You don’t need a lot of mechanical aptitude to realise that the battery is fairly central to your car’s operation. When it goes bad, everything shuts down.
Modern batteries are more or less maintenance free, and once installed, are usually left alone until they go flat and need replacing. That said, here are a couple of small tech tips to help you monitor and promote your battery’s life.
First, you can check on your battery’s health very simply, with a multimeter. A 12V battery, when fully charged, will read 12.6V or above. Set your multimeter to read DC voltage, touch the positive and negative probes to the appropriate terminals, and you will get an instant reading. If it reads below 12.6, your battery is beginning to discharge. 12.4V indicates about 75% charge, and anything below 12V suggests the battery is nearly discharged. If the voltage is too low, you may find that it begins to affect the drivability of the car. You can see below that my battery is reading 12.59V.
You can use the same test to help determine if the charging system is working as it should. With the engine running, the voltage at the terminals should read between 13.7-14.7V. If the reading is below that, your alternator is not providing enough charge; above that, and your system is overcharging, which could have some very dangerous results.
The second thing you can do for your battery is to keep the terminals clean. Sometimes you will find that corrosion has bulit up on the terminals, and this should be removed, as it will hinder the battery working as it should. A bit of corrosion is not unusual, but if you find a lot of it building up, there is a problem with your charging system. In general, it is a good idea to inspect the terminals and keep them clean, because a proper connection is key to promoting the flow of current.
Cleaning them is simple. Disconnect the battery terminals (always remove the negative terminal first). Mix a bit of bicarbonate of soda (baking soda) with water, and grab a wire brush. Dip the brush in the mix, and start scrubbing both the posts and terminals until they are nice and shiny. A good, clean, metal-to-metal contact is what you want to achieve.
You can see below that a previous owner thought it would be a good idea to coat the terminals on my Subaru’s battery in a thick layer of grease. People sometimes do this to prevent corrosion, but that was more necessary back in the day than it is with modern batteries. Now, it usually has the effect of just attracting dirt and making a mess. It is better to simply give them a clean every now and then, ensuring they are fully seated on the post, and tight.
These few small things will help promote your battery’s health. Keeping the terminals clean will ensure your battery operates as efficiently as possible, while keeping an eye on the voltage will prevent you from finding yourself stranded unexpectedly.