Is Your Battery Bad? A Simple Guide to Load Testing Batteries
If your battery is struggling to produce electricity, it might be facing a chemical issue. To get the most out of your battery, regular maintenance is key. Early detection of problems can save you from sudden breakdowns and costly repairs. That's why load testing batteries is so important. This process measures the amperes generated by a battery, ensuring it can produce enough power to start your vehicle's motor.
How to Load Test Batteries
Your vehicle's battery often goes unnoticed until it fails. However, a little maintenance can prevent unexpected issues. The most accurate test involves checking the battery voltage and fluid condition using a DC voltage meter and hydrometer, both of which are available at local stores. If problems persist, there are additional troubleshooting steps you can take. Wondering if your marine battery is on its last legs? Here are some tell-tale signs and a guide to help you through load testing batteries.
Tools You Need
For non-sealed batteries, use a good temperature-compensating hydrometer. For sealed batteries, a digital voltmeter is essential. It’s also useful for troubleshooting electrical or charging systems. Ensure your voltmeter has 0.5 percent accuracy or better, as analog voltmeters are not precise enough for millivolt variations.
Inspect the Battery
Look for common issues like a broken or loose alternator belt, a wet or dirty battery top, low electrolyte levels, and swollen or corroded cables. Also, check for corroded battery posts, loose cable terminals, loose hold-down clamps, or a damaged or leaking battery case. Replace or repair these items as needed and top up the battery fluid with distilled water.
Recharge the Battery
Recharge the battery to 100 percent state-of-charge. For non-sealed batteries with a significant difference in gravity readings between cells, equalize the battery using the manufacturer’s procedures.
Remove the Surface Charge
Surface charge can make a weak battery appear good and vice versa. Remove it by letting the battery sit for 4 to 12 hours in a warm room.
Measure the State-of-Charge
Use the recommended table to gauge the battery’s state-of-charge with the electrolyte temperature at 26.7°C (80°F). If the temperature isn’t 80°F, use the Temperature Compensation table to adjust specific gravity readings or open circuit voltage. Confirm the manufacturer’s specifications for a fully charged battery. For non-sealed batteries, test the specific gravity in each cell using a hydrometer. For sealed batteries, use a digital voltmeter to measure the open circuit voltage between the terminals.
Some batteries have a built-in “Magic Eye” hydrometer that tests the state-of-charge in one of the six cells. If the indicator is red, light yellow, or clear, it indicates a low electrolyte level. Recharge and refill non-sealed batteries before proceeding. If it’s a sealed battery, replace it. If the state-of-charge is below 75%, recharge the battery before proceeding. Replace your battery if:
There is a significant gravity difference between cells.
The battery doesn’t recharge to at least 75% state-of-charge.
The built-in hydrometer doesn’t indicate a good state-of-charge.
A digital voltmeter shows 0 volts, indicating an open cell.
A digital voltmeter shows 10.45 to 10.65 volts, indicating a shortened cell.
Load Test the Battery
You can load test your car’s battery if it has a good built-in hydrometer indication or 75% state-of-charge. Use a battery load tester and apply a load equal to half the CCA battery rating for 15 seconds. Alternatively, use the starter motor to switch on the engine for 15 seconds. For deep cycle batteries, apply a known load and measure the discharge time until the battery reaches 10.5 volts. Completely charged batteries are considered bad if they have 80% or less of their initial rated capacity.
Bounce Back Test the Battery
Remove the load, wait for ten minutes, and measure the state-of-charge. If it bounces back to less than 75% state-of-charge, recharge and re-load test the battery. Replace the battery if it fails the load test again.
Recharge the Battery
If the battery passes the load test, recharge it to prevent lead sulfation and restore maximum performance.
Upshot
Don’t let small battery problems go unnoticed, as they can lead to bigger issues and damage beyond repair. Load testing batteries helps you identify and resolve issues early. During the test, ensure the battery is fully charged for an accurate reading. Contact us for reliable power and batteries.