Equipment: Renogy Rover MPPT 20A charge controller (100Vmax). 2 (or 3) X 100W Renogy mono panels (20Voc, 6Asc). Series connection.
I'm planning to feed 2 panels in series into the charge controller. They'll be permanently mounted on the RV roof. When the campsite is shaded, I would like to add a 3rd, identical, portable panel in series which I can lay out where sun is available. 3rd panel will be disconnected and stored when moving camp. Batteries will remain connected at all times.
Can I simply unplug the series and insert the 3rd panel in series without any arc protection? Won't 6A of current draw an arc when I disconnect to add or remove the 3rd panel? Should I take steps to prevent a 40V charge accumulating across the open contacts? How well will MC4 connectors hold up to this arcing, or to the contact wear of frequent reconnects? Should I use Anderson power connectors instead of MC4 to frequently reconnect? SAE connectors? Should I use a switch with some sort of bleed resistor to prevent an an arc?
Perhaps I'm just a worry-wort. I do realise the arcs I'm asking about are small. Perhaps the controller and panels have protection built in, but I'm also concerned with the connector contact lifetime. Please relate your opinions and experience with panel switching and suitability of connector types for frequent reconnecting.
Post by Gary in Michigan on Apr 20, 2019 3:41:47 GMT
Hello, Just reading your RV set up and have a couple of comments. First, using MPPT on a 12v battery bank and 2 panels in series is ok, but remember when those panels are shaded you may get close to zero input into the charge controller as you will need at least 18V of PV input to charge the battery. Using series from the RV roof down to the unit does eliminate have four wires and thus you can have two on the roof. However, with DC at the voltage you're talking about, the so-called arc would be minimal and downstream from the controller. IMHO, I would wire a separate portable set of wires to the controller since while in shade the delta between the two roof panels and the portable panel in full sun may not be that great. I have found that for small systems if you're worried then running parallel eliminate shading issues that MAY occur in panels with crappy bypass diodes and then when you connect the portable panel, then again the delta would be zero or near zero. For example, in my garage I sun a saraphim 290W panel and plug it in directly using a 90XT connector since I am no longer a fan of anderson powerpole connectors (15,30,45 amp) variety and they seem to fail or break after repeatly using them. Bottom line, I would NOT worry about an ARC as you can always put an inline automotive fuse on the portable PV run and let the fuse take the arc. The arc will NOT be at the controller unless the wires are loose.
Thanks for your input, Gary. I have abandoned the Anderson connectors and simplified the wiring. I'm going to use a Marinco trolling motor connector, because it has a through-wall mount and twist lock. I'll just mate it with a short circuit when not using the roving panel.