If I have my bcd436 scanner plugged while it also has batteries in it,will it do any harm?\thx for reading.
The 436HP cannot charge it's batteries while also scanning. When you boot it up, with a USB cable connected between the scanner and your PC (or a USB power source), you'll get a prompt asking whether or not you want to enable charging. If you say "yes" by pressing the E/enter key.
Once it has fully started up, if the cable is still connected, you'll be asked if you want to enter serial port mode (for controlling the sanner via a program such as ProScan), or go to :Mass Storage Mode", which is what you need to download programing files from Sentinel (or other software). If the scanner is running, scanning channels, or in Mass Storage Mode, it will not charge the batteries.
The charge function on the scanner is not a "Smart Charger". The length of the charging time is set in the menu. The current provided for charging is low, around 200mah. That's so that when charging an already fully charged battery, it will not overheat and cause damage. You are better off to use an external 'smart' charger, that controls how much charge is being sent to a set of batteries. These also may have functions to recondition a battery that may have acquired a 'memory', which will show as a fully charged battery (based on the voltage it shows), but it really is not, and your scanner, or other battery powered device, will only operate for a very short time.