Rerouted 320s Battery Load through Victron to allow load monitoring

dCliffhanger

I noticed that my new 2020 320S Victron 75\15 Solar controller's Load terminals were unused. Twelve volt power is routed straight to the power converter from the battery on\off switch. So, although my solar controller gives me good solar charging and battery voltage information, it does not monitor battery usage at all.  After a good deal of asking why not and researching options, I came up with a plan to take full advantage of the Victron's monitoring capabilities. 

Most simply stated, I bought a multi-terminal (1-0-2) switch, cut the 10 gauge red positive wire providing power to the converter and redirected it into the switch. Then I ran wires from the Victron +-  Load terminals into the switch.  This allows choosing where the power comes from, straight from the battery or through the battery monitoring Victron.  I connected the output wires of the switch back to the cut positive converter feed wire and to the common so all functions and circuits work as normal.  However, with the shore power unplugged I can now choose power circuit 1, which functions same as the original. Or, I can choose circuit 2 which gets it's battery power through the Victron, and gains the ability to monitor battery usage such as how many amps I am drawing at any given time.  I hope to leave it in this position. The other bonus choice I get is circuit 0 which cuts all power from the battery.  This may duplicate the master battery switch in the tub. So now I'll be able to be twice as Off! However, there has been discussion of whether or not the tub switch cuts power to the emergency brake system (which would be dangerous and illogical). With my new switch I can leave the tub switch on to be sure there's power to the brakes and still turn off power to everything else. Note that solar charging still continues with switches on or off. My Victron has a maximum load capacity of 15 amps which should handle any routine 12v power needs.  Except, I realize now that my 3way frig draws about 11amps so no other large draw would be simultaneously supportable. However when boondocking and running on battery, I expect the frig will be on propane so no problem.  My inverter could easily exceed the 15 amp limit so I wired it straight to the battery.

I don't know why Nucamp didn't wire my unit this way in the first place to fully utilize full Victron functionality. I suspect that because solar was an add on option, the panels and victron controller were wired in after the standard wiring was completed. They sure use a lot of electrical tape and anchors!  It was a somewhat scary project that I was confident about - in theory. Though, there were a few times I had to take a deep breath waiting for either darkness or fire. 

Cbusguy

The load monitoring is a know weak point with the controllers.   While you bypassed the controller to wire your inverter straight to the battery,   many before you have not and damaged the controller.    

you may want to be careful as the trailers AC battery charger may charge the battery through your solar controller and exceed the rating.

dCliffhanger

Cbusguy said:

you may want to be careful as the trailers AC battery charger may charge the battery through your solar controller and exceed the rating.

Good point. It does sound like that there could be a possibility of "reverse flow" through the Victron's load terminals if battery voltage dropped low enough to trigger the charging cycle. Hmmm that is a concern. Any chance you could point me to any of the posts discussing this?  I'd not picked up on that being an issue.  For now I'll do some experimenting and monitoring.  It sounds like it would be wise to switch to my original circuit 1 before plugging into shore power. Thanks for picking up on that!

Cbusguy

There are no post on this forum,   It may have been a victron or solar power reddits I read,  

dCliffhanger

I'm going to explore the feasibility of putting a diode into the circuit to protect against reversing back through the controller. I'm unsure how much resistance or load\drain they would add - which I'd hope would be very small otherwise I'd be defeating the whole purpose of managing the load to gain efficiency.

I left home for day with the system off shore power and connected through the load terminals with only the minimal, parasitic, draws. I came back to find that the controller Load circuit in "Off" status and wouldn't stay on even after configuring it to "Always On".  Frustrating!  Further reading revealed that there is a physical jumper on the controller that set's the load to "Off". Gonna pull that and see if I can regain configuration control.

dCliffhanger

Well I pulled my solar controller again and found there was No jumper installed. Pulling it out was supposed to be the fix. Now, as soon as I switch on the Load terminals it turns off. First tries it would stay on for a little while and display power draws like it's supposed to. I've seen comments on the Victron site where theirs turn off when in Float mode and then connected to a fairly heavy load like a frig. Mine is turning off connected to the AC\DC converter. It may have a high initial power up draw that's causing the issue... very frustrated - especially since it started out working fine. It's sounding like a hardware\programming issue.

Tundra57

A diode will cause a voltage drop of approx 0.7v accross it's juction. So your output voltage will be that much less. Also watch it's rating. The higher current ones need a heatsink.

dCliffhanger

I am taking a pass on this for now. Invested too many hours without results on a problem that sounds like a hardware\programing issue. Tundra57's pointing out the loss of voltage (power) installing a diode is further disincentive. The one other theoretical cause I've though of is the inrush current caused by the converter when it comes on line receiving power from the Victron. Don't know how to work around that without eliminating it from the circuit and redirecting all dc circuits directly to the Victron.  If I want power monitoring, it sounds like I'll need to invest in one those shunt based battery monitors - which Victron also sells. I'm sure they'd like that. Grumble.....