Connecting charge controller without a negative battery cable.

[Tyler0404]

Hello, I am hoping someone can guide me and let me know if my newly purchased 30amp MPPT charge controller will work without a negative battery cable. The current charge controller than came installed on the trailer is a 10am PWM controller and there is no negative battery cable connected to it, but it is still working. I just swapped out the 50w solar panel than came factory installed for a 200w solar panel. I would like to upgrade the charge controller as well but have run into this snag of no negative battery cable. Will the new charge controller still work without the negative battery cable?

 

[Contributor]

https://www.easttowestrv.com/files/brochures/0000/0000WaySolarKitUserManual.pdf

go to page 7 for installation instructions.

 

[Tyler0404]

https://www.easttowestrv.com/files/brochures/0000/0000WaySolarKitUserManual.pdf

go to page 7 for installation instructions.

Thank you. I have actually already been looking at this diagram because that is for the current charge controller I have installed. However I am trying to change this to a Renogy 30A charge controller and I am confused because I should have a positive and negative wire connecting to the new charge controller for both the battery and solar panel, however I only have access to the three wires currently in my charge controller. I hope what I am saying is making sense.

 

[Contributor]

If I understand you correctly, your rv is pre wired with a 3 wire system. The Renogy controller uses 4 wires, 2 wires in and 2 wires out. Follow the red wire from the solar panel that currently goes to the battery and connect it to the + solar input to the controller. Then you need to add a new wire from the controller + output to the battery + input.

 

[Grid Point Designs]

Hello, I am hoping someone can guide me and let me know if my newly purchased 30amp MPPT charge controller will work without a negative battery cable. The current charge controller than came installed on the trailer is a 10am PWM controller and there is no negative battery cable connected to it, but it is still working. I just swapped out the 50w solar panel than came factory installed for a 200w solar panel. I would like to upgrade the charge controller as well but have run into this snag of no negative battery cable. Will the new charge controller still work without the negative battery cable?

Most solar charge controllers will "power up" and look live when they have a connection to solar (assuming it's daylight). The battery connection is of course required for it to start charging and dumping power to the battery, but it will still power up when it's getting power from solar only.

A charge controller will require a negative to the battery to begin charging, this is the only way to bring the battery into the electrical loop. If the charge controller is only connected with a positive cable to the battery, the battery isn't in the loop and won't charge.

It looks like the middle black wire is the one that should lead to the battery.

 

[John From Detroit]

There is a negative battery cable.. However you may not know where it is. IT may run to the chassis.. Also it may be "Before" the charge controller... Depending on the controller the negative in and out may be effectively the same (Connected internally) so somewhere between the panel and the controller out is a connection to the battery negative.. Else it can not work.

 

[Contributor]

 

[Contributor]

Above is the way the RV is currently wired, 3 wires are used. Unconventional but the wiring is already there. To go to a 4 wire system he needs to disconnect the red positive wire from the battery and redirect it to the new controller. Fairly straight forward except for fishing out the wires. It may be easier to run new wires, just depends on how everything is routed now.