Signs that a Car Battery may be Shorting (+ How to confirm?)

A car whose crank is slower and takes longer to turn over, or one that does not have enough power to start the car could be a case of battery drain by accessories switched ON, weak connections, or even an internal battery fault.

But how can you tell if your battery has an internal short? How does it even affect the performance of your car?

In this post, I’ll share some common signs that can point to an internal battery short, common causes of internal shorts in the battery, and whether you should fix it.

Quick answer: A car battery can develop an internal short circuit that affects the battery’s ability to hold and supply the electrical power to the car’s systems. Depending on the nature of the internal short, the battery may have varying abilities to supply the necessary electrical power to start the car.

A battery with an internal short such as a dead cell usually measures sub 12 V, about 10.4 -10.7 V from 5 cells if one is shorted. Voltages will be lower if the 2 or more cells have short-circuited.

Unfortunately, these signs are common to a number of faults in the car and are not confirmation of an internal short-circuit.

Read on for how you may be able to confirm that the car has an internal short.

Signs of a Car Battery with an Internal Short-Circuit

If the car battery has an internal short-circuit then it may demonstrate any of these symptoms:

#1. Slow crank or car engine fails to turn over (Note: This is not confirmatory)

The car battery may crank the car slowly or fail to crank at all.

#2. Low battery voltage (Note: This is not confirmatory)

Measuring the battery voltage can also point to a shorting battery too.

Its battery voltage will be usually low typically in the range of 10.4- 10.7V DC for one shorting cell. A voltage of 8.42V DC can point to 2 shorting cells for example.

#3. High battery temperature

The car battery temperature increases significantly as it is being charged.

It will feel extremely warm or hot during charging and vent off if the battery has an electrolyte.

Unfortunately, either of these signs is not a confirmation of a short.

To confirm a battery short, use a professional grade battery analyzer or tester to check the battery status to confirm if the battery has suffered any internal damage such as a short circuit and should be replaced.

These testers usually feature a display that can indicate a bad cell(s).

Alternatively, you can have your car battery tested at an auto repair shop.

What Happens in a Car Battery in case of an Internal Short?

An internal short may develop in the battery as it ages, if its build quality is not good or if it’s when it is exposed to severe vibration.

Over time, the separators for the positive and negative plates can fail leading to the positive and negative plates touching hence the short circuit.

Also, particles of the plates can disintegrate over time, pile up and short out the plates from the bottom or the sides of the plate.

Can You Fix an Internal Short?

In my opinion, if your car battery is confirmed as having an internal short, replace it with a new one instead for reliable operation of the car and peace of mind.

Tips to Prevent Premature failure of Car Battery

For the maximum lifespan of your car’s battery, always charge it to recommended voltages. If using an external charger, make sure it is set to the correct battery type to automatically select the appropriate maximum voltage.

Secondly, use a charger with a current rate (amps) as recommended by the battery manufacturer to avoid overheating of batteries.

Also, always maintain batteries above 12. 4V when storing them and regularly top them up should the battery voltage drop.

Final Word

If your car battery is shorting, the voltage will drop considerably below the 12V range, about 10.4 – 10.7V if one cell is shorting, and higher in case of more cells are short-circuiting

While this can point to a shorting battery, it is not necessarily confirmation and the surest way is to have it tested using a professional battery analyzer or at an auto car repair facility.

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