How to Test Your Car Battery
Does your car battery contain enough power to start your engine during cold weather. The only way to know if your battery is fully charged or not is to measure the battery’s state of charge with a voltmeter. You can use an analog or digital voltmeter, but a digital meter is easier to read and will give you a more accurate reading.
First, make sure the ignition key is OFF, and all the vehicle’s lights are OFF.
To check your battery’s state of charge, connect the RED or POSITIVE voltmeter test lead to your battery POSITIVE terminal. The positive terminal will be marked with a PLUS symbol. and the battery cable that is connected to the positive terminal is often color coded RED.
Connect the BLACK or NEGATIVE voltmeter test lead to your battery NEGATIVE terminal. The negative terminal will be marked with a minus symbol (-), and the battery cable that is connected to the negative terminal is often color coded BLACK.
Note the reading on your voltmeter and refer to the chart below:
Battery Voltage and State of Charge (at 80 degrees F): (NOTE: Subtract 0.024 volts for every 10 degree F drop in temperature)
The photo at the top of this page shows a battery voltage reading of 12.29 volts, which means the battery being tested is low with only about half a charge. The battery needs to be recharged.
Is Your Battery Low?
If your battery voltage is less than 12.45 volts (75 percent charged), it is low and should be recharged. This can be done by connecting a portable battery charger to your battery, or by driving your car for 15 to 20 minutes at 40 mph or faster.
Automotive lead-acid batteries should be maintained at a 75 percent charge level or higher for best performance and life. If the battery is allowed to run down and is not brought back up to 75 percent or higher charge within a few days, the battery may be permanently damaged. Sulfation can prevent the cell plates inside the battery from accepting a full charge. Over time, this will lead to diminished battery performance and life.
Why You Need a Good Battery for Reliable Cold Weather Starting
A good battery is essential for reliable starting, especially during cold weather because cold weather increases the cranking load on the battery. Oil gets thicker at low temperatures so it takes more amps to crank a cold engine when you try to start it. At 0 degrees F, the number of cranking amps it takes to start a cold engine may increase as much as 2X. At minus 15 degrees below zero F it can take 3X or more amps to crank the engine depending on the viscosity of the oil in the crankcase. The thicker the oil, the harder is it to crank the engine.
At the same time, cold temperatures also sap the battery’s ability to supply amps. At 0 degrees F, most batteries can only deliver about 65% of their normal cranking amps. At.20 degrees, battery power is cut in half!
How To Tell If Your Battery Is Good or Bad?
A GOOD battery is one that will accept and hold a charge, and is capable of producing close to its rated amperage output. A BAD battery is one that will NOT accept or hold a charge, or cannot produce adequate cranking amps. A GOOD battery can be recharged and returned to service but a BAD battery needs to be replaced.
Most car batteries only last about 4 to 5 years, and may only last 2 or 3 years in a late model car that is not driven frequently enough or far enough to keep the battery fully charged. Hot climates can also shorten battery life to 2 to 3 years.
If your battery is 4 or more years older and is not holding a charge (keeps running down), or it does not seem to crank your engine a normal speed, you probably need a new battery.
Chronic undercharging can cause premature battery failure regardless of the age of the battery. Car batteries are not designed for deep discharge (running all the way down), unlike a marine and RV battery which can handle being fully discharged. If a car battery is run down and left in a discharged state for very long (say a week or more), the plates may become sulfated and not accept a full charge when the battery is recharged. Over time, this will diminish battery capacity and cause it to eventually fail.
Undercharging can be the result of a faulty charging system (low charging voltage), or driving short distances during cold weather with lights, heater, heated seats, defrosters and radio all on. If the charging system can’t replace the amps that your electrical system is using, your battery will gradually run down until eventually it won’t start your car.
How to Test Your Car Battery
Does your car battery contain enough power to start your engine during cold weather. The only way to know if your battery is fully charged or not is to measure the battery’s state of charge with a voltmeter. You can use an analog or digital voltmeter, but a digital meter is easier to read and will give you a more accurate reading.
First, make sure the ignition key is OFF, and all the vehicle’s lights are OFF.
To check your battery’s state of charge, connect the RED or POSITIVE voltmeter test lead to your battery POSITIVE terminal. The positive terminal will be marked with a PLUS symbol. and the battery cable that is connected to the positive terminal is often color coded RED.
Connect the BLACK or NEGATIVE voltmeter test lead to your battery NEGATIVE terminal. The negative terminal will be marked with a minus symbol (-), and the battery cable that is connected to the negative terminal is often color coded BLACK.
Note the reading on your voltmeter and refer to the chart below:
Battery Voltage and State of Charge (at 80 degrees F): (NOTE: Subtract 0.024 volts for every 10 degree F drop in temperature)
The photo at the top of this page shows a battery voltage reading of 12.29 volts, which means the battery being tested is low with only about half a charge. The battery needs to be recharged.
Is Your Battery Low?
If your battery voltage is less than 12.45 volts (75 percent charged), it is low and should be recharged. This can be done by connecting a portable battery charger to your battery, or by driving your car for 15 to 20 minutes at 40 mph or faster.
Automotive lead-acid batteries should be maintained at a 75 percent charge level or higher for best performance and life. If the battery is allowed to run down and is not brought back up to 75 percent or higher charge within a few days, the battery may be permanently damaged. Sulfation can prevent the cell plates inside the battery from accepting a full charge. Over time, this will lead to diminished battery performance and life.
Why You Need a Good Battery for Reliable Cold Weather Starting
A good battery is essential for reliable starting, especially during cold weather because cold weather increases the cranking load on the battery. Oil gets thicker at low temperatures so it takes more amps to crank a cold engine when you try to start it. At 0 degrees F, the number of cranking amps it takes to start a cold engine may increase as much as 2X. At minus 15 degrees below zero F it can take 3X or more amps to crank the engine depending on the viscosity of the oil in the crankcase. The thicker the oil, the harder is it to crank the engine.
At the same time, cold temperatures also sap the battery’s ability to supply amps. At 0 degrees F, most batteries can only deliver about 65% of their normal cranking amps. At.20 degrees, battery power is cut in half!
How To Tell If Your Battery Is Good or Bad?
A GOOD battery is one that will accept and hold a charge, and is capable of producing close to its rated amperage output. A BAD battery is one that will NOT accept or hold a charge, or cannot produce adequate cranking amps. A GOOD battery can be recharged and returned to service but a BAD battery needs to be replaced.
Most car batteries only last about 4 to 5 years, and may only last 2 or 3 years in a late model car that is not driven frequently enough or far enough to keep the battery fully charged. Hot climates can also shorten battery life to 2 to 3 years.
If your battery is 4 or more years older and is not holding a charge (keeps running down), or it does not seem to crank your engine a normal speed, you probably need a new battery.
Chronic undercharging can cause premature battery failure regardless of the age of the battery. Car batteries are not designed for deep discharge (running all the way down), unlike a marine and RV battery which can handle being fully discharged. If a car battery is run down and left in a discharged state for very long (say a week or more), the plates may become sulfated and not accept a full charge when the battery is recharged. Over time, this will diminish battery capacity and cause it to eventually fail.
Undercharging can be the result of a faulty charging system (low charging voltage), or driving short distances during cold weather with lights, heater, heated seats, defrosters and radio all on. If the charging system can’t replace the amps that your electrical system is using, your battery will gradually run down until eventually it won’t start your car.
Limit Short Rides
Quick car rides prevent your car’s battery from fully charging. Maintain your car’s battery power by driving it frequently and for extended periods.[2] If you don’t use your car often, consider investing in a portable car battery charger. These portable chargers can jump start your battery without another vehicle in case you’re ever stranded.
A battery that’s not securely fastened could vibrate, potentially resulting in internal damage and short circuits.[2] Have your battery terminal checked regularly – especially if you frequently drive on bumpy roads – to ensure it is tightly and properly positioned in the mounting bracket.
Turn Off All the Lights When You Exit
Accidentally keeping your headlights and car door lights on can put a heavy toll on your vehicle’s battery.[2] To keep yourself from forgetting, post a note on your dashboard, attach a sticker reminder on your car remote or park in a direction where you must walk past your headlights to get to your destination.
Battery terminals corrode over time but keeping them clean from buildup is a great way to extend the life of your car battery. Scrub the terminals with a toothbrush dipped in a baking soda and water mixture. Then, using a spray bottle with cold water, rinse the mixture off and follow up with a thorough drying with a clean cloth.[2]
Test Your Battery Often
Knowing the condition of your car battery matters when you want to maximize its life. Test your battery’s output voltage level with a car battery tester to keep track of how well you’re maintaining it and if you’re due for a new one.[3]
Turn off functions like the radio or air conditioner when your engine isn’t running to put less wear and tear on your battery power. Extended periods of idling also can wear a battery down.
Care for Your Whole Car
Your car is comprised of many parts working together. Making sure you are taking your car in for routine tune ups, as well as properly storing your vehicle are also simple ways to ensure your battery’s lifespan can reach its full capacity. The battery is just one component of a well-running car, so make sure to properly maintain all parts of your car to extend its life and the life of your battery.
No matter how well you maintain your car battery, you can’t always foresee when it may die. Learn more about roadside assistance and how it can help you in the event of an emergency.
Check out these tips to help extend the lifespan of your car battery.
- Limit short rides Quick car rides prevent your car’s battery from fully charging. Maintain your car’s battery power by driving it frequently and for extended periods.
- Keep your battery tightly fastened A battery that’s not securely fastened could vibrate, potentially resulting in internal damage and short circuits. Have your battery terminal checked regularly.
- Turn off all the lights when you exit Accidentally keeping your headlights and car door lights on can put a heavy toll on your vehicle’s battery.
- Control the corrosion Battery terminals corrode over time but keeping them clean from buildup is a great way to extend the life of your car battery.
- Test your battery often Test your battery’s output voltage level with a car battery tester to keep track of how well you’re maintaining it and if you’re due for a new one.
- Don’t use electronics while idling Turn off functions like the radio or air conditioner when your engine isn’t running to put less wear and tear on your battery power. Extended periods of idling also can wear a battery down.
- Care for your whole car Making sure you are taking your car in for routine tune ups, as well as properly storing your vehicle are also simple ways to ensure your battery’s lifespan can reach its full capacity.
Best Wireless: TOPDON BT Mobile Lite Car Battery Tester 12V
Clamp the TOPDON BT Mobile Lite 12-volt battery tester in place, open the app on your phone, and follow the prompts. That’s all it takes to run a cranking, charging, and battery test. The tester is compatible with iOS 8.0 or later, Android 4.3 or later, and Bluetooth.
Battery Monitor TOPDON Car Battery Tester 12V, Bluetooth Voltmeter Wireless Automotive Alternator Load Tester, Battery Analyzer Charging Cranking Tester for Car Truck Motorcycle ATV
Test your car battery with the ease of wireless technology.
49.99
Best Premium: FOXWELL BT705 Car Battery Tester
This is one heavy-duty battery tester. The FOXWELL BT705 works for 12V regular flooded, AGM flat plate and spiral, as well as gel batteries. It reads battery health, car cranking voltage and time, and charging status. FOXWELL designed the easy-to-read tester to report passenger cars and heavy-duty truck battery health in only three seconds.
FOXWELL BT705 Car Battery Tester 12V 24V,100-2000CCA Automotive Battery Load Tester Battery Analyzer Digital Charging System Alternator Tester Cold Cranking for Heavy Duty Truck Boat Marine SUV ATV
A high-quality tool for car mechanics and car owners.
129.99 155.99 Save 17%
Battery Indicator: DROK Battery Tester
DROK made battery capacity testing easy breezy. The tester is applicable for lithium, lead-acid, and iron phosphate batteries. It features a large and simple-to-read LCD display. It’s great for small vehicles, golf carts, medical devices, and more.
DROK 12V Battery Capacity Indicator, DC 5V- 66V Lead Acid Battery Percentage Voltage Tester 12V 24V 36V Electric Quantity Volt Detector Meter Panel Gauge Lithium Battery Status Monitor for Car Vehicle
This device is simple to use and applicable to a wide range of batteries for small vehicles.
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Britta Kallevang Britta is a professional writing tutor and freelance writer that is trained in journalistic, technical, and creative copywriting. At LifeSavvy, she researches products, writes about the items, and shares what she’s uncovered with readers. Her writing is comprehensive and sometimes a bit silly. Read Full Bio »