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How to Tell If Car Battery Is Bad

Fernando the electronics guy is an electronics engineer. He earned his Bachelor of Science in Electronics Engineering from UC Riverside.

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Your car battery is acting up. You’re worried. You’re thinking of pulling your whole car apart. But, before doing so — how to know if the car battery is bad?

How to Tell if Car Battery is Bad: Weak Car Battery / Bad Battery Symptoms

If your car battery is in its early stages of failing, you’ll notice dimmer lights

  • Headlights
  • Exterior lights
  • Interior lights

You’ll also notice a weakening operation of other electrical components:

  • Power windows
  • Power steering
  • Windshield wipers
  • Defroster
  • Stereo
  • Display Cluster
  • Etc.

A bad battery may also cause other specific electrical problems:

  • When you turn the key, there is a clicking noise under the hood or the engine cranks slowly.
  • Car starts only when pressing the gas pedal.
  • Engine stalling. Fuel injectors need electricity. Bad battery means a stall.
  • Unresponsive throttle due to electrical actuation.
  • Airbag and engine oil lights turning on due to incorrect voltage.
  • Battery leaking battery acid. You’ll see this commonly at the terminals of the battery. This will usually also lead to the smell of sulfur – rotten eggs, if you will.
  • Etc.

As you can see, a failing battery can cause chaos on a vehicle well equipped with electrical/electronic components.

Bad Battery vs. Bad Alternator

Flat Battery

If your vehicle won’t start, it may be a bad battery (AKA flat battery), a bad alternator, or a bad starter.

Bad Alternator

Since the alternator generates and regulates the electrical current charging your car battery, it is crucial to have a working alternator.

Needless to say, the alternator also has built-in rectifier diode(s) to both convert alternating current (AC) to direct current (DC) and regulate the direction of the generated current to stop discharging while only allowing charging of the battery.

The signs of a bad alternator:

  • You have a bad battery. A bad alternator will either damage or worsen your car battery over time.
  • No-starting or trouble starting
  • Dimming lights with changing brightness
  • Battery not being charged while car is running
  • Battery discharging overnight
  • Squealing sound coming from under the hood (usually the alternator bearing) that may get louder when the heater or sound system is on
  • Hearing whining/fuzzy noise on your AM radio (set to lowest range), caused by a failing alternator’s generated electromagnetic noise.

Bad Starter

The symptoms of a bad starter are common and often times leave consumers confused about what needs to be fixed, leading to expensive repairs elsewhere. The starter, a small motor powered by the battery, is attached to your engine / transmission to get things spinning to allow your engine to turn, thus transmitting power to your transmission.

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Symptoms of a bad starter:

  • No sound, whirring sound, grinding sound, weird sound. Anything out of the usual could mean a bad starter
  • Dashboard lights up but car won’t start. No dimming. Perhaps not electrical.
  • Jumpstarting won’t work. Engine won’t crank. Battery is fully charged (minimum 12 V)
  • Blown starter fuse.
  • Failed starter relay
  • Smoke coming from these areas after turning the key to turn on the car. Perhaps a short.

So – bad battery, bad alternator, or bad starter? It’s easier to check the battery health first. It’s also a lot easier to stop by your local auto retailer for a quick starting system test. They’ll hook up their electronic apparatus to your battery and test the whole system. They’ll let you know what is failing and what isn’t with dead accuracy.

How to Start a Car With a Dead Battery

The most common way to start a car with a dead battery is to jumpstart it:

  1. Find another car to help you jumpstart your bad battery / dead battery. Position both cars close enough to connect batteries via jumper cables. Don’t let the vehicles touch each other.
  2. Turn off both vehicles.
  3. Clamp positive to positive on both batteries.
  4. On the good battery, clamp negative.
  5. On the bad battery’s host car, clamp negative on any ground on the vehicle. Careful not to touch positive and negative clamps together.
  6. Turn on the good car.
  7. Crank the bad car.
  8. If this doesn’t work, wait 15-20 minutes with all cables exactly the way you attached them. This will slowly charge up the bad battery enough to retry again.
  9. Retry again.
  10. If this still doesn’t work, consult a technician.

How to Tell if Car Battery is Bad: How to Start a Car With a Dead Battery Without Another Car

Remove the dead battery and take it to an automotive retailer. They will charge it for you while also allowing their electronic battery charging systems the opportunity to give you feedback on whether or not your car battery is bad.

Option 2: Pop out your powerful portable jump starter with no damage to your battery. Jump your vehicle with it and get going.

If your battery is flat it is highly convenient and recommended to carry a powerful portable jump starter. Electronics guy recommends the NOCO lithium jump starter above.

How to Know if the Car Battery is Bad? No matter what you’re waking up to do in the mornings, it’s no question having a bad battery do bad things such as not be ready with you is out of the question. You’re a busy person with busy things to do. Don’t let a flat battery be your reason for not being out.

These portable battery booster packs hold a charge that can bring your car battery back to life. Their end clips – called terminator clips – are the same ones found on conventional jumper cables.

Old jump packs used to be composed of lead-acid batteries. But the ones above that I recommend are lithium-ion battery powered. More current, better technology, more dependability.

Why choose lithium-ion jump starters:

  • 4X more power per volume
  • 6X more power per weight
  • Slower discharge rate (only 3-5% / month)
  • Long cycle life
  • Low maintenance, lasts longer
  • Power and capacity advantages
  • Cheaper
  • Good against cold weather (CCA, or Cold Cranking Amps, in cars)

This is all about dependability. The jump starter that I recommend above will keep you moving.

Take Care of Your Battery

If you have a bad battery, this won’t damage the alternator or the starter, but it mau cause other problems. If you have a bad alternator, this may damage the battery. If you have a bad starter, the engine won’t crank but the failure won't damage any other components.

It is recommended to change a battery when it is due for it. Failing to change a battery when it is showing symptoms of failing may lead to damage in other areas of the vehicle.

The Only Battery and System Tester I Recommend

FURTHER READINGS

https://www.tiresplus.com/blog/batteries/unmistakable-signs-car-battery-is-failing/

https://www.silvhornautomotive.com/services/electrical-system/
http://automotive.electrofern.com/

https://mechanics.stackexchange.com/questions/23925/non-functional-gas-pedal-engine-stalling-dead-battery-broken-alternator

https://www.lesschwab.com/article/starting-problems-how-to-tell-if-its-the-battery-or-alternator.html

https://electrofern.com/electronics/

https://www.quora.com/What-is-the-relationship-between-a-gearbox-and-a-starter-in-a-manual-and-an-automatic-car

https://www.consumerreports.org/car-battery/jump-start-car-with-dead-battery-a1028630350/

https://www.autozone.com/diy/battery/lead-acid-vs-lithium-ion-jump-starters

Sources

How to charge a system. Basics. electrofern.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2022 electronicsguy

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