I know this is not a smart watch but it is related to time and something I found that seems very strange with an Android cell phone. I assume this would also happen with a Smart Watch.
I’m not sure why I decided to investigate this tonight but I have an Samsung cell phone with a removable battery - a Galaxy S5. It is not being used and is not on any cell network. Here is what I did:
- Turned on Airplane mode (it was already on actually since it’s not on a cell network) so there would be no cellular connection - not even for emergency use.
- Turn off Wifi
- Turned off GPS (location completely off)
- Turned off Bluetooth.
All those were actually off anyway but I verified all were OFF.
Checked the time on the phone. 7:30PM correct time…
Removed the back cover and pulled out the battery. I let it sit for 3.5 hours with no battery.
After 3.5 hours I put the battery back in and turned on the phone.
Airplane mode still on
Wifi still off
GPS still off
Bluetooth still off
Time upon boot up was 11:02 PM - the Correct Time!
How could the phone know what time it is when it had no battery for 3 and a half hours and no connection to cellular, the Internet, GPS, Wifi or anything that it could get the time from?
Are our phones / smart watches ever really off? Is there a secret tiny nuclear battery in there? Alien technology? Powered by TIME itself?
I have a couple theories. What are your thoughts?
Alright, here’s my theory.
Some of devices have capacitor which saved power only for time, and we know just for keeping time the power needed is very very low (no screen, no input, etc) and perhaps 3.5 hours is not enough to empty your phone capacitor.
That is one of my theories but having removed the main board in this phone before I am having a hard time seeing any capacitor big enough to hold enough charge to even keep a clock chip running and I’m thinking the clock chip is probably integrated into the CPU. I know a fair amount about basic electronics and while the idea of a capacitor is enticing I still have a hard time imagining there is a capacitor on that board big enough to hold that long. I believe it would take an electrolytic type capacitor of at least some physical size too large to fit on that board to hold a charge at enough voltage to keep anything in the phone running IMO. Even super caps I’ve got drain fairly fast once disconnected from a power source and they are huge in size. I will make a longer test though as that theory is probably the most reasonable. Thanks for giving your thoughts on this!
Even more strange is that my finely tuned computer locked up just as I was posting the above answer… Time is doing strange things right now
I have never dissasebled a smartwatch, but i thought that it maybe has a simililar battery like CMOS battery on pc motherboards
Thanks for your thoughts. I don’t believe there is any type of CMOS battery in cellular phones or watches. My other theory was that during the boot up process it might somehow do a quick check with a cell tower even though it’s not registered and the cell radio is turned off (Airplane mode). However after leaving the battery out for 12 hours it has now lost not only the time on boot up but it thinks it is June of 2017. So best guess is what I said earlier and also Maszter93 that it has some sort of capacitor in there that at least keeps the clock alive for several hours. I know clock chips don’t use much and even with an LCD display on a bedside clock it has run 10 years on a single AA battery. Quite amazing!
As further evidence that Maszter93 and one of my two theories was correct I pulled the battery out of the phone while it was off and put a high quality voltmeter across the terminals on the phone where the battery plus and minus make contact. It was reading about 800 millivolts or 0.8 volts. After a minute or so it had dropped to around 650 millivolts but seemed to be leveling off at that point. So there does seem to be a capacitor in the main board that can hold a small charge for quite a while. I’m guessing that is by design so that when you replace a battery in this unit it does not immediately lose date and time.