diff --git a/README.md b/README.md
index 17347cf..23b64d7 100644
--- a/README.md
+++ b/README.md
@@ -229,6 +229,27 @@ with the default vehicle prefix: `saic/<saic_user>/vehicles/<vehicle_id>`
 | /refresh/period/inActiveGrace/set        | grace period (sec)                                   | After the vehicle has been shutdown, the gateway continues to query the state for 600 seconds (default value). The duration of this extended query period can be modified with this topic.                                            |
 | /location/findMyCar/set                  | [activate,lights_only,horn_only,stop]                | Activate 'find my car' with lights and horn (activate), with lights only (lights_only), with horn only (horn_only) or deactivate it (stop).                                                                                           |
 
+## Charging type values
+
+The `/drivetrain/chargingType` topic publishes the raw `chargingType` value reported by the SAIC API. The API does not
+document it. The meanings below were reported by users in
+[#398](https://github.com/SAIC-iSmart-API/saic-python-mqtt-gateway/issues/398) and checked against about 89k logged
+API responses from one vehicle (Mar 2024 – Oct 2026). They may differ between models.
+
+| Value | Reported meaning                                   | Checked against logged data                                                      |
+|-------|----------------------------------------------------|----------------------------------------------------------------------------------|
+| 0     | Car in deep sleep                                  | Not supported: 31 isolated samples between values 1 and 3, not a sustained state |
+| 1     | Car just parked                                    | Consistent (near-zero battery current)                                           |
+| 3     | HV battery in use (driving, or remote A/C on)      | Consistent (battery current under load)                                          |
+| 6     | AC charging                                        | Confirmed (on-board charger input current present)                               |
+| 7     | DC charging                                        | Confirmed (about 200 A battery current, no AC input)                             |
+| 9     | Charging stopped from the infotainment             | Unclear: both samples follow DC charging while plugged in                        |
+| 10    | Charging ended                                     | Supported: 17 of 24 samples follow AC charging while plugged in                  |
+| 16    | Car unplugged while charging was still in progress | Never observed                                                                   |
+
+Values 2, 4 and 12 were seen only 1 to 3 times each. 4 and 12 appeared around the start or end of charging, which could
+mean a transition state. Their meaning is unknown.
+
 ## Home Assistant auto-discovery
 
 The gateway supports [Home Assistant MQTT discovery](https://www.home-assistant.io/integrations/mqtt#mqtt-discovery). It