Testing Automotive Batteries

Early Classic Cars primarily used magnetos to power their engines and the starter was simply a crank inserted in the front of the crankshaft. Their lights were simply kerosine or oil lamps mounted to the front or rear of the car. Cadillac introduced the first electric starter in 1912, and soon after the rest of the auto manufacturers followed suit, with nearly all manufacturers offering electric start by the 1930s, although the crank hole remained for many years after.

The introduction of an electric starter also required an onboard battery to power the starter. These lead-acid batteries became the standard for automotive use due to their reliability and relatively low cost. These batteries consisted of lead plates submerged in sulfuric acid electrolyte, although more than a century old this technology is still used on lower cost batteries today.

Throughout the 20th century, advancements in battery technology led to improvements in performance, durability, and reliability. These advancements included sealed maintenance-free batteries, calcium-calcium grids for reduced water loss, and improved construction techniques. Absorbed Glass Mat (AGM) Batteries have become the battery of choice for many enthusiasts. In these batteries the battery acid is absorbed in glass mats rather than being free flowing. Their design allows them to deliver more power and be more resistant to damage from vibration in a totally maintenance free construction.

The battery in your Classic Car represents a significant investment and properly maintaining it can yield years of trouble free performance. However, over time any battery will eventually fail but before heading out to purchase a new battery there are a few tests you should perform first on your battery to ensure the problem isn’t somewhere else. We join Mark Simpson in the shop to demonstrate some common battery tests.

Visual Inspection: This involves checking the battery for signs of physical damage, corrosion, or leaks. Any abnormalities may indicate a problem with the battery.

Voltage Testing: Voltage testing involves using a multimeter to measure the voltage across the battery terminals. A fully charged battery should typically measure around 12.6 volts or higher. If the voltage is significantly lower, it may indicate a discharged or faulty battery.

Load Testing: Load testing involves applying a simulated load to the battery while monitoring its voltage and/or current output. This test helps determine the battery’s ability to deliver power under load and can identify weak or failing batteries.

Hydrometer Testing: For traditional flooded lead-acid batteries, a hydrometer can be used to measure the specific gravity of the electrolyte. Variations in specific gravity can indicate the state of charge and overall health of the battery.

Electronic Battery Testers: Specialized electronic testers are available that can perform comprehensive diagnostic tests on car batteries. These testers typically measure parameters such as voltage, internal resistance, and conductance to assess the battery’s condition accurately.

Overall, a combination of these testing methods is often used to evaluate the health and performance of car batteries accurately. Regular testing and maintenance are essential for ensuring reliable starting and electrical system operation in your classic car.