Installing Battery Monitor

[newRVer]

One of my projects that I am planning for over the winter is to install a Battery Monitor. Right now I am looking at the Victron BVM-700 as I already have a Victron MPPT solar controller and like how that is working and the Bluetooth connectivity option.

Question...how have you wired wired the monitor shunt connection if part of the load is directly connected to the battery and pulling power all the time (i.e levelers, BIM, etc) and the rest of it goes through the 12V disconnect?

[ependydad]

You should move everything AFTER the shunt. The only thing coming off of the negative side of the battery should be the shunt. Otherwise, your measurements will be inaccurate.

[newRVer]

Originally Posted by ependydad

You should move everything AFTER the shunt. The only thing coming off of the negative side of the battery should be the shunt. Otherwise, your measurements will be inaccurate.

Agreed. However, I am more interested in the logistics and wiring part of this project. Did other people install the shunt in the battery step well or somewhere else? Also, since I am considering a change in batteries, I might want to wait until I know what type of batteries (and dimensions) so I can plan the battery monitor install accordingly.

[n-e-d]

Installed Trimetric shunt in stairwell battery box. Plenty of room with original batteries

[ScottBrownstein]

After I had mounted my shunt to the frame by the batteries I found this innovative bracket that someone had made by flattening 3/4"copper tubing. Easy, safe and low profile. Should have done it myself that way.

[Wandering]

Originally Posted by n-e-d

Installed Trimetric shunt in stairwell battery box. Plenty of room with original batteries

N E D. Can you share a picture of installed shunt. Planning to do the same.

[n-e-d]

Will try to get one by tonite

[newRVer]

Originally Posted by ScottBrownstein

After I had mounted my shunt to the frame by the batteries I found this innovative bracket that someone had made by flattening 3/4"copper tubing. Easy, safe and low profile. Should have done it myself that way.

Now that's an innovative approach assuming you have enough clearance above the batteries.

[newRVer]

I should mention that after getting a chance to read the installation instructions, this may be simpler than I thought. I.e. the shunt actually connects to the negative terminal.

[n-e-d]

Shunt is to the right of the box... I am looking down from top step

[Wandering]

Originally Posted by n-e-d

Shunt is to the right of the box... I am looking down from top step

THANKS n-e-d

[Sagecoachdriver]

Like n-e-d, mine is also to the right in battery compartment in step well. As stated before, all connections are made after the shunt.

[CurtPutnam]

Would one of you be so kind as to explain what a shunt is and its function?

[aeblank]

Originally Posted by CurtPutnam

Would one of you be so kind as to explain what a shunt is and its function?

It is a current measuring device.

Specifically a very accurate resistance. Electronics can measure the voltage drop across the resistance, and calculate the current it would take to get said voltage drop.

[CurtPutnam]

Originally Posted by aeblank

It is a current measuring device.

Specifically a very accurate resistance. Electronics can measure the voltage drop across the resistance, and calculate the current it would take to get said voltage drop.

Thank you! Homemade shunt = accurate resistance how? Just curious, don't waste time unless you enjoy explaining.

[aeblank]

Originally Posted by CurtPutnam

Thank you! Homemade shunt = accurate resistance how? Just curious, don't waste time unless you enjoy explaining.

Homemade shunt? No.
The copper bar connecting the shunt to the battery was homemade (flattened copper pipe, bent, with holes drilled).

I don't mind explaining. Hopefully it makes sense now.

[Steve-W]

A shunt has be calibrated for a specific value. A shunt as used in a battery monitor is just a big high current resistor. The value of the resistor is extremely low, verry difficult to measure without lab grade test gear. They are calibrated so that the voltage drop across the shunt is a specific ratio of the current passing through it. In a lot of cases 1 to 1000. The readout or whatever device is connected to it is designed to interpet this ratio.

Calibration is done by using a current source calibration supply which puts out a higly accurate and stable current, a calibrated meter is then used to measure the output ratio at various point throughout the range of operation of the shunt. Calibration is acheieved by altering the resistance of the shunt. This is done by grinding away some of the material (mostly copper).
The test gear used is recalibrated every 60-90 days traceable to the National institutes of standards.
There you have it. At least when I was building them for nuclear plants in the late 70’s. What is most likely used today is these devices we are referring to here are not required to meet the same accuracy requirements and may only be calibratd at one point within the range of operation.

Building one at home, it’s possible but not accurately without very expensive test gear.

[johnbryanpeters]

Originally Posted by ScottBrownstein

After I had mounted my shunt to the frame by the batteries I found this innovative bracket that someone had made by flattening 3/4"copper tubing. Easy, safe and low profile. Should have done it myself that way.

That installation would concern me regarding mechanical stress on the shunt over time, not to mention exposure to electrolyte vapors. I wound up building a power distribution panel.

[CurtPutnam]

Thanks for the shunt explanation(s)

[TitanMike]

Originally Posted by johnbryanpeters

That installation would concern me regarding mechanical stress on the shunt over time, not to mention exposure to electrolyte vapors. I wound up building a power distribution panel.

I'm getting ready to tackle the installation of a Vectron 702 on my travel trailer.

I already have a similar power distribution system on the tongue of my Micro Lite 25 BDS with the battery switch enclosed in a weather resistant enclosure. In my part of the country I would be more concerned about the shunt being exposed to weather and ice melt "salts" than in a battery enclosure with electrolyte vapors. A battery has to get cooking pretty good in order to discharge a lot of electrolyte with the normal hydrogen gas it gives off.

I'm considering moving my ground connections to just inside the trailer in one of the storage compartments that are along the front wall of the trailer and within just 3' of the batteries (I have two mounted on the tongue). This would allow me to weather shield the shunt.

I also will be mounting my converter in the same area so it will be close to the batteries in order to minimize voltage drop. One "panel" will have the shunt, a 100 amp fuse, and 600 W converter (1200 W peak) mounted on it so I can keep track of all my "add on's" in one place qmd away from corrosive hazards.