Connecting solar controller to inverter or converter feeds

[Fisherguy]

I have a PD9280 and a Xantrex 600 watt inverter up front in our trailer under the front sofa. Each one is connected to my golf cart batteries with it's own 4ga cables, fuses are on the A frame in a weatherproof box, 100 amp fuse for the PD, 80 amp for the inverter.

Now I'm adding solar panels (3-120'S) and a Tristar 45 watt PWM controller; I don't want to remove the trailer underbelly to run more cables to the battery for the controller, so do you think it's ok to connect the controller to the 4ga going to the inverter, or should I change the wiring so the inverter is fed by the same 4ga going to the PD converter allowing me to connect the controller to the 4ga that used to go to the inverter? (Hopefully you know what I mean?)
( ... or am I worrying too much) 😉
Thanks

[Fisherguy]

Chris, wow, that's quite the system you have, how may watts are you putting on the roof and how big is your battery bank?

[BFL13]

I have my solar charging at the same time as the inverter is drawing along the neg wire between the Trimetric shunt and the battery. But before that they use separate neg wires to the far end of that shunt, and their positives take separate paths to the battery.

The Trimetric does not record "net" amps, but only the amps to the battery left over from other loads drawing on the solar or charger. If the loads exceed the solar amps, then the Tri shows minus amps from the battery to make up the difference.

The issue (if there is one) is what happens on a single wire with amps going one way and amps the other way--do you get net amps or does it get the solar controller mixed up as to what the battery voltage really is? I don't know, and am hoping the guys on here can explain it.

[Fisherguy]

Oh ya, Joe also said something about the inverter being a high compacitance load, but I think at that point he was thinking the inverter would ONLY be wired to the controller, no battery at all. (He was confused me thinks)

[christopherglen]

As long as the solar output is less then the inverter input, the wires will only ever see less current then there is now. I plan on putting solar on my trailer, and attaching it to the inverter/chargers DC terminals - 4/0 cables to the agm bank.
I have 3 existing converters (100,85,55 amp) already attached there. I run the 100 amp in double conversion off a 20 amp circuit, the 85 off a 15, and the 55 is on my Costco 2000 watt inverter generator. I normally run the IC's 150 amp charger. Dry camping I run the 150+100 off the genset until the IC amps drop below 100, then I shut down the 100.. My inverter is rated 3000 watts running, so a 250 amp charge (peak) is less then the 300 amp rated and 600 amp peak load.

[Fisherguy]

MrWizard wrote:
Connect it to the wires for the inverter
The inverter is never going to draw more than what it always use,s
If part of that power amps is from the solar , that just less from the batteries, very unlikely to do an over load on the inverter circuit

If the PCM controller is basically putting out a square wave as it pulses is there a chance it would cause noise on the inverter input? If they were on separate battery feeds would the battery help 'filter' the pulses?
... or am I thinking too much again? 😄

[Fisherguy]

BFL13 wrote:

pianotuna wrote:
Just do it. It is not as if you are dealing with 90 amps.

If he has the 80amp PD going as well as say 20 amps of solar, he would equal his 100 amp fuse on that path. If he passed the solar along the inverter wires it would only add up to the solar amps on that 80 amp fuse there.

I am not clear on what happens if the amps are opposing direction on the same wire. What would the solar controller think is going on if it is trying to pass 20 amps to the battery along a wire that had 10 amps coming the other way to the inverter?

You do have inverter/chargers using the same DC wire set for both functions, but I am unclear if that would ever be at the same time.

I was never going to connect the controller to the PD cable for just that reason, I was going to have the inverter and the controller on the same cable, so I'm thinking when watching TV the inverter draws about 8 amps, if the solar controller is putting out 20 amps the net flow would be 20 - 8 = 12 amps TO the batteries.

I asked Morningstar, originally their tech support guy "Joe" didn't understand the question and said no, inverter and controller on the same leg is not a good idea, then he said he'll ask one of their engineers, then emailed and said he talked the the other tech support guys and said I'd be okay. So not exactly a glowing endorsement... 😉

[MrWizard]

Connect it to the wires for the inverter
The inverter is never going to draw more than what it always use,s
If part of that power amps is from the solar , that just less from the batteries, very unlikely to do an over load on the inverter circuit

[time2roll]

Use existing #4 wire is fine.

[BFL13]

pianotuna wrote:
Just do it. It is not as if you are dealing with 90 amps.

If he has the 80amp PD going as well as say 20 amps of solar, he would equal his 100 amp fuse on that path. If he passed the solar along the inverter wires it would only add up to the solar amps on that 80 amp fuse there.

I am not clear on what happens if the amps are opposing direction on the same wire. What would the solar controller think is going on if it is trying to pass 20 amps to the battery along a wire that had 10 amps coming the other way to the inverter?

You do have inverter/chargers using the same DC wire set for both functions, but I am unclear if that would ever be at the same time.

[pianotuna]

Just do it. It is not as if you are dealing with 90 amps.