12 Volt – Where to start?
Setting up a 12 volt electrical system can be very daunting to begin with. But if you break it down into steps, it is understandable and a very rewarding task. Not much beats making your own power!
In a very simplistic view, when finished, your 12V system will look something like this:
- Solar panels generate power
- Feeds into a MPPT controller (to regulate current)
- Then runs into battery bank
- From your batteries to a circuit breaker
- Finally, circuit breaker into your power outlets and accessories (EG: Lights, water pump, cigarette lighters, etc…)
But before we get ahead of ourselves, we need to work out how much power we think we’re gonna use. We’ll work in Watts then convert this to Amps (Current).
Here’s a simple spreadsheet you can download to help you out.
Make a list of all your 12V appliances (including lights)
For each appliance list how many Amp hours (Ah) it takes to run (have a look on the appliance or it’s manual)
Estimate how many hours each appliance will be used per 24 hours
Multiply the Amp Hours (Ah) by the hours used per day for each appliance. This gives you the total estimated amps used per day for each appliance.
Sum all of the daily amps used by each appliance to give you a total for all appliances.
NB: For appliances other than 12V, a conversion from Watts to Amps will need to be made (the downloadable worksheet takes this into consideration), using this formula:
Current (Amps) = Power (Watts) / Volts (12 in this case)
Here’s an example:
Say we have a Macbook Pro that charges at 65 Watts using 240V. The current used under different voltages will roughly be:
At 240V => 65 / 240 = 0.27 Amps
At 24V => 65 / 24 = 2.70 Amps
At 12V => 65 / 12 = 5.40 Amps
So for our needs of calculating usage for a 12V system, charging or powering our Macbook Pro will draw 5.40 Amps per hour (please note that an inverter will be needed to do this, but we’ll talk more about this in the future).
Sweet, now we have an idea of the overall amps we might need in a typical day!
The next step is to work out how many batteries and solar panels we’ll need.