Mounting Smart Shunt

Pong · February 2021

Hi all. New Tab owner here and novice at most things electrical, electronic, or mechanical. Despite this, I'm switching out my single Interstate Group 24 81Ah for two Trojan-105 6v 225Ah. (Many thanks to those who have described and provided photos and details on their install). I'm also planning on setting up a Victron Smart Shunt in the front tub of my 2021 320. I'm not worried about Bluetooth range. My plan is to route the wires and attach the shunt into a project box to keep things protected (thanks to those who have documented this). Unfortunately, the negative load wires from the camper are quite short so I cannot mount to the front of the tub and the narrow space behind the tub seems to preclude managing an attachment there. The situation is made worse in that I'll have to cut off the original ring terminals and replace with the appropriate size (they are too small - 5/16 vs the 3/8 needed for the shunt) and that will make the cables even shorter.

Right now I'm thinking of mounting the project box on the outside of my battery box lid using 3M Dual Lock tape. From what (admittedly limited amount) I have seen and read, this is supposedly better than Velcro. Has anyone here used the Dual Lock for this or similar project? If I set up the shunt in this way, a second line of defense against the project box detaching from the battery box could be a strap around both. Comments on my plan or any suggestions would be greatly appreciated. Thanks.

Oneota · February 2021

I'm rather curious about your project. What I see on the Victron Smart Shunt are plastic side tabs with holes-could you screw or better nut and bolt this to your battery box cover?

Pong · February 2021

My idea is to 1. bolt (or Dual Lock) the Smart Shunt into a small ABS project box made for protecting wiring from the elements; 2. route the cables into the box; THEN 3.Dual Lock the project box to the battery box lid. I'll feel more comfortable having the shunt and it's connections better protected in the project box rather than exposed in the tub. Hope that explains more clearly.

pthomas745 · February 2021

I mounted mine in a small project box, and it fits securely just sitting inside the propane box.

If you are talking about how short the negative cable is from the battery: for me, the best thing I did during my install is just change that whole cable out with a longer, much more flexible cable. Once I did that, the rest of the project was a breeze. Several choices of length here.

https://www.amazon.com/Black-Marine-Battery-Copper-Tinned/dp/B01DRFRFSY/ref=sr_1_6?dchild=1&keywords=Geoking&qid=1613855644&sr=8-6

Pong · February 2021

@pthomas745 - so is your project box just loose in the front tub and not anchored other than by the battery to shunt connections? I am concerned that it would move around too much on bumpy roads and loosen. Do you not find that to be the case?

I appreciate your comment about changing out the cables, but doing that is not possible for me. Until I started working on battery upgrade and Smart Shunt install, I was petrified hooking up jumper cables! I'm researching and researching and stretching my limits, but your (undoubtedly great) mod is just too much. Thanks though.

kbdigitiqe · February 2021

I used this box for my shunt and it perfectly wedges down into the “tray” at the back of the tub behind the battery and stays put no problem, plus I can pull it out if need be:

SOCKiTBOX – The Original Weatherproof Connection Box – Indoor & Outdoor Electrical Power Cord Enclosure for Timers, Extension Cables, Holiday Lights, Power Tools, Fountains & More – Size Small – Black https://www.amazon.com/dp/B009RX5GI2/ref=cm_sw_r_cp_api_glt_fabc_1XD8S5QWDVP5ZW2RDDAW?_encoding=UTF8&psc=1

Sharon_is_SAM · February 2021

I agree with @pthomas745. Just replace the cable leading from the shunt and attach it to the negative terminal in the junction box under the front of the TaB. You can attach the negative SCC wire in that box, too.

pthomas745 · February 2021

@Pong your first few trips on a battery can be a little stressful.....but, with your trailer and care and feeding of your battery.....you need to get used to it. The replacement of the battery cable is as simple as...anything. And, it will make the install of your shunt so completely easy. (You are installing a shunt but intimidated by your battery!? :)I think you have more skills than you want to admit!

The shunt is fairly heavy, and the box that I used to mount it in wedges nicely inside the tub between the battery box and the side of the tub. So, it isn't going anywhere. With that nice flexible battery cable, I can pick it up and move it around a bit if I need to.

I'm "intimidated" around batteries, too. Whenever I'm taking a cable off, I try to cover the other cable connection with a small towel or piece of cardboard, etc. Just being careful.

Pong · February 2021

OK, so when @pthomas745 mentioned changing the whole cable I though he was speaking of going from the front tub all the way to the converter!! I did say I am a novice.

Funny, but I feel quite confident in adding the two 6volts and the Smart Shunt. It all seems straightforward, now that I've scoured this forum and watched a bunch of You Tube videos, including a very helpful one from Victron. There is no DC power in the rig now. I moved (well, my husband provided the muscle power) the battery out for the winter and pulled fuses prior to that. Once I figured out the fuses and which wire went to what, and disconnected the battery successfully my confidence increased, at least with respect to DC.

While changing the cable might be in my future, I'm inclined to hold off on that if I can wedge the box in the back of the tub as the negative wires will reach there. It's cold here in northern NH (although things are expected to "warm" to the upper 30s next week) and hanging around in the big old drafty barn is not much fun. We'll be taking the Tab out in mid March, so I think installing the batteries and the SS will be enough before then. Maybe this summer

For future reference, is the junction box obvious or will it require removing any underbody covers to access?

@kbdigitique thanks for the link to the box you used, and to others, thanks for the suggestions and encouragement. I'll let you know how it all works out.

wolfeel2000 · February 2021

I just finished installing my Victron Smart Shunt in a Pelican case that I had sitting around. I bolted the shunt and case to the battery box lid (machine screws with the heads inside of the battery box so there is nothing sticking down towards the battery). It seems to work. I ran the wires inside of a 3/8" wire loom and used heat shrink tubing on all of the connections.

Tomorrow I will tackle hooking up a 60W solar panel I had sitting around. hopefully the charge controller I have works. If not, I will wait and upgrade to a Victron MPPT controller so I can eventually switch to Lithium batteries. I need to figure out what my power usage is using the Smart Shunt first. I don't want to oversize/undersize my battery bank.

Pong · February 2021

@wolfeel2000 thanks for your input. It's good to have feedback from someone who has gone with a battery box lid mount... always good to have options.

Sharon_is_SAM · February 2021

@Pong - follow the curved front of the trailer just behind and under the front tub. The photo below shows what is behind the removable cover.

https://us.v-cdn.net/5021717/uploads/editor/7k/goe6ndgzkzei.jpg

https://us.v-cdn.net/5021717/uploads/editor/2u/5nxe0b15ew2c.jpg

https://us.v-cdn.net/5021717/uploads/editor/1w/ehviu6tm0eiz.jpg

Horigan · February 2021

If your plan is to permanently mount the junction box to the battery box lid, I would use either fasteners or 3M VHB mounting tape. If you want a removable mount, then the Dual Lock should be fine.

pthomas745 · February 2021

@Pong, I apologize for "splaining" something that you were clearly already doing. I thought you were not wanting to change out the battery cable from the battery to the shunt.

As soon as the wiring from the battery compartment slips in toward the trailer, I'm done. Way above my paygrade. I do enjoy looking at the pictures of the junction boxes and bus bars, etc. Maybe someday!

Pong · February 2021

Thanks @Horigan and @Sharon_is_SAM. I have the tire mounted under the front on the 2021. Wonder if that is covering the junction box? Rhetorical question for tonight. I'll go take a peak tomorrow.

Pong · February 2021

@pthomas745 - please, no apologies - I very much appreciate your input and your support. You would have to go much further to merit apology expectations from me.

This morning I’ve found myself examining @Sharon_is_SAM ‘s photo and diagrams in great detail. Maybe I’m becoming an armchair electrician too!

Thanks again everyone.

MarkAl · February 2021

@Pong there is variability of T@Bs

a suggestion is to put your trailer's year and model in the Signature line - it helps to get the best answer back. Cheers - it's an adventure!

Pong · February 2021

@MarkAl, done. Thanks for the suggestion.

Pong · February 2021

The camper junction box was easily found and free of the spare.

Thanks again to all those who have contributed to my knowledge and confidence. My plan is in place. Not just waiting for the Verna-style battery box to arrive to get to work.

Pong · March 2021

Hi all. I finally got to work on my upgrade from group 24, to 2 6v FLA Trojan batteries and installation of the Victron Smart Shunt as the temperature got up from highs in the 30s to a high of about 57 yesterday. My husband provided the brawn hefting those 65# monsters into a "Verna-style" box after attaching said box to the front tub with sheet metal screws. After lots of agonizing about the Smart shunt over the past few weeks - which project box, which gland size, where to mount, etc, I realized that there is room to attach the shunt above the batteries. inside the battery box, thus eliminating the need for project box and associated peripherals.

I will be mounting the shunt (hopefully) using Dual Lock. After cleaning the area with alcohol, letting it dry, and warming the area with a hair dryer I affixed a piece of the Dual Lock to the inside of the box, above the battery. For the best chance at good adhesion I will let the piece of DL sit, without any load, for a day or so. I've also added the companion DL to my shunt and will let that "cure" as well. Worse case, we will attach the shunt with small bolts.

While waiting for the recommended "cure time", I reconnected the camper and roof top solar wires to the battery directly so that I can work in the camper with some heat and so that the batteries will remain charged. Unfortunately, our brief spell of warmer weather will be short lived and I don't want those FLAs discharging in the cold, unconnected to a power source.

So, step one is accomplished, including what I think are pretty solid crimps on the neg/ground terminals. (I had to change out the negative terminals to 3/8 inch so they would fit onto the shunt.) In the next few days I'll disconnect the negatives, install the Smart shunt, and reconnect to the shunt as per many excellent videos and the quick start instructions provided with the shunt.

Thanks to everyone who helped with links, photos, comments and encouragement. I will post again when all is done.

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