fusing controller

poorman137

New Member
Joined
Sep 22, 2021
Messages
3
make sure you use a circuit breaker -2 pole- on the output of the PV controller. One pole for solar panel disconnect & one pole for output disconnect. This way if the controller output goes over current & trips, the breaker, it shuts off the solar panels. The way everybody is telling you to fuse the output is wrong. Their way ,If the controller output fuse blows then the panels will burn out the controller.
 

FilterGuy

What, me worry?
Joined
Nov 26, 2019
Messages
4,729
Location
Los Gatos CA
If the controller output fuse blows then the panels will burn out the controller.
The subject of damaging the SCC by disconnecting the battery has been debated *many* times on the forum. There is almost a religious belief that disconnecting the battery before disconnecting the solar will damage the controller but there is not much evidence that this is true in real life.

From the controllers point of view, How is the fuse blowing any different than the BMS disconnecting? Victron will explicitly tell you that this is not a problem for their controllers. There are still some controllers out there that have manuals that allude to this but even those do not appear to have the problem and are advertised as working with systems using BMSs... so they must be able to survive disconnects. If the controller can not be disconnected while the panels are still connected, it is not a good controller and probably should not be used on systems with BMSs.

In one recent thread, the poster reported that one of the companies told them that the controller burning out due to the output fuse blowing is covered under waranty but if you manually disconnect and the controller burns out it is not covered under waranty...... Say what? How does that make any sense?

@Will Prowse once commented that he intentially tried to damage all of his different controllers by disconnecting the battery and was unable to damage any of them.
 

740GLE

Solar Addict
Joined
Apr 30, 2021
Messages
641
I’d wager those that do have issues with disconnecting the battery from the SCC before PV have more to do with transient voltage spike above max VDC input under high current charging. Also might be issues if pushing max VOC of their PV string.

More robust controllers prob deal with it better than economy controllers
 

Zil

Just another ass on the web
Joined
May 27, 2020
Messages
1,339
The fuse protects the wire from battery discharge in case of short circuit. It doesn't protect the output of the controller. Put the fuse at the positive battery terminal. Also repeat what FilterGuy and 740GLE has said. Three times so it sinks in.
 
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