Installing Battery Monitor

[OYO]

Just thought I'd show my BMV-700 install. Thanks for the knowledge I gained from the previous posters on this thread!

[n-e-d]

nice job

[TitanMike]

Originally Posted by n-e-d

nice job

+1 on the nice job.


I've been working on getting mine installed using somewhat the same approach as yours. I used an 8X8 Non Metalic, water tight enclosure I picked up off the shelf at Home Depot and included a 100 amp ANL type fuse in mine along with the shunt. Since I have two batteries mounted side/side on my trailer tongue I just mounted the box between them.

Have all assembled but am waiting for a day over 40 degrees and with no rain (rained straight here for the last 20 days with daytime temps high 30's, low 40's) to finish the final connections.

Still working out the final routing for the monitor cable and a #4 wire that will go to my converter.

Side note. since I have two batteries and a selector switch that allows me to isolate them if necessary, I have meticulously kept all wires between battery and switch, and battery to common ground point EQUAL IN LENGTH. This gives me as true a parallel connection as I can get with the only variations in resistance being the internal resistance of the individual batteries. Why? Because on paper it looks good and it was no big deal as I make my own cables. A $30 crimping tool that allows me to crimp all the way down to 1/0 terminals with ease. Looks like a set of bolt cutters only with crimping instead of cutting jaws. Some heat shrink in black or red and you can't tell one of my cables from one you might buy off the shelf at an A/P store (just a heck of a lot cheaper).

When I finish my project, all primary battery wiring up to the converter/distribution panel will be #4 with the exception of the tongue jack and slide motors. They connect directly to the battery (in a frame mounted J-box) with their own inline fuses so I'm not going to bother with them. All current from the battery(s) will still run through the shunt which will be the common ground for the batteries and 12 V system. Regardless of the number of grounds going to the frame, the power will still flow through the shunt.

I've changed my mind about running a direct cable from power panel to battery using #4 wire except for the negative connection on my Inverter. That said I'm upgrading the main negative connection to the frame from a ring terminal and self tapping screw to a regular panel type lug attached to a bare metal point on the frame with a much better self threading screw designed for grounding.

[DefenderBob]

Sorry to resurrect this thread - just looking for a bit of confirmation before I do this install - I've read a number of threads with varying levels of information, etc, but always come back to this one.

TL|DR - Where to place the shunt WRT negatives going to the frame of the trailer - necessary to maintain the TT frame in the equation?

Our setup (mini-lite 2509s) from factory is all neg lines are connected via wire-nut under the trailer - then a single wire comes from that nest and grounded to the trailer frame.

On the battery, a single wire comes from the negative post to the frame in a different area.

When installing the shunt - I've read a few things and believe the options are:

1. Install the shunt in a (new) sealed box (similar to what OYO did above), on the frame near the existing cluster of neg lines, removing the single wire attached to the frame and attach it to the shunt instead, then go from the other (correct) shunt side to the frame. No change on the battery neg post

2. Install the shunt in a (new) sealed box (similar to OYO) next to the battery, where the battery neg post is attached to the shunt and removing the single wire from its current position on the battery post, to the other (correct) shunt side, where it will remain at its current connection to the frame.


Both approaches seem like they are missing something - maybe the TT frame should be eliminated from the equation?

3. Install the shunt in a (new) sealed box (similar to OYO) next to the battery, where the battery neg post is attached to the shunt, remove the wire attached to the frame from the cluster of neg wires from #1 above and run a larger wire to the load side of the shunt.

This seems more "correct" but then I have nothing going to the frame.


The other addition will be adding a pos and neg for a Renogy 20a MMTP solar charger and removing the existing Zamp lines from the rig. Pos will follow the same path as the zamp wires (to a terminal on the shutoff switch that goes to pos terminal on the battery) and the neg will go to the load side of the shunt. That seems correct to me.


Any feedback is welcome!

[TitanMike]

The important part is that all current going into and out of the battery go through the shunt. There can be ground connections at many places along the frame but the connection from battery ground to frame is the one place you can be sure you are measuring all charge/discharge current.

There should be only one wire connected to the negative battery post and it should go to the shunt.

[ependydad]

I agree with TitanMike. I upsized the wiring between the frame and the battery, so I remove that wire completely. I added a new wire from the negative terminal on the battery to the correct side of the shunt. I then added a new wire on the far side of the shunt to the common grounding point on the frame (that screw). Easy peasy.

I don't have any good pictures of it, though.

Here was my working diagram (not sure if that was posted earlier or not):


Here are my batteries. The long black negative cable on the left-side is the one that goes from the most distant battery to the shunt (my positive comes off of the closest battery):


And here's the shunt itself in the lower right corner:

[MendocinoExplorer]

Cool! Thanks for the diagram.

[DefenderBob]

Thank you for the feedback and detail all!

Will be going down path #2, where the shunt will be in close proximity to the negative battery post, with the neg battery terminal connected to the shunt, and the existing neg wire from the battery to TT Frame connected to the other end of the shunt.

Will be removing the Zamp neg wire out of the box on the frame and replacing with the req. wire for the Renogy system, and leave the connection of that nest of wires connected to the frame.

That should shore up the system.