Why Car Battery Terminals Might Get Hot? (For Beginners)

I saw all kinds of problems people had with car batteries. One of the main questions is related to why terminals are hot to the touch or even why they are melted.

This is my definite answer for everyone who wonders.

Do car battery terminals get hot?

Car battery terminals do get hot in abnormal situations where loose connection, corrosion buildup, and incorrect cable size create resistance. Bad starter and alternator overcharging will put unnecessary stress on the battery, causing terminals to get hot.

Are battery terminals supposed to get hot?

Not paying attention to the battery terminal connections could cost you lots of trouble. That’s why it is very important to check your terminals from time to time and make sure that everything is tight and clean.

In normal circumstances battery terminals are not supposed to get hot. If every connection is tight and clean out of the corrosion heat shouldn’t be present.

In case you touched your terminals right after you cranked up the engine and it takes longer than usual, you can expect terminals to be slightly warm to the touch.

This happens because the starter draws lots of power, so the battery warms up because of the instant burst of high energy delivered to the starter.

One of the main problems terminals getting hot is resistance. If energy flowing throughout an electrical system is restricted with corrosion buildup or loose connections, this alone could create an enormous amount of heat to the point that it can catch fire or melt plastics or even lead.

Will loose car battery clamps cause terminals to get hot?

Loose battery terminal clamps will cause terminals to get hot because the gap between terminal and clamp will restrict the flow of electricity, making sparks jump between them. This gap creates resistance and sparks will generate heat, making terminals to get hot or even melt.

Bolts that are not tight enough will over-time undo by themselves and create loose connections. Or even if you repeatedly clamping and un-clamping, it will surely make terminals polished too small.

Clamps will not be able to grab on terminals, even if you tighten the bolts all the way.

When putting back clamps on battery posts, always make sure to tighten bolts making clams not fall of terminals.

It’s recommended before installing the clamps to put grease on terminals, this will ensure there are no micro gaps between them, and also it will make an air-tight seal making an even stronger connection.

Check this articles where I talked more about car battery terminal grease.

How can corrosion buildup cause car battery terminals to get hot?

Corrosion buildup over the terminals creates resistance, making electricity to slow down and making terminals hot.

Over time corrosion will eat the lead terminals making them weak, including clamps.

That’s why it’s very important from time to time to check on terminals and make sure if you see corrosion formation to act right away and clean it.

Terminals will not only get hot, but car performance will suffer too. For example, It can take longer to start an engine. And cranking it longer will heat up the entire battery, including terminals.

By the color of the corroded terminals you can distinguish between materials clamps are made of.

Do broken copper wires inside car battery cables warm-up terminals?

Broken wires inside cables cause resistance too. Because some of the wires are broken inside, the entire cable will have less available copper mass to put the same amount of electricity through the cable. Thus, heat is created.

No matter where inside the cable wires are broken, the entire cable will overheat. And because copper is metal, heat will travel all the way to the battery making terminals hot.

It’s best to check cables every once in a while to make sure that everything works as it should. Cables shouldn’t be hot to the touch.

If they are, one of the causes might be that wires are broken. In this case you should visit your mechanic to diagnose the issue and replace the cable if it’s needed.

Will corroded copper wires inside car battery cables produce heat on the battery terminals?

Corroded copper wires inside the cable create resistance making the cable to overheat. Heat is transferred through the cable to the battery causing hot terminals.

Cables are made from copper and rubber for insulation. Over time, rubber will degrade and that will cause cracks. Water will go inside making copper wires to oxidize.

Water in combination with copper will create corrosion inside the cable. This corrosion buildup will restrict electrons from flowing freely. Where is the resistance, there’s the heat.

What are car battery terminals made of?

They are made out of the lead. It is very logical because anode and cathode plates inside car batteries are also made out of the same metal. So, it’s convenient to weld cells and terminals together accordingly.

This material is used in such applications because it’s very powerful. It can deliver high Cold Cranking Amps that a starter is required in order to start an engine.

Since the beginning of the modern automotive industry, battery internals are made out of the lead, including terminals. Plates are submerged into sulfuric acid in concentrations anywhere from 15% to 35%. The remaining is distilled water.

Terminals are then connected to the positive and negative sides sticking out from battery internals.

What would cause battery terminals to melt?

High resistance and high current flow will cause battery terminals to melt. When electrons are restricted to pass through, it will create heat.

Depending on the amount of resistance buildup near battery, that much heat will be generated. Resistance can be too high to the point that terminals can melt.

The melting point of lead is 621.5 °F (327.5 °C). So you can imagine what kind of resistance must be created to be able to produce such heat or higher.

High resistance can be created by corrosion buildup, loose connections between clamps and terminals, cracks on clamps that will cause gaps between.

Sometimes it can be caused by a bad starter or a bad alternator.

A starter can draw too much power and as a negative effect, it will create very high heat.

On the other hand, an alternator can have a bad diode. This can cause the battery to overcharge, and as a side effect high heat can melt the terminals.

The danger of aftermarket car battery cables.

Should you replace car battery cables with aftermarket ones? This is a very tricky question.

You should always consult with your mechanic before purchase a new set of cables.

The main concern with the aftermarket cables is the build quality. Can they withstand the current needed for your vehicle?

Always check gauge wire thickness to the specs of your vehicle required. Check the crimping work too.

The cable insulation is one more thing that you should check. Consider materials and also wall thickness.

Alternator can overcharge battery making terminals hot

If your terminals are hot to the touch you should consider checking the alternator. It may be overcharging your battery which is not good news.

Hot terminals are not the only thing that a bad alternator can do. Overcharging will make battery electrolytes inside to boil out, releasing gases making the battery to swell up.

This will not melt terminals but it can kill the battery if not addressed immediately.

Losing acid out of the car battery will expose lead plates to the air making them to oxidize. This oxidation can never be reversed. So, the battery will die.

Bad alternator work in such a way that it pumps more Voltage than is really needed leading to overcharging.

One more thing, before replacing a battery, always consult the owner’s manual or ask your mechanic what kind of battery type to buy for a replacement. Not all batteries are the same. But most of the car batteries are heavy for sure, this should not confuse you.

If you choose a battery brand that does not meet car manufacturing specs, it can lead to overcharging, although an alternator is good. So, does a car battery brand matters, for real?

Do not use any electronics inside your car when starting the engine, here’s why

When starting an engine, one thing to consider is to turn off all of the electronics inside your car.

If you choose not to do so, it will put higher stress on the car’s battery making it hotter than it should be.

Terminals will most likely get hot too, because all the electronics will suck power from a battery before you even start the engine.

Yes, it’s just a short period of time. It will only happen in a second or two. But, when the starter pulls power to start an engine, it’s a very high burst of electrons, and it will warm up the battery more, which is really unnecessary making terminals to be hot too.

It’s best to make a routine before you shut the engine off to turn off all of the electronics. This way, you will ensure an easy start of an engine making as little stress on your battery and electrical system of a car.

Sources

https://no.co/blog/ultimate-guide-to-clean-and-remove-car-battery-corrosion#:~:text=Anhydrous%20copper%20sulfate%20changes%20to,increases%20resistance%20within%20the%20circuit.

https://www.concordia.ca/content/dam/concordia/services/safety/docs/EHS-DOC-146_LeadAcidBatteries.pdf