Originally Posted by wareaglewalt
I have 2 Zamp obsidian portable suitcases: 100 watts per suitcase. Currently one suitcase connects to the other and then runs into the Zamp connector on the tongue frame. Dunno about serial or parallel. The 180 watts on the roof go into a 150/35 Victron controller. The PWM controller on the portables shows full when the batteries are showing barely 70%. Itís annoying and inefficient. So Iím hoping adding another controller for the portables will fix this. If the rooftop are charging at 12 amps, Iíd like the portables to be at least close to that and not just 2-3 amps or showing full. Is this a reasonable expectation?
If your Victron controller is 150/35 and you only have 180 watts on the roof you should be able to just wire the two Zamp portable panels to that controller. Not all panels need to have their own controllers.
Parallel connection means that the positives all connect together on one side, and all negatives connect together on the other side. They may not all connect together at the same point in the harness, but all your panels will have their positive wires feeding the same side of the controller and the negatives on the other.
Serial connection for panels mean that you're connecting your panels with the positive lead of the first panel connecting to the negative lead of the next panel. This would continue with all your panels - positive to negative - until all your panels are daisy chained together. The positive & negative leads from the two end panels are then connected to the controller.
When you connect panels in parallel you keep their output voltages the same, but the amperage output from them all is added up. For example, if you have two panels with an output of 5 amps @ 20 volts, when connected in parallel they'll have a cumulative output of 10 amps @ 20 volts.
Connecting panels in serial does the opposite, adding the voltage but keeping the amperage the same. Those same two panels with an output of 5 amps @ 20 volts connected in series would have a cumulative output of 5 amps @ 40 volts.
Why choose serial or parallel? They each have advantages... Panels connected in parallel do better if you have partial shading. The panels in the sun continue to function at their full capacity and only the panel in the shade is affected by the shade. A downside for parallel connection is voltage drop on the wires connecting them, as you are dealing with lower voltages and higher amperages. Higher amperage requires a larger diameter wire to avoid voltage drop.
Panels connected in series have the advantage of being able to use a smaller gauge wire or a longer wire without voltage drop, since they have a higher voltage/lower amperage output. A downside of series connection is that if one panel is in the shade it will bring down the entire series of panels it's connected to. This is not so serious a problem with portable panels though as you can move the panels to keep them all in the sun.
So, how do you know if you can connect them all to your existing controller without overloading it?
You have a Victron 150/35 controller, which I believe can handle up to 150 volts of input from the panels and can output up to 35 amps of charging to your batteries. This means that the cumulative voltage from your panels has to be under 150 volts to make use of them optimally.
The Zamp 100w portable panels you have each have an output of up to 26v and under 5 amps. If you connected your two panels in parallel you'd be connecting anywhere up to 52 volts to your controller, depending on sun conditions. The amps would be under 5, which means that you would have less issue with voltage drop over your lead cord to the panels.
The two panels on your roof have similar outputs - about 25 volts each. Assuming that they are connected to your controller in parallel, they are sending about 50 volts or less to it. Combine this with the voltage from your two portable panels and you're still well under the 150 volt max on the controller.
If this were my setup, I'd wire a connection for my portable panels to feed them into the Victron 150/35 controller parallel to the roof panels. Then I'd set up a suitable 30-50 foot cable to connect the portable panels to this connection so the panels could easily be positioned in the sun while the trailer sits in the shade. You may need to bypass any controllers built into the portable panels from the circuit to do this.
Sorry for the super long post, but there was a lot of information here to lay out.