In doing maintenance preparatory to DRR, I pulled the Battery Filling Systems
caps. There was good news and bad news. I have the gravity reservoir that has a valve to turn initiating water flow to the cells. Each time I fill I get two caps that leak a bit. And then I get further leakage from several cells from battery boiling.
Good news is I have always had water in the cells. Bad news is they have always been at least 1/2" overfull. The BFS caps operate the float within a 1/4" swing up & down, i.e. full down is 1/4" below full up. My floats allow the battery to fill to within 1/2" of the top of case, except the two that leak which probably go full up w/no air space. My floats are marked "20" which appears to correspond w/20 mm below bottom of the bayonet thread. I should have something in the 30-35 range to keep water at the bottom of the battery's collar extensions down into the cell. 30 would be a real nice compromise allowing sufficient head space to preclude boil over. I have Interstate U2200 batt's. The push button/12V pump system on our 06 never leaked. Part of my leak problem may be that the gravity feed has the reservoir above the batteries so that filling (which takes a while) leaves water in the tube lines above the cells even after shutting valve & that has to go somewhere, and even a teeny leak will put water either on top of batt's or overfilling a cell. Guess I'll call BTS on Monday for replacement caps & floats.
The good news is that the caps, once you figure out the trick, are way easier to remove than I had previously excperienced. The bottom part of the cap that includes the bayonet is free (sort of) to rotate about the top part that has the float window. Grasping the top with one set of fingers, and rotating the bottom with the other hand will release the cap for cell inspection. They may be stuck at first, but after they start moving it is easy enough to remove each cap one at a time for inspection without removing the tubing. To get one broken free you can turn the top CCW (against the bayonet stop of the bottom part), then twist the top/bottom together CW, then hold the bottom still & turn top CCW; repeat as necessary till the cap is free, about 1/4 full turn of the bottom.