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I'm trying to set fuse/breaker values surrounding the charge controller and am wondering if it's capable of feeding any current to a short circuit on either side. If a fault occurs on the pv panel side, what current can pass through the device from the connected batteries?
Thanks
You shouldn't get any fault current to flow though the PV side from battery, otherwise you'd be heating your PV from battery at night.
Having said that, it's always a good idea to have circuit protection between the battery and MPPT - anything can happen.
My favourite are DC rated MCB's (make sure that polarised ones have + to the battery not MPPT). Good fuses are fine too. A good 45A fuse should be fine in your case. Try and avoid "automotive" type blade fuses, they tend to run hotter than a $2 pistol.
Thanks! I'm thinking of a fuse/breaker like this one. What do you think? What is an example of a DC rated MCB - brand name? - Link? Would you consider a fuse like this to be an "automotive" type blade fuse?
A separate but related question - I often see fuse or breaker protection between the pv panel and the charge controller, but my pv panel, for example, a 320W panel, has a short circuit capability of 10 amps - pretty much the same as the max load current. What's the point of putting in a fuse rated higher than the short circuit current?
Hi Van. For pv > mppt, 'Noark' double pole work fine (lots of sizes). This is a US link, and note the accessory solar label kit: https://www.tro-pacific.com/products/noark-500v-dc-mcb-16a?dfw_tracker=43985-8712935702593&gclid=Cj0KCQiApvbhBRDXARIsALnNoK1Us1vCX7Q2kOYcThCB85IfabS0dpi-4LBluKPq1OUtUNsPLnbYW1EaAu_BEALw_wcB
My own Victron dealer (Australia) recommends them, and being a standard din mount, also supplied me with a tidy little wall mounted enclosure.
Those ANL fuses (I call them forklift fuses) are good for the main battery cables. Victron actually use them inside some kit.
The button/lever ones are rated for lower V, and are ok for mppt > batts, but they can get hot and cause spurious trips. So don't buy one rated too close to the A you put through them. I've found a 20% margin not enough, so ended up at like 85%. Cheap junk abounds there too, so take care.
And of course fusing and breakers are to protect your *wires*, so if you step up the rating - step up the wire size.
Hey @WKirby and @JohnC I have to think I'm missing something here. If the MPPT cannot pass through any fault current from the + bus, and the pv panel short circuit current is the same as the pv panel load current, what possible fuse or breaker protection makes sense between the panel and the MPPT? Seems like only a disconnect is in order.
If you only have one or two parallel strings in to one MPPT then you can get away without fuses on PV. Any more then two strings then you really need fuses for each string.
I like fuses anyway because I'm crazy like that.
