I have not yet, but one of the great things about this radio is that you can run it off of USB. I run it all day every day and have yet to run it dead because I keep it on USB when I'm near my computer at home or at work (which is most of the time LOL). It also charges while I sleep. I initially was not planning on charging the batteries in the radio, but it's just too convenient for me not to use the internal charger.
What prompted this question was the fact I got my 436 just yesterday. I let it charge all night last night and part of this morning. I took it to work with me tonight, and within two 1/2 hours of it running I started getting the low battery warning. I have not changed any of the settings on the radio., so I guess I need to check all that now.thanks very much for all the input.