Canon 30d and Battery Life

[Swimmer]

I have the Canon battery and a Stirling Tech 1800ma battery. Probley only about 30 hours total on each. With the Tamron 28-75 lens, the batteries would last for several hours of "continuous" use. Maybe the Canon 100-400 IS lens is a battery blaster...it seems like I can only get about an hour or less of "continuous" use with that lens (I'm certainly not complaining though ). Is this normal?

[Steve Foss]

Swimmer, that's not normal at all. IS lenses take about 30 percent more battery power, but I shoot the 20D with two batteries in the battery grip all day long with the 100-400L IS and often don't need to change batteries at all. If, however, you're staying focused on a subject for a long time with the IS engaged, you'll use up battery a lot faster than if you don't keep the IS going. Maybe that's what you mean by "continuous use." There are times when a person has to lock focus and compose the image and keep the lens ready and IS on in order to wait out a bird or animal to turn just the way you want it, but unless that's the case, I don't keep the shutter button depressed half way for any length of time at all between shots.

IF you were engaging the image stabilization a lot and IF your batteries were short of full charge already and IF it was quite cold out, which drains batteries, then with all those factors combined I could see the scenario you presented. Other than that, I don't know what it might be.

I'm pretty obsessive about my batteries. Even if I only shoot for half an hour, I pull them from the camera when I get home and charge them fully. Many types of batteries, if run down and not charged back all the way, will never achieve their maximum charge again, and I've never wanted to take that chance.

Since the SterlingTek batteries are so inexpensive, Swimmer, it might not be a bad idea to plop down the extra $30 for the set of two and make sure they're totally charged after you get them and then see how things go. Totally flat batteries for the 20D/30D will recharge completely in 3 hours on the Canon chargers. I always leave them in longer, just to be sure, which doesn't hurt them.