Fuse vs breaker
Ask For Help or Advice
-
We are going to install a Renogy 50A dc to dc with solar charge controller. We have watched some video and everyone seems to use a MEGA fuse. Renogy recommends a 75-100A fuse. A friend suggested using a breaker. Could someone advise as to pros and cons of each, please? I don’t understand much about electrical so please keep it as simple as possible. Our rig is a Ram Promaster self converted.
- We are going to install a Renogy 50A dc to dc with solar charge controller. We have watched some video and everyone seems to use a MEGA fuse. Renogy recommends...
I've install a couple DC-DC chargers. First was a Renogy 40A and used on the truck side a 60A terminal fuse and 60 amp switchable breaker and on the RV battery side at first a 40 amp switchable breaker. No problems worked great. loveyourrv.com/renogy-40 I now have a SRNE 50 amp DC-DC charger with MPPT and have the same 60 amp terminal fuse on the truck battery and on the RV battery side I have a switchable 60 amp breaker. Works great. loveyourrv.com/testing-ou Fuses are likely a bit cheaper but I find it nice to have a breaker with the switch for working on things. Fuses and breakers have different time delays as to when they will blow. Its best to try and get as low of a fuse or breaker that will work and not nuisance blow. Also use large enough gauge wiring so it doesn't overheat and have too much voltage drop. The manual usually gives you some specs.
-
Okay. Thanks Ray! I am passing this info on to a friend who is going to help us and understands way more than me.
- Okay. Thanks Ray! I am passing this info on to a friend who is going to help us and understands way more than me.
Here is a clip that shows my Renogy 40A DC-DC charger repurposed in my truck box power station youtu.be/TH71g7VZEcg?t=900
The fuse or breaker on the output side is pretty easy to figure out as it will be a constant amperage, like just under 40 amps for a 40 amp model or just under 50 amps for a 50 amp model. The input side of the charger fusing is a little more tricky to figure as the length of the wire run between the vehicle battery and the charger and the thickness of the wire will affect the amperage draw. In my setups, 60 amps on the input side has worked well and is low enough to protect the 4 gauge wiring if a short circuit were to happen.
-
That helps a lot. We will have about 5’ of wire from the vehicle battery to the 50 amp DC-DC. Thinking 6 gauge will be okay? And a 75-100 amp fuse?
-
A 100 amp fuse for a 50 amp DC-DC seems excessive to me. I'd be inclined to use 75 at the most based on the chargers I've used. But maybe the Renogy isn't very efficient at the power transfer. If it were me, I'd use a clamp-on amp meter to see what the actual input amperage draw is when the DC-DC charger is outputting close to its max 50 amps and then add about 15-20% extra margin above that for the fuse. You might find at that short wire length you don't need the fuse to be very high. 6 AWG wire should do the job with such a short run.
-
I have just installed the Renogy 40A DC DC charger in my 5th wheel. I used 4 gauge wire (from a jumper cable - I think I got that idea from Ray) to run from the truck battery to the truck bed, through an Anderson connector and then to the charger at the front of the 5th wheel. I probably have at least 20 to 25 feet of cable from the truck battery to the charger. I measured 54 amps of current out of the truck battery but it was enough to continually trip that 60 amp breaker. I've upgraded to a 70 amp breaker and hoping it will solve the problem. I also have a 50 amp breaker after the charger and it has worked fine. The current is consistently 40 amps (+ or - 1 amp) coming out of the charger.
-
Thanks Jeff for the info. We have decided to go with the 6 gauge wire and 75Amp fuse from van battery which is located under the driver side feet. The 50 DC-DC/Solar charge controller and house batteries will be located just behind the driver seat. Renogy included their own 60amp fuse for the output from the unit.
