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Discussion Starter #1
Yesterday I attempted to start hooking up the electrical system in my van, and I have run into a road block at the first step. Hoping someone in this forum with more electrical experience can tell me where I have gone wrong.
Specs:
We have a Renogy 12V 50A DC-DC charge controller with MPPT (part DCC50S). I connected the starter battery to the charge controller with 4AWG wire (Renogy's recommendation). I have the input charge running through a 80A breaker to serve as overload protection & cutoff switch. The output from the charge controller then runs through a 60A ANL fuse to our battery bank (2 100AH Li batteries). When we turned everything on to test everything works as expected for 2-3 mins then the breaker trips. Any ideas what I have done wrong? I don't see where the system could be shorting, but I am also not really sure how to troubleshoot this sort of electrical issue. I did notice all the other draws on the starter battery are fused, is where I tapped onto the starter causing the problem? The other possibility I thought of is that voltage drop is causing the issue since the wire run is pretty long (~20 feet), but given that this is a 50A controller I wouldn't expect the draw to be anywhere near 80A (right?).

See photos below

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Discussion Starter #3
For the ground - the negative of the input is tied to a common negative bus that then goes to the Renogy controller. The negative bus then has a chassis ground.

Does the fuse on the starter battery relate to why the breaker is tripping or does it just need to be there for safety to protect the wire run? (I will add one either way I'm just wondering if that is the cause of the breaker tripping.) Is there a post on here about how to add another fuse to the starter (like what is already on there) or is it easier to just buy and inline fuse and put in near the start of the run?
 

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2018 136 HR Ont.
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The lack of a fuse should not trip the breaker. Lots of info on installing a fuse. Please search.
 

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Perhaps check if the connection points are getting hot.
 

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2018 159 High Roof gas, BC, Canada
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Does the fuse on the starter battery relate to why the breaker is tripping or does it just need to be there for safety to protect the wire run? (I will add one either way I'm just wondering if that is the cause of the breaker tripping.) Is there a post on here about how to add another fuse to the starter (like what is already on there) or is it easier to just buy and inline fuse and put in near the start of the run?
@83Grumman is right about a fuse being needed at the starter battery. It's for safety. You are using a chassis return to the battery. Imagine the massive short if your positive cable insulation wears through and touches an unpainted part of the body.

I have a Renogy 40A DC-DC charger.

[Obligatory "I'm a noob" too]

For my prototype build, I cheated and piggybacked on the 70A fuse that runs to the upfitter's connection. Because it is "behind" the 70A fuse, my connection to the DC-DC charger is protected. I don't currently use the upfitter connection so I have all of the 70A's capacity.

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I'm redoing my electrical as I speak and so I already have a circuit breaker in hand that I will put in line with the positive cable. (And for the sharp-eyed, I'm relocating the thin AWG 18 wire to behind the cig lighter and its fuse; its purpose is simply to light the LED on a switch I use to turn the DC-DC charger on and off. It too is protected by the other 70A fuse it's sitting behind.)

You need to do at least my cheat or put in a fuse if you use the upfitter connection. I'm using a circuit breaker so that I can turn turn off the connection easily.
 

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2018 159 High Roof gas, BC, Canada
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You might want to invest in a clamp ammeter or shunt/hall-effect battery monitor to see what's going on.

Maybe the circuit breaker is blowing before its rated 80A because I'm pretty sure the Renogy charger isn't drawing that much from your engine battery. But I'm not conversant in using chassis ground for the house circuit and thus don't know if your lithium bank is somehow accidentally linked directly to the engine battery. Being a noob, I went with the easier to understand completely separate circuit for the house.
 

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@83Grumman is right about a fuse being needed at the starter battery. It's for safety. You are using a chassis return to the battery. Imagine the massive short if your positive cable insulation wears through and touches an unpainted part of the body.

I have a Renogy 40A DC-DC charger.

[Obligatory "I'm a noob" too]

For my prototype build, I cheated and piggybacked on the 70A fuse that runs to the upfitter's connection. Because it is "behind" the 70A fuse, my connection to the DC-DC charger is protected. I don't currently use the upfitter connection so I have all of the 70A's capacity.

View attachment 66983

I'm redoing my electrical as I speak and so I already have a circuit breaker in hand that I will put in line with the positive cable. (And for the sharp-eyed, I'm relocating the thin AWG 18 wire to behind the cig lighter and its fuse; its purpose is simply to light the LED on a switch I use to turn the DC-DC charger on and off. It too is protected by the other 70A fuse it's sitting behind.)

You need to do at least my cheat or put in a fuse if you use the upfitter connection. I'm using a circuit breaker so that I can turn turn off the connection easily.
I’m having trouble installing my 40A DC-DC and was wondering if it’s necessary to connect the input ground to the starter battery ground. Right now I have the input ground connected to the chassis at the same connection point as my output ground and the unit won’t turn on. IMG_1779.MOV
There’s a video of what I have going on. Anyone who sees this and is able to help would be greatly appreciated
 

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Discussion Starter #9
Thanks everyone so much for the advice! We got a new breaker 80A breaker (1 day amazon prime!!) and it is no longer tripping! Troubleshooting found that the old 80A breaker was tripping at 40A! Crazy, that breaker was brand new.

Also thanks for the feedback on having a fuse at the battery, will follow the advice of using the 70A upfitter fuse already installed as we don't need it otherwise. :)

Looking forward to posting pics once we are done with our build!!! :D
 

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2018 159 High Roof gas, BC, Canada
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I’m having trouble installing my 40A DC-DC and was wondering if it’s necessary to connect the input ground to the starter battery ground. Right now I have the input ground connected to the chassis at the same connection point as my output ground and the unit won’t turn on. IMG_1779.MOV
There’s a video of what I have going on. Anyone who sees this and is able to help would be greatly appreciated
I have my electrical mostly all apart at the moment, but I remember the DC-DC install went smoothly for my prototype build. Basically 5 connections:

1 + 2) Positive and negative from the engine battery to the corresponding pos and neg input of the Renogy
3 + 4) Positive and negative from the Renogy output to the corresponding pos and neg bus bars of my coach electrics
5) the thin wire that turns on the Renogy to a Positive source on the van and controlled by a simple switch on the dash to turn it off and on.

It worked right away.

Again, I'm a noob and so I didn't use the chassis ground for my coach circuit like you did. I ran a dedicated Negative line to everything. I'm not saying you're wrong as the OP and others seem to have done it this way.

If you have time, test it the way I did it.
 

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I have my electrical mostly all apart at the moment, but I remember the DC-DC install went smoothly for my prototype build. Basically 5 connections:

1 + 2) Positive and negative from the engine battery to the corresponding pos and neg input of the Renogy
3 + 4) Positive and negative from the Renogy output to the corresponding pos and neg bus bars of my coach electrics
5) the thin wire that turns on the Renogy to a Positive source on the van and controlled by a simple switch on the dash to turn it off and on.

It worked right away.

Again, I'm a noob and so I didn't use the chassis ground for my coach circuit like you did. I ran a dedicated Negative line to everything. I'm not saying you're wrong as the OP and others seem to have done it this way.

If you have time, test it the way I did it.
Chassis ground return my PM alternator charging circuit (just like I believe PM does with the alternator - or so I assumed & did not really research that assumption). The big issue with negative run chassis ground is making sure your ground connection is substantial & not corroded over time ( I actually ran 2 braided cable ground straps to separate chassis frame locations that were both over sized for a single strap - ie redundancy ). Imam not an advocate of running parallel chassis grounds, I just wanted 2 independent points of failure due to exterior corrosion possibilities & I do not like crawling under the PM chassis on the ground (took an additional 15mins & $15). Corroded or poor chassis grounds would be one of the first connections I would trouble shoot if experiencing issues with the PM Alternator charging system.

All my DC circuits are 2 wire “red & black” the black being negative “run” back to the fuse panel. I would not chassis ground run negative back to the batteries on any distribution circuits.
 
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