OK, I intend to have 200W solar panel output on the roof of the coach at 26V this spring. Just enough to keep the batteries charged I hope.
Should I install catastrophic fuses? What size. if any?
I'd say 30 or 40 amp -- 1 on the hot line between the panels and your solar controller and one between the controller and the batteries. (another between the batteries and the inverter if you connect one)
I installed a 250 amp fusible link down where the solar goes into the battery connection at the electrical bus. I also have breakers up where the solar goes into and also out of the controller. You can't be too safe when a lot of amps are available. Northern Arizona Sun and Wind and Midnite tech recommended this.
Arrows point to the fusible link.
Pierce
Volts times Amps equals Watts, Watts divided by voltage equals amps. 200w divided by 12v equals 16.67 amps. 25 amp fuse would protect. I think solar panels can be shorted out (please double check) and not be damaged.
Scott
is it ok to short circuit a solar panel - Google Search (https://www.google.com/search?q=is+it+ok+to+short+circuit+a+solar+panel&client=safari&channel=ipad_bm&sxsrf=APq-WBveg3sk2ZnG4DXE77KPCeSYYRUAyw%3A1646367167520&source=hp&ei=v5EhYsLdGdrEkPIPwImL2Aw&iflsig=AHkkrS4AAAAAYiGfz-2bhkarMHgkbWmDcIZu5KCa5eqV&oq=can+solar+panels+be+shor&gs_lcp=Cgdnd3Mtd2l6EAEYAjIGCAAQFhAeMgYIABAWEB4yBQgAEIYDMgUIABCGAzIFCAAQhgMyBQgAEIYDOgcIIxDqAhAnOgQIIxAnOgcILhDUAhBDOg4ILhCABBCxAxDHARDRAzoFCAAQgAQ6EQguEIAEELEDEIMBEMcBENEDOg4ILhCABBCxAxDHARCjAjoICAAQgAQQsQM6EQguEIAEELEDEIMBEMcBEKMCOggILhCxAxCDAToLCC4QgAQQxwEQrwE6BwgAELEDEEM6CwgAEIAEELEDEMkDOgUIABCSAzoICC4QgAQQ1AI6EQguEIAEELEDEMcBENEDENQCOggIABCxAxCDAToLCAAQgAQQsQMQgwE6BQgAELEDUMCYAViHlAJgiM4CaAVwAHgAgAGJAYgB2BSSAQUxNi4xMJgBAKABAbABCg&sclient=gws-wiz)
No - you will not damage a solar panel by shorting it. Solar panels are designed to be continuously operated at very very close to their short circuit current. A good quick test of a solar panel is to run it short circuited into an ammeter.
is it ok to open circuit a solar panel - Google Search (https://www.google.com/search?q=is+it+ok+to+open+circuit Yes. It does not hurt them to be disconnected—open circuited. Leaving anything out in the sun and rain will cause eventual degradation. +a+solar+panel&client=safari&channel=ipad_bm&sxsrf=APq-WBvdnuGsk_yivY3Vmic92oSFv20ieQ%3A1646367212388&ei=7JEhYqKnF8fAkPIP6K-YcA&ved=0ahUKEwiizfTmy6v2AhVHIEQIHegXBg4Q4dUDCA0&uact=5&oq=is+it+ok+to+open+circuit+a+solar+panel&gs_lcp=Cgdnd3Mtd2l6EAM6BwgAEEcQsAM6BwgjELACECc6BQgAEIYDOgYIABAHEB46CAgAEAgQDRAeSgQIQRgASgQIRhgAUNAOWKk0YK1CaAFwAXgAgAGLAYgB7gmSAQMzLjiYAQCgAQHIAQjAAQE&sclient=gws-wiz)
Yes. It does not hurt them to be disconnected—open circuited. Leaving anything out in the sun and rain will cause eventual degradation.
Trying to amplify Mr. Davidson's remarks, a circuit breaker can carry continuously about 75% of its rated current. That being said, for protection multiply your maximum current by 1-1/3 and choose accordingly.