How To Charge Car Battery With DC Power Supply?

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Using the appropriate car battery charger,  along with a suitable step-down transformer, you can very easily charge your car battery to such a voltage that it will conveniently start your car without stress. The step-down transformer is used to prevent damage to your charger due to exposure to excessive current from the supply grid.

The transformer reduces the current that is supplied to the charger such that only suitable current will get to it without the risk of any damage. (Read Also: Can You Charge A Marine Battery With Your Car? Find Out Now)

How To Charge Car Battery With DC Power Supply? Electricity is either supplied as DC or AC. Direct current(DC) does not alternate or in other words, it flows in only one direction, whereas AC or alternating current constantly keeps alternating at about 50 to 60 times per second. Most electrical gadgets or electronics come with voltage requirements that are far less than what is provided by the supply grid to our homes.

For this reason, a step-down transformer is necessary in order to regulate this power supply such that our equipment will not come to any harm. Similarly, where any gadget requires a power supply that is above what is supplied to our homes from the supply grid, a step-up transformer can boost this power supply voltage to meet that which is required.


The electricity that is provided by the national grid which supplies our homes and places of work or industries is in the form of AC. This alternating current is then fed into a transformer which will convert it from AC to DC which is suitable for our uses. This transformer changes the current from AC to DC and also reduces the voltage to that which is suitable for use.

Direct Current can be used to charge our batteries, but in order to do that perfectly, we need some specific tools for the execution of the process. These are a voltage regulator or stabilizer, a car battery charger, and jump cables or wires, to make the necessary connections. The process of car battery charging with Direct Current is done according to the steps below

Table Of Contents

How to charge a car battery with DC Power supply with steps

Step 1

After assembling all those tools that are required to charge your car battery from a DC supply, connect the terminals of the charger to those of the car battery meticulously. Ensure that you connect the negative or black terminals of the charger to the negative or black terminals of the battery, which may both have a (-) sign or NEG  symbol printed on them. (Read Also:How Many Watts Does A Car Battery Charger Use?)

Next, connect the positive or red terminal of the charger to the positive or red terminal of the battery. Both of these terminals may have a (+) sign or POS embossed on them. The general rule is that during connection, join the negative terminals first before the positive.

While during disconnections, remove the positive terminals first before the negative ones. After this connection, carefully inspect it to make absolutely certain that there are no mistakes, otherwise, you stand the risk of damaging the battery, car charger, the voltage regulator or even causing a fire. So, be very careful, please.

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Step 2

Thereafter, proceed to connect the voltage regulator to the wall socket and ensure that it is working very well. It is, it will show you the input voltage as well as the voltage output it is giving out.

Step 3

From this stage, you should then go ahead to connect your battery charger to the voltage regulator. You should be able to see all the necessary readings of the charging battery from the car charger, which will enable you to make all the necessary adjustments to suit your battery. To get the most out of your purchases at all times, we are pleased to recommend a widely accepted Amazon car battery, the Delphi BU909R Max Start AGM Premium Automotive Battery, Group Size 94R( Reverse Terminal)

Step 4

Whenever the charger indicator shows you that charging has been completed, disconnect the charger and battery according to the steps we have outlined previously,  and thereafter remove the charger from the voltage regulator or wall socket, as the case may be.

Depending on whether you charge the battery while it is in the car or it has been removed, proceed to test whether the battery is actually charged,  by either touching the terminals with one another or by trying to start the car. Chargers determine not only the speed at which you get your batteries resuscitated, but also how long the voltage lasts in the batteries.

Can A Car Battery Be Charged With AC?

No, you cannot charge a car battery with AC because, car batteries have a single polarity and as such, charging them with AC will either not work at all, or worse, the batteries may eventually get damaged completely. (Read Also: How To Charge Multiple Batteries With One Charger)

The only way you can use AC in charging a car battery is by using a rectifier that can convert the AC to DC. A rectifier has four diodes that prevent current from flowing in different directions and when used along with a capacitor, it will conveniently smoothen the power output, and the battery can then be charged, but otherwise, AC cannot be used in battery charging.

Additionally, there should be a separate circuit to regulate the charging and make it safe. You may also use a Zener diode or a DC  voltage regulator in order to obtain pure DC output that can be used to charge a car battery.

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Are There Risks Or Advantages In Charging With DC?

Yes, there are risks, if adequate safety measures are not taken. For instance, a voltage regulator and a step-down transformer must be used to ensure that the voltage supplied to the car charger is not excessive to constitute any threat to it.

Similarly, a rectifier containing several diodes can also help in ensuring that the current does not flow in different directions, which may damage the charger, the battery, or both of them.

There is also the issue of using different circuits that will regulate the charging for safety. However, the obvious advantage of using DC in battery charging is that, when you regulate its supply very well as you ought to, you can get your car battery charged without any complaints and in a short time too.

How Long Does It Take To Fully Charge A Car Battery This Way?

A lot of factors combine to determine how fast or how slow you get your battery charged using DC. Some of these factors are how fast or well your charger operates and also the extent of voltage drain in the battery. However, if all these factors work in your favor, charging your car battery should not take more than a couple of hours between three to four hours.

The specifications of your battery also determine how fast or slow your battery can be charged; good and highly rated batteries charge much faster than counterfeit, copied, or fabricated ones.

Batteries that have stayed dead for prolonged periods also take longer to charge when compared to those that have just run down recently or not too long ago,  due to mistakenly leaving the car’s lights on or even faulty car alternators.

Does This Method Of Charging Effect The Battery?

Though it depends on the point from which you are looking at it, charging with a DC supply may not really have any negative effect on your battery. However, to make certain of this, you must make sure that only the correct voltage gets to the battery and where necessary, only DC power gets to the battery.

Once these modalities are all put in place, this method of charging your car battery is simply just great and not in any way injurious to either the battery or even the charger itself. You must equally make sure that whatever the case may be, the battery does not get overcharged either by using manual means to prevent that from happening or through the use of charger automation.

How Can You Make This Method Of Charging Better?

To make it better, you need the help of all the indispensable accessories like the voltage regulator, which will ensure that only the right voltage eventually gets to the battery charger and also that only DC is used in the charging with the aid of a rectifier,  which can readily convert AC to DC.

It may be necessary to use a step-down transformer too, in order to ascertain that excess voltage does not get to the batteries to protect them from both overcharging and damage. All these measures will both improve the process of battery charging and also safeguard your battery by allowing it to last longer.

Compare Charging  Car Battery By Both AC and DC

AC cannot be used in charging a battery for the myriads of reasons we have explained previously. However, where you must use it, make sure that it is converted into DC first with the help of a rectifier. This is because since AC changes direction constantly, it means that it may end up not charging the battery, constituting a threat to the battery, or even the charger itself.

However, in charging with DC, all you may be required to do will not be more than making sure that only the right quantity of voltage is put to work in charging. Conclusively, therefore, AC should not be used in charging a car battery but DC, which is great for that purpose.

What Tools Do You Require To Charge A Car Battery With DC?

The basic tools required to charge a battery with DC are not more than a voltage regulator, a car battery charger, jump cables (or any other good conducting wires), a rectifier, a car battery itself, and a step-down transformer. You also need hand gloves and protective eyeglasses as well, to protect you from harm in case you touch any corrosive item or electrolyte.

How To Charge Car Battery With DC Power Supply – Conclusion

It should have become pretty clear by now that practically everything depends first, on the quality of items you buy and secondly, on how well you use and maintain this equipment. To ensure that you get as few complaints as possible about what you buy, we have seen to it that globally accepted products are brought to your notice.

Maintenance is of paramount significance when it comes to how well this equipment serves you and also how long it last. This is much the reason why we have not left anything to chance in this regard. It is our sincere belief that should you hearken to what you have learned here, most problems associated with car batteries and their accessories will be a thing of the past.

When you are in the dark about something, you are always advised to get in touch with your suppliers either through the links we have provided or their customer care services. The user manual that comes with this equipment bears information you are likely going to find useful with these issues. Feel free to reach out to them, since your satisfaction is what they will not treat with levity; that’s their watchword and also their motto.

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