Solar Switches - Sail Magazine

Solar Switches

Jack Fyfe of Westerly, Rhode Island, asks:"I‘ve really enjoyed reading about Nigel Calder’s solar projects, because I am getting two 24-volt Sanyo 205 watt panels and two Morningstar MPPT controllers. I’m using AWG 2/10 wire for the 25–foot run from the dodger where the panels are located to the battery switch. I wonder whether connecting the charge controllers to the
Author:
Publish date:

Jack Fyfe of Westerly, Rhode Island, asks:

"I‘ve really enjoyed reading about Nigel Calder’s solar projects, because I am getting two 24-volt Sanyo 205 watt panels and two Morningstar MPPT controllers. I’m using AWG 2/10 wire for the 25–foot run from the dodger where the panels are located to the battery switch. I wonder whether connecting the charge controllers to the battery selector switch might save me from having to run wires from starboard to port (under an already crowded floor) to the two 24-volt battery banks. I plan to run each solar panel to one bank through the two MPPT controllers—in other words two separate systems. This arrangement, I think, will let me send the panel outputs to either or both banks by means of the battery selector switch."

Nigel Calder replies:

You can wire the positive cables back to the battery switch, but be sure you include the necessary over-current protection (fuse) at the point where you connect to the switch. In principle, you can pick up a ground anywhere as long as the ground cable from that point back to battery negative is big enough to carry all the loads being grounded through that cable. I don’t have your wiring schematic to refer to, but if I understand it correctly, I don’t see a problem wiring two separate controllers to the battery switches and then using the switches to determine which bank is charged.

That having been said, there might be a more cost-effective solution. What about wiring the two 24-volt panels in parallel to a single controller, then wiring this back to the battery side of one of the battery switches? The panels would then be hard-wired to this bank, which you can designate as the house bank. Install a paralleling relay between the two banks and when the first bank is charged the second will be paralleled in.

Tapping 12 volts off half a 24-volt solar array won’t damage the panels, but it will cause imbalances that will negatively impact performance. There’s also a chance that the 12- and 24-volt battery banks will try to balance out through the solar panels circuits, and that could wreck the controllers. So don’t do it. Stay with the 24- to 12-volt DC-to-DC converter!

Related

180625-01-Lead-Horiz

Dongfeng wins Volvo Ocean Race

Forty-five thousand miles of hardcore ocean racing culminated in a breathtaking final winner-take-all 970-mile sprint from Gothenburg, Sweden to the finish at The Hague on Sunday. With Dongfeng Racing Team, Spanish entry Mapfre and Holland’s own Team Brunel all tied on points ...read more

SouthernOcean

The 50th Anniversary of the Golden Globe

Here we go! The 50th anniversary of the Golden Globe, the first singlehanded nonstop round-the-world race, is upon us. On July 1 one tribute event, the Golden Globe Race 2018, will start out of Les Sables d’Olonne, France, with a fleet of 19 amateur skippers setting out in ...read more

180621-X01-Landing-Page

Volvo Ocean Race Cliffhanger

After racing over 44,000 miles round the world and battling their way past the world’s great capes, including the Cape of Good Hope and Cape Horn, it’s all come down to the final 700-mile leg from Gothenburg, Sweden, to the Hague. Brunel, Mapfre, Dongfeng: going into the ...read more

Stearns Photo

Racing the Solo Mac for a Cause

There are plenty of reasons to do a Chicago-Mac race, and Rich Stearns, who has done literally dozens of ‘em should know. This year, though, he’s doing the Solo-Mac for an especially important reason: to help those with prostate cancer.“Two years ago, I was diagnosed with ...read more

TOTW_PromoSite

SAIL's Tip of the Week

Presented by Vetus-Maxwell.Got a tip? Send it to sailmail@sailmagazine.comRafting dangerOne unseen danger when sailing yachts lie alongside one another for a convivial night is that if they happen roll to a wash or begin to move in an unexpected sea, the spreaders can clash ...read more

180615-01 Lead

A Dramatic Comeback in the Volvo

After winning three of the last four legs in the Volvo Ocean Race (and coming in second in the fourth), Dutch-flagged Brunel is now tied for first overall with Spanish-flagged Mapfre and Chinese-flagged Dongfeng following the completion of Leg 10 from Cardiff, Wales, to ...read more