by Jim McNeece 2003 U320 40′ 12/13/13
There are 3 issues in this Trimetric installation – installing the shunt, finding a place for the display, and running the signal wire from the shunt to the display. All of these, for me, required more work than first realized – took me most of a day to complete.
Installing the shunt was the most difficult for a variety of reasons.
The shunt must be connected directly to the battery negative terminal to correctly record the battery state. Remember, current flows OUT of the negative terminal when a battery is in use and into the negative terminal when charging, so you cannot have the charger connected between the shunt and battery negative terminal. (Here is a very detailed description of how current flows in a battery/battery charger system.
On my coach there are two connections directly on the battery terminal – the coach ground wire and the battery charger. I had to remove both these connections from the battery and connect them to the opposite end of the shunt. The other end of the shunt was connected to the battery negative terminal with a short piece of heavy-duty cable fabricated at a local battery store ($20).
I hate working on batteries. Something always goes wrong. Sure enough, as I was using a wrench on one of the batteries and thinking that I should have put electrical tape around the other end so it wouldn’t short out if it touched some part of the chassis, I touched the wrench to the chassis. A blinding flash of light and molten pieces of wrench went flying. It was momentary and nothing was seriously damaged (except, maybe, my underwear). Well, that’s not totally true. It happens the wife was standing right there when I did this. So I had to explain that: No, I was not electrocuted; No the coach was not on fire; No the batteries had not exploded; and, most difficult, Yes dear, I was stupid. So, my ego suffers.
Anyway, the shunt got installed at the cost of one Craftsman wrench and my ego.
Deciding where to put the display was a bit of a challenge. The display, to me, is butt ugly. The logical, less obtrusive location was the same as others with this model coach – in the small cabinet next to the existing electrical info panels.
I did not want to have to open a door to check the Tri-Metic, so I replaced the solid wood door with a smoked acrylic door to match the one next to it. I got the acrylic from these guys estreetplastics.com. I ordered two because I wasn’t sure if what I ordered would be exactly the same smokiness as the existing one. I’m glad I did. The ones I ordered are just a little darker than the existing one.
It took a bit of woodworking to get the inside of the cabinet rebuilt so that part of it would still be useful for storage. A couple of photos show the end result (doors open, doors closed). The smoke gray acrylic does an excellent job of covering up the ugliness.
Running the signal wire from the shunt to the display wasn’t very difficult. I just drilled a couple of holes in the walls between the three bays, poked the wire through an existing opening in the floor behind the kitchen pantry, and fished the wire up into the overhead cabinet. The last couple of photos show the wire run (the gray wire).