My first non-OEM battery was a Lenmar battery for my then state of the art, early 90s' Panasonic mini DV camcorder (yep, at $3,500 and it was used). Since then, I have used third party batteries on most of my cameras from the original Digital Rebel 300D to the 1D Mark II and everything in between. Many people worry that cheap batteries will ruin their expensive camera, but from my own experience, the occurrence is rare.
Why third party batteries? One word: cheap.
Let's do a bit of math. The original Equipment Manufacturer (OEM) battery for the 1D Mark II was roughly $250 plus taxes. I ordered TWO third party replacement batteries for under $50, including shipping. These batteries lasted much longer than the Canon equivalent.
The LP-E8 battery for the Rebel 550D (T2i) is $85CAD plus taxes. I ordered TWO third party equivalent, for the price of $12USD (yes, two batteries for twelve dollars), and that included shipping. Again, these batteries last longer than the Canon batteries. Yesterday, I shot 375 RAW files, plus a few minutes of video, on the third party battery. At the end of the day, the battery meter still showed full. I shot another 130 RAW files today, and the battery still shows 2/3 full.
For the price paid, I am more than happy with the results. Are there any really bad after market batteries? For sure. I ordered some for the PSP, and they were a piece of #$%@%. Those were from dealextreme, which I find most stuff I bought were horrible.
I need another battery for the Panasonic G1, and the OEM price is $90CAD. Panasonic disabled support for unauthorized third party batteries, but guess what? Compatible batteries are available from many eBay sellers, fully compatible with the latest firmware. I think it was just greed on the part of Panasonic, trying to force everyone to buy their overpriced battery. If they were concerned about third party battery damaging the cameras, they should just state clearly in their manual that damage by third party battery is not covered under warranted. Let the user decided and take the risk. Can you imagine your car manufacturer says that you can not use third party engine oil on your car?
Sorry Panasonic, I won't be buying your overpriced battery either.
Batteries for the Rebel 550D. They are almost identical except writing on the battery.