DC to DC Charger Replacing Charging Relay

[johnwgy]

Hi, new to the forum and first question. New to me and first ever motorhome 2007 Holiday Rambler Admiral 30SFS (Monarch) and adding 300 amps lithium house batteries. In my front bay electrical panel I have the charging relay which I understand should be disconnected when installing lithium house batteries so as not to overload the alternator. I am going to install an ignition switched Renogy 40 amp dc to dc charger. My thought is to remove the coach battery side buss bar from the relay and connect the chassis battery input from the Renogy to the chassis battery stud. I would then connect the output from the Renogy to the house unswitched stud which would route back to the house battery. All instructions I have seen show running wires from the chassis battery to the rear battery compartment and connecting the Renogy there but it would seem logical that installing as I have mentioned above would accomplish the same thing and save long lengths of wire. Has anyone installed this way or do I need to run direct wires.  I next will need to source a convenient ignition on trigger source for the Renogy, I really need to find wiring diagrams for my coach to help.  

   

[RNMCBR]

John,

On my 07 Diplomat I also installed a DC-DC charger to charge the lithium house batteries from the alternator. I used a Victron 30A isolated dc-dc charger. I mounted the charger in the battery compartment and connected the input to the stud fed by the alternator and the output to the stud fed from the house batteries. Then I simply unplugged the IRD module from the circuit board in the front run bay. This preserves the capability to manually combine both banks while disabling the direct  house battery charging capability. I’ve run this setup now for 2 1/2 years and it functions flawlessly. 30A is not much but it seems adequate to charge the lithium house batteries while I’m underway. 
BTW, I also installed a second charger wired opposite the first one to keep my starting batteries charged while plugged into shore power, running the generator or harvesting solar power. At first I was skeptical this would work but after getting an OK from Victron I did it. This too has operated nicely for the same amount of time. 

Your circuit board looks like mine. I think your IRD module is the circuit board mounted under the green fuse puller. If you unplug the connector from  that board it will disable your IRD function. 

[johnwgy]

RNMCBR from your description it would seem that my gas model may be wired differently. As far as my wire tracing goes my battery compartment only has a house connection which then feeds to a post by the generator then on to the front compartment 12volt non switched terminal. I do have a another power wire in my battery compartment that shared a stud on the house disconnect switch that goes through a 80 amp circuit breaker that I haven't traced yet, I will check that tomorrow maybe it's a charge wire, as of now I don't know what it's for or where it goes. Tracing wires without a circuit diagram is slow going, I'm amazed how many wires there are and most are hidden above the gas tank or somewhere else inaccessible.

[RNMCBR]

Sorry, I did not catch that your coach is a gas model. Your front run bay circuit board still looks like mine though.

[johnwgy]

I have never seen diesel or gas wiring before so it's all a learning curve for me and I'm not sure what is unique to each. I will continue seeking all advice

[RNMCBR]

I don’t know much about the differences but it seems likely to me that they would be very similar. 

[Martinvz]

The board looks the same as my LaPalma, also gas. There does not appear to be a Big Boy that most of the diesel coaches have. So, the house gets charged when driving but the chassis is not charged when parked, and this can be problematic. 
I have been considering a dc-2-dc charger but nit quite there yet. 

[Paul J A]

You may want to look at a 

BlueSea ML-ACR.

Solenoid ML Series 500A 12V ACR https://www.amazon.com/dp/B001VIXLRO