battery drains 25-30% in 24hrs, in watch mode

Same situation here on my Fenix 5S and my boyfriend's Fenix 5. Both watches batteries are tottaly unusefull since last week. It has happened suddenly in one single day. 

My wife fenix 5s 5 yeras old battery same isue. My frend Fenix 3 still working no problem 7 years old. So its fenix 5 serries isue. Support asked for battery change 250 eur. Garmin going to trash bucket. Wife will never buy again garmin watch. 

So, I'm not done with this! I've now swapped my battery for a brand new one and I can confirm the draining issue is still there. With the new battery my usage has gone from 25% a day to about 21%. This to me says something is in their software that is specifically targeting and draining the Fenix 5. 

I feel this could be a similar situation to Apple's 'battery gate'!!!.

I'm far from done with my investigations but will report back on the findings and more than likely reach out to other users to form a study. Please hang onto your watch incase it's needed.

What annoys me is the lack of willingness of Garmin to listen to reasonable people about a problem with their software that is negatively impacting hardware. It has now cost me time and money to come to a conclusion that they themselves should have come to. Really they should be thanking me, and sending a brand new watch for the work I've done...

I've swapped my battery for a brand new one and can confirm my battery draining issue still exists. I'm leaning towards their software... Funny how it just impacts older models eh...?

So I can now conform this is absolutely not the case as I have just swapped my battery for a brand new one. My battery drain has gone from 25% a day to 21% a day. The problem exists in your software, and is forcing users on older models to upgrade prematurely... I'm far from happy that I've had to spend a considerable amount of my time and effort to reach this conclusion when it's something Garmin should have done after listening to customers.

I'm tempted to decompile some of the firmware updates...

I've swapped my battery for a new one and the main battery drain issues still seem to be there... I'm leaning towards a software issue, which is what I initially believed to be the problem.

Hi! Similar case here. I'm decided to go to the end of the case. 

Please, take a look to this thread, I replied to the OP: Fenix 5S Plus sudden increase in battery drain - fēnix 5 Plus series - Wearables - Garmin Forums

I'm software engineer so I think that I can help.

Also I have 6 pro, one year younger then wife watch, If will be the same after some time, I am finishing with garmin watches too. 800eur watch for 3 years not for me.