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How to Charge a Car Battery – What to use, How to hook up a car battery charger

Blog_How to Charge a Car Battery - What to use, How to hook up a car battery charger

Whether you are parking your car for the winter or are just not driving it on a daily basis you always want to make sure that when you go to start it, your car will start reliably whenever you need it.  Having a battery maintainer or charger is an essential tool to have that can save you some grief by either preventing a dead battery or helping to bring one back to life, while in other cases help you jump start your car.

In this post, find out the 3 types of battery chargers you can use, how to maintain or charge your battery and why you don’t want to overcharge them.

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A car battery will normally self-discharge slowly over time, but nowadays, cars have many more computers onboard and some are always on.  From alarm systems, remote starter systems to keyless entry and dashcam systems with park mode, these all slowly drain the battery when the car is off.

If you don’t drive your car much regularly and only take short trips, you might be caught off-guard one day when your car won’t start because of a dead battery.  A perfect example of this is when COVID-19 happened.  A lot of people started working from home and not driving their vehicles on a daily basis.  Many were caught off guard with vehicles that won’t start because the batteries lost too much charge.

To prevent this, you want to have and use a battery maintainer or battery charger.  Preferably, you want one that won’t overcharge your battery.  Overcharging these types of batteries can lead to irreparable damage.  Damage that could cause the battery to have lower capacity, lower lifespan or even lower power output for the rest of it’s useable life.  Continually charging a battery that is full can also result in a damaged/dead battery that you will need to replace.

Because of this, you want a charger that will monitor and stop the charging when the battery is full.  Here are 3 types to consider.

NOTE: Always read the manual of the charger to understand the dangers and precautions you need to take.

Battery Float charger / Maintainer

The first type is the most basic… a Float charger.  No fancy computers inside or any smart algorithms.  Just a charger that charges and stops charging when the battery is charged.  These are typically slow chargers meant for maintaining the charge on your battery.

Great for portability, for maintaining the charge of a good battery and available at a good price point.  Read to the end to find out why this one is good to have around even if you have one of the next two types of chargers.

Battery Float charger / battery maintainer to charge a car battery
Battery Float charger / battery maintainer to charge a car battery

Smart battery charger / Maintainer

Smart battery charger / smart battery maintainer to charge a car battery
Smart battery charger / smart battery maintainer to charge a car battery

The second one is an automatic charger with a micro-processor that controls the charging and has fancy features to revive and recondition batteries that need it.  The latest ones even have temperature sensors that properly charge batteries in different climates, multi-stage charging to ensure maximum battery life and even support for different types of 12V batteries [Wet, MF, Gel, AGM and Ca, etc…].  These also have safety features that protect you in case you hook up the terminals incorrectly.  Smart chargers come in different varieties with different features and with varying amperages to give you normal to rapid charging.

Again, these ones will stop charging the battery when full and kick into maintenance mode to prevent damage to a full battery.

Battery charger / Maintainer with Engine start

The 3rd type is a charger/maintainer that includes Engine Start or Jump Start mode.  You can use these to boost a car when needed.  Something handy to have around especially if you live in cold regions.  There are old school ones that are not micro-processor controlled and ones that are that have features to revive and recondition batteries too.  In the end, pick one that suits your needs.

If you’re looking for a car battery charger, we’ve provided several links to good chargers further below, so check those out!

Now that you know what to use to charge or maintain your car battery, how do you do it?

First thing is to always practice safety… wear safety glasses and gloves as there are strong acids in car batteries.  Then watch our “how to change a car battery safely” video to find out more about car batteries and how not to cause a short circuit.

Watch how to change a car battery and not get shocked!

Charging is very simple with these chargers.  You attached the Red or positive clamp to the red terminal of the battery.  Then you attach the Black or negative clamp to a solid, unpainted metal part of the car.  Make sure this metal part is away from the battery and the fuel line.

Then plug the charger into the power outlet and that’s it.

For smart chargers, you have additional steps to select the appropriate modes.  Each brand is different so you should make sure to follow the instructions manual.

The reason you connect the negative or black clamp away from the battery is that when the battery is charging it may release hydrogen gas which is explosive at high enough concentrations.  So this is just a safety precaution as charging sometimes produces sparks that could ignite the hydrogen gas.  

This is also why proper ventilation and safety gear like safety glasses and gloves are important.

NOTE:  If you have a Mercedes, BMW or any vehicle that has specialized or dedicated terminals for connecting the positive and negative clamps of the charger to, then use those instead of connecting elsewhere or directly to the battery.  This will look like the terminals used in the video for the Mercedes-Benz SLK350 where I did not connect to the battery directly.  Always check your owner’s manual for more specific information.

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Sometimes smart chargers are too smart for themselves.  The safety features that prevent sparking or provide reverse polarity protection can get in the way.

For example, if a battery is too discharged, the voltage it provides may be too low for the smart charger to properly detect that it is connected to a battery.  Or, it may think that a battery is damaged (when it isn’t) and refuse to charge.  In these cases, it may not start charging at all.  So, having a non-micro-processor controlled charger around can be useful as these don’t care.  So you can use them to charge the battery to a point where the smart chargers will properly detect them and be able to charge.

We hope this post helps you keep your car running when you need it most!  If you enjoyed it, please share on your social media or with one person you think it will help.  We appreciate your support.

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