Welcome to Nikonians! Congratulations on your new D3100.
Camera batteries need several charge and discharge cycles before they reach maximum capacity.
Were you using Live View to capture the 40-50 images? The reason I ask, is Live View drinks batteries.
The intent is to foster a community of "real people" instead of mysterious web-personalities with anonymous screen names. Doing this helps to establish and maintain a safe, civil and friendly environment.
Thanks in advance. Good Luck and Enjoy your Nikons!
I don't have any experience with a D3100; However, I would do what the error message says, and recharge the battery. Then continue to use the camera, and see if it happens again. You should probably try to see if the camera is faulty first, but I recommend always having a backup battery.
Hopefully, others will be familiar with this particular problem.
Battery doesn't sound like it's fully holding the charge. I always buy at least one spare for each of my cameras (for the power hungry ones I'll get two). Get a good battery, confirm it's not the camera or the charger that's the problem.
My D3200 documentation said you can permanently damage the battery if you discharge it to far. When the battery is to low my camera shutter is disabled as well, the way it was designed. I can only guess that yours is the same.
The battery is the original genuine battery that came with the purchase, so I'm hoping it's because I haven't gone through a few charge/discharge cycles.
I'm glad to hear that the D3200 has a feature that disables the shutter to prevent battery damage - at least I know it's probably not a defective camera as I can't imagine the D3100 would be that far off from D3200...
Hopefully in a few days I'm able to see improvement in the charge of the battery...