Question: Can NiMH batteries be charged in the DS-4000?

The NiMH battery packs bundled with the DS-4000 can be charged in the recorder when using the included cradle and AC adapter.  The optional replacement AC adapter D-7AC (sold separately) may also be used to charge the battery packs in the cradle.

If you opt to use the Olympus BR-401 AAA NiMH batteries to power the DS-4000, note that these batteries cannot be charged in the cradle. However, they can be charged externally in the BU-400 NiMH Battery Charger, which is available exclusively in the B-90SU NiMH Quick Charger and Battery Set. (The batteries included with the set are AA, not AAA.)

Replacement battery packs, cradles and AC adapters are available from Olympus Professional Dictation Products dealers.
Verification Source: Olympus Website