I had a major problem with my Nikon D80 lately, in that after taking 1-2 pictures or just leaving it on for around half a minute, it would give me a battery warning before turning itself off. This happened with several battery packs, all originals, fully charged, and persisted after cleaning battery contacts. When turning the camera off and back on, it would display full battery charge again, only for the problem to return straight away.
Concluding that it was a defect with the camera itself, I replaced the lens with the cheaper kit one, in preparation for sending the camera in for repairs. Then I noticed that the problem went away. Now, I can't reproduce the issue even if I put the other lens back on.
While I understand that a bad contact between the camera body and the lens can cause a variety of issues, this particular symptom seems strange to me. Is it possible for a bad lens contact to cause the camera to falsely think its battery is drained? Or can it actually cause a drop in voltage like that? I want to be sure that it's actually physically/electrically possible to have been the cause, because if it's just a coincidence that the problem went away after changing the lens, it's sure to return next time I'm out trying to shoot.