Battery Monitor Install

I finished the Trimetric 2025-RV battery monitor installation in my 2005 LTV Free Spirit van with 2 house batteries.  Running wires is the hardest part.  The monitor requires a shunt to be in between the battery negative and all other connections on the negative/ground side.


Originally, my van had each battery with a ground wire from the van metal to each negative post.  The driver side battery also had the negative cable to the inverter.  The monitor requires all the cables from the battery negative to go to the shunt and then an additional cable goes from the shunt to the vehicle ground.  Since none of the cables except for the inverter cable would reach to the shunt, I elected to get 2 new battery neg to shunt cables of equal length (in case that helps).  I used a piece of the old inverter cable I replaced for the shunt to ground.  It was larger than really needed but I had it so all it needed was a new connector for the end.

Glue backer board to bin

Marking location for shunt

Mount shunt, drill hole for wire

Shunt wired

First decision was to determine where to put the shunt.  I did not have room to mount the shunt in one of the battery boxes.  The van has a big storage box mounted under the floor in the back of the van between the two batteries, also in underfloor boxes.  I decided to mount the shunt inside the box to protect it from the elements and run the cables to it from underneath the van.  It sounds easier than it was.  I got a scrap piece of luan plywood and glued it to the inside top of the box to provide a more substantial mounting area after painting it.  That worked well.  I connected the cables to the shunt (the 2 battery neg to one side and the vehicle ground and inverter neg cables to the other side of the shunt.  Bent them and drilled 4 holes with a 1" hole saw for the cables to come in from the outside.  I used red plastic hole protectors to keep the cables from ever abrading.  After getting the shunt cabled, I used wire ties to keep them tidy and from possibly shifting.  Then, under the van to neatly route each cable ( labeled on each end to keep track of which is which) to it's destination.  Then I used plenty of cable ties to keep them in place.  That took an entire, long day of work to complete.

Wiring Plan for the Battery Monitor

Chosen location for monitor

Exposed door pillar

Once the shunt part was completed, the next step was to run the monitor wires from the battery and shunt to the location of the monitor.  All the advice I found said that monitor needs to be in a very visible place so it is easy to see and keep track of how the batteries are doing.  In deciding where to put it, I had two things to consider: visibility of the monitor and a route to get the wire to it.  I bought a 25 foot length of wire made up for the monitor so I had plenty of wire to work with.  I decided to try to put it on an upper cabinet right by the sliding door.  I started by taking off the plastic cover for the door pillar between the passenger seat and sliding door.  Next was the plastic step for the passenger seat where I found a weep hole in the metal to under the van big enough for the cable and a small flex tube leaving a bit of room for water to seep out still.  It was clogged up anyway.  Then I took off the trim over the sliding door that forms a pocket.  A bit of poking about and it showed there was a path for the wire to make it to the monitor location.

Removed panel above side door

Inside cabinet for wire route

Removed wire cover

After determining I had a path, then it was back under the van to find the path to the passenger step well hole.  I decided to run from the storage box to the driver's side where all the house wires run up half way to the front of the van then go across the van width, then up along side the fresh water tank on the passenger's side up to the weep hole.  The reason I went along the driver's side wires was to avoid getting near the exhaust and muffler and finding places to tie the cable to.  I encased the wire in small flex tubing the entire under van route to protect it and liberally used wire ties to keep it tidy and safe.  I used a wire tie to firmly hold the flex tube seams together, then wrapped the seam in electrical tape.

Remove screw covers for 3
screws in step well

Weep hole found in step well

Monitor wire run up weep hole
 in flex tubing

After getting the wire thru the weep hole, I ran it over to the column and up to the cavity behind the headliner, then thru the cavity behind the trim over the sliding door.  I drilled a hole from inside the cabinet thru the vinyl wall liner, then got a piece of sort of stiff wire to use as a fish.  I got that wire thru the hole and down to the place over the door where the cable was.  I taped the fish wire to the end of the monitor cable and pulled thru.  Victory at last!

Monitor wires connected to shunt

Monitor opened

Wire block on monitor board 

Next was mounting the monitor itself on the wall of the cabinet.  I decided to cut off one of the mounting ears so it would be right next to the DC plug outlet cover plate.  This allowed the cable to fit into the wiring cover mounted inside the cabinet.  I removed the monitor from the outside case and screwed it to the cabinet.  For the top side, I drilled a hole thru the case and screwed it in.  I also drilled a hole for the cable.  Then I ran the cable thru the access hole.

It was finally time to wire the cable to the shunt and to the monitor.  First was the shunt wiring.  The first thing was to remove the fuse from the red battery pos connection.  The monitor cable requires 3 wires to go to the shunt and one wire with a fuse on it to go to the positive terminal of one of the batteries.   The cable I bought for it had the same color wires and in the correct twisted pair as specified by the Trimetric instructions.  They had peeled the outer wire cover back 2 feet which was sufficient to get the red, fused wire to the driver's side positive terminal (encased in a flex tube).  That left an extra 2 feet of the other 3 wires (2 black and 1 white) at the shunt where they are connected to the small screws.  After making the connections, I folded the excess wires, used a wire tie to hold them, then put them into a flex tube and wire tied that to keep them out of the way.

Installing the Monitor board
 into the box

Monitor installed

Monitor wire inside cabinet.
Wire cover hides it

Panel reinstalled over side door

The final step was to use a really small flat blade screwdriver and wire the 4 monitor wires to their terminals.  I labeled each wire and the paired twisted wires helped as well.  They had a chart on the cover box to show which wire goes to which terminal.  Once the wires were connected, I put the monitor back into the cover and screwed it in.  All that remained was to coil the excess cable, wire tie it and tuck it up so it would be hidden by the wire cover.  Screw on the wire cover and done.

Except for re-installing all the pieces I took off to get the wire to it's location.  And connecting the negative cables to the negative posts on the batteries and put the fuse back in the red wire fuse holder.  Then its time to learn how to use the monitor.

I made a checklist for installing it - here.