That little battery - what does it really do?

We hear, over and over, that when someone has camera trouble they should remove the main battery and the small watch battery "to reset the camera". Canon tech support has told people this, too.

Many "experts" on POTN have said that the watch battery keeps the memory powered that holds your custom settings and adjustments.

In my Canon DSLRs (300D, 30D and 50D) this is not true. All the watch battery does is keep the date/time clock running when the battery is removed. Nothing more.

These cameras of mine worked just fine with the watch battery removed, as long as I didn't mind resetting the date/time after removing the battery. Even when the power switch has been turned off (on the 30D and 50D, not sure about the 300D with power switched off).

I've used my 50D for the last three days with the watch battery in my pocket.

So this got me to wondering: is this true of all Canon DSLRs?

I haven't used any 1D or 5D models, and none of the newer Rebels, so I don't know.

But we can find out! Calling for adventurous Canon owners - give it a try! Let us know.

I have a half-memory that says some later Rebels don't even have this battery - true?

I can speak for the 300D (original Digital Rebel), 30D and 50D.

Anyone else?

-js

If you pull out the main battery to recharge it, does it remember custom function settings? For example, if you configure it to remove AF from the shutter button does it remember that setting?

krb wrote in post #10825477
If you pull out the main battery to recharge it, does it remember custom function settings? For example, if you configure it to remove AF from the shutter button does it remember that setting?

Yep. On all three of my cameras all custom functions were retained. Except AEB, I suppose, which is set to shut off with power off.

-js

The newer Rebels (450D/XSi, 500D/T1i, 550D/T2i) don't even have those little batteries. They have a little capacitor or rechargeable on board to do the same thing.

Honestly the advice to pull both batteries seems silly but they are really trying to clear the settings for all the users who have messed themselves up and don't know it. All the "it works fine in auto mode but not in creative" which means they've set some custom function wrong and they don't know what it is, while the auto modes override those settings. There is a reset function and I don't know why people don't suggest that first, always the suggestion is pull both batteries and wait half an hour when a proper reset would probably do the same or better in seconds...

i Just did it on my 1D3..left it out for about 30seconds. None of my settings changed in the camera. Could this possible clear some kinda of internal memory storage thing..like a cache and kinda reboot the camera like you do with a PC

I've never removed the little battery from any of my cameras...

FWIW, The 7D owner's manual describes the battery as the 'date/time (back-up) battery' so I guess that's all it does.

it make sense, as they probably use flash memory to store custom setting.

tested functions cleared by removing both battery & cmos battery for 5 minutes.

10D = Date & Time, and CF functions cleared (and yes I set shutter release if no cf card to "not possible" afterwards)
20D = Date & time only (mirror lockup set to test cf functions)
1D MK II = Date & tme only
1D MK III = Date & time only

That's an interesting result with the 10D. I say that because the 10D and the 300D use mostly the same firmware, except it's crippled in the 300D.

Lots of us installed the Russian hack that enabled some of the 10D features on our 300Ds.

-js