I did a fair bit of research into expected battery life for the current Garmin latest release watches as I was not sure which I should go for mainly because all the battery info is pretty confusing. But basically if you work out how much tine you spend as smart watch and how much activities at what level you can estimate your use case.
| Forerunner® 935 | Forerunner® 955 | fēnix® 7S – Sapphire Solar Edition | fēnix® 7 – Sapphire Solar Edition | fēnix® 7X – Sapphire Solar Edition | epix™ (Gen 2) | |
|---|---|---|---|---|---|---|
| Smart Watch | 7.14% | 6.67% | 9.09% | 5.56% | 3.57% | 6.25% |
| Smart Watch Solar | 7.14% | 4.55% | 2.70% | |||
| GPS Only | 8.33% | 4.76% | 5.41% | 3.51% | 2.25% | 4.76% |
| All Sat | 10.00% | 7.69% | 5.00% | 3.17% | 6.25% | |
| All Sat Multi | 23.53% | 13.33% | 8.70% | 5.56% | 10.00% | |
| Rainforest (est) | 7.36% | 4.80% | 3.07% | 5.29% |
Note: Smart watch are % per day as claimed by Garmin. GPS Activities% per hour as claimed by Garmin. Rainforest estimate activities are for maxed out all sat multi real world activity observed in reviews.
To work out your use case, count the number of Smart Watch hours and activity hours and multiple it by the appropriate rate. eg my fenix 7X SS and routine over 2 days is 46 hours Smart watch and 2 hours running. Average per day = (46/24 x 3.57 + 2 * 3.07)/2 = 6.49125% per day (100/6.49125 =15.4 days).
I have had some hassles with Fitbit batteries so I data log battery use. I have adapted that to monitor my Garmins. I data log every percent loss in smart watch mode and the battery level at the start and end of any activity in a spreadsheet. This allows me to monito day to day and activity battery use separately.
My observations thus far, the Garmin smart watch battery life is over estimated and real world activity performance is better than the claimed Garmin values. I am seeing a Smart watch of 4-5% per day and activity rate of about 3% per hour on my fenix 7X SS.
