Voltage (Volt) and Current (Ampere)
What is a volt (V): The volt is the unit of measurement for voltage, which is the "pressure" that pushes the electrical current through a circuit. Think of it like water pressure in a pipe: the higher the voltage, the harder the current is pushed.
What is an ampere (A): The ampere is the unit of measurement for current, which is the amount of electrical current that passes through a point in the circuit in one second. In the water example, it is the amount of water flowing through the pipe.
Their relationship: Voltage (V) × Current (A) = Power (Watt). This means that to get high wattage (power), you can have either high voltage with low current, or low voltage with high current.
How we use Watt, Volt, and Ampere in a van:
- Step 1: Look at the Watts (What you consume). Every appliance you buy for the van states how many Watts it is. For example, a refrigerator might be 60W and an induction cooktop 1500W. This shows you how much energy the appliance "sucks."
- Step 2: Choose the Volts (Your battery system). When setting up the van, you decide whether your main battery will be 12V (the most common for small vans) or 24V (for large vans with many appliances).
- Step 3: Calculate the Amperes (Cable thickness and fuses). Divide the Watts of the appliance by the Volts of your battery. The result shows you how many Amperes of current will pass through the cable. Based on these Amperes, you buy the correct cable thickness and the appropriate fuse to prevent the van from catching fire.
A simple practical example:
If you have a 45 Watt appliance, see how the current (Ampere) changes depending on the Volts it operates at:
- At 12V (like the van battery): The appliance draws 3.75 Amperes (45 / 12 = 3.75) when operating.
- At 24V (like a larger battery): It draws half as much, just 1.87 Amperes (45 / 24 = 1.87).
- At 220V (like home wall outlets): The "pressure" is so high that the appliance draws minimal current, just 0.2 Amperes (45 / 220 = 0.20).
So as we increase the Volts, the Amperes decrease. The fewer Amperes we have, the smaller cable cross-sections we need. Therefore, we choose the system that is most advantageous for us depending on the appliances we have.
In most vans, 12 volts is more than enough with an inverter option for 220v, but when we want to run heavy appliances like air conditioning, then it might be better to go for 24v or even 48v.