topcon GPT-2003

I recently purchased a Topcon GPT-2003. I also bought a brand new battery. I have turned off the tracking lights, and any other power sucker i can find, but i only get three hours per battery. I have two batteries that will work 8 hours each on my GTS-226. the instrument sounds like there is something running inside it, it makes a slight humming noise, and I suspect that is what is killing the batteries. I have turned the reflector less off in the data collector, and my distances are checking fine, so I do not think that the reflectorless edm is running, but then again it could be. Has anyone dealt with this issue before?