Do I fuse solar charge controller into a lynx distributer

[MikeV]

I understand the importance of fusing wires but I am a little confused with my current setup.

Overview: I am setting up a new lithium battery system in my RV. I have 2, 100AH batteries that feed into a Lynx distributer. I understand that fuses should go as close to the power source as possible to protect the wires. Since the power source in this scenario is from the charge controller, what do I gain by placing a fuse in the lynx distributer?

I already have a 30A in line fuse that I have at the charge controller. So do I put the same size fuse in the lynx distributer? Do I over size this fuse?

I do not use the solar charge controller to power anything. I don't think there would be a situation where the battery would send power to the controller.

Thanks you in advanced for your help.

 

[John Frum]

Having over-current protection as close as possible to the positive terminal of the battery is really critical because a dead-short upstream of the OCPD can be catastrophic.
For the branch charge current circuits its less critical because the short circuit-current is much less.
When you think of it that way it makes sense to fuse the branches as close to the busbar as possible.
The battery is going to be highest current source of into any short on a branch circuit.

 

[Firstascent]

When you say you have the 30a fuse at the charge controller do you mean on the battery side or the solar panel side of the controller.

I’m using a lynx distributor as well, I have inline MC4 fuses at my branch connection before it goes to my MPPT, then after the MPPT on the battery side I have a circuit breaker (mostly for future maintenance purposes to cut incoming power, then finally I have a MEGA fuse at my lynx distributor.

I would fuse your controller, and since you’re using the lynx it’s super easy and inexpensive for some extra security.
Btw, anything connected (properly) to the lynx distributor has to be fused anyway, otherwise it won’t be connected to the battery mains busbar

 

[400bird]

Yes, you should put in the fuse.

If the charge controller has a 30 amp fuse it probably has smaller gauge wires than the circuit to your inverter?

For example, if you have 100 amp fuses (and the correct wire) to both batteries and the inverter. Then smaller wires and and 30 amp fuse in charge controller only (no fuse in the lynx).
What happens if you have a direct short in the wiring between the lynx and charge controller? You'd have to push over 100 amps through your 30amp wire before the 100 amp battery fuse blew.

Seems like you've got to consider both the batteries and SCC as current sources.

 

[Firstascent]

I don't think there would be a situation where the battery would send power to the controller.

Thanks you in adv

Meant to add that the battery will send current to your controller too.
For example, if I don’t have any panels connected to my controller, my controller is still being powered on via the batteries. So you do need to keep that in mind there is still current

 

[time2roll]

Assuming the wire is large enough to handle 120% of the solar and mounted close to the lynx and in a protected area.... I would skip the fuse.

 

[AmpD]

I'm curious about sizing the fuse from the scc to the distributor as well. I was having a hard time finding a mega fuse under 60 amps.