The NiMH battery packs (BR-402 or BR-403) bundled with the DS-4000 can be charged while the recorder is resting in its cradle. Connect the cradle to a power outlet using the included AC adapter or the D-7AC replacement AC adapter (sold separately).
The DS-4000 also accepts Olympus AAA NiMH batteries (BR-401), which must be charged externally using this optional charger, and AAA alkaline batteries, which cannot be recharged. Do not attempt to charge the Olympus BR-401 AAA NiMH batteries — or any alkaline batteries — in the bundled cradle.
Verification Source: Olympus Website