This past weekend, I had a little scare with my nearly three year old 7D.
Friday, I charged both LP-E6s (genuine Canon) in preparation for a trip to a seaside wildlife refuge on Saturday. Installed them in the grip, and I was set.
Saturday, went to the refuge, and shot about 1,800 images over the course of 12 hours or so, using a 100-400. There was an occasional light rain, but I was mostly in the car, and in any event, the camera got little more than sprinkled on. It was never "wet".
Sunday, went to another refuge, and was happily shooting hummingbirds and goldfinches at the wildflowers. Suddenly, I would get one image, but the second in the burst would bring on an "Error 30". This went on for some minutes.
Thinking it could have been more water than I thought from Saturday, I started by removing the grip, and trying each battery individually. Once I got a short burst, but that was all. And another time I briefly saw the "set clock" screen before it shut down again. I also tried it without the lens, but it still would not power up.
By this point, the camera wasn't even turning on, just a blinking battery outline in the top LCD. So, I packed things up for the day. I'd shot about 200 more images on the day.
Got home, and charged the LP-E6s again. Both started at one blink. When the first was charged, I tried it in the camera again. Still nothing.
Monday, I stopped in at a home center and picked up a new CR1616 coin cell. I figured I didn't have anything to lose by changing it, even if the 7D would need to go to Canon.
Got home, popped in the new coin cell, and all is well! Grip, both batteries are fine, and even better, all the photos from the weekend had the proper date and time.
A good outcome, to be sure, but I was a bit surprised that there was no warning at all that the coin cell needed replacing.
So, just thought I'd remind folks, if they don't already, to carry a spare coin cell, especially if the one in the camera is more than 2 years old. They're only $4, and last a long time in storage. The ones I got said (in the fine print) they were good through sometime in 2021 in storage!