ISSUE DESCRIPTION
Description of the issue:
Since Sim Update 7 (1.9.18.0), the Cessna Citation Longitude shows a persistent amber “BATT DISCHARGE L-R” CAS message with both engines running and generators online. The Garmin electrical synoptic shows both main batteries discharging.
Using the Dev Mode electrical debugger, I traced the cause: the generators regulate at 28.00 V, but the lithium-ion main batteries sit at ~28.8 V near full charge. Because the batteries are at a higher voltage than the generators, the batteries carry the electrical load instead of the generators. They discharge until they fall to ~28 V (~97% capacity), and only then does the generator take over.
This was not present in SU6. The same symptom was reported during the SU7 beta (also affecting the Vision Jet and PC-12) and was not fixed for release.
FREQUENCY OF ISSUE:
Every flight.
EVIDENCE
- Cockpit with both engines running at idle and generators online. The CAS shows BATT DISCHARGE L-R, and the electrical synoptic shows BATT L at -43 A and BATT R at -67 A.
- Dev Mode > Electrical system > Instance, batteries at 97%. Both main batteries report Charge state CHARGING (~0.2 A) at 27.99 V, while their Supplier runtime values simultaneously show ~47 A being supplied (L: 46.33 A / 1296 W, R: 48.11 A / 1346 W).
-
Battery config: C1 capacity 44 Ah, charge C rate 1.0, nominal 26.25 V, resistance 0.05 ohm. Per the discharge curve, output voltage at full capacity is 28.80 V, above the generators’ 28.00 V.
-
Quick access with batteries near 100% (BATT L switched off, BATT R on, engines running): r_main_battery supplies 72.09 A / 2048 W with capacity falling, while r_main_generator is ON but carries 0 W / 0 consumers. All right-side buses sit at 28.41 V (battery voltage); the left side sits at 28.00 V (generators).
-
Same flight after forcing all battery capacity to 30% (battery voltage ~26 V): r_main_generator immediately picks up the load (91.72 A / 2568 W, 61 consumers), r_main_battery drops to 0 A, and all batteries switch to charging.
This confirms the right generator works correctly. The batteries seem to be out-voltaging the generators whenever they are near full charge. Forcing the batteries low is not a workaround: the generators recharge them to ~97% (~28 V) and the issue returns.
REPRODUCTION STEPS
- Load the Cessna Citation Longitude, cold and dark, with batteries at full charge.
- Turn on BATT L and BATT R, start the APU, and start both engines.
- Leave both generators online (bus tie opens automatically).
- Wait 5+ minutes.
- Observe: BATT DISCHARGE L-R appears on the CAS, and the electrical synoptic shows both batteries discharging.
- Optional: open Dev Mode > Electrical system > Quick access. The main batteries supply the buses while r_main_generator carries little or no load.
Expected: Generators should regulate above battery charge voltage, so they carry the bus load and charge the batteries. The BATT DISCHARGE message should not appear with generators online.
SETTINGS
Platform: PC, Steam
Sim version: 1.9.18.0 (SU7)
Community folder: [empty / list add-ons]
Last version where it worked: SU6
ADDITIONAL INFO
The electrical system log also shows these parsing errors. They are probably unrelated, but are included for completeness: circuit.2, circuit.55 and circuit.71 defined as CIRCUIT_INVALID, duplicate dme1_line / dme2_line names, and placeholder_circuit_2 not connected to any line.
