Wiring back to house battery?

[Johnboyy]

This is my wiring plan for a van conversion. Renogy 50A charger, battery and 1000Winverter. I'm using circuit breakers on all the main circuits and then a fuse box for the individual house loads.

Ignoring the blue and green lines for a second, everything is straightforward and simple. I have a 35mm2 wire from the battery to the inverter, rated to 240A and a 150A breaker for the inverter.

Cable runs are short, less than a metre total.


Which got me to thinking. Do I need to run a feed direct from the battery positive to the 50A breaker feeding the fuse box or could I put in the green wire and go from the 150A breaker input terminal. I can't really see why not?

The flip side then is the blue wire from the charger to the same terminal. I'm thinking that's a bad idea because we want the charger seeing the battery voltage at the battery terminals? or does it matter? I know the total load could be 260A there which exceeds the cable anyway so not applicable but curious for future knowledge sake.

 

[Mashurst]

Chaining breakers on the input side is no problem as long as the wire is up to the current. So, the green wire seems OK if you eliminate the red wire feeding the second breaker from the battery.

Keep in mind that circuit protection's purpose is to protect the wire, not the device. To do this effectively, the protection device needs to be as close to the source as possible. Because the wire between the source and the protection device is not protected from a short, you want to minimize the length that is unprotected.
A short at 1 can start a fire, melt stuff, or otherwise do bad things. A short at 2 will just pop the breaker.

 

[Johnboyy]

Chaining breakers on the input side is no problem as long as the wire is up to the current. So, the green wire seems OK if you eliminate the red wire feeding the second breaker from the battery.

Keep in mind that circuit protection's purpose is to protect the wire, not the device. To do this effectively, the protection device needs to be as close to the source as possible. Because the wire between the source and the protection device is not protected from a short, you want to minimize the length that is unprotected.View attachment 856516
A short at 1 can start a fire, melt stuff, or otherwise do bad things. A short at 2 will just pop the breaker.

Sorry I never saw an alert for your reply.

Yeah cable 1 is in a flexi conduit and as short as possible for that reason. All my breakers are well below wire rating so should all trip before anything bad happens. (But I put 2 in a conduit too for the sake of it, 150A is a nice bit, I'd rather avoid it being exposed more than necessary

I've the high current and high voltage sides wired but right now only have one fuse in the box for the fridge. Had to put a finish on things for now as we're on a boat to France tomorrow!

 

[Mashurst]

Am I correct that the outlined wire is connected directly to the battery?

If so, I would be very concerned about this setup. The sheathing obviously keeps the wire from being abraded but it would not keep it from being caught in something and sheared or just connected by something falling on it terminal. It looks physically well protected behind the cover so you may well get away with it. I just want to point out that I see unprotected runs like this in a lot of builds and they are an unnecessary risk.

Circuit protection should be closer to the source to prevent the possibility of a dead short causing a fire. If this were my setup, I would mount a master breaker or fuse right above the battery or even right on top of it. Then I would take one run over to where you have your breakers now and bus them all to that one lead going back to the battery and protect each individual run as you have done sized for the wire used in each sub-circuit. This would also eliminate multiple connection to the single post of the battery which can also lead to a "hot" high resistance connection. Ideally you never want to stack terminals on a post.

Again, the function of circuit protection is to protect the wire not the device and it can only do that for the part of the wire that is after the protection. Thus, the part before the protection should be absolutely minimal.

I hope I'm not stepping on any toes. I'm just trying to share best practice.

 

[Joe917]

Blue Sea Systems 5191 MRBF Terminal Fuse Block 30-300A

Space-saving, ingition-protected MRBF 5191 fuse block for high amperage circuits such as DC main feed, inverter, windlass, bow thruster etc. 58VDC, 300A rated.

www.12voltplanet.co.uk

Or similar, fused for wire size.