You can charge a Milwaukee battery without its original charger, but your options depend on the battery type and what equipment you have on hand
If you have lost or damaged your Milwaukee charger, you are not locked out of using your battery. Milwaukee makes several battery types—18V, 20V, and 12V lithium-ion batteries are the most common in their power tool line—and each can be charged through alternative methods. The safest and most practical route is usually buying a compatible charger from Milwaukee or a third-party manufacturer. If you need to charge when ready, a few workarounds exist, though they carry real risks if done incorrectly.
The method that works depends on whether you have access to another Milwaukee charger, a universal charger, or basic tools and patience. Some approaches work only for specific battery models. Before you try any workaround, check your battery's voltage and connector type—this information is printed on the battery itself or in your tool's manual.
Key Takeaways
- A compatible Milwaukee charger or universal lithium-ion charger is the safest way to charge your battery and costs between $30 and $80 depending on the model.
- If you have another Milwaukee tool that uses the same battery type, you may be able to borrow its charger, since Milwaukee chargers are often compatible across the same voltage line.
- Charging through a USB port or car charger works only for Milwaukee batteries with built-in USB ports, and only if the battery supports that feature.
- Attempting to charge a battery by connecting wires directly to the terminals is dangerous and can cause fire, explosion, or permanent battery damage.
- Milwaukee batteries have internal protection circuits that prevent overcharging, but only when used with proper chargers—workarounds bypass this safety feature.
Buying a Compatible Replacement Charger
The most straightforward solution is to purchase a charger designed for your battery's voltage. Milwaukee sells single-bay and dual-bay chargers for 12V, 18V, and 20V batteries. A single-bay charger typically costs $30 to $50, while a dual-bay model runs $50 to $80. These chargers are available at home improvement stores, tool retailers, and online marketplaces.
When you buy a replacement, match the voltage on your battery exactly. A 20V charger will not work with a 12V battery, and vice versa. Milwaukee also makes fast chargers that reduce charging time from 60 minutes to 30 minutes or less, though these cost more. If you own multiple Milwaukee tools, a universal charger that accepts several voltage types may save money over time.
Third-party manufacturers like Dewalt, Makita, and others make universal lithium-ion chargers that work with Milwaukee batteries, provided the voltage matches. These are often cheaper than Milwaukee-branded chargers and perform the same function. Read the product description carefully to confirm compatibility with your specific battery model.
Borrowing a Charger From Another Milwaukee Tool
If you own other Milwaukee power tools, check whether they use the same battery voltage. Milwaukee's 20V system is their most common line, and chargers within that system are usually interchangeable. A charger sold with a Milwaukee drill, impact driver, or circular saw will typically charge any 20V Milwaukee battery, regardless of which tool it came with originally.
The same applies to 18V and 12V batteries—chargers within each voltage family work across the product line. Before you borrow a charger from a friend or family member, confirm that both batteries have the same voltage printed on them. Using a charger rated for a different voltage can damage the battery or the charger.
Using a USB Port if Your Battery Has One
Some newer Milwaukee batteries include a built-in USB port on the battery itself, separate from the main charging terminals. If your battery has this feature, you can charge it using any standard USB-C or micro-USB cable connected to a wall adapter, laptop, or power bank. This method is slow—it may take several hours to fully charge—but it works without a dedicated charger.
Check your battery's manual or the battery casing for a USB port. If you see a small rectangular or oval opening, that is likely the USB charging port. Plug in a compatible cable and connect it to any USB power source. The battery will have an indicator light that shows charging status. This method is safe because the battery's internal protection circuit manages the charge rate.
Charging Through a Car Charger or Power Inverter
If you have a car charger designed for Milwaukee batteries or a universal 12V car charger, you can charge your battery from a vehicle's cigarette lighter socket or USB outlet. Some Milwaukee chargers come in car-compatible versions. Check the charger's specifications to confirm it works with your battery voltage.
A power inverter—a device that converts DC power from a car battery to AC power—can also run a standard Milwaukee charger if you plug it into the inverter. This is useful if you are working on a job site away from a wall outlet. Inverters range from $30 to $150 depending on wattage. Make sure the inverter's wattage is at least 150W higher than your charger's rated power draw.
Why Direct Wire Charging Is Dangerous and Not Recommended
You may read online about charging a lithium-ion battery by connecting wires directly to the positive and negative terminals. This method is extremely dangerous and should never be attempted. Lithium-ion batteries require a charger that monitors voltage and current in real time. Without this monitoring, the battery can overheat, swell, catch fire, or explode.
Milwaukee batteries have internal protection circuits, but these circuits only work when the battery is connected to a proper charger. Bypassing the charger entirely removes all safety controls. Even if the battery does not fail when ready, direct charging can permanently damage the cells, reduce capacity, or cause the battery to fail unpredictably during use. The risk is not worth the few dollars saved by avoiding a charger purchase.
Checking Battery Health Before Charging
Before you charge your battery using any method, inspect it for physical damage. Look for cracks, dents, or swelling on the battery casing. If the battery is visibly damaged, do not attempt to charge it—damaged lithium-ion batteries can fail during charging. Contact Milwaukee's customer service or take the battery to a retailer for safe disposal.
If the battery appears intact, check that the charging terminals are clean and free of corrosion. Wipe the terminals gently with a dry cloth if you see any buildup. Corroded terminals can prevent proper charging or cause the charger to shut off. Once the terminals are clean, the battery is ready to charge using any of the safe methods described above.
Frequently Asked Questions
Can I use a Dewalt charger on a Milwaukee battery?
No. Dewalt and Milwaukee use different connector designs, even when the voltage is the same. A Dewalt charger will not physically fit a Milwaukee battery. You need a charger designed specifically for Milwaukee batteries or a universal charger explicitly rated for Milwaukee compatibility.
How long does it take to charge a Milwaukee battery with a USB port?
USB charging is much slower than a dedicated charger. A full charge typically takes 4 to 8 hours depending on battery capacity and the power output of your USB source. A standard wall adapter provides faster charging than a laptop or power bank. Check your battery's manual for the exact charging time.
What happens if I use the wrong voltage charger?
Using a charger rated for a different voltage can damage the battery, the charger, or both. A charger with too high a voltage will overcharge the battery and cause it to overheat or fail. A charger with too low a voltage will not charge the battery at all. Always match the voltage printed on your battery to the charger's rated voltage.
Can I charge a Milwaukee battery in the rain or wet conditions?
No. Never charge a lithium-ion battery outdoors in rain or in wet conditions. Water can damage the charger and create an electrical hazard. Always charge indoors in a dry location. If your battery or charger has been exposed to water, allow them to dry completely before attempting to charge.
Is it safe to leave a Milwaukee battery charging overnight?
Yes, it is safe to leave a Milwaukee battery on a proper charger overnight. Milwaukee chargers have built-in circuits that stop charging once the battery is full and prevent overcharging. However, leaving a battery on a charger for weeks at a time can reduce its lifespan. Unplug the charger once the battery is fully charged if you do not plan to use it soon.