Victron MPPT grounding

[HappyCampers]

Hey WTWers!

Hope you are enjoying summer, camp life, etc...

With fishing and hiking seasons in full swing and gas prices off the charts, our camper has mostly sat since our eastern Oregon trip. This has allowed me to put my attention towards planning and installing a basic solar system.

The heart of this a Victron Smartsolar MPPT 100/20. I was initially looking at the smaller Victron MPPT units, so hadn't anticipated there to be an additional grounding wire screw (located on the left side cooling fins). After doing a pretty thorough forum search I remain uncertain as to where to ground this.

The additional ground wire for my battery relay switch (not the battery negative) was also connected to the negative buss bar in the battery box. When I recently replaced this, I grounded the new unit the same way. Is it okay to do the same with this MPPT ground wire?
Alternatively, wondering if putting it behind the nearest cabinet bracket screw would provide sufficent grounding. Since the smaller units don't even have this ground wire screw, perhaps it's not even critical to install a wire?

It seems there are a lot of folks on here with the Victrons, so hope to hear from you!

 

[Jack]

You want to wire your battery negative directly to the MPPT "Bat -" terminal (or thru a common connection at your negative buss bar). With DC, "ground" is your negative, with AC, ground is a third conductor, although it is tied to AC neutral at the mains panel.
Wire the battery plus (fused) to the "Bat +' terminal. 12 gauge will handle 20 Amps.

Connect your solar panel positive and negative to the "PV +" and "PV -", respectively.

MPPT "Load" is optional. If you connect it, the MPPT will prevent your battery from being discharged below a certain level. This is particularly important for AGM batteries but also useful for lithium batteries. Since it's easy to change the discharge voltage with bluetooth, you can set your AGM level to 11.55 V (about 30%) charge. If the MPPT cuts power from your AGMs and you need a few more amp hours, bluetooth into the MPPT and temporarily lower the voltage to 11.35 V (about 20% SoC). For lithium, 12.9 V is roughly 20% SoC. If the MPPT cuts power unexpectedly, you probably have a load your are not aware of. Find it and shut it of.

To setup, disconnect the wire coming into your camper fuse block (the "hot" side of the fuses) and tape the end so it cant short. Then connect a new wire (12 gauge is OK) from the hot side of the fuse block to the MPPT "Load +". Connect the MPPT "Load -" to your negative buss bar.

 

[HappyCampers]

Hi Jack,

Thanks for taking the time to share that information. I probably wasn't entirely clear, but my question has to do with the additional ground screw not associated with the PV, battery, or load connection points. This is located on the cooling fins on the left side of my Victron MPPT 100/20.

For the time being, I have wired it to the negative buss bar, but haven't connected everything up yet. Still waiting on the mounting brackets. Some additional sleuthing has led me to believe this is correct, but hope to get confirmation.

 

[Vic Harder]

I would not worry about that extra ground. If you are really concerned, just run a short jumper to the battery ground side of the MPPT itself.

Are you including a Victron shunt/BVM in your setup? If so, then all your grounds to the shunt, not the battery negative post.

 

[HappyCampers]

Thanks Vic! Was strange to not see this previously addressed. Maybe because it's so obvious or maybe I didn't search far and wide enough?

I had not considered looping it over to the battery negative on the MPPT. Will do this since I already have a wire attached and would be a pain to remove now that controller is screwed down in tight quarters.

Yes, the Victron Smart Shunt was the beginning of all of this obsessing about battery life, solar, etc...!!! All of my grounds are wired to a buss bar, then pass via single wire through shunt to battery negative. Love the bluetooth functionality!