Questions about ground wire sizing, quick disconnects, and cable lengths.

WNCGUY

New Member
Joined
Sep 26, 2021
Messages
85
The deeper I get into my project the more questions I have. I am so grateful to have found a place where so many are knowledgeable and willing to share the knowledge.

My questions.
Inverter grounding.
Inverter is a GoWISE, 1500w. The manual states "The earth conductor is permitted to be 1 common size smaller than the DC positive (+) conductor (Example. DC += 2 AWG = 4 AWG)" Following this example, my 1/0 DC positive cable would suggest the use of 1 AWG ground cable. This inverter has a very small ground post, looks to be about a #10 all thread so I do not think the GOWISE suggestion is possible.

Victron Lynx Power In (Hack to add fuses).
What is the minimum size ground wire to run the chassis?

Victron Smart 12-12/ 30amp DC to DC Charger
I am using a 6 AWG power in cable protected by a 60amp fuse between the vans 12volt battery to the Victron charger and would like to include a quick disconnect for this single cable. Please suggest options for this connector.

Battery Cable Lengths.
System includes 2 SOK 100ah batteries wired in parallel. Positive cable will run from battery #1 through a class T fuse then to an on/off switch mounted on the Victron Lynx Power in. Negative cable runs from Victron Lunx Power in to shunt and then to battery #2. My question is must the pos and neg cable runs be the same length and should the length of class T fuse and length of the battery shunt be included in the length measurements?

Inverter Cable Lengths.
Both the Pos and neg cables runs from Victron Lynx Power in, to the inverter. Do these cables need to be the same length?
 
Chassis case ground is fine at #8 copper on the inverter. This is preferred to be a separate independent ground direct to the frame.

Lynx would be best to have a full size ground to match the largest cable. However assuming the inverter has both DC cables full size to the battery it would be OK IMO to go a bit smaller.

For the DC-DC I would have recommended a Bussmann Hi-Amp breaker with a switch.

The single legs that carry full power to/from the battery do not have to be the same length as they are part of a series loop. The parallel interconnects on the batteries need to match for best balance. The additional lengths added for the shunt and class-T fuse do not matter. Again they are all in series.

The main DC cables from the bus to the inverter do not need to be same length. Although it is best to have them parallel together along the same path so as not to create an inductive loop.
 
Chassis case ground is fine at #8 copper on the inverter. This is preferred to be a separate independent ground direct to the frame.

I already have some #6 cable along with the correct size ring connector so will use it.
Lynx would be best to have a full size ground to match the largest cable. However assuming the inverter has both DC cables full size to the battery it would be OK IMO to go a bit smaller.
Both battery and inverter are using 1/0 cables, if I have enough 1/0 left over I will use it for a ground, if not and it is ok to use #6 I will use it.
For the DC-DC I would have recommended a Bussmann Hi-Amp breaker with a switch.
Any particular reason you would use a breaker over a fuse here, ease of shut off when working on system?
The single legs that carry full power to/from the battery do not have to be the same length as they are part of a series loop. The parallel interconnects on the batteries need to match for best balance. The additional lengths added for the shunt and class-T fuse do not matter. Again they are all in series.
Understood, battery parallel interconnect jumpers must be the same length, the single pos and neg cables can be different lengths, this makes it easier working in the limited space I have.
The main DC cables from the bus to the inverter do not need to be same length. Although it is best to have them parallel together along the same path so as not to create an inductive loop.
Please tell me more about "Inductive loop"? It looks like the pos and neg inverter cables will be 18-20" long each.
 
Any particular reason you would use a breaker over a fuse here, ease of shut off when working on system?
Had asked about a switch. The breaker does both. Fewer connections and components is better IMO. Can lift the fuse for service although not very convenient for daily shut down.


Please tell me more about "Inductive loop"? It looks like the pos and neg inverter cables will be 18-20" long each.
I have read that if a loop is made it can induce current in certain objects. Just lay the cables together. Same as 120vac wire is laid together except for the end connections.

"Tie, tape, or twist cables together to reduce self-inductance. Run positive and negative cables through
the same knockouts and conduit."

Outback see pg 18
 
I started assembling things today, first thing I did was wire a maxi fuse holder to the battery to power the DC to DC charger, I just may upgrade to a breaker in the very near future. You mentioned daily shutdown, should the system be shutdown daily? I think I did read in the Victron manual I can shut the DC-DC charger down with the Victron Connect app.

Will be sure to apply some electrical tape to the inverter wires.
 
So if the DC-DC drains the chassis battery when parked the vehicle will need a jump start the next morning.
But all the details were not given... just that a switch was desired.
 
My preference for protecting circuits where a switch is also needed is the 285 series circuit breaker.


60 amp fuse is a little high for that circuit. The DC-DC charger will output up to 30 amps. But on the input side it could be as high as 40 amps, maybe more. Let's call it 40 amps. 40 amps x 1.25 (fudge factor to avoid nuisance trips) = 50 amps. A 50 amp breaker is more appropriate.
 
My preference for protecting circuits where a switch is also needed is the 285 series circuit breaker.


60 amp fuse is a little high for that circuit. The DC-DC charger will output up to 30 amps. But on the input side it could be as high as 40 amps, maybe more. Let's call it 40 amps. 40 amps x 1.25 (fudge factor to avoid nuisance trips) = 50 amps. A 50 amp breaker is more appropriate.
I used a 60 amp fuse between the vehicle battery and the Victron, as recommended in the Victron 12-12/30 charger manual. I will use a 50 amp fuse at charger connection in the hacked Victron power in.
A breaker is in the near future after I am assured all is working well.
So if the DC-DC drains the chassis battery when parked the vehicle will need a jump start the next morning.
But all the details were not given... just that a switch was desired.
I sure hope it won't drain the vehicle battery; my understanding is the charger's electronics will sense if the vehicle is running of not. All of this is pretty new to me, so I'm just a step above knowing nothing about nothing.
 
Last edited:
Back
Top