What is the car's charging system?
An automotive charging system is made up of three major components: the battery, the voltage regulator and an alternator. The alternator works with the battery to generate power for the electrical components of a vehicle, like the interior and exterior lights, and the instrument panel. An alternator gets its name from the term alternating current (AC).
On to the battery:
As you know already, without a battery, your car is going to have one heck of a time running. But the battery is only one component of the main electrical system of your vehicle. The other side of the electrical system that powers your car is the alternator. Lets start by talking about the battery.
A battery, in concept, can be any device that stores energy for later use. A rock, pushed to the top of a hill, can be considered a kind of battery, since the energy used to push it up the hill (chemical energy, from muscles or combustion engines) is converted and stored as potential kinetic energy at the top of the hill. Later, that energy is released as kinetic and thermal energy when the rock rolls down the hill. Not real practical for everyday use though.
Common use of the word, "battery" in electrical terms, is limited to an electrochemical device that converts chemical energy into electricity, by a galvanic cell. A galvanic cell is a fairly simple device consisting of two electrodes of different metals or metal compounds (an anode and a cathode) and an electrolyte (usually acid, but some are alkaline) solution. A "Battery" is two or more of those cells in series, although many types of single cells are usually referred to as batteries - such as flashlight batteries.
As noted above, a battery is an electrical storage device. Batteries do not make electricity, they store it, just as a water tank stores water for future use. As chemicals in the battery change, electrical energy is stored or released. In rechargeable batteries this process can be repeated many times. Batteries are not 100% efficient - some energy is lost as heat and chemical reactions when charging and discharging. If you use 1000 watts from a battery, it might take 1050 or 1250 watts or more to fully recharge it.
Part - or most - of the loss in charging and discharging batteries is due to internal resistance. This is converted to heat, which is why batteries get warm when being charged up. The lower the internal resistance, the better.
Slower charging and discharging rates are more efficient. A battery rated at 180 amp-hours over 6 hours might be rated at 220 AH at the 20-hour rate, and 260 AH at the 48-hour rate. Much of this loss of efficiency is due to higher internal resistance at higher amperage rates - internal resistance is not a constant - kind of like "the more you push, the more it pushes back".
Typical efficiency in a lead-acid battery is 85-95%, in alkaline and NiCad battery it is about 65%. True deep cycle AGM's (such as Concorde and Deka) can approach 98%.
Batteries are divided in two ways, by application (what they are used for) and construction (how they are built). The major applications are automotive, marine, and deep-cycle. Deep-cycle includes solar electric (PV), backup power, and RV and boat "house" batteries. The major construction types are flooded (wet), gelled, and AGM (Absorbed Glass Mat). AGM batteries are also sometimes called "starved electrolyte" or "dry", because the fiberglass mat is only 95% saturated with Sulfuric acid and there is no excess liquid.
Flooded may be standard, with removable caps, or the so-called "maintenance free" (these are sealed batteries that you cannot re-add acid or water to). All gelled are sealed and are "valve regulated", which means that a tiny valve keeps a slight positive pressure. Nearly all AGM batteries are sealed valve regulated (commonly referred to as "VRLA" - Valve Regulated Lead-Acid). Most valve regulated are under some pressure - 1 to 4 psi at sea level.
You put the key in the ignition, and the car starts, but what happens under the hood?
Turning the key over sends a signal to the solenoid on the starter to move to the "On" position, when it does this, a flow of electricity goes from the battery to the solenoid that engages the starter and moves the flywheel allowing the pistons to compress air and gas in the cylinders, at the same time the distributor is also moved to the on position and gets intial current from the battery to send to the corresponding spark plug to create a spark allowing combustion to happen inside the cylinder.
What is an alternator?
Alternator (n.) - An electric generator that produces alternating current.
That definition tells you as much as getting a file from the CIA. The alternator has two jobs, carry the electrical load of the vehicle while the motor is running and recharge the battery.
Alternators are typically found near the front of the engine and are driven by the crankshaft, which converts the pistons' up-and-down movement into circular movement. Some early model vehicles used a separate drive belt from the crankshaft pulley to the alternator pulley, but most cars today have a serpentine belt, or one belt that drives all components that rely on crankshaft power. Most alternators are mounted using brackets that bolt to a specific point on the engine. One of the brackets is usually a fixed point, while the other is adjustable to tighten the drive belt.
What is a voltage regulator?
The voltage regulator of a car could be one of two types. The grounded voltage regulator regulates the amount of negative ground that goes into the rotor, while the grounded field voltage regulator controls the amount of positive ground that goes into the rotor. Both actions change the amount of direct current created by the alternator, which increases or decreases the amount of current provided to the battery as necessary to keep the amount of current within safe levels.
Okay now I know what the parts are and how long winded you can get explaining batteries. So how can I tell if I have a problem with one thing or another?
Voltage regulators will be a pretty fast diagnosis because if you are blowing out fuses or your radio or other electronics experience damage or get way too hot, that will tell you they are getting too much power.
However, that is fairly unlikely. Most issues with the charging system will revolve around the battery and alternator. Normally this will be due to the fact that you are not able to start the vehicle, or it will shut off at a very inoppurtune moment. Most shops and parts stores will be able to test your alternator to see if it has failed.
If you know the alternator is good then the battery needs to be worked on or replaced. If your battery is a maintenance free battery, you'll need to replace the battery. However if it is not, you may be able to recondition the battery by having acid and distilled water added to bring the specific gravity of the battery back to a point where it can continue to be used. If you are going to have this done, have it done by a mechanic or battery specialist. The reason is that these people will have the proper safety and testing equipment to recondition the battery.
If the alternator needs to be replaced, you can do this job yourself, because with most alternators you have 2 wiring clips and 2 bolts to remove, but you will be doing a lot of swearing in the process of trying to get the serpentine belt back on correctly and the tension roller back into the right position.
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