Metabo HPT®'s MultiVolt™ pack is one of the cleverest batteries in the cordless world — a single pack that powers 36V tools at full voltage and 18V tools with double the capacity. So can it run a 140 dB battery train horn? Short answer: yes, in 18V mode — but there's a catch you need to know before you spend a dollar.
The short answer: the battery works — the mount is the problem
Electrically, a MultiVolt pack is more than qualified to run a battery train horn. On any 18V-style tool interface, the BSL36B18 pack delivers 18 volts and a full 8.0Ah of capacity — more stored energy than the 6Ah packs we sell as add-on accessories. A train horn's compressor draws power in short bursts, not continuous runtime, so an 8Ah pack will fire blasts all weekend without blinking.
The catch: BossHorn doesn't currently build a horn with a native Metabo HPT® slide mount, so a MultiVolt pack won't click straight onto any of our models. That leaves you three real routes, all covered below:
- Route 1 — cross-brand adapter: slide your Metabo HPT pack into a third-party adapter and run it on a horn built with a DeWalt®-style mount.
- Route 2 — DIY build: assemble a horn from a DIY kit using a donor Metabo HPT 18V tool shell, so the finished horn takes your packs natively.
- Route 3 — use your second platform: most garages run more than one battery brand — buy the horn that matches the other packs you already own.
How the MultiVolt™ 18V/36V battery actually works
MultiVolt is Metabo HPT's answer to the voltage wars: instead of making you choose between an 18V line and a 36V line, one pack serves both. Inside the BSL36B18 are ten 21700 lithium-ion cells. The tool you attach it to decides the wiring: a 36V tool runs the cell groups in series for 36 volts at 4.0Ah, while an 18V tool runs them in parallel for 18 volts at 8.0Ah. Metabo HPT rates the pack at over 1,440 watts of output, it weighs 2.1 lbs, and the UC18YSL3 charger refills it in about 52 minutes.
Three compatibility facts matter for horn purposes:
- The switch is automatic. There's no selector on the pack — the terminals of the tool determine whether it behaves as a 36V or an 18V battery.
- It's backward compatible at 18V. Metabo HPT states the MultiVolt pack powers any Hitachi or Metabo HPT 18V slide-style tool. That's the mode a horn would use.
- It doesn't work in reverse. A plain Metabo HPT 18V battery will not run a 36V MultiVolt tool — the upgrade path only flows one way.
The smaller BSL36A18 pack follows the same logic at lower capacity: 5.0Ah at 18 volts, 2.5Ah at 36 volts. Either pack lands comfortably inside the 2Ah–12Ah range our horns are rated for, and a horn will only ever see the 18V side. There is no 36-volt advantage to chase here — the compressor is an 18V-class load, and doubling voltage is not how a horn gets louder.
Metabo HPT® is not Metabo® — check which one you actually own
Before you order anything, make sure of which brand is stamped on your packs, because two different companies sell tools under nearly the same name in the US:
- Metabo HPT® is the former Hitachi Power Tools. The North American rebrand took effect on October 17, 2018, after investment firm KKR bought Hitachi's power-tool division and formed Koki Holdings. Same tools, same green livery, same battery rails — only the name changed. MultiVolt is this brand's system.
- Metabo® is the original German manufacturer, which runs its own 18V platform called CAS (Cordless Alliance System), shared with dozens of European pro-tool brands. Metabo CAS packs use a completely different rail and terminal layout from Metabo HPT packs. Nothing in this article applies to them.
Every adapter and donor-shell option below is built around the Hitachi-style 18V slide rail that Metabo HPT uses. If your packs say Metabo without the HPT, the adapter route dead-ends — skip to Route 3.
Three ways to run a train horn on your MultiVolt™ pack
Route 1: a cross-brand adapter on a DeWalt®-mount horn
Third-party adapters that mount a Metabo HPT or Hitachi 18V-rail battery onto DeWalt® 20V MAX™ tools are widely available from Amazon, eBay, and specialty adapter shops. Slide the MultiVolt pack into the adapter, click the adapter onto the Quad Train Horn for DeWalt® 20v Battery, and the horn sees what it expects: an 18V-class pack with plenty of capacity behind it. Four powder-coated trumpets, up to 140 dB, wireless remote included — no vehicle wiring anywhere in the chain.
The honest caveats, same as any cross-brand adapter setup:
- Adapters are third-party products — none are made or endorsed by Metabo HPT or any other battery brand, and most listings are built and tested around standard 18V packs, so confirm a listing explicitly supports MultiVolt packs before buying.
- An adapter stacks a second set of contacts between pack and horn — one more thing to work loose under vibration in a truck bed.
- Adapters generally pass power only; charge the pack on its own Metabo HPT charger.
We break down the full landscape — which brand pairs have adapters and which don't — in our guide to running a train horn on a different brand's battery with an adapter.
Route 2: build one from a DIY kit and a donor tool
The DIY route skips adapters entirely. A DIY Train Horn Gun Kit supplies the quad trumpets, manifold, compact compressor, and wiring; you supply a donor tool — a brushed 18V drill or driver you don't mind sacrificing, whose battery interface becomes the horn's battery interface. Pick a donor that accepts Metabo HPT® 18V packs, and the finished horn takes your MultiVolt and 18V batteries natively, no adapter in the chain. It's a genuine afternoon project, and we walk through every step in our drill-battery train horn build guide.
Route 3: match the horn to your other battery platform
Here's the practical reality: almost nobody runs Metabo HPT exclusively. If there's a Milwaukee®, DeWalt®, Ryobi®, or Makita® pack anywhere in your garage, the simplest move is to buy the horn built for that mount and keep the MultiVolt packs on your tools. The top of that lineup is the Extreme Series Train Horn for Milwaukee® 18v Battery — 150 dB+ output on any M18™ pack, with remote options reaching up to 2,000 ft. Our battery compatibility chart lists every platform we build a mount for, from 18V through 24V systems.
FAQ
Does a train horn ever use the 36V mode?
No. Whether through an adapter or a donor-shell build, the horn presents an 18V-style interface, so the MultiVolt pack automatically runs in 18V mode at its full 18V capacity — 8.0Ah on the BSL36B18. The 36V mode simply never engages, and the horn loses nothing because of it.
Will a MultiVolt pack click directly onto a Milwaukee®- or DeWalt®-mount horn without an adapter?
No. Every battery brand uses its own rail geometry and terminal layout, and Metabo HPT's slide rail doesn't match any of them. Without an adapter, the pack physically won't seat — the same reason a DeWalt pack won't click into a Milwaukee tool.
Do German Metabo® CAS batteries work with the same adapters?
No. Metabo CAS is a separate platform with its own rail, and the Metabo HPT/Hitachi adapters won't accept those packs. CAS owners should go straight to Route 3 and pick a horn matching another platform they own.
What about older Hitachi 18V slide batteries?
They ride the same rail. Hitachi-branded 18V slide packs from before the 2018 rebrand fit the same adapters and the same donor shells as Metabo HPT packs, so both routes work identically — you'll just get fewer blasts per charge from an older, smaller pack.
How many blasts will a MultiVolt pack deliver?
Our quad horns deliver 500+ short blasts on a standard 2Ah pack. A BSL36B18 running in 18V mode carries four times that capacity at 8.0Ah, so charge anxiety is not a factor — the pack will outlast any tailgate, trail day, or hunting weekend.