Solar System: design/install

oceanstater

Member
Apr 2, 2020
48
I'm a little confused. The plug pictured below ran to the old FLA battery on the tongue (black 10ga).
IMG_1320.jpeg
The aux/charge line, also black 10ga, runs back to the WFCO where it splices into a 14ga red wire that leads to the battery fuse on the DC circuit board.

1. Are you saying I should take the black wire from this plug on the tongue, splice it and the breakaway switch + to the aux/charge line at the tongue? The aux charge line will be running to the Renogy alternator input.
2. The white wire from this plug I was planning on extending from the tongue back to the fuse block as there is currently only a 14ga white wire going back there.
schematic 3.jpg
 

TSQ

Active Member
Mar 28, 2021
221
Niagara Region, ON
I think your V2 was fine. I'm having trouble picturing what is there currently, but if you make it look like the schematic it should be good.

The only change I'd make is to have the AC ground go directly to the trailer frame, not via the Renogy negative (see attached).

Schematic v2.1.png
 

SteveP

Super Active Member
Platinum Supporting Member
May 21, 2015
2,477
I'm a little confused. The plug pictured below ran to the old FLA battery on the tongue (black 10ga).
View attachment 83871
The aux/charge line, also black 10ga, runs back to the WFCO where it splices into a 14ga red wire that leads to the battery fuse on the DC circuit board.

1. Are you saying I should take the black wire from this plug on the tongue, splice it and the breakaway switch + to the aux/charge line at the tongue? The aux charge line will be running to the Renogy alternator input.
2. The white wire from this plug I was planning on extending from the tongue back to the fuse block as there is currently only a 14ga white wire going back there.
View attachment 83872
You previously stated there are only 14 ga wires back from the tongue so splicing the battery plug wire into the aux wire would give you 10 ga back to the WFCO, you could take it from there any where you wanted. If you don't need it just use it to power the breakaway switch.

The white wire should already be attached to the neg side of the WFCO, attaching it to the frame at front gives you another path for return, so you would only need to run 10 ga from your add on fuse panel to the WFCO.
 

oceanstater

Member
Apr 2, 2020
48
TSQ and SteveP. Thanks again for the help. I like the idea of splicing the breakaway + into the black 10ga plug at the tongue (saves me from having to run a wire all the way to the back). The only existing 10ga that runs all the way back to the WFCO is the black + alternator line from the 7-pin so I do want to run a 10ga white - back to the WFCO to balance it all out. This I'll splice into the same plug at the tongue. I suppose upgrading the white wire from my fuse block to the WFCO (currently 14ga) to 10ga would be a good idea depending on whether I can get into the guts of the WFCO to do it....

schematic v4.jpg
 

TSQ

Active Member
Mar 28, 2021
221
Niagara Region, ON
TSQ and SteveP. Thanks again for the help. I like the idea of splicing the breakaway + into the black 10ga plug at the tongue (saves me from having to run a wire all the way to the back). The only existing 10ga that runs all the way back to the WFCO is the black + alternator line from the 7-pin so I do want to run a 10ga white - back to the WFCO to balance it all out. This I'll splice into the same plug at the tongue.
I'm not sure that will work - if I understand correctly that #10 black is now being repurposed as the +12V charge <-> DC-DC charger alternator input. That means it will only have power on it when it is plugged into the tow vehicle. If you trailer disconnects it will lose power, so your breakaway brakes will not work in that situation.

If you are trying to avoid running another wire you could reuse the old #14 white wire for the breakaway brakes (taking power from your new fuseblock as originally planned) - just add a bunch of blue heatshrink at each end to identify it as brake power.

I suppose upgrading the white wire from my fuse block to the WFCO (currently 14ga) to 10ga would be a good idea depending on whether I can get into the guts of the WFCO to do it....
Not really necessary, it will carry less power than it used to because the internal WFCO charger is disabled (and it worked fine before).
 

TSQ

Active Member
Mar 28, 2021
221
Niagara Region, ON
Got it. If I’m not using that #10 black wire on the tongue do I just tape it up and stow it?
Sorry, I'm lost.

I thought that #10 black on the tongue was the wire you were using to go between the 7 way connector and the Renogy alternator input (shown on the left side of your schematic). Or is this an additional one?
 

oceanstater

Member
Apr 2, 2020
48
Sorry, hard to visualize everything in written form. Unless I am mistaken, the 10ga black wire from the 7-pin connector on the tongue goes 2 places: 1) connects to the FLA battery on the tongue via 2-pin connector as shown here:

connector.jpg

and 2) travels back to the WFCO as illustrated here (in red instead of black):
breakaway-wiring-diagram.jpg
 

TSQ

Active Member
Mar 28, 2021
221
Niagara Region, ON
I see what you mean now. Yes, I'd just tape it up well.

Also, that #14 white may be grounded somewhere so it may not be able to be repurposed as a breakaway power cable as I suggested yesterday.

@SteveP had a good point as well - if the negative from your 7 way connector is grounded somewhere up on the tongue you could just rely on the trailer frame as a negative conductor back to the fuse block instead of running another #10.

Personally I always to like to run a wire and only use the frame as a chassis ground (not as a conductor) but many/most? people do use it as a negative conductor.
 

oceanstater

Member
Apr 2, 2020
48
Final questions and I promise I’ll be done and posting pictures of the install. 1) do I need to be running 6ga wire from the Renogy DCC to the fuse block? Battery to fuse block + and - is 6ga but it seems impossible to connect that size wire to the individual circuits. 2) what size fuses should be installed in the fuse block (Renogy DCC/Victron 15A charger/WFCO/breakaway switch). Many thanks.
 

TSQ

Active Member
Mar 28, 2021
221
Niagara Region, ON
#10 will be fine for the Renogy DCC30S as it tops out at 30 amps. You will probably want to use a 40A fuse on the DCC30S so use wire rated to 90C (NEC 310 allows #10 copper wire with 90C insulation to carry 40A).

Victron 15A charger - should say in the manual, if it doesn't I'd go with 20A.
WFCO - since it is a 8725 I'd use a 25A. Or a 20 would probably be fine (expecially if you have LED lights) and reduce the number of different size fuses you need.
Breakaway switch - Single axle with 7" brakes? 15A would be fine, or a 20A. Some people don't fuse their breakaway switches. I fuse mine.

A few notes on the DCC30S: When charging from the vehicle alone it will pull up to 400W over the tow vehicle 7 way connection, at voltages down to 11.5V. 400W / 11.5V = 34.8 amps (worst case scenario).

Different tow vehicles are capable of supporting different amperages on the +12V charge line so check yours (my Odyssey setup is only good for 30A). The 7 way connectors are typically only good for 30A. You risk damaging the connector and/or your vehicle wiring if they are not capable of supporting a ~35A charge rate.

In addition, with too high of a charge rate the DCC30S may also cycle on and off continuously as the high amperage causes the voltage to drop below the low voltage cutout (12.7V or 11.5V depending on your configuration). Basically when the vehicle is started the voltage rises above the cut-in setpoint and it turns on. Then as the amperage ramps up the voltage drop on the +12V charge wire drops below the cut-out setpoint and it turns off. Then the voltage rises above the cut-in setpoint and it turns on again. Then as the amperage ramps up the voltage drops below the cut-out setpoint and it turns off again. etc.

(I used a DCC30S for a year and went through this all already)

But you can use the Renogy BT-2 bluetooth module to set the current limit of the DCC30S to 20A if you need to. This would limit the charge rate from the tow vehicle to 14.4V (maximum trailer battery voltage) x 20A (maximum charge rate) = 288W / 11.5V (minimum tow vehicle battery voltage) = 25 amps (worst case scenario).

For my Odyssey I also had to connect the IGN sense wire on the DCC30S to the trailer running lights and have my lights on whenever I wanted it to charge reliably.

Note that if you set a 20A current limit on the DCC30S you could use a 30A fuse instead of a 40A on the fuse block.

But don't worry about the DCC30S setup until after you get your wiring done.
 




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