If you come out in the morning and discover your car battery is dead, it could be a one-time mistake of leaving the interior or the headlights on overnight, but this may also be pointing to something more serious. It’s easy to jump-start your car, but leaving this problem unresolved can leave you stranded on the side of the road. Here are the most common reasons why a battery will keep losing its power.

Please note safety is paramount, car batteries contain sulphuric acid that can cause serious burns. Always protect your hands and eyes when working around a battery. If you come into direct contact with battery acid, flush with plenty of water and seek immediate medical attention in a severe case.

Faulty Charging System

Faulty Alternator

A faulty charging system will drain the battery if you’re using the radio, lights, and other high-current-draw accessories while driving. Although the charging system consists of many parts, the alternator is the heart of the system. It recharges the battery when the engine is running. A faulty alternator can kill a battery if bad diodes or an internal voltage regulator prevents it from charging the battery. Or a diode can leak, allowing current to flow after the vehicle engine is shut off. A worn or loose drive belt, or a weak belt tensioner, will also interfere with the charging.

Parasite Drain

Parasite Drain

Parasitic drain is caused by a short circuit or an electrical device that remains “on” when it should be off. A common parasitic drains include bad light switches in the glove box, under the hood or in the trunk. The bad switch allows these lights to come on when they shouldn’t. Modern vehicles have clocks, radio presets, security alarms, computer modules, and other sophisticated systems that constantly drain the battery. If your car sits for a few weeks without being started, these may lower the battery voltage enough to keep your engine from starting. Poorly-installed aftermarket accessories like sound system amplifiers, lighting, power inverters can drain the battery and cause problems with sensitive electrical systems and this can be very difficult to pin down.

Short Drives

Starting your car draws the most power from the battery. Not giving the alternator a chance to recharge the battery could explain why the battery continues to die, or doesn’t seem to last long as it should.

Poorly Maintained Battery

A weak or poorly maintained battery is usually the main reason a battery dies. Dirty battery top can “leak voltage” between the terminals draining the battery when not in use. Clean the top of the battery with a brush and a solution of baking soda and clean water to keep dirt and debris from falling into the cells or you can order a battery cleaning solution from the store.

Make sure the battery is securely seated in the battery tray. A loose battery that is bouncing around can short internally, causing it to discharge. Having the positive terminal short to the vehicle body can result in a fire or explosion. And remember, batteries do not last forever. Depending on the climate and driving conditions, expect to replace your battery every three to five years.

Corroded or loose battery terminals can not only keep your car from starting, but prevent the battery from fully recharging as you drive. Clean the terminals with a baking soda solution or order a battery cleaning solution from the store before removing them from the battery (ALWAYS REMOVE THE NEGATIVE CABLE FIRST!). Clean the terminals and battery posts with a wire brush, then securely tighten it.

Extreme Temperatures

Extreme temperatures can wreak havoc with a battery chemistry. Cold slows the chemical reaction, heat speeds it up. Humid temperature keeps a battery from recharging because water evaporates from the battery’s electrolyte, preventing chemical energy from converting back to electrical energy. Adding distilled water to a battery may rejuvenate the electrolyte. If not, you may need to replace the battery.

On the other hand, a battery only has half of its potential power at 0 degrees. At the same time, motor oil thickens, requiring more battery power to start a vehicle. Never attempt to jump-start a frozen battery—it can explode. It also means it’s time for a new battery.

All batteries eventually die of old age. Basic battery maintenance can prolong a battery’s life and help prevent it from discharging. Once per month, check the battery terminals for corrosion and be sure they are clean and tight. Check the electrolyte level in batteries with removable caps and make sure the battery is secured in its tray.