If your garage runs on Craftsman red and you bought into the V20 system at Lowe's, here's the short version: the same battery that spins your drill will fire a 140 dB train horn. No air tank, no wiring, no adapter. Below is exactly which V20 packs fit, why the "20V MAX" label is nothing to worry about, and how many blasts you get on a charge.
The short answer: yes, your Craftsman V20 battery fits
A battery-powered train horn is built like a cordless tool. Inside there's a small compressor, a set of trumpets, and a battery dock molded for one specific pack. Slide your battery onto the rails, it clicks home, and the horn is live. So the real question is never "is my V20 pack strong enough" — it's "does this horn have a Craftsman dock." It does. BossHorn builds dedicated Craftsman 20V horns, so the pack you already charge for your impact driver is the same pack that runs the horn.
That matters because the V20 platform has a huge installed base. It's the house cordless system at Lowe's, which means a lot of trucks, farms, and workshops already have two or three V20 packs sitting on a charger. If that's you, you already own the expensive half of the setup.
"20V MAX" vs 18V: why the label doesn't change a thing
There's a recurring worry that a Craftsman "20V" pack is somehow a different class than an "18V" Milwaukee or Ridgid pack. For a train horn — and honestly for any tool — that worry is misplaced, and the voltage math is the reason.
A Craftsman V20 pack is built from five lithium-ion cells wired in series, each cell sitting around 3.6 volts nominal. Five times 3.6 is 18 volts — the working voltage under load. Craftsman's own spec sheet lists the V20 battery at a maximum initial voltage of 20 volts and a nominal voltage of 18. That "20V MAX" on the label is just the no-load peak reading of a freshly charged pack, about 4 volts per cell before you put any draw on it. Milwaukee, Bosch, and Ridgid choose to print the 18V nominal number instead. Put a V20 pack and an M18 pack on a meter under load and they read the same 18-volt class.
The compressor inside a horn reads volts and draws amps. It does not read the brand name on the pack. And the load is gentle: a train horn fires in short bursts — a one- or two-second blast, not the sustained minutes a circular saw pulls. Each blast sips a tiny fraction of the charge, which is about the friendliest duty cycle you can hand a battery. The takeaway: voltage sets the volume, and your V20 pack has every volt a horn needs.
Which Craftsman V20 packs fit the horn
This is the easy part, because Craftsman runs one platform. Every V20 battery is compatible with every V20 tool — there's no "high-power-only" dock or sub-line that locks you out. So any V20 pack you own mounts on a V20 horn. The current lineup at Lowe's:
- 2.0 Ah — the compact pack, rated for up to 1.5x the runtime of the older standard V20 battery. Lightest to carry.
- 4.0 Ah — the everyday sweet spot, rated for up to 3x the capacity of the standard pack.
- 6.0 Ah — rated up to 4.5x the standard pack's capacity. A leave-it-on-the-horn size.
- 9.0 Ah — the big one, rated up to 6x the standard pack. Maximum blasts between charges.
- V20 Advanced (RP) — Craftsman's most powerful V20 packs yet, sold in 3.0 Ah and 6.0 Ah. They mount the same dock; you just get more headroom.
On the horn side, the Craftsman dock comes in two sound tiers: the Dual Train Horn for Craftsman 20V at 130 dB for everyday signaling, and the Quad Train Horn for Craftsman 20V at 140 dB when you want the full freight-train wall of sound. Both snap onto any V20 pack in the list above.
How long does it run? Sizing a V20 pack to your use
Because a horn fires in short bursts, amp-hours translate almost directly into blasts: roughly double the Ah, double the blasts on the same charge. Voltage sets the volume; amp-hours set how many times you can hit it. Here's a practical way to match a V20 pack to how you'll actually use the horn.
| V20 pack | Roughly | Best for |
|---|---|---|
| 2.0 Ah | Up to ~1.5x standard runtime | Occasional use — a tailgate, a campsite, a few warning blasts on the trail. Lightest pack. |
| 3.0 Ah Advanced | More power, mid capacity | A compact upgrade when you want extra blasts without the weight of a big pack. |
| 4.0 Ah | Up to ~3x standard capacity | The everyday sweet spot. Plenty of blasts for a day of off-roading, farm chores, or boating. |
| 6.0 Ah | Up to ~4.5x standard capacity | All-day events and heavy signaling. Leave it on the horn and forget about it. |
| 9.0 Ah | Up to ~6x standard capacity | Maximum blasts between charges, at the cost of size and weight. |
One thing worth saying plainly: a small 2 Ah pack does not make the horn quieter. Loudness comes from voltage, and a 2 Ah V20 pack delivers the same 18 volts nominal as a 9 Ah pack. The small pack simply runs out of blasts sooner. So if you only fire the horn now and then, the compact pack is plenty — save the 6 Ah and 9 Ah packs for events where you'll be leaning on it.
Where a V20 horn earns its keep
The reason power-tool owners go for a battery horn over a wired truck setup is freedom. The whole unit lifts off and moves wherever you do. Pull the pack off your drill, snap it on the horn, and you've got 130–140 dB in your hand with nothing bolted to a vehicle.
That portability is why V20 owners use them across the board: clearing deer or coyotes off a field at the farm, moving stubborn livestock, signaling on a job site, warning a trail when an off-road rig comes around a blind corner, hailing a friend's boat across the water, or just bringing the loudest noisemaker to a tailgate. The horn doesn't care whether it's mounted, handheld, or tossed in a UTV cargo box — it runs as long as there's a charged V20 pack on it.
If you ever decide you want the absolute loudest option and don't mind buying into another battery system, the same principle carries straight across platforms — Milwaukee M18 owners, for instance, step up to the Extreme Series Train Horn for Milwaukee® 18v Battery in the 150 dB+ tier. But for the V20 owner, there's no reason to switch ecosystems just to get loud. The Quad already hits 140 dB on the batteries you own.
FAQ
Do I have to buy a battery from BossHorn?
No. The whole point of the Craftsman-specific dock is that your existing V20 packs work. If you'd rather keep your tool batteries on the tools, BossHorn sells compatible 20V packs and chargers as optional add-ons, but they are not required.
Will a small 2 Ah V20 pack really run a 140 dB quad horn?
Yes. Volume comes from voltage, and a 2 Ah pack delivers the same 18 volts nominal as a 9 Ah pack. The small pack just runs out of blasts sooner. For occasional use it's plenty; for all-day signaling, step up to a 4 Ah or larger.
Do the newer V20 Advanced (RP) batteries fit the same horn as my old V20 packs?
Yes. Craftsman's V20 line is one platform — every V20 battery, including the Advanced 3.0 Ah and 6.0 Ah packs, shares the same interface and is compatible with every V20 tool. Any of them mounts on a Craftsman-dock horn.
Is Craftsman V20 the same as DeWalt or Black+Decker 20V MAX?
They're all 20V MAX systems built around the same 18-volt-nominal cell math, but the battery feet are shaped differently, so packs don't cross between brands without an adapter. The clean answer is to get the horn built for your dock. If you're curious whether cross-brand adapters are worth it, we cover that in the adapter guide linked below.
Can one horn accept both Craftsman and another brand's batteries?
No. Each horn ships with one brand-specific dock. If your shop is split between Craftsman and, say, Ryobi, pick the horn for the brand where you own the most — or the biggest — packs.