You may be able to operate your Newton MessagePad with Nickel-Cadmium (NiCd) batteries in the alkaline battery holder. Apple, however, does not support their use and recommends that you use NiCd battery packs designed specifically for the Newton MessagePad.
If you do put NiCd batteries in the MessagePad's alkaline battery holder, each battery must have .22 Amp-hour (Ah) capacity. If you use batteries with a different capacity, the MessagePad may fail to operate and/or may suffer damage.
Alkaline and NiCd batteries function differently in the MessagePad. If you put an alkaline battery holder filled with NiCd batteries into your MessagePad, the MessagePad will treat the batteries as if they were alkaline instead of NiCd. This may cause the MessagePad to shut down more quickly.
Note: The Newton MessagePad will not recharge any batteries that are in the alkaline battery holder. Also, do not insert the alkaline battery holder (with any type of batteries) into the Newton Battery Charger. This may damage both the batteries and the charger.
EXTENDED TIL INFO - *The following information is for Apple Internal & Support Providers Only*