Battery is an energy level from 5 to 100. Sleep charges it, and time awake drains it, faster under stress and during hard workouts. Each day starts where the day before ended, so a short night or a long hard day carries into the next morning.
01How sleep charges it
An hour asleep at your usual resting heart rate and usual HRV charges 6.25 points, so 8 hours at your usual levels adds 50. A lower heart rate or higher HRV than usual charges faster, up to 1.3 times that rate. A higher heart rate or lower HRV charges slower. Sleep never drains Battery.
Time in bed that your tracker recorded without a sleep stage charges at half the rate. Time awake in bed charges nothing. Charging slows above 75 and reaches zero at 100, so a good night usually lands in the 80s or 90s.
| Night | Charge |
|---|---|
| 8 hours asleep at your usual levels | +50 |
| 8 hours in bed, half awake, heart rate 10% up, HRV 20% down | +16 |
Starting from 42, the first night ends at 87 instead of 92, because charging slows above 75.
02How waking time drains it
Each waking hour drains 1 point, plus 0.04 points for each point of Stress. A calm day at Stress 20 drains about 1.8 points an hour, or 29 over 16 hours. Quiet time charges a little instead. When Stress is under 15 and your heart rate is within 10% of your usual resting heart rate, Battery gains 1.25 points an hour.
During a workout, each 5 minutes drains by its heart rate zone or its Stress, whichever costs more.
| Heart rate zone | Drain per hour |
|---|---|
| Zone 1 | 4 |
| Zone 2 | 6 |
| Zone 3 | 9 |
| Zone 4 | 12.5 |
| Zone 5 | 16 |
When your watch records no heart rate, the level holds until the next reading.
Battery uses the same usual resting heart rate and usual HRV as Stress, the medians of the last 60 days. Titan needs readings on at least 36 of those days before Battery has a level. The first day with no earlier level stored starts at 50. See personal baselines.
03The Battery screen
Tap the Battery card on Today to open the Battery screen. The card shows your level now and your 7-day average, which is today's level averaged with the final levels of the six days before.
Current charge
The battery shows your level now. A bolt appears while the level is higher than it was an hour ago. The word under it names the band.
| Level | Label |
|---|---|
| 85 to 100 | Charged |
| 60 to 84 | Partially Charged |
| 30 to 59 | Low |
| 5 to 29 | Depleted |
The caption under the label reads "Last charged to" with the top of your latest rise of 2 points or more and its time. Before any rise, it reads "Last reading" and a time. Charged adds up every rise in the day, and Drained adds up every fall. The level at bedtime plus Charged minus Drained equals your level now.
Charge through the day
The chart runs from last night's bedtime to now, or to midnight for a past day. The line is your level. A shaded band marks sleep and another marks each workout. Tap the chart to read the level at any time. A break in the line means your watch recorded no heart rate then.
Sleep and activity
Last night's sleep and each workout get a row with its start, end and duration. The number on the right is the level at its end minus the level at its start. A row with no heart rate inside it reads "No readings". The sleep row shows time in bed when your tracker recorded no sleep stages.
Daily charge
Each bar is the level at the end of that day. Today's bar is the level now. Pick 7 Days, 30 Days or 60 Days. The trend table below compares your 7-day rolling average today with the same average 3, 7, 14, 30 and 90 days earlier.
04Gaps and missing levels
A day with no heart rate reads "No battery reading" on the Battery screen, and the Today card reads "No data". The list reads "No sleep or workouts yet" today and "No sleep or workouts recorded" on a past day. If Battery stays blank, check that Titan can read Heart Rate, Resting Heart Rate and Heart Rate Variability in Apple Health. See HRV not showing.
Battery has no settings of its own. Use RMSSD for HRV, at Settings > Recovery & Sleep, changes the HRV it reads, and Titan rebuilds Battery history when you switch. To recalculate Battery history yourself, open Settings > Health & Connected Apps and tap Clear Recovery Cache. This also recalculates Recovery, Sleep and Stress.
The Apple Watch app shows the Battery level synced from your iPhone.
