Tape the batteries as shown with electrical tape, which can be re-used a few times at battery changes, even in the woods if you're careful.
IMPORTANT note. The water seal contacts the flat surface of the GPS case. Be sure the black tape is only on the batteries. There will be a strip of tape on each side of the batteries, the other is not visible, it's below the batteries. Experiment a little to find the tautness of the tape on each side that allows the cover to be installed easily, without over-stressing the 1/4 turn latch!!! Notice the impressions made by the battery cover in the black tape. This "engagement" will immobilize the batteries in the vertical direction, which is what you want.
The first step is to immobilize the batteries as above. The next step is to add dielectric grease to protect the plating on the terminals. For 2-stroke use (dirtbike), consider damping the contacts (as below) with neoprene. A fourth step would be to arrange a reliable source of external power.
If there are black deposits on the battery terminals, this is carbon buildup caused by sparking because of engine vibration. To get any life out of the batteries you must stop the movement of batteries and the lifting at the terminal connections. This problem is most common on single cylinder motorcycles, especially un-balanced engines such as 2-stroke.
Inside the battery case, the batteries are suspended between two springs.
At certain frequencies (RPMs) the batteries jump around and lift off the
terminals, creating a small spark each time they disconnect. After several
thousand sparkings, a black carbon residue builds up between the contact
and the battery terminal. Even though the batteries are not dead, the
electricity can't get out thus the GPS thinks they're dead and shuts down.
You can scrape the residue off the battery, but the scratches allow more
oxygen into the spark, and it seems to return even faster. It's difficult
to clean the contacts anyway, especially out in the woods. For this reason
we advise using external power right from the start if possible and don't
contaminate the terminals, someday you may need to run on batteries to
get home if your external power arrangement craps out.
At the very least tape the batteries and use dielectric
grease (click here to order
a 1 oz tube) on the terminals to shut out the oxygen which prevents
a burning spark.
"Duracell" batteries appear to have tougher terminals and last
longer under vibration than "Energizers" and"Costco".
This is a photo of the eTrex. GPS 60 has similar terminals. These metal terminals can crack when used on a 2-stroke motorcycle. To protect the battery terminals, stuff a little foam rubber behind the flat metal springs. Suggested sources - neoprene, or foam earplugs, computer mouse pad, or anything to damp the vibration. Don't put so much that you damage the terminals when installing the batteries. You only need a little to damp the resonance condition of the metal leaf terminal.