Uniden UBC73XLT Owner's Manual page 16

WARNING!
Set REG. ALK. BATT./NI-MH BATT. to NI-MH BATT.
only if you are using rechargeable batteries.
Never attempt to recharge non-rechargeable
batteries. Non-rechargeable batteries can get hot or
burst if you try to recharge them.
4. Install two batteries in the compartment as
indicated by the polarity symbols (+ and -)
marked inside.
Setting Up Your Scanner
16