Sony A7 III How The 'Internal Battery' (date & time) Is Kept Charged In The a7iii Camera

[Paul-WB5AGF]

(background)
I've had my a7iii Camera for four years and in the past year-or-so have sometimes had the problem of the camera asking to have the date & time information entered when it was turned-on.

Until just the past few days I had assumed that the camera had a small board-mounted battery (or 'super-capacitor') which was being kept charged whenever there was a 'regular battery' (charged) in the battery compartment. I now have evidence that is somewhat incorrect.

My standard practice (for several years) has been to keep a charged battery in the battery compartment even when the camera was stored in its camera bag. The fact that I've experienced the problem with the date & time query shows that the 'internal battery' is charged in some other method. (comment) I use an external charger to charge the batteries and so do not routinely use the Sony microUSB Charger plugged into the camera.

On the Web Page:

ILCE-7M3 | Help Guide | Setting language, date and time

Sony says :

This camera has an internal rechargeable battery for maintaining the date and time and other
settings regardless of whether the power is on or off, or whether the battery pack is charged
or discharged.

To charge the internal rechargeable backup battery, insert a charged battery pack into the
camera, and leave the product for 24 hours or more with the power off.

If this is the only way that the 'internal battery' (date & time) is kept charged then everyone who uses an external charger (instead of charging the regular battery while in the camera through the use of the Sony microUSB charger plugged into the camera) would also experience the problem of being asked to have the date and time entered when they turn on their cameras. I suspect that my having had this problem is due to my practice of leaving my a7iii Camera in its camera bag for long periods and only turn it on to take a few pictures (which I immediately transfer to my computer) and then turn the camera off and put it back into the camera bag.

Thus ... I believe that the 'internal battery' (date & time) is also charged when the camera is turned-on (i.e. being used). It is people like me, who only briefly turn-on their a7iii Cameras, and who use an external battery charger, who are likely to have the problem.

From now on I am going to regularly plug the Sony microUSB charger into my a7iii Camera (with a fully charged battery in the battery compartment) to keep the 'internal battery' (date & time) charged.

(signed)

Paul, WB5AGF (my Amateur Radio Call)

 

[maxzoom]

My experience was with a NEX5e. I left the camera unused for over a year and the NP-FW50 battery and the internal supercapacitor became fully discharged. The NP-FW50 had no problem taking a charge but the camera supercapscitor was much more reluctant.I too became frustrated with date and time prompts even though the battery had full charge. It took more than a week but eventually the camera retained date and time. It would seem the charging current for the supercapacitor is exceedingly small and possibly only slightly larger than the supercapacitor leakage plus the current drawn by the RTC system.

 

[Paul-WB5AGF]

Hello 'maxzoom' ;

I agree with your comment "It would seem the charging current for the supercapacitor is exceedingly small"

The fact that Sony says "leave the product for 24 hours or more with the power off" says to me that recharging
the internal supercapacitor (or battery) is a slow process.

I have had the microUSB charger plugged into my a7iii Camera (with a fully charged battery in the battery
compartment) for more than 24 hours and am hoping that this will have recharged the internal supercapacitor
(or battery) sufficiently.

Regards;

Paul, WB5AGF