By Syed Ahmer Imam
This blog will demonstrate to you how to use a multimeter to test the battery on your car to see if it's bad or not.
Symptoms With A Bad Battery or A Bad Alternator:
Some symptoms that you could have with a bad battery or a bad alternator are that your battery light is ON on the dash, the engine not even cranking at all, or cranking slowly or there's clicking when you start the engine. But the engine doesn't start so just clicking the battery seems weak or is it dead, the interior lights or headlights seem weak? And stuff like that.
These symptoms could be a sign of a bad battery or alternator, this blog right now is going to focus on the good and bad battery aspects.
One of the first ways you could tell if your battery's going bad is you put your key in the ignition and turn it to the run position you will see there is the battery light with an engine check light and that lets you know that the battery light is working most cars test the voltage of the battery through the battery light. So if that blows out you won't be able to tell if your battery's bad or not unless the battery doesn't show you any bad sign itself i.e. starting your car in the morning and it doesn't have enough power to start the engine and a lot of times I could trigger another light like a check engine light, so what should happen is when you will start the car. It'll shut off, if it shuts off then your battery is good.
How to test your Battery?
To test the battery what you want to do first is you want to turn the headlights on for about two to three minutes this will get rid of any surface charge the battery may have as we wait what you want to do is you want to turn on your multimeter and you want to set it to 20 volts DC or something above 15 volts as car batteries voltage range under 15volts DC.
So set your multimeter to 20 volts DC, which is what most multimeter has of their standard range. Now turn on the headlight for about two to three minutes and after two to three minutes you have to shut the lights off and make your way over to the battery.
There are two terminals on the battery negative(Black) and positive(Red), your multimeter has two leads positive lead(Red) and a negative lead(black), the negative terminal is our ground now. You have to connect the positive lead(red) of the multimeter to the positive terminal(red) of the battery and the negative lead(black) of the multimeter to the negative terminal(black) of the battery and you will be able to see the voltage on multimeter display i.e. if it goes to 12.8V DC which is excellent, but you want to have around 12.6V DC which is the standard range for a good battery. So if your battery is showing around 12.6V DC, that means your battery is good.
But just because your battery is showing voltage around 12.6V DC when the engine is turned off even if this is a good voltage doesn't mean your battery is good, the battery could be holding a charge but doesn't have the Cold Cranking Amps (CCA) to start the car's engine. That's what you have to test next.
So you have to start the car engine with a multimeter attached to the battery, now if your battery is good and it is showing voltage around 12.6V DC when the engine is turned off, it shouldn't drop below 10V DC if the voltage drops below 10V when you start the engine then you have a battery problem.
When you are going to start the engine with a multimeter attached to the battery, you will see it drop down and then it popped back up, and then it will show around 14.2V. When you start the engine then the increase in voltage is because the alternator is charging the battery. Now if you see the voltage drop down to about i.e. 10.10V or 10.05V DC and rose right back up to around 14.2V, that means your battery is good. This way you can check your battery that has enough cranking amps and that the cells are good. If Cold Cranking Amp (CCA) drops down below 10V like your battery starts to go below 5V then your battery's garbage. You need a new battery.
Cold Cranking Amps (CCA):
The estimation of the number of amps a battery can convey at zero degrees Fahrenheit for 30 seconds and not drop down beneath 7.2 volts DC is called the measurement of Cold Cranking Amps (CCA).
Problem With an Alternator:
If your multimeter shows more than 14.5V when the engine is in running position then you have an alternator problem because the alternator is overcharging the battery. However, if your multimeter shows the same voltage as it's showing when the engine is turned Off around 12.6V, or with a little bit of increment when the engine is in running position then it could also be pointed towards that you have an alternator problem in most cases because the alternator is bad and it isn't properly charging the battery.
Battery Life:
Batteries are supposed to last about four years and that's what most of them are warrantied to but only 30% of the batteries that are manufactured and sold today reach that four-year mark.
Corroded And Lose Connections With Safety And Precaution:
Now if you are having problems with your battery and this doesn't solve it unless you also want to see to make sure your terminal connections aren't corroded or lose. If there's a little bit of corrosion on the terminals of the battery then what you might want to do is get some sandpaper and some WD-40 or silicon grease and just need to sand the terminals, if there's corrosion on the battery's terminals like blue-green crystal and corroded then you should need to use safety goggles and gloves as if your terminals are corrosive it could hurt your hands and it could hurt your eyes.
Let's see a battery with bad terminals that are dirty so here's a good example of what I was talking about if that happens then you want to clean off your battery's terminals. So take a piece of sandpaper and that'll do the trick. You need to just lose and pull up the terminals from the post and sand up the corroded terminals.
Once you get all that dirt and everything out of the terminals and also sand the post terminals down of battery. So you will see the clean post come off pretty well. Clean the inside of the terminal's wires with sandpaper, so they attach and slide back on the battery post easily. Then lastly, tighten the terminals back completely with a ratchet then retake the readings through a multimeter same as explained above.
One more thing after you are done cleaning off the posts hit them with some WD-40 or apply dielectric or silicon grease on the terminals to prevent them from rusting and getting corroded again.
Types of Batteries:
There are basically three types of batteries are there in the market;
1. Maintenance-Free Battery.
2. Maintenance Battery or Water Lead Acid Battery.
3. Dry Cell Battery.
Maintenance-Free Batteries:
They don't need any water to fill them up periodically that's why it is called a maintenance-free battery.
Maintenance Battery or Water Lead Acid Battery:
If you have a battery that needs water then they'll have caps up at the top of the battery in between terminals. It requires periodic maintenance to be filled up with water.
You want to make sure that they're not filled to the top of the cap, but there is a quarter of an inch over the Electro the metal piece that's inside the battery, most battery has an indication mark on them which tells you that till where you have to fill the water.
Remember don't fill your battery with minerals or tap water because it has minerals that will damage the battery. You need to fill it up with distilled water as it doesn't have any extra minerals or anything that's in your water getting into the lead-acid battery or it is better to fill your battery with pure tonic deionized distilled water as it contains acid but it is diluted.
Dry Cell Battery:
Absorbed Glass Mat (AGM) vehicle batteries are alluded to as dry cell batteries since liquid can't get away. Albeit dry cell vehicle batteries are costly, they last more than customary wet cell batteries. They likewise have more ability to wrench the motor in a terrible climate.
If you have multimeters or you are afraid to do it yourself then you could take your car to a major part store and they'll test your battery for free. They have better equipment that will thoroughly test your battery and you will get a good idea that how much life is left in your battery.
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