Battery life on Nikon D3100?

Just bought it and was curious should I buy a back up battery for when I'm out taking pictures. Yes, I'm just starting out, I like to take pictures so I thought I would buy something more than a point and shoot.

Buy a backup battery. Battery life depends on how much you use it, whether you use a flash, type/brand of battery.

Battery life

* how many photos can be shot on a single charge (550 shots in the case of the D3100)
* how long can you use the battery before needing to replace it.

I have Nikon Li-ion batteries that are over 10 years old and they still work flawlessly.

The key is to NEVER use the battery until it is completely flat and if you happen to, make sure you recharge them right away. After about 400 charges, the battery will not hold a charge as long as it did when new. This is why it is important that you only recharge the battery just before you intend to use the camera (overnight is what I do)

I always buy a second battery for every camera I own.

Yes and No

Its battery life is fine fine. It will probably get around 500 shots. Your memory card will be half full at the time your battery is complaining.

But as always it can't hurt to have a second battery. After all you never know when you are on a short trip with the family and just before that lovely sun going down your battery is going down. You rather don't want that right?

Personally I own another DSLR and seriously I only have to change batteries at the end of a day to the Zoo with going out to dinner etc.those batteries last a long time.