2016 Tab 320 Outback Edition Electrical Distribution

SteveS

I am planning a solar installation on a friend's 320 Tab.     As has been noted, there doesn't seem to be any manufacturer supplied electrical schematics available.   I have accessed a few owner generated schematics on this forum that are helpful, but not complete.    Unfortunately I don't have ready access to the trailer to be able to use my multimeter to check out some of the wiring to answer a few questions I have.    I was hoping some some owners who have delved into the wiring might be able to shed some light on a few questions I have.

1.  The owner generated schematics indicate there is one positive lead from the trailer junction box to the trailer battery which passes through the battery disconnect switch.    (In the junction box, this positive battery lead is electrically connected to the WFCO converter battery charging line (thru panel fuse) and the seven prong plug from tow vehicle.    This indicates to me that the tow vehicle battery cannot charge the trailer battery while towing unless the battery disconnect switch is in the shut position.    My supposition is in conflict with the owners manual electrical section which states "The charge in the 12 volt batteries can be replenished, depending on the tow vehicle, from the tow vehicle alternator thorough the 7-way cord.   The charge will flow to the batteries regardless of the battery disconnect switch position.   Likewise, if on or off, the solar panel is still charging the batteries."   

Have owners noted if the battery disconnect switch position affects the ability of the tow vehicle to recharge the trailer battery?     Has anyone found a schematic for wiring to supplement Rick Parco's beautiful  2016 schematic/info sheet?

2.   It is not intuitive to me how 12V power from the trailer battery gets to the 12V loads.    It would make sense that all 12V loads are powered via the 12V fuse panel in the WFCO Power Converter.    This is certainly the case when the 12V DC is being supplied by 120VAC power thru the converter.    Is the trailer battery connected electrically to the WFCO Power Converter 12V output upstream of the fuses?    This would make sense so that load fuses would be in line regardless of source of DC power (Converter or trailer battery or tow vehicle battery).   If this is the case, what is electrical connection from trailer battery to upstream of the DC load fuses?    Is the electrical connection thru the battery charging fuse/circuit in the DC fuse panel?    I.e., does current flow both ways thru fuse circuit depending on whether trailer battery is being charged from shore power or shore power is not connected and trailer supplying DC loads?

3.   How does the 40A reverse battery protection fuse in the DC fuse panel of the WFCO tie into the power distribution?

I hope to have more access to the trailer to be able to try and figure some of this out, but was hoping to get a head start with other owner experience and input.

Thanks for you patience wading through these questions.

Steve S 

MuttonChops

Disclaimer:
    I'm on-the-road without full access to my electrical wiring files
    So these answers depend more on memory than (owner created) documents.

SteveS said:
1.  . . .  indicates to me that the tow vehicle battery cannot charge the trailer battery while towing unless the battery disconnect switch is in the shut position.
. . . conflict with the owners manual electrical section which states "The charge in the 12 volt batteries can be replenished, depending on the tow vehicle, from the tow vehicle alternator thorough the 7-way cord.   The charge will flow to the batteries regardless of the battery disconnect switch position.   Likewise, if on or off, the solar panel is still charging the batteries."   
Have owners noted if the battery disconnect switch position affects the ability of the tow vehicle to recharge the trailer battery?     Has anyone found a schematic for wiring to supplement Rick Parco's beautiful  2016 schematic/info sheet?

You are correct the Battery Cut-Off Switch must be in the "On" [shut] position for the TV to help charge the trailer battery.  More important the Battery Shut-Off Switch must be "On" for the emergency brake feature, caused by a trailer uncoupling while driving, to operate.

The Manual Section you are referencing is old/out-of-date/wrong.
However, solar panels are indeed normally wired to the battery so the Battery Disconnect Switch position does not prevent solar charging.

Other owners have created schematics similar to Rick Parco's with different style or levels of detail.
Some can be found within threads but not on the Resources Page. {or my traveling laptop }

SteveS said:
2.   . . . Is the trailer battery connected electrically to the WFCO Power Converter 12V output upstream of the fuses?   
. . . what is electrical connection from trailer battery to upstream of the DC load fuses?    Is the electrical connection thru the battery charging fuse/circuit in the DC fuse panel?    I.e., does current flow both ways thru fuse circuit depending on whether trailer battery is being charged from shore power or shore power is not connected and trailer supplying DC loads?

The WFCO Power Center 12VDC Fuse Panel is the 12VDC Power source (that is the fuses are being used) independent of the actual 12VDC power generation source; Shore Power via convertor or Battery.

I for one do not know how the Two 12VDC sources are actually connected inside the Power Center, just know the 12VDC Fuses are active.  And yes, current can/does flow both directions to/from battery via its fuse.

SteveS said:
3.   How does the 40A reverse battery protection fuse in the DC fuse panel of the WFCO tie into the power distribution?

I do not how the Reversed Battery Protection fuse is wired within the WFCO.
Do know it works as designed and will blow if the trailer battery is installed backwards.
Which protects both the WFCO and Battery from damage.

Denny16

For adding solar, I would recommend using the Victron MPPT 75/10 for a 100 watt install or the 75/15 for 200-watt panels.  Most TAb owners doing this, mount the controller in the tub where the battery is, and wire the controller to the battery on one side, and the solar panel on the other controller connection.  

For portable solar panels, use a SAE connector mounted to the tub or Anderson connectors on the panel cable.  The tow vehicle 7-pin connector is wired to the battery connection returning to the power converter in the trailer.  The battery switch needs to be on for the trailer emergency brake system to work, and to charge the battery from the TV.
 Cheers 

Grumpy_G

Regarding 2 and 3, the power distribution center has two 12V input connections. One from the converter, the other from the battery. The latter one has the reverse polarity fuses between the input terminal and the rest of the 12V system. 

SteveS

Thanks all for your quick and illuminating responses.   Great to get validation regarding the battery disconnect switch.    With your input, I think I figured out the battery/12VDC distribution.    A single red positive voltage lead goes from the junction box back to the WFCO controller.   That lead is electrically connected in the junction box to the tow vehicle alternator via the 7-way plug and to the trailer battery via the battery disconnect switch.

(I'm guessing) The lead gets to WFCO box where it is wired to both the 30A battery charging fuse downsteam side AND to the 40A reverse power fuse.    On the other side, the 40A fuse is connected to the DC distribution bus for supply to all DC loads (except Battery charge 30A fuse which is connected to a separate converter battery charge ckt and would be silly anyway).

With trailer battery wired properly and no shore power, 12 VDC flows from trailer battery, thru battery disconnect switch, to junction box, to WFCO, thru 40A reverse pwr fuse and onto 12VDC distribution bus, then thru individual ckts to lights, fridge, etc.

With shore power available, 120VAC is converted to 12VDC and sent to distribution bus and off to the loads thru the ckt fuses.   Converter also sends appropriate near 12VDC to 30A battery charging fuse back to trailer battery for charging.   

If battery was hooked up backwards with shore power energized, there would be current surge thru 40A fuse back to trailer battery...this explains reverse pwr fuse ckt.   

Not quite sure what voltage on DC bus would be with shore power charging trailer battery since output of battery charging ckt thru 30A fuse floats on trailer battery and therefore is electrically present back on DC distribution bus via 40A fuse.

At least that is what makes sense to me.     I may contact WFCO people to see if I can get confirmation or  what the actual setup is.  Or open up WFCO unit to eyeball the wiring.     Haven't found a WFCO converter - distribution panel wiring schematic yet.   Not that it matters too much, but I like to know how stuff works. 

Thanks again.  

stepheng

@SteveS I’d also like to know how the WFCO works and what controls the switching between the DC circuits and the battery charging circuit.  

Seems like the battery charger should only connect to the battery when trailer is connected to shore power and the 120/12V converter should supply the power to the 12V loads (lights, fridge, etc). If the 12V output of the converter was also connected to the battery when on shore power it seems that the charger would not work properly and be able to control its three charging stages (bulk, absorption and float).

Let me know if you have made any progress on figuring this out. 

Grumpy_G

There appears to be some misunderstanding, there is only one converter/charger. The 8735 power center is a little different from the larger ones in that it uses one of the fused connections to connect to the battery. That's typically #6 which is somewhat confusingly labeled "battery charger". It serves as charging output when the converter is connected to 120V and it serves as feed to the power center when running on battery. 

ScottG

Think of voltage as flowing downhill. On shore power, the converter provides a higher voltage than the battery, so that extra voltage is pushed to the battery for charging purposes. Without shore power, the battery voltage is higher (since the converter is providing 0V) so the battery pushes voltage to the distribution panel to power your 12VDC devices.

Same wire, different direction. Any "switching" is just the result of this reversal of voltage potential.

SteveS

A little more information after I was able to hookup both trailer battery and AC shore power and pull fuses to observe effect.     My question was how did the 40A (reverse pwr) and 30A (batt chging) fuses work in the DC distribution scheme.    First, as noted, there are two power inputs WMFO Unit, 120VAC shore power and 12VDC from trailer battery (and tow vehicle alternator when towing which uses same wire +12VDC wire in to WMFO from junction box).  To figure this out, I monitored DC loads (ceiling light) first with only trailer battery powering WMFO and pulled 30A and 40A fuses, then with only 120 VAC shore powering WMFO (with no tow vehicle and battery disconnect switch open) and pulled fuses.   

With trailer battery only powering WMFO, DC loads remained powered with 40A fuse pulled, but not with 30A fuse pulled.     Thus, as noted above and contrary to my previous supposition, DC power is applied to DC distribution bus via 30A battery charging fuse.    40A fuse not in the circuit between trailer battery and DC loads.

With 120 VAC only powering WMFO, DC loads were deenergized when 40A fuse pulled, but remained energized when 40A reinstalled and 30A fuse pulled.   Thus, 40A fuse is between AC/DC converter output and DC distribution bus.

It makes more sense to me now, at least.    

Denny16

Makes sense to me, and was my understanding, the 40 amp fuse was on the power converter side of the DC circuit.  

Cheers 

stepheng

The PD4135 wiring diagram shows an internal relay that disconnects the battery from the DC circuits and connects the battery to an internal charger when connected to shore power. I’m guessing that the WFCO works the same way based on @SteveS observations above.  

If we could disable the WFCO’s internal charger we could connect a Victron IP22 charger to replace it. 

As an alternative we could pull the 30A fuse and connect our own fuse and a relay to switch between the victron charger when on shore power and the battery to supply the DC circuits when no shore power present.