Microtek CX4 - Manual (Page 11)

Ensure the polarities of the batteries are placed in the correct positions.
7. Slide back the batteries' compartment cover.
Please pay attention when replacing batteries:
Do not mix used and new batteries.
Do not recharge used batteries or expose them to fire or water.
Replace new batteries as soon as possible after the old batteries have
run out of power. You may use a soft cloth to remove any acid if the
batteries leaked. Clean your hands immediately if the fluid gets onto
your hands.
If you do not intend to operate the projector for a long period of time, take
out the batteries.
10