Battery Status Meter Installation

Like several others on this forum I am a data junkie, but I am also a tightwad and am unwilling to spend the money for the Tri-Metric meter. After some searching I found what seems like a really nice solution. This is a small display unit, about 2 inches by one and a half and shows the battery charge level and current consumption or charge rate.

The charge level is shown as a percentage, remaining amp hours, and a battery graphic. It also shows remaining charge lifetime in days, hours, and minutes at the present consumption rate. There is also a display of the battery voltage and current, as well as a computed wattage usage.

I got the meter from Amazon for about $35. Do a search for "Battery Coulometer" on Amazon to find it.
This is what came in the package, the display unit that mounts where you can see it, the shunt unit that mounts to the battery, and a cable to connect them. What was not included was any instructions! After some searching on the web I found a one page document which I can provide if someone wants it, but the installation is actually quite straightforward, and the operation is also pretty easy. And the document is only barely in English!

I will go over the steps I used to install the meter, it is not too difficult using hand tools plus a power drill. There are a few of the tools that are a little bit out of the things you might have in your kitchen drawer, I will point them out in the descriptions.

I first cleared out all the stuff from my right storage area and the right upper cupboard. Switch off the battery disconnect switch in the lower storage compartment, then remove the fuse panel cover, then the five screws holding the cover for the battery compartment. I then put tape over the positive battery terminal for safety and removed the bolt for the negative battery terminal with a 7/16" wrench.

I made a heavy jumper using a piece of 1/8" by 1/2" copper strap. You could also use a short piece of heavy wire, #8 or #10 gauge and ring terminals. The jumper needs 1/4" holes.

You also need about a foot of smaller wire, #16 to #20, preferably red to match with the trailer wire colors. Strip back about 1/4" of insulation from each end. One end is connected to one of the fuse block terminals, I used the one for the TV, third from the bottom. On my trailer I needed a T5 Torx star wrench to turn the screw. The other end of this wire goes into the little terminal strip on the shunt board labeled B+; it requires a really tiny flat blade screwdriver; put the wire into the hole then tighten the screw. Then the black trailer ground wire that was removed from the battery is connected to the P- terminal of the shunt board. You need a #3 Philips screwdriver for this, a really big one. Then the heavy jumper is used to connect the shunt B- pin to the negative terminal of the battery. If you use a solid strap that is probably sufficient to hold the shunt board in place. If you use wire and ring terminals you might want to stick the shunt board down with something to keep it from moving around; possibly some double stick foam tape.

At this point you can test the meter. Plug the small cable into the shunt socket, lining up the connector ridges to the socket slots. Plug the other end of the cable into the display and turn on the battery switch; the meter should light up and you can play with it. Now turn the battery switch off again and move on to the display installation.

I decided to mount the display on the upper cupboard door to be easily visible. I removed the metal wiring cover inside the cupboard which is held in place with two screws you can't see; a standard Philips screwdriver will get them. Now, the most difficult part of the installation. The interconnect cable must be routed from the battery compartment to the cupboard. There is already a bundle of wires going through but it is too tight to add the cable. After consulting with Cary, I drilled a hole from the cupboard at a 45 degree angle from a spot just inside where the wiring cover sits. Be very careful here as running into that bundle of wires would be a major disaster. You also need to start back far enough to avoid damaging the front of the cupboard panel. I tried using a 3/8" drill bit, but it was just too tight for the cable connector so I ended up using 13/32 which worked well. Vacuum up the chips in the cupboard and battery compartment.

I bent the connector of one end of the cable to be parallel to the wires, then tightly wrapped some tape around it to keep it as small a diameter as possible. I included a scrap of wire in the tape to use to pull the cable through the hole. I threaded the scrap of wire through the hole, then pulled the cable through. After removing the tape the connector can be plugged into the shunt socket.
I then removed the cupboard door by taking out the hinge screws. I put tape on the door and marked the cutout. I then drilled two holes and removed the material with a jig saw.


I mounted the display panel in the hole with two tiny screws. The unit did not come with the screws but fortunately one of the things I have is a collection of tiny screws salvaged from broken plastic toys and a couple of these worked fine. Doesn't everyone save stuff like this?
After reinstalling the door on its hinges I added a small cable guide to hold the cable out of the hinge. I routed the cable with the other wires and replaced the metal wire cover leaving the cable coming out of the notch at the top; there is plenty of room for the cable to move when the door is opened and closed.

Then replace the battery compartment panel and fuse panel cover and turn the battery switch back on. The meter should now be working. Now you can put all the junk back in to the storage areas!

Setting up the meter requires the battery to be fully charged and some information about the battery. I plugged in the shore power and left it on over night to charge the battery. The battery capacity is marked on my battery label as 78 amp hours. After fully charging the battery, the voltage (with the charger disconnected) is 13.2 volts. I did some searching and decided to use 10.0 volts as the discharged voltage as any lower than this will damage a lead-acid deep cycle AGM battery.

The meter has three buttons, up, down, and a funny arrow thing I call "the bottom button". When the battery is fully charged and the charger turned off, push the up arrow and hold for at least three seconds; the meter will record the fully charged conditions. Then push and hold the bottom button and a settings menu will appear with values for capacity (CAP), charged voltage (FULL), and discharged voltage (ZERO). The up and down arrows select the value to set and the bottom button then selects the digit to change with the up and down buttons. Push and hold the bottom button to select another parameter. If you don't push anything the display will return to the normal screen in about a minute.

If anyone else wants to attempt this and my description is not completely clear, please feel free to shoot me a PM and I will be happy to elaborate.

 

Rotus,

In looking at the various "coulometers on Amazon, I noticed there were several wireless models. No reviews on any of them, I wonder how well they might work.

Randy

Onepeak DC 120V 200A Wireless Ammeter Voltage KWh Watt Meter Car Battery Coulometer Capacity Tester Power Monitor - - Amazon.com

 

Randy,

That is an interesting unit, it seems similarly capable to the one I used and not much more expensive. The color display is snazzy. The wireless aspect is intriguing, it might save the difficult drilling of a hole for the cable that my installation required. However, the display unit still needs power so it would have to mounted somewhere where power is accessible and it appears to need 5V which would have to be supplied by a phone charger or something. Also, the galley stainless steel counter top is grounded and extends over the entire battery compartment and could interfere with the RF signal from the sensor module to the display; this is really hard to evaluate if the two parts would be able to communicate wirelessly. The RF path is highly susceptible to metallic barriers; it could work just fine or fail completely. The only way to know is to try it.

If you give it a shot please let us know how it comes out.

 

@rotus8 I really appreciate the write up on this. I added this same coulometer to my new dual battery set-up and your instructions were great (particularly since, like you, I didn't receive any instructions with the unit). I ended up installing the display next to the fuse cover. It's pretty easy to flip the lid to check battery status. System is working well!

 

Great job!

 

I just added one of these meters to my Fridge Auxiliary battery box. Works great there, and a lot easier to install than in the trailer.