Rand McNally Foris 850 has poor running time on NiMH

Hello from Pocatello,

I recently bought a Foris 850, Rand McNally's only hiking/biking GPS. It takes two AA cells, and runs all right on alkaline cells. However, it's a real NiMH battery hog. I tried several brands of NiMH cells on it, including Eveready, Duracell, Fujifilm, etc. It won't even turn on for some batteries, and for the ones it will turn on, the power seems to run down too fast. For example, simply asking it to find a route to the closest gas station can take the battery down more than 5% of the original 100%!! Anyway, I have some Eneloops on order, since Eneloops have such a great reputation and since I read some magazine review online saying something about that GPS running well on Eneloop batteries. Also got an "individual cell" charger on order so I can really make sure the cells are fully charged. Would that help, you think? Do you have any experience using NiMH batteries on a Foris 850? I'm very frustrated about this strange issue! Thanks in advance. By the way, I did remember to set the battery preference to NiMH.