[BUG] Dual battery aircraft log picks only one battery when imported into the application

[arpanghosh8453]

Discussed in #118

^{Originally posted by ryanmrash-lgtm March 5, 2026}
I've found when importing logs from my DJI M30T, that paired batteries do not record the same time of flight. Example: battery 1A shows 50 flights at 9hrs 47min total time, while its mate 1B only shows 15 flights with 3hrs 44min flight time. This is consistent through all 5 pairs of batteries. Rarely do number pairs get mixed. I suspect these logs only record 1 battery as a primary? Maybe left battery is recorded rather than both battery slots? I have no idea how the aircraft logs which battery is primary...

DJIFlightRecord_2025-05-09_.22-46-53.txt

Response

Unfortunately the extracted raw log does not have the second serial, so I don't think we can integrate this yet. The database design also assumes so and that is why we only take telemetry from the first battery slot (two batteries would have near identical stats if they are used together and one is not brick). This is a software limitation from our side at the moment.

The primary battery depends on which slot you put that in, and if you always use them together, then you would know that one serial automatically means presence of another, you can select all flights by flight serial or by selecting both battery serial from the filter drop-downs. i hope it's not a big inconvenience.

DJI_frames_two_battery_r.zip

[ryanmrash-lgtm]

When I can, I will attach another file directly from the controller. I downloaded a bulk of these from Airdata, perhaps those files may have been stripped of some data while on their servers. I appreciate the work you’re doing!

[arpanghosh8453]

@ryanmrash-lgtm When I said I could not find the other battery serial, I meant that the log parsing library I am using currently shows this parsing behavior. The original log file must have this info, because AirData can show that it has two batteries on their interface when imported. I meant here this is an upstream parsing library problem and I can't currently fix it, given the limitation is coming from the library limitation. The current database structure also assumes only one battery per aircraft. The log files you provided earlier did not have any stripping because I tried uploading them to AirData and they can show it got two separate batteries. the log files are downloaded as-is from there.

I will keep this thread open, so other users with enterprise drones can find about this. Thank you for using this application!

[arpanghosh8453]

Implemented with 4595d1c

Work around Battery Pairing Guide (with battery-pair.json)

This feature lets Open Drone Log treat two battery serial numbers as one logical pair for usage and maintenance tracking.

It is useful for aircraft that alternate between two physical batteries where flights may be logged under either serial.

What This Feature Does

If a pair is defined (for example SN123456:SN654321), Open Drone Log will:

• Sum battery usage for both serials and show the same combined values on both battery entries:
  • Flights
  • Flight hours
  • Cycle count (uses the highest observed cycle count across the pair)
• Use pair-aware values in the Battery Maintenance section
• In flight details, show paired batteries in a single capsule as BatteryA + BatteryB
• Group/sum the donut chart Flights by Battery by battery pair
• Apply maintenance reset to both serials when maintenance is performed on one serial in that pair

File Location

A file named battery-pair.json is created automatically at startup if missing.

• Desktop mode: app data directory (same root used by the app database) - Check the settings of the app to know the location (one folder level up than the log folder)
• Docker/web mode: data directory used by server (DATA_DIR), typically /app/data. This is not a profile level, but a server level setup, so if you are using this under a managed instance, please ask the server owner/admin to add the battery serial pairs for you. It will be applied on all profiles sharing the battery pair.

Definition : Array of SN pair strings

[
  "SN123456:SN654321",
  "SN112233:SN332211"
]

Desktop Mode Setup

1. Start Open Drone Log once.
2. Locate the app data directory.
3. Open battery-pair.json.
4. Add your pairs in the supported formats.
5. Save the file.
6. Restart the app.

Docker/Web Mode Setup

1. Start the server/container once (this creates battery-pair.json if missing).
2. Open the file in the mounted data directory:
   • Typical internal docker path: /app/data/battery-pair.json - you can map this to any external location on the host.
3. Add your pairs in the supported formats.
4. Save the file.
5. Restart the Open Drone Log server/container.

Important Notes

• Serials are normalized internally (trimmed, uppercase).
• Pair order does not matter: A:B is the same as B:A.
• Invalid entries are ignored silently:
  • Missing :
  • Same serial on both sides (A:A)
  • Empty serial values
• Conflicting/chained pair definitions are not merged into larger groups.
  • Example: A:B and B:C is ambiguous. Use explicit, non-overlapping pairs only.
• Battery pairing is read at startup; restart required after editing battery-pair.json.
• Performing maintenance on one serial applies reset to both serials in the pair.

Quick Example Scenario

Given:

[
  "SN123456:SN654321"
]

And flights:

• 10 flights logged with SN123456
• 6 flights logged with SN654321

Result in UI:

• SN123456 battery usage row shows 16 flights (with combined hours/cycles)
• SN654321 battery usage row also shows 16 flights (same combined values)
• Flights by Battery donut has one segment for this pair with value 16
• Flight detail battery capsule shows SN123456 + SN654321