Short answer: yes. A DeWalt® FLEXVOLT® 60V battery slides onto the same rail as a 20V MAX™ pack and automatically switches itself down to 20V the moment you click it in — so a horn gun built for DeWalt 20V MAX batteries runs on it with no adapter, no rewiring, and no risk of frying anything. Better yet, FlexVolt packs carry some of the biggest capacities in the entire DeWalt lineup, which translates directly into more blasts per charge.
The Short Answer: FlexVolt Runs the Horn Gun — at 20V
FlexVolt is DeWalt's dual-voltage battery line. Every FlexVolt pack is designed to power both 60V MAX tools and standard 20V MAX tools, and DeWalt states plainly that the battery "automatically switches voltage when you change your tools." There is no switch to flip and no setting to remember. Drop a FlexVolt pack onto any device built for the DeWalt 20V rail — including a battery-powered train horn gun — and the pack delivers 20V MAX output, exactly like a standard pack would.
That means the horn's compressor sees the same voltage it was designed for. It will not run harder, hotter, or louder. What changes is how long you can keep blasting, because FlexVolt packs are physically bigger and store far more energy than typical 20V packs.
One important direction note: this compatibility is one-way. A FlexVolt pack works on 20V-class devices, but a standard 20V MAX pack cannot power a 60V tool — DeWalt molds physical tabs into 60V tool battery slots specifically to keep 20V packs out. For a horn gun owner, only the first direction matters, and it works in your favor.
How a Dual-Voltage FlexVolt Pack Actually Works
A standard DeWalt 20V MAX pack holds five or ten lithium-ion cells. A FlexVolt pack holds fifteen, and the clever part is in the wiring. The pack contains an internal switching mechanism that reconfigures how those fifteen cells connect the instant the battery meets a tool's terminals:
- In a 60V tool: all 15 cells wire in series (a 15S1P configuration), stacking their voltages to deliver 60V MAX.
- In a 20V-class device — like a horn gun — the tool's terminal layout flips the switch, and the cells regroup into three parallel banks of five (5S3P). Voltage drops to 20V MAX, and the three parallel banks triple the amp-hours.
That is why a FlexVolt battery carries two capacity ratings on the label. A pack marketed as 9.0Ah delivers 9.0Ah at 20V, or 3.0Ah at 60V — same energy, different arrangement. When it's sitting on a horn gun, you always get the big number.
Voltage housekeeping, since horn spec sheets love to mix these up: "20V MAX" and "60V MAX" are peak, fresh-off-the-charger figures. Nominal working voltages are 18V and 54V. That's the same math behind every battery platform, and it's why a 20V MAX pack and an 18V pack from another brand are functionally the same class of battery.
What FlexVolt Capacity Means in Blasts per Charge
A horn gun's compressor only draws current while you're on the trigger, so battery capacity converts almost directly into number of blasts. We broke down the math in our guide to how many blasts a train horn gun gets per charge — the short version is that a standard 5.0Ah pack already delivers hundreds of short blasts. FlexVolt packs raise that ceiling considerably:
| Pack | Capacity in the horn gun (20V mode) | Nominal energy (18V basis) | vs. a standard 5.0Ah pack |
|---|---|---|---|
| 20V MAX 5.0Ah (reference) | 5.0Ah | 90 Wh | — |
| FLEXVOLT 6.0Ah | 6.0Ah | 108 Wh | 1.2× the energy |
| FLEXVOLT 9.0Ah | 9.0Ah | 162 Wh | 1.8× the energy |
| FLEXVOLT 12.0Ah | 12.0Ah | 216 Wh | 2.4× the energy |
| FLEXVOLT 15.0Ah | 15.0Ah | 270 Wh | 3× the energy |
If a 5.0Ah pack is good for a few hundred short blasts, a 12.0Ah FlexVolt pack carrying 2.4 times the energy puts you comfortably into four-digit territory between charges. For a weekend of tailgating, a boating trip, or a season of scaring coyotes off the back forty, one big FlexVolt pack can be the only battery you bring.
To be clear, capacity is the whole story here — there is no loudness bonus. Decibel output is set by the horn's compressor and trumpet configuration, not by how many amp-hours sit under it.
The Trade-Off: FlexVolt Packs Are Big and Heavy
Fifteen cells weigh more than five. Retailer listings put the FLEXVOLT 9.0Ah pack (DCB609) at about 2.2 lbs, versus about 1.4 lbs for a standard 20V MAX 5.0Ah pack (DCB205) — and the 12.0Ah and 15.0Ah packs are heavier still. The pack is also taller, which changes how the horn feels in hand.
In practice, that splits FlexVolt use on a horn gun into two camps:
- Handheld use: a 6.0Ah or 9.0Ah FlexVolt pack adds noticeable heft but stays comfortable for a pistol-grip horn you hold and trigger yourself. The extra base actually gives the horn a wider, more stable foot to stand on.
- Mounted use: if the horn rides on a truck bed rail, UTV roll cage, or boat rail and fires from a wireless remote, weight stops mattering entirely. This is where a 12.0Ah or 15.0Ah pack shines — maximum runtime, zero handling penalty.
Which Horn Guns Take a FlexVolt Pack
Any of our horns built for the DeWalt 20V battery rail will run on a FlexVolt pack, because the pack presents itself as a normal 20V MAX battery. The flagship option is the DeWalt-compatible 5-trumpet horn gun with wireless remote, which pushes up to 150 dB — pair it with a high-capacity FlexVolt pack and a remote, mount it out of the way, and you have a set-and-forget signaling rig. There's also a dual-trumpet version for DeWalt batteries if you want something more compact for the glovebox or boat locker.
If your battery drawer is red instead of yellow, the equivalent on the Milwaukee® side is the 5-Trumpet Horn Gun for Milwaukee® 18V Battery. Worth noting: Milwaukee's M18™ line is single-voltage, so there's no dual-voltage switching to think about — every M18 pack from 2.0Ah to 12.0Ah runs the horn the same way.
What Not to Try
A few dead ends worth flagging before you spend money on them:
- Don't go hunting for a way to run the horn gun in 60V mode. The horn gun's compressor is an 18/20V-class motor. FlexVolt's 60V mode simply never activates on a 20V-class device — and that's the correct, safe behavior, not a limitation to engineer around.
- Don't force a higher voltage into an 18V-class device by other means. Feeding 60V into electronics built for 20V is an over-voltage event that can destroy the compressor. FlexVolt is safe precisely because the pack itself does the down-switching.
- Skip sketchy cross-brand adapters for this job. A FlexVolt pack needs no adapter on a DeWalt-rail horn, and stacking an adapter under any battery adds a failure point where high current flows.
FAQ
Will a FlexVolt battery physically fit my horn gun?
Yes — FlexVolt packs use the same slide-rail interface as standard DeWalt 20V MAX packs, so they mount on any horn gun built for DeWalt batteries. The pack itself is taller and wider at the base than a compact 20V pack, so give it a glance if your horn lives in a tight storage cubby, but on the tool interface itself, fit is not an issue.
Does the 60V rating make the horn louder?
No. The pack switches to 20V MAX output on a 20V-class device, so the compressor runs exactly as it does on a standard pack. Loudness comes from trumpet count and compressor design; the battery only decides how many blasts you get before recharging.
Can I charge a FlexVolt pack on a regular DeWalt 20V MAX charger?
Yes. FlexVolt batteries charge on standard DeWalt 20V MAX chargers — the port is the same. Big packs just take a while on a basic charger: DeWalt specs a 6.0Ah FlexVolt pack at roughly 90 minutes on the standard DCB115 charger versus roughly 60 minutes on the DCB118 fast charger, and the 12.0Ah and 15.0Ah packs proportionally longer.
Which FlexVolt size makes the most sense for a horn gun?
For handheld use, the 6.0Ah or 9.0Ah packs are the sweet spot — huge runtime without turning the horn into a dumbbell. The 12.0Ah and 15.0Ah packs are best when the horn is mounted and triggered by remote, where their weight is irrelevant and their capacity means you might charge twice a season.
I already own FlexVolt packs — should I still buy a spare 20V pack for the horn?
Not necessarily. If your FlexVolt packs already rotate through your 60V tools, any one of them doubles as the horn's power source. Owners who run the horn daily sometimes dedicate a compact 20V pack to it just to keep the FlexVolt packs free, but there's no technical reason the horn needs its own battery.