How to Charge Battery Pack | The 4 Basic Steps

Charge a battery pack by connecting the charger to its input port, waiting for the indicator light to show full, and unplugging it.

Most rechargeable battery packs work the same way, but the exact steps vary by brand. Knowing whether you’re charging a power bank, a cordless tool battery, or a gadget battery makes the difference between a full charge and a frustrated hour of blinking lights. Here’s what applies to nearly every pack on the market.

What You Need Before Charging

Gather three things: the battery pack itself, the correct charger or cable, and a power source like a wall outlet or USB port. Using the manufacturer-approved charger matters more than people think.

If you’ve lost the original cable, check the pack’s input port before grabbing any cord you own. A mismatched cable can charge slowly or not at all.

Step-by-Step: How to Charge a Battery Pack

The basic sequence works for nearly every pack, from Milwaukee tool batteries to Belkin power banks. Follow these steps in order.

1. Plug the charger into the power source first. DeWALT’s manual is explicit: connect the charger to an appropriate outlet before inserting the battery pack. This prevents sparking and protects the charger’s electronics.
2. Insert the battery pack into the charger. Milwaukee instructions say to align the pack with the bay and slide it fully into place until it seats. You should feel or hear it click. A half-seated pack won’t charge.
3. Check the indicator light. A blinking light means charging is in progress. On DeWALT chargers, the left indicator blinks red while charging. Milwaukee packs may flash quickly if too hot or cold, or flash slowly if waiting for another pack to finish.
4. Wait for the light to go solid or steady. On a single-stage DeWALT charger, the left light stays solid red when complete. Two-stage chargers show both lights steady. Philips packs illuminate all 4 LEDs when full.

One note: for a USB power bank, the process is simpler. Philips says to plug one end of the Micro USB cable into the pack and the other into a USB power source, then wait. Belkin’s US guide says the same — connect the supplied cable to the pack’s input port and attach the other end to a wall charger. If you’re ready to buy a pack that also keeps your hands warm in winter, our battery pack heater roundup covers the tested options.

How Long Does It Take?

Charging time depends entirely on the pack and the charger. A larger pack, like a 12 Ah tool battery, takes longer than a small phone power bank.

If your pack seems to charge forever, check the temperature. Cold packs charge slower, and some chargers refuse to charge a pack that’s too hot or too cold. Milwaukee warns that a rapid blink can mean the pack is outside its safe temperature range.

Temperature Limits and First Use

Temperature is the most common reason a pack won’t charge. If your garage is freezing in January or sweltering in July, charge the pack indoors.

New packs need attention too. DeWALT and Milwaukee both instruct users to charge Li-ion packs fully before first use. Sony notes there’s no need to discharge a pack before recharging — topping it off doesn’t hurt the battery’s capacity, despite the old “memory effect” myth.

Charging a Device From the Pack

Once your pack is full, charging a device from it is the reverse of charging the pack. For a Philips pack, plug the USB-A end into the battery pack, the other end into your device, and press the power button on the pack to start the flow. Most power banks wake up with a button press or automatically when they sense a connected device.

The common mistake is pressing the button before plugging in the device. Connect first, then press — otherwise the pack may shut off after a minute of “no load.”