Uniden BCD396XT Reference Manual page 204

If the scanner detects an illegal voltage (voltage outside the allowable range), it displays Voltage
and you cannot turn on power.
I llegal Voltage
When the scanner is turned on:
If the battery is good, the scanner charges the battery and it operates ordinarily. When the scanner
cannot judge the battery to be a good one at once, the scanner checks the battery and the battery icon
is displayed.
If the scanner judges the battery good, the scanner starts charging and the battery icon disappears.
If it cannot regard the battery as good within 60 seconds, the scanner stops checking and the battery
icon blinks.
204