car losing charge

[brianmay]

Not really a teslamate issue, but wondered if anybody had experience with older cars unexpectedly losing charge.

For example, last night car charged to limit of 70% at 00:15 midnight, then just over 3:15 hours later - it at 03:30 was at 63% percent charge and had to charge for 45 minutes to bring it back to 70%.

Most of this time - 3 hours 2 minutes to be precise - it was in the sleep state - according to Teslamate.

It was a colder night (12-13 degrees C according to BOM), but not convinced this was an issue. And an older car (2016 Model S).

[JakobLichterfeld]

7% is a huge drop, I assume it is the rebalancing, which accounts for normally 1-3% and then the cold battery. Or your battery slowly dies :-)

[brianmay]

Doesn't always happen. So maybe it is re-balancing or something.

LLM came up with this SQL query, hope it is correct (getting distracted with unrelated stuff):

teslamate=# WITH ordered AS (
  SELECT
    p.date,
    p.battery_level,
    p.car_id,
    p.drive_id,
    LAG(p.battery_level) OVER (PARTITION BY p.car_id ORDER BY p.date) AS prev_battery_level,
    LAG(p.date)          OVER (PARTITION BY p.car_id ORDER BY p.date) AS prev_date
  FROM positions p
  WHERE
    p.date >= NOW() - INTERVAL '3 months'
    AND p.battery_level IS NOT NULL
)
SELECT
  date::timestamptz AT TIME ZONE 'Australia/Melbourne'      AS date,
  prev_date::timestamptz AT TIME ZONE 'Australia/Melbourne' AS from_time,
  prev_battery_level AS from_level,
  battery_level      AS to_level,
  (prev_battery_level - battery_level) AS drop_pct,
  car_id
FROM ordered
WHERE
  drive_id IS NULL
  AND prev_battery_level IS NOT NULL
  AND (prev_battery_level - battery_level) >= 3
  AND NOT EXISTS (
    SELECT 1 FROM charging_processes cp
    WHERE cp.car_id = ordered.car_id
      AND ordered.date BETWEEN cp.start_date AND cp.end_date
  )
ORDER BY date DESC;
          date           |        from_time        | from_level | to_level | drop_pct | car_id
-------------------------+-------------------------+------------+----------+----------+--------
 2026-05-11 06:00:47.97  | 2026-05-11 02:21:19.67  |         70 |       67 |        3 |      1
 2026-05-07 16:09:01.63  | 2026-05-07 13:16:01.886 |         70 |       67 |        3 |      1
 2026-04-25 08:05:57.468 | 2026-04-25 02:43:26.239 |         60 |       57 |        3 |      1
 2026-04-20 03:34:38.45  | 2026-04-20 00:21:40.401 |         70 |       64 |        6 |      1
 2026-04-09 09:54:15.241 | 2026-04-09 09:04:14.292 |         90 |       87 |        3 |      1
 2026-04-04 13:34:04.345 | 2026-04-04 11:30:52.644 |         69 |       66 |        3 |      1
 2026-04-02 08:30:53.876 | 2026-04-02 03:56:08.951 |         70 |       66 |        4 |      1
 2026-03-04 07:02:56.82  | 2026-03-03 23:42:52.311 |         70 |       64 |        6 |      1
 2026-02-23 02:10:37.972 | 2026-02-22 23:59:24.058 |         70 |       64 |        6 |      1
(9 rows)