What keeps a car battery from overcharging?

Actually, the batteries function is to start the engine supplying 12 volts of power to your starter. Once running the alternator takes over and recharges the battery while supplying current to operate all electrical components of the vehicle. there is what is called a voltage regulator built inside of the alternator that controls the output of the alternator. The readings of the alternator output should be 14 volts plus or minus a 1/2 volt. This extra 2 volts recharges the battery and keeps the volts from dropping below 12 volts which is required for the ecm (computer) to operate. So after this long explanation. The part name you are looking for is called the Voltage regulator...........gl

K; Even a new battery desires the charge to be topped up as you pressure (The extra you pressure the easier the charge) too many brief journeys and many starts will drain even a brand new battery, in the wintertime the temperature is a element which being lessen makes the engine oil stiffer and far less fluid; this means the battery has to work extra hard to begin the engine, it's constantly a good idea to have the auto in impartial and in addition press down on the grasp while you attempt to , this may dispose of the introduced burden of an oil stiff equipment box.( the gearbox is connected to the engine even when the engine is in neutral, so dipping the snatch takes away relatively a load from the battery). The Alternator is a devise that generates a cost as soon as the car engine is working, this fees up the battery. In winter; the rear window heater, the display wipers, headlights, fog lights, heater fan,(Diesil starter heater) all draw current from the battery as good as turning over the bloodless engine, correctly it's getting battered from all quarters so be specified before opening your engine to have all these little extras turned OFF when you consider that the battery is BEING murdered: an extended force would support in keeping a batteries charge or buy a trickle charger from a Motor explanations shop, use this to charge the battery at weekends or whenever you suppose it is in need. If all of this fails then it might be the Alternator at fault, however it's iciness once more motor factors can obtain a alternative however a mechanic would be needed to suit it.

In all actuality, it is the physical properties of the battery itself. It is virtually impossible to over charge batteries. A 12 volt car battery will never put out more than 14.34 volts. Any excess overcharge will be dissipated as hydrogen gas which is vented out of the battery. Sever overcharge will cause the battery to burst or catch fire. Read the Wikipedia article on batteries.

Car battery does not supply current to spark plugs. There is an internal current generating machenism composed of solenoid, coils and magnets that generates current for spark plugs. But that machenism rotates when engine rotates. Both are inter dependent. In such scenario there is a need of some external force that initiate the rotation of entire system. That part a battery plays. In absence of a battery there is a need of push start. Like you might have seen in WWII documentaries there is a man who, with hands, make an aircrafts propeller rotate to start the aircraft.

The regulator, part of the electrics.

where the regulator is placed

THE REGULATOR ??