Intermittent power problem Canon 5D Mark iii

[CW7647]

My Canon 5D Mark iii (2 years old) has an intermittent power problem, as described below. It may simply be a question of cleaning the terminals that the battery connects to. I haven’t tried since I can’t reach them at the bottom of the battery compartment.

Details as follows:

• this is a recent problem in the last 3 weeks
• the problem occurs with all three Canon batteries that I use
• from time to time when the power is on, the camera suddenly loses all power and displays an “empty” battery image
• sometimes it happens of its own accord while no demand is being placed on the camera
• but more usually it occurs at the moment of focusing (I use back focus on the * button)
• it is often fixed by turning the power off and then on again. This fixes it half the time
• it is always fixed by turning the power off, removing and then re-inserting the battery
• needless to say this is very annoying!

Since coming back from a trip, while transferring images from the camera to my computer, I noticed that the (almost) full battery started showing “empty”.

The transfer was completed successfully, and when the camera was disconnected from the computer, the battery showed that it had lots of charge left. Very puzzling!

[ebiggs1]

It could be lots of things but despite the fact you have three batteries, I still think it is the batteries.  Can you get a brand new fresh battery.  Make sure it is not from the same place where you bought the batteries you have now.

Second thought is your charger.  Can you try a different one?

[TCampbell]

It sounds like either the battery terminals aren't getting a solid contact or there's a fault (something loose or grounding out) inside the camera.  But if something were genuinely loose or grounding out inside the camera, then power cycling or even re-inserting batteries would probably not fix it -- which makes me suspect it's still something outside the camera.

Are any of the batteries new, or are they all about the same age as the camera?

Batteries only last a few years but it'll depend on how they were used.  In other words if all three were used about the same and enough charge cycles to be at the end of their reliable life... it might be time to replace them.  

It's difficult for the internal battery terminals to get dirty unless the battery itself had something on the battery iteself when you inserted it.  You can try a bit of denatured alcohol on a cotton swap to reach in and clean the terminals.  Also, inspect the batteries to make sure they're all clean.