How to test a battery using the camera

[Mike S.]

We have a Canon SD550 compact that uses a 3.7 volt, 790 mAh, Li-ion, NB-3L battery. This is the original Canon battery that came with the camera which is about 2 years old. We only used the camera very occasionally for special events like weddings, birthdays, Christmas, etc. The battery seems to work fine and allows taking pictures with the LCD display on but we only take about 20 photos per event.

Now we will be going on a trip and I want to test the battery to see if it can hold a sufficient charge similar to a new battery since we might be taking a lot of pictures per day. Is there a way to determine this by using the camera without having to keep snapping pictures until the battery dies? Something like leave the camera on with the LCD display on and see how many hours the battery lasts?

[Glasstream15]

For me, a battery that's 2 years old would become a spare. I would get a new one. Li-Ion batteries don't care if they are used or not, they slowly lose the ability to hold a charge. And 2 years old is probably down to about half life.

[griptape]

I bought this:
http://www.newegg.com/Product/Product.aspx?Item=N82E16830994011&Tpk=NB3LA
when I first bought my SD550. It's served me extremely well, and is certainly cheaper than the Canon branded battery.