How Long Does A Trickle Charger Take To Charge A 12V Car Battery?

Every car owner has, at some point in their vehicle ownership journey, dealt with a drained battery. If you haven't, consider yourself lucky. You might have left your car at a shop, gone on vacation, or only use it occasionally as a secondary car. The truth is, most vehicles aren't designed to sit unused for extended periods, and depending on how long it's been sitting, it can lead to battery drain. Fortunately, this common problem has a simple solution. A trickle charger.

A trickle charger is a type of car battery charger that delivers a low electrical current to a battery (usually 1-3 amps) over an extended period in small increments. This is very low amperage, hence its name "trickle" charger. This gadget is designed to maintain the charge rather than rapidly get it to full capacity. As a result, trickle chargers may take between 24 and 48 hours to fully charge a dead 12V car battery (set to 2 amps).

Still, the time it takes to charge a 12V car battery will depend on three variables: the battery capacity, charger output, and the state of discharge. As a rule of thumb, opt for a smart trickle charger (with a microprocessor). Unlike older models that continuously feed power and need supervision, smart chargers automatically adjust the charge and shut off when the battery is fully charged. Reducing the risk of overcharging and damage. 

The time it takes for a trickle charger to fully charge your battery depends on several factors, including the charger's amperage, the battery's size, its current state of charge, overall condition, age, and even the surrounding temperature. If you only occasionally drive your car, using a trickle charger can help maintain your 12V battery at optimal levels and prevent common battery drain issues.

Trickle chargers work differently from jump starters or manual and automatic chargers in that they deliver a slow, low amperage charge. Fortunately, there's a simple formula to help you calculate how long it'll take to charge a battery with a trickle charger: Time (hours) = Battery Capacity (Ah) / Charger Current (A). Therefore, a 1-amp battery charger will typically take 48 hours to fully charge a 48Ah battery (48Ah ÷ 1A), while a 2-amp battery charger will take 24 hours (48Ah ÷ 2A). 

Actual charging times can vary slightly in real-world settings. Larger batteries generally take longer to charge (have greater capacity to store energy), so a small ATV battery will recharge faster than a truck's larger battery. If your vehicle has been sitting for several months and the battery is discharged, it will take significantly longer to charge than one that's only been unused for a few weeks. Older or sulfated batteries may also take longer to charge, or may not charge fully at all. Additionally, if you live in a colder part of the world, the low temperatures will slow down your charging process compared to warmer climates.

 While a 12V battery may not shock you, anything related to electric current is dangerous and considered a fire hazard. Therefore, you must be extremely careful when using trickle chargers on your 12V car battery. For starters, don't pick the first charger you find on the shelf and use it on your car. Ensure it is compatible with your vehicle's 12V battery. For extra precaution, check that it has an automatic shut-off or float mode to prevent overcharging.

It's also important to know how much your 12V battery is drained before charging. Invest in a multimeter to monitor your battery voltage. A fully charged battery should read around 12.6-12.8 volts. Depending on the trickle charger you purchase, it might feature an in-built multimeter.

Trickle chargers are ideal for vehicles that are used occasionally, such as classic and luxury cars, bikes, and ATVs. These chargers should only be used when leaving a vehicle unused for weeks or months. If you can afford it, consider getting smart chargers. They are designed to adjust amperage automatically and will switch to maintenance mode when fully charged. If you just purchased a trickle charger and are unsure how to use it, start by reviewing the charger's handbook and your vehicle's owner's manual for instructions and safety guidelines.