How To Wire New Car Equipment

Before adding any equipment to your car it’s important to know how much extra power or Amperage you will need.

This will help you determine what cable size you need and if you need an extra battery.

 Depending  on what equipment you add on and how often it’s used you need to check your battery capacity to make sure you won’t be running out of power.

Circuit protection

Always add some protection to you Circuit.

Protection devices include fuses, circuit breakers, switches.

The inline fuse, the least expensive means of protection. If connected close to the power source provides protection for both the wiring and the connected device 

Cable Size

It’s essential to use a cable size that will deliver adequate voltage to the equipment installed. You need to calculate voltage drop using the maximum current that the equipment draws - not the average. But if the same cable is used to feed other loads or charge batteries, then you need to add this additional current when calculating the cable size needed.

The best way to know how much Amp you are already using is to your cable with a clampmeter .

In the case the cable feels warm when running at full load, then you are losing significant power due to the cable being too thin.

Common wire gauge conversion

Gauge ref:            Section:

     8B&S                           7.91mm2

     6B&S                          13.56 mm2

     3B&S                          25.72 mm2

     2B&S                          32.15 mm2

     1B&S                          39.55 mm2

To choose a wire gauge the need to know the cable length and the current draw or wattage.

The term wire gauge refers to the thickness of a wire. Wire gauge can be used to determine electrical resistance and the current handling capability of the wire.

B&S is a commonly used measure of wire gauge, B&S means Brown & Sharpe and B&S is equal to AWG American Wire Gauge.

  

Battery size

To calculate how much battery capacity (in Amp hours) you will need, you need to know the current consumption of  equipment (in Amp hours ) under the conditions that you will be using it, plus the time before you can recharge the batteries.

For long battery life, you need to plan to use only 50% of the battery capacity and to recharge them within a few days. You would only use up the full battery capacity if there was no other option available.

Solar Charging

To avoid damage to your batteries you should always plan to recharge batteries fully in one day, although in winter this may mean the equivalent of 2 hours of peak charge current from a panel.

"Amps aren't amp hours"

Amps are used for Instantaneous current flow  for a compressor fridge this could be 6 amps when working hard, reducing to 2 amps when the contents have cooled down, then zero when the thermostat cuts out.

Average current - amps - for a fridge you need to average out over 24 hours, because the instantaneous current consumption varies with operations.

Total Current Consumption - Amp hours – mean you multiply amps by hours, so if your fridge uses 2 amps average, then over 24 hours it will use 48 amp hours.

The daily amp hour usage of a fridge is comparable with battery capacity in amp hours.

Also you can add amp hour usage for different loads - e.g. if your Tent light uses 1 amp and you use it for 4 hours a night i.e. 4 amp hours per day, then your total draw from the battery per day will be 48 + 4 amp hours.

Better Connectors

Make sure all your wire connection are tight and properly secured.

Use appropriate connectors :

- Cigarette Lighter Plug (Cigarette Lighter plugs can be a hazard because they were never designed for drawing power continuously)
Anderson Powerpole 30 - these Red and Black connectors with silver contacts are rated at 30 amps. They can take cable up to 10 Gauge or 5mmsq.
Anderson SB50 - these are the smallest of the grey Anderson connectors, they have silver contacts, rated to 50 amps. They can take cable up to 6 Gauge or 13mmsq.

Wiring:

Make sure you use correct size cable.

Make sure the cable are properly attached and locate in protected area where they won’t physical damage.

Make sure the cables have good insulation.

Wiring are source of shortcut which could lead to fire.

If more power is required for your project you can add either a jumstarter  a deep cycle battery and use a solar panel to keep them charged.