Can You Bring Power Tool Batteries on a Plane?

The answer people find online is usually right about the rule and wrong about the arithmetic. The rule is a watt-hour (Wh) limit, and almost everyone works it out with the voltage printed on the front of the pack. That number is a maximum, not the nominal voltage the regulation uses, so the arithmetic comes out 11 percent high on every DeWalt 20V MAX pack. It is why a 5.0 Ah pack gets described as sitting right at 100 Wh when it is 90.

The three Wh bands and what each one allows

The US rule is 49 CFR 175.10(a)(18), and the FAA's PackSafe pages and IATA's passenger guidance put the same numbers in plainer language. Everything turns on the Wh rating of each individual pack.

Three conditions sit on top of the bands. The packs must be for your own use, since the FAA prohibits batteries carried for sale or distribution. Each spare must be protected from short circuit. And a damaged or recalled pack may not travel in either bag, which matters for a tool battery that has been dropped off a scaffold or has a cracked case.

Wh is nominal voltage times Ah, and 20V MAX is 18 V

The federal definition in 49 CFR 171.8 is short: the Wh rating of a lithium-ion battery is its rated capacity in ampere-hours multiplied by its nominal voltage. The FAA's own tip, "multiply the battery voltage by the Amp hours," leaves out the word nominal, and that gap is where the confusion starts.

DeWalt prints the answer in the footnote on its battery pages: maximum initial battery voltage, measured without a workload, is 20, 60 and 120 volts, and nominal voltage is 18, 54 and 108. "20V MAX" is the voltage of a freshly charged pack at rest. Under load it averages 18 V, and 18 V is what goes into the Wh rating. DeWalt's Australian FlexVolt shipping sheet does the arithmetic the regulatory way: an 18 V 5.0 Ah pack is 90 Wh, and a 10.8 V 2.0 Ah pack is 21.6 Wh.

The same company's US product page for the FlexVolt 9.0 Ah pack promises "180 watt hours of energy in each battery pack." That is 20 V times 9.0 Ah. The rated figure is 18 V times 9.0 Ah, or 162 Wh. Both are over 160, so the verdict does not change, but the two numbers drift apart on one company's own pages.

Milwaukee lists its M18 HD12.0 pack at 18V and Makita lists its LXT BL1860B at 18V, so on those packs the printed voltage is already the one to use. Whatever the brand, the most reliable figure is the one printed on the pack's rating label. The DeWalt shipping sheet points to the label on the underside of the pack, and the FAA notes that newer lithium-ion batteries carry a Wh rating marking.

Every common 18V pack size, worked out

Because the three big 18V platforms share a nominal voltage, one table covers them all. The rated column is 18 V times the capacity. The "MAX arithmetic" column is what you get using 20 V instead, shown so you can see where the shortcut misleads.

Makita lists the BL1860B at 18V and 6.0 Ah, which makes it a 108 Wh pack: allowed with approval, two at most. Milwaukee lists the M18 HIGH OUTPUT HD12.0 at 18V and 12.0 Ah, which makes it 216 Wh, over the 160 Wh ceiling, so it cannot go in either bag as a passenger.

12 V class packs. DeWalt's sheet works its 10.8 V 2.0 Ah pack out at 21.6 Wh. At 10.8 V the 100 Wh line sits at 9.2 Ah, and even if you use 12 V the line is at 8.3 Ah. Ordinary 12 V class tool packs are far below either, so they are carry-on items with no approval on any reading of the voltage.

Higher-voltage platforms. The arithmetic gets tight fast. At a 36 V nominal rating, 100 Wh arrives at 2.8 Ah and 160 Wh at 4.4 Ah. Read the Wh off the label rather than estimating it. DeWalt's 60V MAX name is a maximum voltage, as its footnote says, and on any platform named that way a small-looking capacity can still be a large pack.

FlexVolt and the transport cap

DeWalt's FlexVolt pack runs at 18 V in 20V MAX tools and at 54 V in 60V MAX tools, and the stored energy is the same either way. DeWalt's shipping sheet says it plainly: the 6.0 Ah pack is 108 Wh, and in 54 V / 2.0 Ah mode "the total amount of energy in the battery remains at 108Wh." The 2.0 Ah figure on the 60V side is not a smaller pack.

The transport cap that ships with every FlexVolt pack changes the classification. Pushed into the terminal slot, it separates the strings of cells so that, in DeWalt's words, one battery pack assembly can be classed as three battery packs during transportation. The label graphic reads 108 Wh without the cap and 3 x 36 Wh with it. DeWalt's quick reference table marks one or more FlexVolt packs with the cap fitted as acceptable for personal air travel, and packs without the cap as not acceptable.

Taken at face value, that moves the 6.0 Ah FlexVolt from the approval band into the no-approval band. The same division applied to larger FlexVolt packs gives 54 Wh per string for a 9.0 Ah pack (162 / 3) and 72 Wh per string for a 12.0 Ah pack (216 / 3). DeWalt's sheet shows the figures only for the 6.0 Ah pack.

Tools in checked bags, packs in the cabin

The TSA's power tool entry is short: power tools, including drills and drill bits, must go in checked bags. Power tools with installed batteries must also go in checked bags, and installed batteries must be protected from accidental activation. Spare, uninstalled lithium batteries must go in carry-on.

The only choice left is whether to leave a pack in the tool. The FAA allows it: the same Wh limits apply to installed batteries, and the device may be checked when powered off and protected from activation. On a drill or impact driver, protection from activation means a trigger that cannot be squeezed by the packing, which in practice means the forward/reverse selector in its center lock position and the tool packed tight in a hard case. A stacking box from one of the modular systems compared here does that job and doubles as the site box at the other end.

Taking every pack out is the better arrangement. The FAA notes that flight crews are trained to recognize and respond to lithium battery fires in the cabin, and a pack in the hold has nobody near it. Removing it also takes the activation question off the table.

A checked case of tools is a high-value bag handled out of your sight, so pack it for both rough handling and loss. A case thrown onto a belt loads its latches and hinges far harder than a case carried by hand, and those are the parts that fail first, as the hand carry box buying guide explains. If the bag goes missing, an adjuster settles from evidence: make, model, serial, photo and receipt, the record described in tool insurance and inventory. Capture it before you leave. The general principles of making a box an unattractive target are covered in tool theft prevention.

Protecting the terminals

Every rule set requires each spare to be individually protected against short circuit. The FAA lists the accepted methods: leave the battery in its retail packaging, cover the terminals with tape, use a battery case, or put each one in its own plastic bag or protective pouch.

On a slide pack the terminals sit in a recessed rail, and the risk is a loose bit, screw or key sliding into it. The options, in order of preference:

1. The snap-on terminal cover that came with the pack, if you still have it. It is purpose-made and an agent can see what it is.
2. The FlexVolt transport cap, which covers the terminals and changes the classification at the same time.
3. Electrical tape across the full terminal slot, not just the contacts, so nothing metal can slide under the tape.
4. One pack per zip bag, with nothing metal in the same bag.

Never put loose spares in a pocket of a tool bag with bits, fasteners or keys. Weigh them too: as the pack weights in electrician tool bag setup show, two 5.0 Ah packs can exceed 3 lb together, and a carry-on full of batteries reaches an airline's cabin weight limit sooner than you expect.

A worked example: one M18 kit, one flight

An installer flying to a job wants to bring two 5.0 Ah packs, one 8.0 Ah pack and one HD12.0 pack, plus an M18 drill and impact driver.

The two 5.0 Ah packs are the easy part. The 8.0 Ah pack is allowed only with the airline's approval, and it uses one of the two slots per person in the over-100 band, so a second 8.0 Ah or a 6.0 Ah pack would fill that allowance. The HD12.0 cannot travel as passenger baggage on any airline under these rules.

For the large pack, the options are to drive it, ship it, or replace it at the destination. Milwaukee's battery manual explains that commercial carriers ship lithium-ion packs as UN 3480 (batteries alone) or UN 3481 (packed with or in equipment), that requirements generally depend on whether a pack is over or under 100 Wh, and that in the US, ground shipments may be excepted from certain hazmat rules if they are under 300 Wh. DeWalt's sheet adds that the shipper is responsible for following dangerous goods rules.

Plan the battery choice backward from the flight. Two 5.0 Ah packs carry 180 Wh between them with no approval needed, which is more energy than one 9.0 Ah pack, and a 9.0 Ah pack cannot fly at all.

Where this answer stops applying

• Your airline can be stricter. The FAA says so on its own page, and many carriers limit power banks and spares by count. Get approval for anything over 100 Wh in writing.
• Other countries follow IATA, with local variation. The IATA table is the basis for most international carriers, but national regulators and airlines can add rules. A connecting flight on a different carrier needs its own check.
• Shipping is a different rule set. Everything here is about a passenger carrying their own packs. Sending batteries by courier or air freight falls under the dangerous goods shipping rules that Milwaukee's and DeWalt's documents describe.
• Damaged packs never fly. A swollen, cracked or recalled pack is forbidden in both bags. If a pack has been dropped hard or runs hot, leave it.
• Heat still matters on the way. A pack left in a parked car at the airport faces the temperatures covered in tool battery storage temperature limits.
• The label wins. Every Wh figure in this article is derived from the published voltage and capacity. If your pack's label prints a different Wh rating, that rating is the one the airline will read.

The thirty-second check

1. Find the Wh on the pack label. If it is missing, multiply the nominal voltage (18 for 20V MAX, M18 and LXT) by the Ah.
2. 100 Wh or less: carry-on, terminals covered, no approval.
3. Over 100 up to 160 Wh: carry-on, terminals covered, airline approval, two per person at most.
4. Over 160 Wh: it stays home or goes by ground.
5. Tools go in the checked bag with the packs removed. Every spare pack goes in the cabin.