to clear a bit of smoke since we try to provide information as clear as possible.
Basicly there are 2 main rules that can be adapted in different forms:
- Voltage = Current x Resistance
- Power = Voltage x Current
The second rule wil be most used in solar, the more voltage offered by a PV-panel, the more power is generated, same goes for the current.
A panel with 18 Volt x 5.5 Amps brings approx. 100 Watts, simple math using Ohm’s law.
Power can be easily accumelated, 2x 100 Watt panels can generate 200 Watts.
It would be a bit simple to assume that just knowing Ohm’s law will bring al the guidelines together to design solar installstions, but it’s certainly basic knowledge.
Most pages on here will also have math and use Ohm’s law, but there is much more in the solar technique. The higher the current, different AWG sizes wire is required, but that is not that different form you own home, most is AWG 10 or 12, but al small light can be connected with AWG 14 or 16 for example. The most important thing is common sense and when in doubt, ask questions.
12 Volts or higher ?
People seem to think just because 12 Volts sounds low it’s easier to work with than 110 Grid for example. This is only partly true and also Ohm’s law can help find out so amazing stuff.
Honestly you old modeltrain probably ran on 12 Volts and nothing ever happened. But things have changed since the train ran on a small transformer with 1 Amps max. Batteries offer much more short circuit current than the old model train.
This is something to be careful with from the beginning. So use fuses, breakers and more fuses if needed, in all our examples we try to use fuses.
Ohm’s law states : Power = Voltage x Current, so this is true for both lower voltages as well higher voltages.
Let’s say you run a small powerdrill of 4.5 Amps on your household grid, this is approx. 110V x 4.5A = 495Watts, nothing fancy, you never thought about this before, be honest.
This same powerdrill is going to be used on solar-power, good battery and a nice DC-AC inverter should take care of that real easily.
DC-AC inverter 12Vdc – 110Vac
Ohm’s law states : Current = Power / Voltage (the same formula, with different writing down)
So 495W / 12V = 41.25A on the input of the DC-AC inverter (a bit more actually, but we handle 100% efficiency in this example).
This puts things in the right persective, you need 6 AWG, to go from the battery to the inverter, much bigger than the modeltrain. On the output-side on the inverter nothing changed, you just have your powerdrill plugged-in at 4.5 Amps.
Ohm’s law can really help, use it !