Just to clarify some of the half answers posted previously: The wires from the panels to the charge controller must be sized to handle the short circuit current of the entire array (additive if parallel array). Because the maximum current under normal conditions is often ~95% of short circuit current, it is essentially impossible to fuse this side with the industry standard 25% safety factor without having the fuse blow prematurely under normal conditions.
The most critical fuse/breaker is on the battery side of the charge controller as the battery bank has a much larger potential to dump high current in a short circuit. This fuse/breaker should be mounted to the charge bus (if available) or as close as possible to the battery. However, it is not a bad idea to have a dual pull breaker between panel and charge controller sized at 10-15% > short circuit current. The main purpose of this breaker is to be able to safely disconnect the panels for maintenance or replacement. To the original poster: How large is your battery bank and how old is it? Lead acid or gel? How large is the solar panel? Knowing these paramater can help us narrow down the likely problems. My guess, is that the most likely cause is you had days of cloudy skies after the hurricane and weren't getting any charge. Or your battery bank may be small or aging and unable to accept a trickle charge anymore. On Sun, Aug 29, 2021, 8:44 PM Dave S via CnC-List <cnc-list@cnc-list.com> wrote: > My 175w and 50w are fused for the gauge of the cable, directly adjacent to > the controller. This is per the renogy manual I believe. 12 awg solar > cable would be likely fused at 20a (assumes 105deg rated insulation) which > at our 20vdc would translate to a BIG 400w panel. (C&C 65?) These bigger > panels are typically 48vdc I believe so the current stays modest. anyway > - no need to fuse at the solar panel. > > The batteries are connected in parallel with copper bus bars and the > positive wires are protected with cube fuses at the battery. (Both solar > and shore power Chargers and the cables to the battery switch) > > Dave 33-2 > > Dave > > Sent from my iPhone > > On Aug 29, 2021, at 7:47 PM, Marek Dziedzic via CnC-List < > cnc-list@cnc-list.com> wrote: > > > > I have that end covered. Proper fuses right at the battery terminals. And > the solar panel is tied to the controller, not the batteries themselves. > But there is some 25’ of cable from the panel to the controller and I > always wonder if that part should be protected as well. The solar panel is > only 50 W, so it cannot produce too much current (and too much heat). But I > wonder what it the proper way to connect it and protect it. > > > > Marek > > > > *From:* Ken Heaton via CnC-List <cnc-list@cnc-list.com> > *Sent:* Sunday, August 29, 2021 6:26 PM > *To:* Stus-List <cnc-list@cnc-list.com> > *Cc:* Ken Heaton <kenhea...@gmail.com> > *Subject:* Stus-List Re: Another Solar question > > > > Really, should there be a short or other electrical failure, the big > source of current that would heat up and burn up the wires and possibly set > the boat on fire, would be the boat's house or starting battery bank. So > the fuse should be as close as possible to where the wires from the solar > panels tie into larger wires or bus bars (or the batteries if wired > direct to the battery bank). As close as 6 inches if possible. > > > > Ken H. > > > > On Sun, 29 Aug 2021 at 19:19, Marek Dziedzic via CnC-List < > cnc-list@cnc-list.com> wrote: > > I have a simple question - the fuse is there to protect the wire; so, the > fuse should be as close to the solar panel as possible, shouldn't it? Where > would you put it? Outside, next to the panel? Or inside, as soon as the > wire goes through the deck? > > > > I bet there are some rules of thumb. > > > > Thanks > > > > Marek > > 1994 C270 Legato > > Ottawa ON > > > > > > Thanks to all of the subscribers that contributed to the list to help with > the costs involved. If you want to show your support to the list - use > PayPal to send contribution -- https://www.paypal.me/stumurray Thanks > - Stu > > Thanks to all of the subscribers that contributed to the list to help with > the costs involved. If you want to show your support to the list - use > PayPal to send contribution -- https://www.paypal.me/stumurray Thanks > - Stu
Thanks to all of the subscribers that contributed to the list to help with the costs involved. If you want to show your support to the list - use PayPal to send contribution -- https://www.paypal.me/stumurray Thanks - Stu
