Short answer up front: if you already own Craftsman V20, Bosch 18V, or Ridgid 18V power tools, a train horn gun built for your platform runs off the same batteries — no adapter, no separate horn pack, no wiring. These three second-tier systems are every bit as horn-ready as the big four (Milwaukee, DeWalt, Ryobi, Makita). Below is exactly why each one works, plus the runtime math and the one storage habit that keeps your pack from going flat.
The short answer: all three platforms are horn-ready
A train horn gun is just another tool that hangs off your battery. It has a built-in air compressor that spins up the instant you squeeze the trigger and stops the moment you let go. Any 18V-class slide-on pack that powers your drill or impact driver has more than enough punch to drive that compressor. Craftsman V20, Bosch 18V, and Ridgid 18V all use the same five-cell lithium-ion architecture as the better-known brands, so a horn designed for their mount treats your battery exactly like the tool it came with.
The catch is the physical mount. Each brand uses its own rail-and-terminal shape, so you buy the horn gun built for the packs you already own. Get the right mount and the pack clicks on the same way it does on your saw. For a full brand-by-brand rundown, our train horn battery compatibility chart by brand lays out every system at a glance.
Craftsman V20: 20V MAX is the same 18V battery
The "20V MAX" label on a Craftsman V20 pack causes a lot of needless worry. It refers to the peak voltage right off the charger; the nominal voltage during actual use is 18V. That's the same five-cell lithium-ion math behind every "18V" and "20V MAX" battery on the market — five cells in series at 3.6V nominal each works out to 18V. A horn gun's compressor is tuned for that window, so it spins to full pressure on any V20 pack.
Better still, the V20 line is fully interchangeable. Craftsman sells V20 batteries in 2.0Ah, 4.0Ah, and 6.0Ah capacities, and every one of them shares the same physical slide mechanism and electrical terminals — the only difference is the amp-hour rating, which sets your run time. The compact 2.0Ah from your drill kit and the bigger 6.0Ah you bought for the lawn tool both fire the same horn. You're not dedicating a battery to the horn; you grab whichever V20 pack is charged.
Bosch 18V: one platform, forward and backward
Bosch's 18V system is one of the most stable battery platforms around. Bosch designed its CORE18V line for both backward and forward compatibility with all Bosch 18V tools and chargers — meaning a current high-capacity pack drops onto an older tool, and an older slim pack drops onto a new one. That same consistency is what makes the platform a clean match for a horn gun: whatever 18V Bosch pack you own slides on and delivers the steady 18V the compressor needs.
If you run Bosch on the jobsite, you may also recognize the AMPShare badge — Bosch's shared 18V system that a growing list of partner brands like Fein and Rothenberger build to. The practical upshot for you is simple: a Bosch-mount horn gun lives in the same battery ecosystem as the rest of your 18V Bosch kit, so the pack on your drill is the pack on your horn.
Ridgid 18V: any generation fits, and the LSA is a bonus
Ridgid's 18V batteries are 100% compatible with all Ridgid 18V tools and chargers, across any generation of the pack — an older slim battery and a current MAX Output pack both fit the same tools. With 30-plus Ridgid 18V tools sharing that single interface, a Ridgid-mount horn gun simply joins the lineup. Squeeze the trigger and the compressor runs off whatever 18V Ridgid pack you slide on.
Ridgid owners get one extra perk worth mentioning. Ridgid's Lifetime Service Agreement gives the original registered owner free replacement batteries, parts, and service on qualifying tools for life. That applies to your Ridgid batteries, not to the horn itself — but it means the packs powering your horn are some of the cheapest to keep healthy over the long haul, as long as you registered them within the window. If a horn battery ages out, your covered Ridgid pack is a free swap.
What about Hart, Bauer, and Kobalt owners?
The same logic covers the warehouse-store brands. Hart (Walmart), Bauer (Harbor Freight), and Kobalt (Lowe's) all run their own 18V/20V MAX five-cell lithium-ion packs with the identical 18V-nominal chemistry — so each has a dedicated horn gun built for its mount. The rule never changes: pick the horn that matches the battery family in your garage, and your existing packs power it. If you're cross-shopping platforms or own tools from more than one brand, the compatibility chart above is the fastest way to confirm which mount you need.
How many blasts per charge?
Because the compressor only draws current during the split second you're holding the trigger, a train horn gun is remarkably easy on a battery. Let go and the draw drops to almost nothing. The lever that sets blast count is amp-hours (Ah): multiply the pack's 18V by its Ah to get watt-hours (Wh), the real measure of stored energy. Voltage is fixed across all three platforms, so Ah is the only variable.
- 2.0Ah × 18V = 36 Wh
- 4.0Ah × 18V = 72 Wh
- 6.0Ah × 18V = 108 Wh
Blast count scales almost linearly with watt-hours, and the math is identical whether the pack says Craftsman, Bosch, or Ridgid on it. Here's a practical ballpark — treat a "short toot" as a roughly one-second honk and a "sustained blast" as leaning on the trigger for two to three seconds:
| Battery pack | Watt-hours | Short toots (~1 sec) | Sustained blasts (2–3 sec) |
|---|---|---|---|
| 2.0Ah | 36 Wh | ~500+ | ~150+ |
| 4.0Ah | 72 Wh | ~1,000+ | ~300+ |
| 6.0Ah | 108 Wh | ~1,500+ | ~450+ |
These are estimates scaled off real-world blast claims and the watt-hour math — pack age, cold weather, and how long you hold the trigger all move the needle. The takeaway: even the smallest pack you own is good for hundreds of honks, and a mid-size 4.0Ah will outlast nearly any event you'd bring it to. The same scaling holds on other platforms too, including the Ryobi ONE+ 18V system.
The 5-hour rule: unclip the pack between uses
One habit trips people up regardless of brand. If your horn gun has a wireless remote, the receiver sits in a low-power standby mode listening for the signal even when you're not honking. That draw is tiny but continuous, so a battery left on the horn slowly bleeds down over a day or two. The fix is simple: pop the pack off the horn whenever you won't use it within about five hours. The battery loses almost nothing sitting on a shelf — only the standby receiver drains it — so an unclipped pack stays ready for weeks. Horns without a remote have no standby draw, but unclipping the pack for storage is still good practice.
What's included
Loudness comes from the trumpet configuration, not the battery brand. If you want the most volume on the family, the 5-Trumpet Horn Gun for Milwaukee® 18V Battery is the loudest in the lineup — and the same design is offered for every major platform, so you can match it to the packs already in your shop.
FAQ
Is a Craftsman V20 "20V MAX" battery too much voltage for the horn?
No. "20V MAX" is the peak voltage off the charger; the nominal running voltage is 18V, the same as every other 18V-class pack. The horn's compressor is built for that range, so any V20 battery fires it without issue.
Will an old Bosch 18V battery still work on a new horn gun?
Yes. Bosch designed its 18V line for backward and forward compatibility, so an older Bosch 18V pack shares the same mount and fires the horn. An aging pack just won't hold as many blasts as it did when new.
Does the Ridgid Lifetime Service Agreement cover the horn?
The LSA covers your registered Ridgid batteries, tools, and chargers — not the horn gun itself. The benefit is indirect but real: the Ridgid packs that power your horn are free to replace for the original registered owner if they wear out.
Do I need to buy a special battery for any of these horns?
No. Each horn uses the same batteries you already own for that brand's tools. Larger amp-hour packs simply give you more blasts per charge. You only buy the horn built for your platform's mount.
Why is my battery dead even though I barely used the horn?
Almost always the wireless-remote receiver's standby draw. Leave a pack on the horn and it slowly drains. Unclip the battery when you're done — especially if you won't use the horn within about five hours — and it stays charged.