Knowing when your battery is dead is pretty easy to understand usually you get in and try the ignition and if you are lucky you might hear some grinding of your starter or just a few clicks of the solenoid but how can you predict or stop this from happening?
In this HowTo we will look at some of the maintenance and preventative measures you can take to make sure your battery won’t let you down.
How long will my battery last?
The first thing you should understand is that all batteries will die over time. It does not matter if you are putting them to daily use or not every car battery that is based on a Lead Acid design will eventually fail due to the sulfuric acids eating the zinc plates.
There is one cure for this that some antique and collector car owners may take. It is to purchase a battery that has service caps and drain the battery before you place your car in extended long term storage.
But for the rest of us the indicator punch-out tab on the top of the battery that either shows its replacement date or date manufactured is the key to how long we can depend on our battery lasting.
Most batteries will last anywhere from 3 to 5 years and this is part of your warranty when you make your purchase. When you get close to 9 months before your batteries end of life you should start looking for good values for a replacement.
Safety First
Before working on your battery you should disconnect it from your car by removing the negative terminal. Some tests will require your battery to be connected but if you are using external equipment to load test or chemically test your battery or if you will be servicing the battery then you should remove both terminals of your battery and if needed remove the battery from the car for servicing. Removing your battery is a relatively simple process and will safeguard your cars electronics from harm.
Testing the voltage in your battery with a volt meter is not invasive and should not cause harm to your battery or your computer.
Always follow your manufacturers recommendation as to how you should work on your battery or any supporting device.
If your battery is leaking always wear gloves. If you will be opening your battery to add water then always wear safety glasses. This is not optional.
How can you test your Battery?
Chemical Tests
Batteries that are sealed can not be tested chemically but if your battery has access caps then a Battery Hydrometer can test the approximate health of your battery by taking a sample of the electrolytes.
Read the directions that come with your tester and fill the tester to the appropriate level with battery fluid.
Read the number of balls that are floating above the measurement mark or look at the indicator for results.
If your battery has depleted electrolytes then it is probably towards the end of its life.
It is possible to replace the battery acid in a serviceable battery but once the acid has eaten enough of the zinc to become weak then the plates in the battery that hold the charge are also in poor condition. Your battery needs to be replaced.
Load Testing
Load testing is the most accurate way to test a battery. It will require that you remove your battery and take it to a service center that will charge the battery to full charge and then place the battery under electric load while testing its output.
The results that the technician is looking for is a reasonable discharge rate at the Amperage rating of the battery.
Every car battery has an amperage rating along with its voltage rating. Most car batteries are 12 volt however the Amperage that a small battery can output is much less then say a large truck battery.
Something like … If voltage was Horse Power then Amperage would be Torque. Torque of the engine is necessary to move the car and in the same way you need enough Amps to turn your starter motor.
Volt Meter Testing
If you have a hand held volt meter that can test the 12volt range you can test your battery and charging system. Connect the volt meter across the terminals of your battery to measure the voltage.
First test the battery with the engine and all accessories like the radio and headlights off.
The correct voltage should be between 11.5 volts and 12.5 volts.
If the battery is undercharged below aproximately 9 volts then you will need to charge your battery before continuing.
If your battery can not hold a 12 volt charge after a few hours of charging you will need to replace your battery.
If you can get your battery to hold 12 volts then attach the volt meter and try to start your car. The volt meter should drop for a few seconds while cranking and then bounce back. If the battery goes dead immediately then you need to replace your battery.
Testing Your Charging System
If you can get your car started with your volt meter attached allow the car to run until it warms up. Within that time your alternator should start charging your battery.
Your volt meter should show a reading above 12 volts but less then 15 volts. Check your manual or manufacture for the exact voltage that your Alternator outputs.
If your alternator is not charging your battery above 12 volts while your engine is running then you may need to service or replace your Alternator. You could also simply have a problem with your battery.
To test if the alternator is charging you will need to connect your volt meter properly between your battery and the charging + Positive wire that is coming from your alternator to read its output. You must consult your test equipment manual and your cars repair manual for exact details on how to take this measurement correctly.
Inspecting your Battery Terminals and Wires
Often corrosion of your battery wires can cause intermittent loss of battery power. If you find that your car will start when it is cold but not after heating up you should check the connections on your battery terminals and the opposite side of the connection on your Alternator and your Starter.
If the connections are all tight then you can check the wires by conducting a voltage drop test from one terminal to the next or you can check the wire for a break by setting your tester to ohms. A good wire should show infinity when tested.
Final Note
As we first said batteries have a limited life. If your battery is defective your warranty should allow for a prorated or full replacement depending on how long after you made your purchase that it fails.
Like changing your cars tires you should read your service manual and learn how to change out your battery. Although most stores will provide free installs if you purchase the battery from them .. knowing how to do it takes very little time and can save you a headache and a tow job.
For the most part a single sized wrench will be needed to remove the terminals and then a second wrench to remove the battery tie-down.