Same issue for me with EL 5. It was brand new so the battery contacts were not dirty. If you leave it in the flash, the battery will drain within a few days even if it's fully charged. I also notice of this battery discharges when it's not in the fla...
EL 5 on my R6 M2 was good and bad. Nice results for lighting. Horrible results on battery draining. I put a fully charged battery in the EL 5, stored with my gear and it was totally drained 3 days later with no use of the flash. this happened 4x ov...
