Why is it that a small amount of corrosion on an auto battery terminal can prevent the engine from starting?

Question

Explain

Answer 1

Corroded material insulates. With enough of it resisting electric current from the battery, the starter motor will not have the energy to turn over the motor. The car will not start.

Additionally, the resistance of the corroded material can prohibit the ongoing recharging of the battery by the alternator. Over time, the battery will lose charge and will be unable to start the car.

Corroded battery terminals are often a sign of severe battery wear. Even if you clean them off, you may well be looking at a battery that is at or near the end of it's useful life.

Answer 2

Because the starter and other components required to start the engine are electrical devices. When corrosion builds up on a battery terminal then current cannot pass from the battery to the devices because corrosion is a non-conductive build-up. You would get the same effect if the ground wire was not properly secured to a clean metal surface, or if it were loose to allow sparks to jump from the metal frame to the wire. Sparks will cause burning and pitting, which leaves a build-up also over time, and again this build-up will not allow current to pass. Hence, a secure fitting will not allow room for sparks to jump, and current will easily pass.
It is best to clean corrosion with a mix of baking soda and vinegar, pour right onto the terminal and cleaned with a metal brush.
Corrosion can also be caused by loose fitting battery caps, allowing fumes to escape resulting in the build-up of corrosion.

Answer 3

Your two batteries are tired out and not able to hold a charge after coming off of a charger. When you measure the battery voltage in isolation it may read 12volts but as soon as any load is put in it the voltage drops to a much lower level. It only needs to drop to 10 volts before it's effectively useless. The "click" is just the starter solenoid trying to engage, but it cannot work properly because the voltage is too low. The red light indicates that your alternator/charging system has a fault. It may be a loose drive belt, or a fuse blown due to trying to charge a clapped out battery, or it may be more serious. You should get it checked at a garage with proper test equipment, a small domestic volt meter isn't good enough. When you are running the ignition system doesn't take much current and the car will run with no alternator and a crappy battery. But as soon as you switch on anything else the drain on the battery becomes very noticeable. A weak battery will soon fail when under electrical load, which is what you're experiencing.

Answer 4

You are looking at corrosion that is external on the battery connection. Inside the connection, where the clamp is attached to the battery post is likely the location of the real, but invisible problem. Lead salts leach from the lead battery post and sets up a black insulating material known as lead oxide between the battery post and inside of the clamp causing a high resistant electrical connection. The oxide inhibits the flow of battery current required by the engine starter as well as preventing the battery from being recharged by the engine alternator while driving.

Remember, the battery connection is two-way. That is, current flows "FROM" the battery during high current demands when starting the vehicle as well as current required by other electrical components, such as headlights, etc. The engine alternator also recharges the battery by supplying current "TO" the battery to keep it properly charged.

As the lead oxide continues to increasingly prevent the flow of current, it is not unusual for the high current draw FROM the battery TO the starter to penetrate the oxide insulation and allow the vehicle to start. However, the lower current flows TO the battery from the alternator may not penetrate the oxide preventing proper charging of the battery. Over time, the battery becomes in a discharged state and the weakened battery will not supply the current necessary to start the engine.

A classic symptom of a progressing high resistant battery connection, is usually noticeable during night driving when headlights and dashlights intensity may increase with higher speeds (engine rpms) and may dim when the engine idles at lower rpms.

It is advisable to have a professional auto tech make such repairs or cleaning by removing the clamps (Negative (-) first and reinstalled last) from the battery and using a battery cleaning tool (brush) available at Wal-mart or most Auto Stores will easily remove the oxides and allow the required two-way current to flow. The weakened battery will likely have to be properly charged with an external battery charger before you continue to start and drive the vehicle.

Visible external battery terminal corrosion is another subject that has been addressed in this forum in the past.(not always correctly as you DO NOT mix baking soda and vineger- it's highly reactive). If you decide to DIY, read and follow safety labels on all batteries and remove "ALL" jewelry when working near a battery, to reduce chances of becoming 1 of more than 6,000 persons injured annually by vehicle batteries.

Answer 5

It only matters what points the corrosion is covering. There may not be a lot there, but if it is in the "right" spot, it will prevent a connection. It's a good idea to clean those battery terminals from time to time, even if you can't see any corrosion.

Answer 6

Generally the corrosion is a symptom of an earlier problem. The connection is generally loose casuing arcing and that helps to generate an oxide on the interior of the connection. You may only see a small amount of corrosion but the real problem is that the oxide is keeping the keeping the connection from allowing sufficient current to start the car.

Clean and "tighten".

Answer 7

If the small amount of corrosion comes between the battery terminal and the leads, you have a poor conductor of electricity in series in the circuit with your starter.

Much of the voltage is thus dropped across this corroded junction and not applied to the starter.

Answer 8

YES it can prevent the car from starting. Clean the terminals and try restarting.

Answer 9

Corrosion, aka rust, does not conduct electricity.
Tadaa....