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How to Jumpstart a Cordless Drill Battery  

Cordless drills are the most popular and essential power tools adored by professionals and DIY enthusiasts. DIYers rely on the convenience of the drills for home improvement projects as it is faster and requires less energy to operate. Being a game-changer tool that has been heavily relied on, it may, unfortunately, cease to power up when an individual is productive, leaving him stranded. These circumstances can occur due to several issues with different parts of the cordless drill. For instance, when the battery cannot hold a charge, damaged carbon brushes hindering current supply, defective motors, switches, and damaged holders that can compromise the stability of the brushes.

These iconic cordless tools come with batteries that are the leading powerhouse. A cordless drill battery not holding charge does not imply it’s dead and cannot be used again. In some instances, the battery may be partially dead and require jumpstarting to be revived. However, since most individuals may encounter such situations for the first time, they may ponder how to jumpstart a cordless drill battery.

Jumpstarting a cordless drill battery can be done through various methods. The different ways include using a tool battery, the car battery, and the transformer method.

 The tool battery method involves utilizing another fully charged cordless drill battery to jumpstart the dead battery by connecting them in matching polarity for about 5 minutes and charging it to full capacity.

 The car battery method involves setting a reliable car battery at 20 amps and connecting its terminals (negative and positive) to those of the dead cordless drill battery through jumpers.  The car battery’s negative terminal is connected to the dead battery’s negative terminal, and so are the positive terminals.  The connection enables the transfer of power from the car battery to the dead cordless battery, enabling jumpstarting.  The car battery can fully charge the drill battery in about 60 minutes.

 Lastly, the transformer method is where a transformer with a rectifier is connected with a clamp to the dead cordless drill battery terminal to jump start it.

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Methods of Jumpstarting a cordless drill

The car battery method 

The essential requirement for this method is a car battery used to revive the dead battery. The car charger should be set at approximately 20 amps. The charger should then be carefully connected to the terminals of the dead cordless drill battery.

The negative end of the car battery should be connected to the negative end of the dead cordless battery and the positive connection to the positive using a jumper wire. The battery should be charged for 5 to 6 seconds. Disconnect and insert the dead battery in the tools battery charger.

If a charging sign is shown on the tool, leave the battery to charge for 60 minutes until fully charged. If the charging sign doesn’t show, repeat the process, this time, leaving the connection for 10 to 12 seconds.

Using another Fully charged Tool Battery

In this method, another similar fully charged drill battery is used to jumpstart the dead battery. This similar battery should be able to charge with the same charger tool. Place the two batteries side by side. Take two short good insulated wires and connect them in matching polarity between the two batteries. Connect one positive end to the other positive end of the fully charged and dead battery. The negative end should be connected to the other negative end.Among the best cordless drill you can fancy having in your tool collection is DEWALT 20V Max Cordless Drill Combo Kit, 2-Tool (DCK240C2).

The method essentially transports some charges from the live battery to the dead battery before jumpstarting. Hold the wires in place for about five minutes or more than disconnect the cables. Place the dead battery in the tool battery charger and check if the battery is charging.

If the battery starts charging, then the process has worked. If it’s not charging, then repeat the process. Leave the battery to charge for about an hour until it’s fully charged. If this does not work again, the battery might be dead and need replacement.

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The transformer method

A charger is an essential apparatus in this method. This transformer should have a rectifier to convert alternating current (AC) into direct current (DC). Connect the rectifier with a clamp or a wire. The positive to a positive end and the negative to a negative end. Keep it plugged for a few seconds for the dead battery to gain some power. Check if the voltage goes up. If it has worked, then you can use a charger to charge it to full capacity.

The video below shows how to revive a cordless drill battery

How to fix an 18v battery

The dreaded flashing red charger light notices a defective 18v battery. This can be caused by leaving the battery in the charger for too long hence draining the power. The condition implies that the battery is not damaged but needs a little boost to function. What’s needed to fix this situation is an AC adapter, a multimeter (optional), and the lithium-ion battery.

The first process is to cut off the end of the AC adapter and separate the stripes of each wire. The wires will be separated into positive and negative based on their colors. The black wire is always negative, while the stripe or solid white is positive.

You then use a screwdriver to remove screws holding the battery and pull the battery case to open. Remove the two plastics on the side by pressing in to remove the battery from the drill and lift the battery pack out. Fix the multimeter to read volts. Choose 20 volts setting for testing an 18 volts battery to get a precise reading.

Test the volts of the dead battery by inserting the red probe (positive) to the positive terminal and the black probe (negative) to the negative terminal and read the voltage in the multimeter. Plug the AC adapter in and boost the dead battery. Touch the black wire (negative) to the negative terminal and the white wire to the positive terminal.

Place and hold the wires for about 15 seconds, and remove the wires (on and off) for about one minute. Then, test the voltage of your dead battery pack again. The voltage should increase. Place the plastic cover back on (just the part that goes into the charger) the battery pack and place it on the battery charger tool to see if it can charge.

If the red flashing light still shows, boost the battery more between 10 to 14 volts and repeat the process until the charger recognizes it and the green light is shown.

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Factors to consider when choosing cordless drill batteries


Power is measured in voltage. A voltage of 4v to 8v is suitable for drilling. For a high-performance screwdriver, a voltage of between 7v to 15v is sufficient. A higher voltage provides the machine with the needed power to torsion through objects.

Higher voltage cordless drills provide power to bore bigger holes and get the job done faster, making them perfect for heavy tasks and projects. The cordless drill should have sufficient voltage for the tool.


Capacity indicates the amount of energy the battery can provide in a certain period. It’s measured in ampere per hour. A higher capacity indicates the higher the cordless drill will take to perform.

A capacity of 1.3 Ah is satisfactory for lightweight applications, while a maximum capacity of 3.3 Ah is recommended for heavy-weight tools. A good cordless drill battery should provide sufficient energy for the intended task and operate for longer hours without being discharged.


A good battery has an inbuilt protection circuit to guard against system malfunction. Before purchasing the battery, the user should know the battery’s protection, its efficiency, and the battery management system.


In some conditions of extremely high temperatures, the battery may not perform well. High temperature may cause internal chemical reactions causing the battery to use the stored energy. Hence self-discharge is ideal, and a good battery should have a low discharge rate.

Some metals like; Lead-acid, Nickel-metal hydride, and Nickel-cadmium are prone to self-discharge than Lithium, Alkaline, and Zinc. The element compound in the battery is a significant factor when choosing the battery for a cordless drill.


Light batteries are easier to use and install. High power density batteries are always considered good when they are lighter. Nickel batteries are always heavier because they are the oldest power tool batteries. With technological advancement, there are lighter and more powerful batteries.

Charge time

Any rechargeable cordless drill tool should have a low charging time. The charge time factor can be decided by how fast the battery discharges power. A battery that discharges power rapidly will take more time to charge than discharges power slowly. For batteries that need regular charging, a battery with a low charging time is recommended.

Cycle life

Cycle life is the number of discharge cycles that a power tool supports. Nickel-cadmium batteries can support about 800 cycles, while Lithium batteries can support a higher number of cycles. A good battery should have a higher number of cycles

Frequently asked questions

Can you jumpstart a car with a cordless drill battery?

A fully charged cordless drill battery with a voltage of between 12- 18 voltage can give enough power to can jumpstart a car. Connect the alligator clips to the car battery terminals, then connect the positive clip to the dead car battery and the other end to the drill’s battery.

Connect the negative clip to the drill’s battery and the other end of the cable to the unpainted metal part of the car. Wait for about 5 to 10 minutes before starting the vehicle.

Can you jumpstart a 12v battery?

A 12v battery can be rejuvenated by adding acid to it. These batteries lose electricity when utilizing chemical reactions. The loss of acidic electrolytes can cause an imbalance in the battery, which weakens it.

Will a jump starter start a dead battery?

A jumps starter with 500 amps can start any vehicle with a dead battery. Most cars’ batteries are 12v. Jump-starters don’t recharge the battery but provide amperage to crank the engine and start the car. Immediately the engine is on, and the alternator charges the battery and powers the electoral system.

How do you fix a lithium-ion battery that won’t charge?

Lithium-ion batteries are rechargeable, but with time they take longer to power up and loses charge quickly. With conditions like these, the battery can be revived by various methods. For instance, fully recharging the battery is completely drained. Then plugged into a power outlet and charged for 48 hours. The batteries can also be jumpstarted using various methods.


Cordless drill batteries are mostly made of Lithium-ion that enables them to store power for a long time and charge faster. This battery is the primary power source that enables the drill to perform various tasks. With time the battery wears out and loses power faster or probably won’t power up. The battery may not be as useless as it seems and can be revived through various methods.

The method involves using another fully charged battery or the car battery to jumpstart the dead battery. The jumpstarting process mainly transfers power to the dead battery, after which the battery should be fully charged. Various factors like the voltage, capacity, charge time, weight, and self-discharge are essential in determining the battery power. A good battery should store power for a longer time and charge faster.

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