When shopping for rechargeable batteries for your digital camera, beware of those off brands that are not genuine original equipment manufacturers parts. While I am sure some are okay, there are many that are less than acceptable. Here we're talking specific configuration Lithium Ion batteries, although the same warning applies to Nickel Metal Hydride cells for smaller point and shoot cameras as well.
For example, I have a battery for my Panasonic FZ-30 that arrived dead, was replaced by the seller, (I had to pay to ship the old one back) and it has held only two charges and is now dead again. Fortunately, I also purchased a Panasonic genuine battery as an additional backup, so when the off brand battery failed without warning, I had something to fall back on. The off brand will now go in the recycle bin.
Problem with many off brands is that they are not subject to the same quality control as OEM parts. They can tell you they use bigger cells, heavier duty cells, etc. If everything they do is better than the original, why is the cost so low? Advertising and packaging certainly adds to the overall cost, but remember, quality costs money and you don't get quality for free. If getting the perfect picture at the right time is important, why trust the moment to a cheap battery? Or a no-name memory card. And, no, I don't sell either.
There is also the potential for damage to that high-priced equipment due to a faulty battery, damage that would not be covered under any camera manufacturer's or OEM warranty. Battery failure at a critical time is bad enough, but what happens if the battery shorts out, overheats, or otherwise fails and damages your camera? You're going to be stuck with repair costs. Try and get a no-name outfit whose product fails, to repair your one, two or even five thousand dollar digital camera, even though the camera is only a few weeks or months old. Not going to happen.
As an update, (9/06) I have been reading in numerous reviews and blogs about how batteries fail in use and how they won't charge. Also, how it seems cameras can suddenly have problems after using some aftermarket batteries that have failed. The people then complain that the camera manufacturer charges them a bundle to fix the camera for non-warranty repairs. Just as I warned about earlier! Saving a few dollars on a no-name battery may seem wise at the beginning, but could cost you big in the end.
Further 12/06 update: Some sellers offer a 30 day, 90 day and even a one year warranty on their camera batteries. They must think this increases the sales appeal to you, the consumer. Now ask them if they will also warranty, in writing, against any damage done to your camera by a faulty battery. Not a chance. Put that battery in, fry the electronics and you own it, lock, stock and barrel! No recourse. Oh, they might replace the battery though, if you ship the bad one back. Then you have a new battery and a junk camera. Great!!
Another note is the battery protection circuitry allegedly built into the batteries. Is it there or not? When you buy cheap can you depend on all the bells and whistles to be present, or were they left out to get the price down to where you will grab and go? You have to decide what's right for you.
I shoot many accident and fire photos, and can't afford to be without the right equipment, working right, at the right time. Can you?
Last, but not least, I have a saying that has served me well throughout life. It's true with most everything:
After you jump, it's too late to wish you bought the better parachute!