What's the input voltage range for a [Wemos D1 board](https://wiki.wemos.cc/products:d1:d1)?

I have a battery pack of 4 AA batteries. This makes 4*1.5 V = 6 V, but I think they can drop as low as 4*1.2 V = 4.8 V. Can I hook the battery pack directly to the input voltage socket? Or is this to much?

What happens when I connect the D1 to the USB to program it? Must I disconnect the battery pack first? Sometimes it would be handy to let the USB cable connected to the debug output on the serial monitor.

I'm aware of [Power Wemos D1 mini from battery](https://electronics.stackexchange.com/questions/300696/power-wemos-d1-mini-from-battery) but that only answers whether 3 batteries are enough.