Depending on how flat your batteries are. If my laptop closed down from lack of power and I restart it, it typically lights up for a second, maybe even displays the IBM screen and then dies down again. The battery symbol will be orange (signalling low power) during that entire time.
In the unlikely (that has so far not happened to me, and I have to think back a long time to remember the last time it happened to my dad) event that they do ask you to prove it to be working, start off by explaining that the battery is flat, you forgot your charger at home or borrowed one off a friend and state that you may only see a quick light-up of the display before it dies again. I think that should be enough.
Alternatively, try to borrow a cable before you leave and charge your laptop quickly. Assuming a somewhat popular brand, there should be someone around somewhere with a similar one.
I would definitely not put the laptop into checked luggage because of the possibility of it breaking due to rough handling. As per this related question, it seems okay to do so though. What seems forbidden is to put the lone battery without the surrounding laptop into checked luggage.
And if you argue that you want to take out the batteries and just check in the laptop — well, think about it. Imagine you are a security official and a traveller has laptop batteries but no laptop? Remember, they cannot check what you checked in at the detectors. I can only imagine a load of questions popping up that I really wouldn’t want to deal with.