If you've already got BLACK+DECKER® 20V MAX™ packs charged up in the garage, you're one slide-click away from a 140 dB train horn. Here's exactly what fits, what doesn't, and the one situation where an adapter actually enters the picture.
The short answer: your BLACK+DECKER® packs work — no adapter needed
BossHorn builds the Quad Train Horn for BLACK+DECKER® 20v Battery with a native BLACK+DECKER 20V MAX battery mount built into the handle. Your pack slides on exactly the way it clicks into a drill or a string trimmer — no adapter plate, no wiring into your truck, no air tank to plumb. Pull the trigger or hit the included wireless remote (160 ft range, with an optional long-range remote that reaches up to 2,000 ft) and four powder-coated aluminum trumpets push out up to 140 dB.
That's the whole answer for most people. If you stopped reading here, you'd be fine. The rest of this guide covers the details that trip people up: why your BLACK+DECKER packs will not fit a horn built for another battery mount, why Craftsman® and DeWalt® packs won't fit yours even though all three brands share a parent company, and which battery size actually makes sense for a horn.
BLACK+DECKER® 20V MAX™ basics: what "compatible" actually means
BLACK+DECKER runs its 20V line under the POWERCONNECT™ name. The promise is simple: every BLACK+DECKER 20V MAX lithium-ion battery works across the brand's 20V MAX power tools, lawn-and-garden equipment, and home cleaning products. One pack, many tools — and a BLACK+DECKER-battery-compatible train horn simply joins that list as one more tool your existing packs can run.
Two spec details worth knowing before you shop:
- "20V MAX" is a marketing number. BLACK+DECKER's own spec sheets state the maximum initial battery voltage, measured with no workload, is 20 volts, while the nominal voltage is 18. That means the platform is electrically an 18-volt system — the same math DeWalt® uses for its 20V MAX™ line and most "20V" homeowner brands use for theirs.
- The pack sizes are modest. BLACK+DECKER's mainstream packs run from the 1.5Ah LBXR20 through the 2.0Ah LBXR2020 up to a 4.0Ah LB2X4020. Higher-capacity packs in this mount exist, but they're third-party.
For the horn, that capacity range is plenty. A train horn draws power in short bursts, not continuous runtime like a saw. On a standard 2Ah pack, the BLACK+DECKER-compatible model delivers 500+ short blasts or roughly 200 sustained two-second blasts per charge. The horn is rated for packs from 2.0Ah up to 12.0Ah, so even the smaller batteries that came bundled with your drill kit will run it all weekend.
Same parent company, different batteries: the BLACK+DECKER® / Craftsman® / DeWalt® confusion
Here's the question that fills tool forums: Stanley Black & Decker owns BLACK+DECKER, DeWalt, Craftsman, and Porter-Cable®. Same corporate parent, similar-looking 20V slide packs — so they all interchange, right?
No. Each brand uses its own rail geometry, terminal layout, and electronics. A BLACK+DECKER 20V MAX pack will not click into a Craftsman V20™ tool, a Craftsman pack won't mount on a DeWalt 20V MAX tool, and neither of them fits BLACK+DECKER equipment. The shared ownership is a business fact, not an engineering one — Stanley Black & Decker deliberately keeps the battery platforms separate, with BLACK+DECKER positioned for homeowners, Craftsman in the mid-range, and DeWalt for the pro trades.
The same separation applies to battery-powered train horns. A horn built with a Craftsman V20 mount needs a Craftsman pack, and a horn with a DeWalt mount needs a DeWalt pack. That's why BossHorn builds a separate model for each platform instead of one "universal" mount that fits nothing well. If your garage actually runs on one of the sibling brands, start with the right guide instead: we've covered Craftsman V20 compatibility and DeWalt 20V MAX compatibility in their own articles.
So when do you actually need an adapter?
Only in one scenario: the battery you own and the horn you want don't share a mount. Say you already bought a horn with a DeWalt-style mount and later switched your tool collection to BLACK+DECKER packs — a third-party cross-brand adapter can bridge that gap. These adapters exist in both directions (BLACK+DECKER pack onto other brands' tools, and other brands' packs onto BLACK+DECKER-mount equipment) and typically sell for about $28 to $41.
Three honest caveats before you go that route:
- They're all third-party. No adapter is made or endorsed by BLACK+DECKER or any other battery brand, and using one can affect tool and battery warranties.
- They add bulk and a failure point. An adapter stacks a second set of contacts between pack and horn — one more thing to work loose under vibration in a truck bed.
- They usually cost more than they save. At $28–$41, an adapter is a meaningful chunk of the price difference between horn models. If you're buying fresh, just buy the horn that matches the packs you own.
We break down the full adapter landscape — which brand pairs have adapters, which don't, and when a DIY kit makes more sense — in our cross-brand battery adapter guide.
Which battery size should you run on the horn?
Short version: the 2.0Ah pack that came with your drill kit is the sweet spot. Here's the practical breakdown:
| Pack | Capacity | On the horn |
|---|---|---|
| LBXR20 | 1.5Ah | Below the horn's 2.0Ah minimum rating — keep it for your drill |
| LBXR2020 | 2.0Ah | 500+ short blasts per charge; lightest option the horn is rated for |
| LB2X4020 | 4.0Ah | Roughly double the blasts; a bit heavier on the handle |
Because the horn only sips power in bursts, chasing a bigger battery buys you blasts you'll likely never use in a single outing. Weight matters more: a smaller pack keeps the horn easy to grab one-handed from a truck cab or boat console.
One more honest note on platform choice. The BLACK+DECKER-compatible model tops out at the 140 dB Quad tier. BossHorn's loudest 150 dB+ tiers — like the Extreme Series Train Horn for Milwaukee® 18v Battery — currently ship for the pro platforms (Milwaukee® M18™, DeWalt 20V MAX, Ryobi® 18V and others). If maximum output matters more to you than using the packs you already own, it can be worth entering a second battery platform to get there.
FAQ
Will a DeWalt® or Craftsman® battery fit the BLACK+DECKER-compatible train horn?
No. Despite the shared Stanley Black & Decker ownership, each brand's pack has different rails and terminals. Buy the horn model that matches your packs, or use a third-party cross-brand adapter with the caveats above.
Do I need to buy a battery to use the horn?
The horn ships without a battery, because most buyers already own BLACK+DECKER packs — that's the whole point of the platform. If you don't, a compatible 20V battery and charger are available as add-ons at checkout.
Is the 18V nominal voltage a problem? The horn says 20V.
No — they're the same thing measured two ways. "20V MAX" is the peak voltage of a fresh charge with no load; 18V is the nominal working voltage. Every tool and horn built for this mount is designed around that same pack.
Can I use aftermarket BLACK+DECKER-compatible batteries?
The horn accepts any pack with the BLACK+DECKER 20V MAX mount, from 2.0Ah to 12.0Ah — which includes third-party packs, since official BLACK+DECKER batteries top out at 4.0Ah. Stick to reputable sellers; cell quality in no-name packs varies a lot.