The Victron BMV-712 Smart battery monitor is more expensive than the SmartShunt but comes with a lot of surplus, a bistable SPDT relay, a buzzer and of course a display featuring four push buttons. Albeit the latter also is a drawback as it is necessary to cut a 53 mm hole somewhere into a panel to be able to mount it. The solution introduced here may not win a design award but is very easy to create. As shown in the photo the BMV fits nicely into a simple junction box which is made of a soft plastic and easy to work. The BMV is 31 mm in depth, the junction box has an inner depth of 32 mm and the lid gives about 2 mm more but the RJ12 plug sits in a recess so no problem attaching the cable.
On the photo you can see a marking at the upper right corner of the BMV I hadn't removed yet. It gives you a hint how I proceeded to make the cutout. I first drew a centered square the size of the attachment flange onto the top of the lid, fixed the flange on the lid with some adhesive tape and pierced holes for the screws into the lid. After fixing the flange with the supplied screws I removed the adhesive tape and used the flange as a ruler to draw a circle at the proper location for the cutout, but that's too large. Thus, after removing the flange, I placed the attachment sleeve inside the circle, centering it properly, and marked the cutout on the lid. Using the 4 cm blade of a tiny pocket knife I completed the task. Everything else is well described in the quick installation guide. The BMV can now be mounted with two small screws anywhere on a flat surface eventually drilling a hole for the cable which can be fed through the back of the junction box or through any of its sides.