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Have a Smart Solar 75/10, working fine. Is there a need to install a fuse between the controller and battery? Didn't see it in the instructions. What fuse rating?
Though I installed a switch back up to the panel after advice, I think I'll also add a switch between the controller and battery as well to de-power the controller when not in use.
Thanks
There should always be a fuse between the battery and the rest of the circuits.
As for its rating, I installed 3 times bigger than the max possible normal current.
According to the manual, Minimum fuse size above rated controller output close to the battery is 20 percent and maximum fuse size over rated Controller output is 40 percent more: ie 100 Amp output = 120 smallest size fuse and 140 amp max fuse size.
Using your formula of a 3 times larger fuse, would you really, put a 300 amp fuse in the line, or use the 140 AMP fuse required by Vicron?
I guess it really doesn't matter, because If the battery fuse blows and the panel array is producing, doesn't that take out the controller anyway?
BUT, if you have other types of controller issues, doesn't the oversized fuse void the Victron Warranty. per the manual?
Have a super day!
Fuses should be sized to suit the cables they protect.
If you look up the cable size that you used between the MPPT and the battery, you will find a current rating. Your fuse needs to be below the current rating of the wire.
I usually size my fuses at 150% of the expected load to eliminate nuisance trips while still providing protection.
Ensure that your cable exceeds that rating and you should be fine.
The fuse (or circuit breaker) should protect the wire from a fault current.
The most likely and highest fault current will flow FROM the battery to the fault (a short to ground for example). This means the wire needs to be fused near the battery.
Generally, the MPPT's maximum output current will be limited by available solar power or the limits of the MPPT itself. So it's not as likely you'll see fault currents flowing FROM the MPPT that exceed the wire rating. But if that is possible, you'd need a fuse at that end too.
I have always installed fuses between Batteries and MPPT and Batteries and Kit.
Between MPPT and Batteries, I normally use a twice the max supported by the MPPT.
I have a quick question to add on here... I'm planning to set up a system in a camper to charge a LiFEPO4 battery from both a DC DC charger (Orion-Tr Smart 12/12-18 isolated) and a solar MPPT (100/20). The DC DC charger specifies 60A fuses on both batteries which I have purchased and installed (battery post mount style). But, the MPPT controller manual specifies a max fuse of 30A.... Am I good using just the 60A battery post fuse, or should I add an additional 30A inline fuse between the MPPT and battery?
Thanks!
The fuses are there to protect the wiring from battery current if the far end shorts. The size fuse at the battery needs to be based on the wiring. 60 amp fuses would require #4 wire (#6 if it is marine wire which has a higher temperature spec) for safety. If you run #10 wire then the battery side fuse should be 30 amps, not 60.
I believe the MPPT will current limit itself but I'd add a circuit breaker on it's output so you can turn it off for testing or when not in use for extended periods since there is some idle current drawn from the battery.
On Page 14, Section 4.2 of the MPPT solar charger manual BlueSolar MPPT 150/100 up to 250/100 VE.Can it says: " The battery supply must be protected by a fuse as per below table." It then gives minimum and maximum Battery fuse allowable sizes.
Maybe this will answer people's questions and settle the fuse size questions.
Like my High School Shop Teacher said 70 some years ago: When all else fails read the Instructions/Manual!.
If I add two 100/20 mmpt controllers together then I would be ok at 120amp fuse between the battery and the mppt? I currently have a 100amp on a 100/20 is with 10 wire . is that too high? I see that its 30amp
