Help: Why does my Anker PowerCore 26800mAh shut down on the 14‑hour Eurail from Berlin to Prague, ruining my intensive German B2 listening immersion?

I’m absolutely frustrated with my recent Eurail trip. I booked a 14‑hour night train from Berlin to Prague specifically to binge‑listen to authentic German podcasts for my B2 exam prep, but the Anker PowerCore 26800mAh I bought last month (the one with the PowerIQ 3.0 and 30W USB‑C PD) died after just 8 hours.\n\n- Powerbank model: Anker PowerCore 26800 (PowerIQ 3.0, 30W USB‑C) – advertised for 30+ hours of mixed‑device use.\n- Train environment: Wi‑Fi spotty, temperature around 28 °C, constant vibration.\n- Language plan: 3‑hour daily listening blocks, using Audible German “Geschichten aus der Geschichte” and the Goethe‑Institut’s B2 listening drills.\n\nI double‑checked the battery health in the Anker app – it still shows 95 % capacity, and the LEDs indicate full charge when I plug it in at the station. I even tried the “Fast Charge” mode, but the train’s power outlet seems to cut out intermittently.\n\nMeanwhile, I managed to complete the Goethe‑Zertifikat B2 two weeks ago, so I’m not lacking motivation or resources – it’s just that my gear can’t keep up with the schedule I set for myself.\n\nHas anyone experienced similar power‑draw issues on long‑distance trains? Are there specific powerbank models that handle the constant voltage fluctuations better, or should I adjust my charging strategy (e.g., use a DC‑DC converter, switch to a higher‑capacity LiFePO₄ pack, etc.)? Any tips would be hugely appreciated, because I’m determined not to let a dead battery sabotage my immersion routine again.