One of my last activations that went differently than planned was on the Altringenberg DL/AL-272. Actually a drive-in. I walked a few meters to it. Tensioned antenna wire, unpacked TRX, connected battery, and cq on 20m. After the 2nd QSO the TRX went off. Hm, battery not charged… 
No matter, spare battery was there 
Connected. TRX did not start. Conclusion. 2 empty batteries in the luggage 
73 Marcel DM3FAM