HP, IBM, Dell, Sony , and others have had to recall many thousands of batteries in recent years because a number of them went up in flames. People have suffered burns due to aftermarket cell phone batteries that flamed out in their pockets. The FAA recently limited the number of lithium batteries we can have on a plane since the fires they start are almost impossible to extinguish. There are videos on the web that show lithium cells bursting into flames, very impressive! Products have been found with the UL label that UL has no record of ever testing, labels are a lot cheaper than actually paying for testing!
The point is that there is junk out there and who can say with any certainty that aftermarket batteries meet all of the specifications of the OEM batteries?
This is a rhetorical question, since the answer is "no one". Even if battery X meets the specs today it may not tomorrow, when the seller gets them from a different (read "cheaper") supplier. The general consensus is that they work, as most of them will under normal conditions. What happens when something goes wrong is when we find out how well the batteries perform. What happens if a short circuit develops inside the camera, and the protection circuit in the battery is not quite right? Cheap tires and brakes work ok too, until something goes wrong. I will not use them.
If a defect is found the OEM is very likely to recall the batch of batteries, the 3rd party supplier is not. If a problem develops the OEM is likely to pay for damages, the 3rd party supplier will probably go out of business and start up under another name next week.
I understand the need to cut costs, and I am not saying that all aftermarket batteries are bad, most are probably good enough but when cost is of prime importance the first thing that gets shortchanged is testing. The next is usually safety. Others have pooh-poohed all this saying their aftermarket supplier makes better batteries than the OEM (highly unlikely), fine, use what you wish and take the risk.
Of course one specification that we *know* 3rd party batteries do not meet is Canon's profit margin spec!
Yes, this is a little long but maybe it will save someone from damaging their camera, or worse!
