Motorola Droid 4 is also known as XT894. It uses a non-removable battery which is covered by a huge sticker. Before you tackle that sticker you have to remove the micro-SIM cover first. Please see below picture.

When that sticker is removed, you can see the battery. However the battery is fixed by several screws, so you have to take the screws down.

Finally the battery is revealed.
Type: Li-Ion
Voltage: 3.7V
Capacity: 1785mAh
Replace Code: SNN5905A, EB41
Compatible with Motorola Droid 4, Motorola XT894