Your car contains a closed circuit that powers every electrical component in the vehicle. This circuit draws its power from a battery, and is responsible for starting the car, and allowing all of the gauges, lights and various instruments to function. Each individual component is wired up to the battery on the positive terminal, and via a system of switches and relays will earth through the chassis of the car and the current will then flow back to the battery via the negative terminal. This will complete the closed circuit, and allow the component to function. It is important to have a basic understanding of the various bits that make up your electrical system, and a general idea of what to be on the lookout for, in case anything goes wrong. In this article we will give you a brief look at a few of the basic elements of the electrical system in your car, and how to maintain them, as well as a bit of an overview of the types of tools that you might expect to need if you decide to carry out some basic work on the electrical system.

How does a battery work?

The first part we will look at is the heart of the whole operation and the source of the power that your car uses to start, as well as run all of the sensors, lights, gauges, heating elements, stereo components and so forth before the alternator takes over the job - this is of course, the battery. Car batteries come in a variety of shapes and sizes, and each offers specific levels of power, durability and compactness, depending on its intended use.

Almost all cars run on a six-cell, 12 volt system (though of course, there are exceptions) which actually means that when fully charged, a battery will measure 12.6 volts - since each of the cells that make it up generate 2.1 volts. Voltage is a measure of essentially the pressure with which your battery can push its power through the wiring and operate the various equipment in your car. The actual amount of energy that is pushed by the voltage is measured in amperes. (Amps)

A car battery will have a rating on it, written as “CCA” which stands for “Cold-Cranking Amps.” This is a measure of the number of amps a battery delivers at -18 degrees C for 30 seconds without dropping below 1.2 volts per cell. The higher the CCA rating, the greater the starting power of the battery in cold climates. Many batteries will also display their “CA” or “Cranking Amps” Which is the same as the above, but measured at 0 degrees C. Either of the two measurements above are important for when you are selecting a battery - the general rule is that the more amperage the battery has, the easier time it will have starting your car. For cars with bigger motors, or that run on diesel, it is important to get a battery with sufficient CCA or CA since the starter motor on these cars needs to output a lot more torque in order to crank the car over.

The other specifications often found on batteries are RC and AH, which means “Reserve capacity” and “Amp Hours” respectively. Reserve Capacity refers to the time in minutes that a new, and fully charged battery will supply a constant load of 25 amps, without the battery falling below 10.5 volts. The higher the RC is, the longer your vehicle can operate if the alternator fails and therefore means that your car is running on battery power only. Amp hours is a rating that is usually found on deep cycle batteries, and is a measure of the amperage that is delivered over a specific number of hours - eg. If a battery is rated at 100 amp hours it should deliver 5 amps of power for 20 hours or 20 amps of power for 5 hours. Different types of battery. There are a few different options to consider when choosing the right battery for your requirements.

The first two broad categories that we can divide automotive batteries into are:

• Starting batteries - These are your everyday batteries used to start your car. They are designed to deliver a short but powerful burst of energy, sufficient to crank over the engine. They will generally remain charged through regular use, since they recoup their expended energy once the alternator starts providing charge to the electrical system.
• Deep-cycle batteries - These batteries are designed to provide a smaller amount of energy over a longer period of time. Whilst they can indeed be used to start a car, they are primarily designed to run accessories such as fridges, winches and other electrical components that draw a smaller but regular current. Within the above categories there are a few further differences between lead-acid batteries, concerned with the materials that they are made from.
• Wet Cell - This is the most common type of car battery, and will either come as a maintenance-free unit, or a maintained unit, that will periodically require that its cells be topped up with water.
• Absorbed Glass Mat - These are very much the same as wet cell batteries, however (as the name suggests) they have a specially designed mat of glass between each lead plate. This matting is soaked with electrolyte and means that there is less of the stuff sloshing around in the battery. It has the added bonus of generally lasting a bit longer than the standard wet cell battery.
• Gel Cell - Yet again, as the name suggests, this battery uses a special gel in place of the standard fluid electrolyte. They are designed to usually be a bit smaller than the equivalent wet cell battery.

What is a fuse?

Between the battery and each component in your electrical system is a fuse. These devices are designed to fail in the event that the system is overloaded to prevent electrical fires and damage to the components themselves. Fuses come in a variety of shapes and sizes, and are rated by the amperage that they can withstand before they fail or “blow.”

The most common type of fuse, which is held in the aptly named fusebox is the spade fuse. These are little horseshoe shaped devices that have a length of very thin wire inside a plastic housing, and come in a few different sizes. The internal wire provides a certain amount of resistance, and will heat up and then burn out if overloaded, breaking the electrical circuit, and so protecting the rest of the system from damage. Fuses of this type are generally colour-coded, but it is always better to check the amp-rating of an individual fuse than relying on the colour of the original and its replacement being the same. Your fuse-box will usually have the circuit that each fuse protects indicated on it, so replacing a blown fuse is as simple as locating which fuse needs to be replaced, and replacing it with the appropriate size and type. Other commonly encountered fuses are the cylindrical glass-tube type. These are often found in-line with stereo components, and will usually sit inside a housing that can be unscrewed to provide easy access to a blown fuse. Some older vehicles will have different types of fuses, but these too can be purchased relatively cheaply, and replaced with general ease. It is important to ensure that any issue that may have caused a fuse to blow is addressed, as simply replacing the fuse may result in the same thing repeating itself.

Working on your electrical system

There are a few simple tasks that can be carried out by the layman with relative ease, that will ensure that your car starts, and your gauges, lights, stereo etc all work correctly.

NOTE: Always be sure to disconnect the battery when carrying out work on the car’s electrical system.

Below are a few of the tools commonly required when working on your electrical system:

• Multi meter - This tool is an invaluable addition to any would-be home mechanic’s arsenal. A multi meter is a device that can be used to measure voltage, amperage, resistance and continuity in your electrical system. There are a variety of different types of multi meter available, from simple analogue offerings, to complex digital varieties, so be sure to check as to which you might require.
• Gloves - When carrying out work on your electrical system, it is a good idea to wear gloves. Rubber or nitrile gloves can protect against small shocks, but wearing thicker work gloves is a good idea if you are carrying out any soldering work, to prevent burns as well as being pricked by wires, when working with them.
• Electrical tape - Taping stuff up with insulating electrical tape can be a good short-term fix in the case of electrical shorts etc. It isn’t recommended that you use electrical tape as a substitute for proper soldering and heat-shrinking.
• Wire Strippers - An incredibly useful tool to own is a set of wire-strippers. You can use pliers to strip wires, but it is awkward and potentially damaging, so instead it’s recommended that you use specially designed wire-strippers. Most types of stripper will have different cutting and stripping notches, that are designed for specific wire gauges. Many of the higher-end options will have crimping features built in, which makes affixing connectors to your wiring an absolute breeze.
• Connectors - Speaking of connectors, there is a wide range of types that can be used - from bullet connectors, to loops, spades and even plugs. Each has its own benefits, but as a rule of thumb, try to replace any damaged or old connectors with the same type.
• Heat shrinks - Heat shrinks are a much better choice than electrical tape when insulating wiring. These little tubes of plastic can be slipped over the ends of wires, before you solder them, then slid up over the join and heated up so that they shrink down and seal the connection. When heating them up, it is best to use a heat-gun (or even a hair-dryer) than the heat from your soldering iron, as this will prevent accidental burn-through or excessive melting and will result in a join that is properly insulated and sealed from moisture.
• Soldering Iron - What budding automotive-electrician’s toolbox would be complete without a decent soldering iron? It is a good idea to watch a few online tutorials on how to use one of these tools, as connecting wires in your car is always done more safely and more permanently by soldering them together as opposed to simply twisting and taping them. Be sure to wear gloves when soldering, as the iron is designed to get pretty hot!
• Bulbs and fuses - It’s always a good idea to carry a selection of spare bulbs and fuses in your glove-box. Be sure to check what type of bulb and fuse your headlights, taillights and indicators use, as replacing these if they fail when out on the road ensures the safety of you and other people!