A cordless battery system now powers more than drills and saws. Power supply adapters turn the same packs that run tools into outlets for laptops, phones, tablets, and radios, which changes how crews work away from wall power. The concept is simple: a 175W supply clips onto a battery and offers a 120V AC receptacle, a USB-C port, and a USB-A port, letting workers set up a charging station wherever the work happens. The practical details of USB charging on the jobsite depend on port selection, battery size, and the draw of the device you plug in.
What a Battery Power Supply Does
A battery power supply is a converter, not a generator. It draws stored energy from the battery and delivers it through fixed outlets at fixed limits. One M18 Top-Off class supply delivers 175W through the AC receptacle, up to 45W through the USB-C power delivery port, and up to 2.4A through the USB-A port. Each port has its own on/off button, so a supply left on a shelf does not drain the battery the way some adapters do. The unit weighs about 0.8 pounds bare, hangs from a rafter hook, and accepts every battery size in its platform, from compact 2.0 Ah packs to high-demand 12.0 Ah packs. The same battery that runs a top-handle jigsaw in the morning can charge a laptop by afternoon.
The rafter hook is a small feature with a large effect. It lets a worker hang the supply at chest height on a ladder or a truss, which keeps the unit out of mud and water and puts the ports at hand level. On a work cart, the same hook or a strap holds the supply upright so cables do not pull it off the deck.
Reading the Spec Sheet
The three numbers that matter are the AC wattage, the USB-C wattage, and the USB-A amperage. AC wattage tells you which small appliances will run. USB-C wattage tells you how fast a laptop or tablet charges. USB-A amperage covers phones and accessories. Ignore the marketing name and check these three values.
Ports and Power Limits
Each port has a ceiling. A 175W AC receptacle will not start a circular saw or a microwave, and the manufacturer says so directly. The supply targets small electronics: laptops, phones, radios, cameras, and chargers for other devices. Match the device to the port and the port to the limit, and the supply works for years.
| Output | Rating | Typical devices |
|---|---|---|
| AC receptacle | 175W max | Laptops, small chargers, monitors |
| USB-C PD port | 45W max | Laptops, tablets, fast-charging phones |
| USB-A port | 2.4A max | Phones, earbuds, small accessories |
| On/off control | Separate USB and AC buttons | Prevents idle battery drain |
| Weight | About 0.8 lb bare | Mounts on rafter hook or work cart |
How Battery Outlets Compare to Other Options
Crews have three ways to get power away from a wall outlet: portable power banks, inverters, and battery power supplies. Power banks charge phones and small USB gear but stop at USB limits. Inverters bolt onto vehicle batteries and deliver household power but add weight and noise. Battery power supplies sit between the two: they run on the battery platform a crew already owns, need no fuel, and produce no exhaust. Smaller compact power supplies in the same family cover light-duty charging and fill the gap between a power bank and a generator.
Fuel and noise settle the comparison on many sites. A generator must be refilled, ventilated, and kept away from occupied work areas, and its exhaust rules out indoor use entirely. An inverter needs a running vehicle or a dedicated battery bank. A power supply draws on packs the crew already rotates through tools, so there is no second fuel source to stock and no engine to maintain.
Speed of Charging
USB-C power delivery changes charging speed. The manufacturer claims up to 75 percent faster device charging than conventional wall chargers, because the PD protocol negotiates higher wattage with compatible devices. A phone that draws 5W from a basic port can pull 18W or more from a PD port, and the supply keeps every port at full output.
Simultaneous Power
Most multi-port chargers split one power budget across all ports: plug in two devices and both charge slower. A supply with independent port circuits keeps each outlet at its rated output. You can charge a laptop through AC, a tablet through USB-C, and a phone through USB-A at the same time without any of them throttling.
Size the Battery for the Job
Battery capacity decides how long the supply runs. The table below shows the general pattern for one platform.
| Battery pack | Capacity | What it supports | Typical session |
|---|---|---|---|
| Compact | 2.0 Ah | Phone and small device charging | A few device top-ups |
| Standard | 5.0 Ah | Laptop plus phones | Several hours of mixed use |
| High output | 8.0 Ah | Laptop, tablet, radio together | Most of a workday |
| High demand | 12.0 Ah | Heavy AC loads and long days | Full shift with margin |
Runtime Estimates
Runtime math starts with watt-hours: multiply the pack voltage by the amp-hour rating. A 12.0 Ah pack at 18V nominal holds roughly 216 watt-hours, enough to run a 45W laptop for close to four hours after conversion losses. A 2.0 Ah pack holds about 36 watt-hours, which covers a phone and a few small top-ups. For heavy loads, high-output mobile power stations built on larger battery platforms take over where a 175W supply stops.
Duty Cycles and Rotating Packs
Running every port at full output drains the battery faster than the sum of the labels suggests, because conversion generates heat and losses. Plan a duty cycle: charge devices in batches instead of leaving everything plugged in all day. A spare battery in rotation doubles the usable time. Mark the packs with tape or a label when they go on the supply, and pull them when the device stops charging or the port light dims. Most crews learn the rhythm of their own loads within a week.
What to Power and What to Leave Plugged In
The line between useful and dangerous is clear. A cordless circular saw still runs on its own battery, and plugging one into a 175W outlet trips the protection or damages the supply. Everything else sorts into two lists.
Devices That Work
- Laptops and tablets for field reporting, estimating, and communication.
- Phones and radios for crew coordination.
- Camera batteries and chargers for a second tool platform.
- Small monitors and test equipment for setup and inspection.
Devices to Avoid
- Heating elements: kettles, heaters, heat guns, and most coffee makers draw far more than 175W.
- Motors with startup surges: many small pumps and compressors exceed the rating on start-up.
- Power tools and kitchen appliances: the manufacturer warns against both in the documentation.
Practical Jobsite Setups
A power supply earns its space when it is mounted where people work. The rafter hook hangs the unit from a ladder, a truss, or a stud, keeping cables off the floor. A clip or strap on a work cart turns the cart into a mobile charging station. Field crews that spend the morning running cordless chainsaws or other high-draw tools can recharge phones and radios from the same packs in the afternoon.
Workstation in a Box
One common setup: a tool bag or cart holds the supply, one spare battery, a laptop, and a phone. At each stop, the crew clips a fresh pack, plugs in, and works. The layout keeps electronics within eyeshot, which cuts the trips back to a wall outlet and reduces the chance of theft. The same setup works for punch lists: an inspector carries the supply and one pack through a building, charges a tablet between rooms, and never walks back to the truck for power.
Charging Discipline
Build a routine around the ports:
- Turn the ports off when nothing is plugged in.
- Keep the supply dry and out of direct sun.
- Rotate batteries so the oldest packs do not carry the heaviest loads.
- Track which packs are charged, which are in tools, and which are in the supply.
A power supply does not replace a generator, and it is not meant to. It fills the gap between a wall outlet and a power bank, using batteries the crew already owns. Before you buy, match the port ratings to the devices you carry, and size the battery to the shift. A 175W supply with a 12.0 Ah pack covers most field reporting, and the whole kit fits in a tool bag. One warning stands out from the manufacturer’s own documentation: heated workwear runs on its own power system, so keep jackets and vests on their dedicated chargers and leave the AC port for electronics.