Battery less than 24 hours

4s

Garmin sent me a replacement 4s and it's drastically better. About 0.5% an hour thus far. Chat with support and they will send you a replacement if necessary. They had me try a few things as stated prior, but nothing helped. 

Not completely. Modern chargers can provide way above 500mA. Some fast chargers are even increasing voltage above 5V. 5V/500mA is/used to be standard for USB. If you connect device which has not properly implemented charging to such charger, may pull out more than 500mA. Charger can even wrongly detect device and provide higher voltage. Consequences are pretty obvious.

Smart watches have tinny battery, not much space for electronics, over voltage/current charging protection and can be easily damaged. And in general, batteries do not like fast charging, regardless what marketing says.

Well I have done nothing but charge my 4s with an Anker power strip w/USB port, have never used a fast charger, and the battery life has never been adequate. 

If it is so easy to fry the battery then Garmin needs to put a warning in the product IFU, and also not have their tech support tell us to charge for 4 hours. 

Advertised 7 days on the 4s is true. Everything on except ox and wifi. Used for 24/7 tracking and notifications, occasionally fooling around with it, few manual ox readings, no excersises.

Congrats that 7 day battery life is "true" for your watch. That has not been the case with mine. 12% battery would be day 4 for my 4s. I have NEVER gotten 7 day batt life despite only using it as a step tracker and a device to tell time. 

I know some still have bad battery life. But now you got a proven reference to exchange your watch if yours doesn't hold up like mine.

To give it one more chance before you feel you need to return it, try the suggestion earlier in the thread - after making sure you have updated to the newest firmware, on the watch do a full reset, then charge the watch for at least 2 hours *after* it says 100%.

Choose one of the built in original watch faces that do not show seconds (or turn the seconds display OFF).

With bluetooth and notifications ON, pulse-ox OFF my test made it to 5 days and still had 42% left, calculated drain was .5% per hour.

If you try this test it should give you a baseline as to whether the hardware itself is at fault or its something else.

Just updated today to 3.5.. I will give it a shot as per your suggestions and will get back with the results, I appreciate it.