The Festool 577705 BP 18 Li 3,0 Ergo I Battery Pack is a compact 18V lithium-ion battery made for select Festool cordless sanders. This is a battery pack designed for cordless finish sanding with better balance, lower hand fatigue, and cleaner dust-managed work. Model Number 577705. If you use an ETSC 125, RTSC 400, or DTSC 400, this is the battery that gives those sanders their intended handling and unlocks Bluetooth dust extractor auto-start.

What makes this battery different from a standard slide pack is the shape. Festool built the BP 18 Li 3,0 Ergo I around the way its cordless sanders are actually used, not around a one-size-fits-all battery format. The result is a lighter, more ergonomic setup that keeps the tool easier to guide across a surface. On finish sanding, that matters because tool balance affects scratch pattern consistency, edge control, and how long you can work comfortably before your wrist starts telling you to take a break.

The 18V platform and 3.00 Ah capacity are matched to these sanders for practical runtime without making the tool feel tail-heavy. Tool Nut lists runtime at about 30 minutes with a charge time of about 25 minutes, which is a good fit for rotation-based work where one pack is charging while the other is in the tool. There is also a built-in charge status indicator, so you can check remaining capacity before starting a panel, face frame, patch, or between-coat sanding pass.

Bluetooth is the real convenience feature here. When paired with a Bluetooth-compatible Festool CLEANTEC mobile dust extractor, the battery communicates with the system so the extractor starts automatically when the cordless sander is switched on. In real shop and jobsite use, that cuts out a step every time you pick the sander up. It also helps keep dust collection consistent, which is a bigger deal with finish sanding than a lot of people realize. Better dust pickup means cleaner abrasive action, less airborne dust, and less cleanup when the job is done.

This battery is intentionally specialized. Festool is clear that it is compatible with the RTSC 400, DTSC 400, and ETSC 125 cordless sanders, and not suitable for all other Festool cordless tools. That is important buying information. If you need one battery that moves across drills, saws, and grinders, this is not that product. If you own one of Festool's cordless sanders and want the setup that keeps the tool slim and comfortable, this is the right battery for the job.

Charging support is also straightforward. Tool Nut lists compatibility with Festool TCL 3, TCL 6, and SCA 8 chargers. That makes it easy to add this pack to an existing Festool sanding setup without changing your charging routine. Tool Nut also notes that for continuous electrical operation, the 18V battery pack can be replaced with the Plug It mains adapter when that setup makes more sense, especially alongside a mobile dust extractor.

Who should buy this? Cabinet installers, finish carpenters, painters doing prep, remodelers, and woodworkers who already rely on Festool cordless sanders will get the most out of it. It is also a smart spare battery if you want to keep sanding instead of waiting on a charger. The big reason to buy it is not just voltage or capacity. It is that this battery preserves the handling these sanders were designed around while adding Bluetooth convenience for dust extraction.

The Right Battery If You Run Festool Cordless Sanders

The Festool 577705 BP 18 Li 3,0 Ergo I Battery Pack is not trying to be universal, and that is exactly why it works so well.

• Who it's for: Anyone using a Festool ETSC 125, RTSC 400, or DTSC 400 who wants the tool to stay light, balanced, and easy to control through finish work.
• Why it stands out: The ergonomic shape and Bluetooth dust extractor integration make it more useful than a generic replacement battery.
• Worth knowing: This is a specialized pack for select Festool sanders, not a go-anywhere 18V battery for the full cordless lineup.

• Which tools does this battery fit? It is compatible with Festool ETSC 125, RTSC 400, and DTSC 400 cordless sanders.
• Can it start a dust extractor automatically? Yes. Its Bluetooth feature can trigger a Bluetooth-compatible Festool CLEANTEC mobile dust extractor when the sander is switched on.
• Is this battery compatible with all Festool 18V cordless tools? No. Festool states that it is not suitable for all other cordless machines.
• What chargers work with it? Tool Nut lists Festool TCL 3, TCL 6, and SCA 8 chargers as compatible.