roaringgirl
Well-Known Member
Why put a fuse between an MPPT and the battery?
Fuses in solar charging circuits
- Thread starter roaringgirl
- Start date
[2574]
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I thought the same as there is a fuse in the MPPT itself. But then I think it’s maybe good practice to have a fuse very close to the batteries.…but I might be making that up…..
lustyd
Well-Known Member
The fuse in the device protects the device from incorrect setup I believe, Victron specifically call this out in their manual.
RJJ
Well-Known Member
The cables from panel to MPPT are higher voltage, lower amps and (depending on instructions) protected by the internal fuse. The regulator chucks out 12v (or 13 or 14.8 or whatever) at high and variable amps. The fuse before the battery protects the cabling which might be safe, depending primarily on diameter, for up to 20A or 50A or whatever.
For example, we have 320W of panels going into a regulator rated for 350W. I installed wiring and a breaker, per the manual, rated for 30A. Which should have been enough (320W/12V = 26.7A assuming 100pc conversion); it turned out that any fully sunny day in August chucked out more than 30A and tripped the breaker, implying the panels were exceeding 320W and the cabling was at risk. Upgraded the wire and breaker to 50A and all's well.
Alternatively you "could" install wires 2 inches thick, but you'd still be left with the connectors. I would stick with the manual.
Also, it's recommended to have the MPPt as close as possible to the batteries.
For example, we have 320W of panels going into a regulator rated for 350W. I installed wiring and a breaker, per the manual, rated for 30A. Which should have been enough (320W/12V = 26.7A assuming 100pc conversion); it turned out that any fully sunny day in August chucked out more than 30A and tripped the breaker, implying the panels were exceeding 320W and the cabling was at risk. Upgraded the wire and breaker to 50A and all's well.
Alternatively you "could" install wires 2 inches thick, but you'd still be left with the connectors. I would stick with the manual.
Also, it's recommended to have the MPPt as close as possible to the batteries.
VicS
Well-Known Member
What Robih says
IF a fuse is fitted between the two in addition to any fuse in the controller it should be close to the battery and would be there to protect the wiring from the very high current that the battery could deliver.
However the wiring between a solar controller and the battery should be short and direct the fuse perhaps only being needed if that is not so.
Richard10002
Well-Known Member
Worth repeating that fuses are fitted to protect the wire against the "unlimited" Amps that the battery can deliver.
Where current is limited, as it is between panels and controller, there is no need for a fuse as long as the wire can carry more than the max Amps that the panels can produce.
Having said that, like many, I have a breaker type switch between panels and controller, so that I can cut the power from the panels without covering them in blankets.
CapPugwash
Well-Known Member
As someone (probably Paul) said to me when asking about fuses, they are for when something breaks. So if the controller gets wet and shorts for example the resulting current could melt the wires and start a fire. So the fuse should be rated to protect the wires in such an event.