Milwaukee is retiring the M18 REDLITHIUM XC5.0 and putting a High Output pack in its place. The new M18 REDLITHIUM HIGH OUTPUT XC5 (48-11-1855) costs $169 and a solvent-resistant version (48-11-1855R) $209. Milwaukee says both deliver 50 per cent more power than the pack they replace, at the same 5Ah.

That framing — more power, same capacity — is the whole story. A battery upgrade that changes the amp-hour rating changes the size and weight of the pack with it; this one does not. Milwaukee places the new XC5 at level 3 on its REDLITHIUM power scale, which it says matches the output of its HIGH OUTPUT XC6.0.

We've elevated the power of the M18 REDLITHIUM HIGH OUTPUT XC5 Battery Pack to a PWR level 3 on the REDLITHIUM Power Scale, while continuing to deliver 5 amp hours of runtime. This power upgrade now matches the power output of our REDLITHIUM HIGH OUTPUT XC6.0 Battery, but in a form factor that is 25% smaller and 30% lighter — Matthew Gabrielse, Senior Product Manager, Milwaukee Tool

Milwaukee attributes the gain to a rebuilt pack: new cell construction, revised electronics and power routing, and better thermal management. The resistant variant adds protection against oils, greases and solvents, which points it at transport maintenance and manufacturing rather than general construction. Both carry a three-year battery warranty.

Availability

Both packs are available now as bare batteries at the prices above. Milwaukee says a starter kit, a 2-pack and a 10-pack of the standard XC5, plus a 2-pack of the resistant version, follow in 2027. The announcement was issued from Milwaukee, Wisconsin, and quotes US pricing.

Why a battery release matters more than a tool release

A pack upgrade reaches every tool on the platform at once, which is why Milwaukee is calling this a system-wide change rather than a product launch. It says the M18 line now runs to more than 300 tools, and that compatibility has held since the system arrived in 2007 — so the constraint on an eighteen-year-old platform is rarely the tools and usually what the battery can push through them.

The 50 per cent figure is Milwaukee's own, measured against its own previous pack, and we have not tested it. Batteries are not a category in our catalogue, so neither SKU has a page here.

Based on a press release from Milwaukee Tool, published 13 August 2026.