Arch Cape Repeater visit December 4, 2010

The main goal for this trip was to top up the battery water level. The three people on the trip were Helen Chauncey, KE7SCS, Dave Rouse, KE7RJK, and Dale Mosby, K7FW. The full task list for the trip:

• Check battery voltage
• Check battery specific gravity
• Add water to battery
• Vacuum up sawdust
• Spray for ants
• Oil door hinges

We took a portable battery pack / inverter combination courtesy of Tim Crawford, KE7TAC which allowed use of a small 110VAC vacuum. Dave first used a dustpan and got the majority of accumulated sawdust off of the floor. We cleaned up the rest of the sawdust from the floor and door jam with the vacuum cleaner. The cause of the sawdust is a bit of a mystery. Most of this seems to be from the core of the door. No ants were found in the building so I really am not sure if this is the cause of the sawdust or not. If it was only from the core of the steel clead door I would think that this was just the door disintegrating. Now with things cleaned up we can monitor the situation a bit better.

The battery voltage was 13.10 volts according to my meter which matches the 13.1 volts displayed by the solar chartging control. My understanding is that the battery voltage is not prticularly useful information when charging as you need to see the batteries at rest an hour in order to have the voltage be a useful indication of charge state. The water level was low, but not too bad, all cells were well covered. Specific gravity was measured as so (in this diagram the upper left cell corresponds to the far corner of the battery bank - imagine the table as if you are standing in the door of the repeater looking down on the batteries):

1.225	1.250	1.225	1.225	1.225	1.225
1.225	1.225	1.235	1.235	1.235	1.250

The values are  the readings as given by the hydrometer. Information I found indicates that hydrometers are generally calibrated for 70 or 80 degrees. The temperature was no where near that, I would guess 40 degrees at the most (there were still patches of heavy frost on the road in places). I found correction factors of 0.003 or 0.004 points per 10 degrees F. A worst case adjustment of 0.016 would give the following corrected SG table:

1.209	1.234	1.209	1.209	1.209	1.209
1.209	1.209	1.219	1.219	1.219	1.234

Based on the specific gravity readings I estimate the batteries around 75 percent charged.

Back to the Arch Cape repeater home page
Some phtotos from this trip:

Dale & Dave outside the repeater with a couple boxes of equipment hauled up.

Dave cleans sawdust from the floor. Note pile of sawdust accumulating on the ground just to the left of the cardboard box.

Dale checks battery specific gravity.

Final step before closing up the buiding was applyng some bug spray along door jam and sill plate.

Back to the Arch Cape repeater home page