Hmm. Knowing now that it's a timer charger, I'm betting it's undercharged batteries. At best, you might be getting half a charge off that charger.

Definitely borrow someone's peak-detect charger, set it for 1 Amp, and run the batteries through a charge cycle. I think you'll be surprised. If not, call Great Planes, not Tower. Tower is owned by Great Planes, but if you want it fixed, you call the manufacturer support line, or email [email protected]. I've ALWAYS had good experiences with them.