Solar Controller Negative connection on Trailer Chassis?

[cruxarche]

Hi All,
My new battery monitor utilizes a shunt on the negative battery terminal and requires that all connections to the negative terminal be through the shunt. The way I am wiring the shunt in a weatherproof box makes access somewhat inconvenient. Instead of wiring additional leads to the shunt can I just connect the negative lead from my solar controller to the chassis?

All of the trailer's negative circuits return through the chassis, as the stock wiring only has one lead coming from the battery and it connects to the chassis. The shunt does not change this setup, but rather simply funnels all the returns from the chassis through the shunt and then to the negative battery terminal. I have searched and found a LOT of contradictory information on this subject. Help appreciated.

Trailer:
simple pup-up tent trailer with 2X6v batteries
it does have shore power capacity via a 30 amp cord and an inverter

Solar:
Renogy solar suitcase 100 watt

Thanks.

Crux

 

[calicamper]

Depends
Many controllers are I forget the term but closed loop. Meaning it goes to the neg battery terminal. I use my output side of the controller to power stuff also. If I ground the neg it will blow up the charger or blow fuses dont ask how I know. It was smoky and tramatic experience ;-)

My layout uses a small isolated grounding bar which has all the various powered items neg tied to along with the neg feed from the powered side of the solar charger (it is not grounded!!!). Simply serves as a clean way to connect multiple neg wires to the system. The battery charging side of the charger is wired pos /neg to the battery directly with in line fuse between them.

The positive output feed from the Charger goes to a small fuse box, which then feeds my lights and small USB charging hub.

Hope that helps you picture the lay out.

My entire system is closed loop absolutely no grounded point anywhere.

 

[cruxarche]

calicamper,
my issue is that if i connect the solar controller negative lead to the battery (as in your setup) it will bypass the shunt and thus the battery monitor. I am trying to figure out if there is any reason I cannot connect the negative lead of controller directly to the chassis, where the rest of the system negatives are connected. Or, is there a reason why I would need to connect it directly to the shunt...

I could wire a negative busbar from the shunt but don't want to if there is no need. I have no other devices that need to connect to the battery or shunt. Everything else is tied into the trailer DC wiring in the trailer.

Thanks.

 

[calicamper]

The controller diagram will determine that. Dont create a short like I did.

It might be that the meter and shunt need to tied in differently to avoid the bypass effect.

 

[cruxarche]

the diagram does indicate the negative lead connecting to the battery terminal. Hence my question. The only other information in the manual (Renogy Viewstar PWM 10 amp) indicates grounding is to "common ground"

 

[calicamper]

Pretty sure its the same issue I had. Some of the other regulars are pretty good with this stuff see if they chime in.

 

[cruxarche]

Will do. Thanks.

 

[SoCal Tom]

I'm not sure if it will work for you, but my shunt is connected on one end to the battery the other end has the Solar charge controller negative lead, and a lead that connects to the chasis ground. I can measure charging from solar, as well as charging from other sources ( as long as they are connected to the chasis), such as vehicle charging.
Tom

 

[dwh]

Some controllers are positive-ground.

That means all the positives - battery, solar, load - are hard-wired together inside the unit, and the switches to control power to the battery, and power to the "load" terminals are switching the negatives instead of the positives.

Which is why you can let the magic smoke out IF you tie the controller's battery neg AND the controller's load neg together. Or if you tie the controller's solar neg to either battery or load neg.


If you have a negative-ground controller (negatives tied inside controller, switches switching positives) AND negative-ground solar panels then it's a non-issue and you could just tie the controller's neg outputs (battery and load) to any common ground bus (like a vehicle frame or bus bar). You could also tie in the solar panel's negative to the same grounding bus if you needed to.

If you have a negative-ground controller and positive-ground solar panels, again it's a non-issue as long as you don't tie the solar panel neg to either the battery or load negs.

If you have a positive-ground controller, it's a non-issue as long as you don't tie the battery neg to the solar or load negs.

That should be about as clear as mud.


In other words, if you have a negative-ground controller, you can ground the battery output to the frame, and also use the load terminals on the controller to control loads that are also grounded to the frame.

If you have a positive-ground controller, you can't do both. It's either/or. But you can ground the controller's battery output to the frame as long as you don't use the load terminals on the controller (most people don't use them anyway), OR keep anything connected to the load terminals on a separate dedicated grounding bus that is isolated from the frame/battery negative.

 

[cruxarche]

I'm not sure if it will work for you, but my shunt is connected on one end to the battery the other end has the Solar charge controller negative lead, and a lead that connects to the chasis ground. I can measure charging from solar, as well as charging from other sources ( as long as they are connected to the chasis), such as vehicle charging.
Tom

SoCal,
That is definitely an option. I am hoping to avoid adding additional connections to the shunt as I am still experimenting and want to avoid unnecessary connections at the point of the shunt. Based on what dwh says, I think I am in the clear to connect the negative lead from controller to the frame.

 

[cruxarche]

Some controllers are positive-ground.

That means all the positives - battery, solar, load - are hard-wired together inside the unit, and the switches to control power to the battery, and power to the "load" terminals are switching the negatives instead of the positives.

Which is why you can let the magic smoke out IF you tie the controller's battery neg AND the controller's load neg together. Or if you tie the controller's solar neg to either battery or load neg.


If you have a negative-ground controller (negatives tied inside controller, switches switching positives) AND negative-ground solar panels then it's a non-issue and you could just tie the controller's neg outputs (battery and load) to any common ground bus (like a vehicle frame or bus bar). You could also tie in the solar panel's negative to the same grounding bus if you needed to.

If you have a negative-ground controller and positive-ground solar panels, again it's a non-issue as long as you don't tie the solar panel neg to either the battery or load negs.

If you have a positive-ground controller, it's a non-issue as long as you don't tie the battery neg to the solar or load negs.

That should be about as clear as mud.


In other words, if you have a negative-ground controller, you can ground the battery output to the frame, and also use the load terminals on the controller to control loads that are also grounded to the frame.

If you have a positive-ground controller, you can't do both. It's either/or. But you can ground the controller's battery output to the frame as long as you don't use the load terminals on the controller (most people don't use them anyway), OR keep anything connected to the load terminals on a separate dedicated grounding bus that is isolated from the frame/battery negative.

dwh,
Thanks for the reply. As far as i know the controller and panels are negative ground. I will confirm. That would make my life easy. I can run the controller positive lead to the battery terminal and the negative to the trailer chassis, where the rest of the DC negative returns are. As far as I know the Renogy model solar suitcase does not require an (earth) ground.

Crux.

 

[dwh]

I can run the controller positive lead to the battery terminal and the negative to the trailer chassis, where the rest of the DC negative returns are.

You can that anyway - even if the controller is positive-ground - just don't let anything connected to the "load" terminals on the controller get grounded to the frame/battery.

Or just don't use the load terminals. You don't really need them. Just run all your loads to the battery through a fusebox.

Like I said, most people don't use the load terminals anyway. They are generally only rated for like 10a. The load terminals with their low-voltage disconnect is intended for stuff like a nightlight on a solar-powered electric gate.

 

[orangeTJ]

If it were my system, I'd connect all negatives to the shunt and not "frame ground" of the trailer. Trailer and vehicle frames are no very good "current carrying conductors"