Just had some weirdness happen. Had a Promaster EN-EL3e fail completely and without any warning. Used it a month ago and it held a full charge, and was rated as 'new' by the nikon battery status monitor thing. Now it won't hold enough charge to turn on the camera (D300).

This was a fairly low used battery, and not subjected to any harsh conditions. Ive never had a lithium ion battery fail like this. Anyone experience a sudden and total battery failure?

With 3rd party batteries, yes.  An EN-EL3 copy on the D100.

All my 11 year old Nikon EN-EL3 batteries are still working great, and the Nikon EN-EL3E batteries that came with the D200 6 or 7 years ago also good and still being used regularly in the D300s.

3rd party batteries fail or loose holding a charge pretty fast, like in 4 to 6 months of average use.

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Lithium Ion batteries tend to fail very suddenly rather than declining gradually. I've had that happen a few times, with Canon and independent makes. I've also seen it with phone batteries. They seem to be performing normally one day and will not hold a charge the next.

While no where near as critical as memory cards, batteries are up there in the list since you can't just chuck easily available batteries like AAs in most cameras.

I don't know what sort of "special sauce" Nikon uses in their OEM batteries, but the 2 third-party batteries I've used have problems of one sort or another, while Nikon OEM batteries haven't had any issues (including 8-year-old EN-EL3 batteries for my D70).  The only time my D70 locked up on me was with a third-party battery.  I got rid of it, and haven't had a problem with my D70 since.  For my D300 I purchased a 2000 MAh third-party battery, which should have lasted LONGER than the Nikon 1500 MAh EN-EL3e.  Never did.  Currently (2 years old) it won't hold a full charge and I have it strictly as a backup (originally I rotated between the OEM and third-party batteries).

No more non-OEM batteries for me...

I've had good luck with most of my third party batteries but a couple did cause some really strange problems.

Never had any problems with my third-party batteries.

I avoid 3rd party batteries from little known online store. I bought an 3rd party battery with my 20D in 2005. I noticed no difference compare to Canon's battery today. It still works fine just like my other Canon batteries. I try to keep all batteries at full charge all the time.

I bought some dirt cheap phone batteries from some Amazon sellers, they all failed in a few months. Lesson learned.