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tcjacobs asked

Travel trailer to a bp 12/24v-65A.

Untitled document-1.pdfI currently have the battery disconnect connected to my battery with the battery + connected to the In connector and the out post connected to the TT main DC distribution block. The _ post of the battery is connected to a disconnect switch, and the BP gnd terminal. I have 3 questions,
1. Can the BP handle this if I connect to shore power and leave the Disconnect switch in the off Position? The TT has a charger/converter
2. When towing can I connect the batter With The disconnect switch on to allow emergency trailer braking? The battery is connected to the tow vehicles charging system I may have the solution hook up the tow vehicle charge cable to the in side of the B P
3. if I connect a pair of schotky blocking diodes across the BP to be forward biased when charging from the tow vehicle or built in converter chargers would this work?

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Kevin Windrem avatar image Kevin Windrem commented ·

I solved the trailer brake issue with a separate battery for emergency braking if the trailer ever separates from the tow vehicle. That way it doesn't matter if the Trailer's DC system is active or not. I have a switch between the trailer DC system and the tow vehicle charge line and the breakaway battery charger. That switch is closed only when the trailer is parked. So when on the road, the tow vehicle's charge line keeps the breakaway battery topped up but is isolated from the trailer DC system.

You could also move the battery disconnect to the positive side of the battery but after the tow vehicle charge line and break breakaway switch. This is how it's normally wired from the factory with tongue mounted batteries but I moved my battery bank to the back of the trailer.

The diode in your diagram is in a direction that would essentially bypass the BP (current would flow through the diode from the battery to the trailer DC system). To have the trailer DC system charge the battery, you'd want the diode in the opposite direction. The voltage drop across the diode might interfere with proper battery charging (ending bulk early).

It would be better to disconnect the trailer's battery charger from the DC bus and connect it directly to the battery (through appropriate fuse/breaker of course), and probably a separate heavy gauge wire from the distribution panel to the battery just for charging.

I don't know what happens inside the BP so can't answer your questions.

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tcjacobs avatar image tcjacobs Kevin Windrem commented ·

I have thought about separating the Battery's charging system and running a seperate cable. However the wiring diagram for the converter charger looks like they cant be separated, The diode is drawn in backwards I had my 13 year old Granddaughter do the drawing but failed to check it closely
As for where the battery disconnect is that is disputed all over the forums. My electronics background says positive side but the side for the negative disconnect is less chance for sparks if you disconnect the neg. Marine installation Rules say disconnect Pos. LOL

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Kevin Windrem avatar image Kevin Windrem tcjacobs commented ·

The concept of "less sparks" when disconnecting the negative side of the battery certainly applies when disconnecting cables but my gut says the system is safer if the positive side of the battery is disconnected as close as practical from to the battery.

If your distribution panel is one of the WFCO units, the charger is a separate sub-system connected with wires to the AC and DC distribution systems. Can't say about other units.

In my revamped trailer electrical system the Victron inverter is the charger so I don't have the same issues you have.

An external charger might be an option for you.

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