DC2DC charge controller install

[Bboyda]

I was wondering several things about a DC2DC install on a travel trailer.
1. Is there a possibility of the charge controller back feeding to the truck electrical through the seven way plug?

2. If feeding to lithiums, and bms shuts them down, what will happen if there is a breakaway event?

3. If the charge controller completes its charge profile (Lithium) what will happen if the service battery/alternator are still in bulk charge mode and there is still a high voltage on the seven way plug?

 

[FilterGuy]

1. Is there a possibility of the charge controller back feeding to the truck electrical through the seven way plug?

No that should not happen. However, check the gauge of wire in that 7 way plug and make sure it is heavy enough for whatever amperage the controller is going to draw.

2. If feeding to lithiums, and bms shuts them down, what will happen if there is a breakaway event?

What do you mean by 'breakaway event'?

3. If the charge controller completes its charge profile (Lithium) what will happen if the service battery/alternator are still in bulk charge mode and there is still a high voltage on the seven way plug?

The short answer is "nothing". The charge controller will just quit taking current.

 

[Bboyda]

I was thinking of using a separate circuit for supplying the charge controller as the 7way does not have the ability to carry the 50 to 75 amps required. Would that change the responses to my questions?

 

[FilterGuy]

I was thinking of using a separate circuit for supplying the charge controller as the 7way does not have the ability to carry the 50 to 75 amps required. Would that change the responses to my questions?

No.

 

[FilterGuy]

I was thinking of using a separate circuit for supplying the charge controller as the 7way does not have the ability to carry the 50 to 75 amps required. Would that change the responses to my questions?

BTW: Make sure you have a separate large wire for both the Positive and Negative part of the circuit.

And now I suddenly realize a good use-case of isolated circuits for the DC-DC converters. If you have a separate negative return going to your engine battery and it is tied through the DC-DC converter to the negative that goes through the 7-way, it creates a great big noisy ground loop. However, if the DC-DC converters keep the two sides isolated, the ground loop is broken.

The isolated version of the new Victron DC-DC charger was breifly discussed over on this thread by @Justin Laureltec

 

[MrNatural22]

@FilterGuy A breakaway event is when the trailer becomes disconnected while driving disconnecting the seven pin plug and activating the emergency backup electric braking on the trailer.

 

[FilterGuy]

@FilterGuy A breakaway event is when the trailer becomes disconnected while driving disconnecting the seven pin plug and activating the emergency backup electric braking on the trailer.

Thank You!

2. If feeding to lithiums, and bms shuts them down, what will happen if there is a breakaway event?

Whether, the BMS has shut them down or not. A breakaway event should not harm things electrically. Any charging that is happening will just stop.

BTW: Are you planning on putting the DC-DC converter in the trailer or in the truck. (I would put it in the trailer.)