Help with Adding DC-DC Charger

[FunSteak]

Our rig is a 2017 Minnie Winnie 26A.

I'm preparing to replace our current lead acid house batteries with lithium. I'm looking for a bit of guidance on understanding the current state, and installing a DC-DC charger, so as not to burn up my alternator. If needed, I'm okay with disabling the boost switch on the dash and will carry a jump pack instead.

Goal is to disconnect charging direct from the alternator and add the DC-DC charger, while not disturbing shore power and generator charging.

The attached photo is what I have now. I'm unfortunately not near the rig at the moment, so am working from photos and the Winnebago wiring diagrams (a bit limited in details). I'd like to better understand a few things.

I believe the heavy red wire on the right with the green sleeve, coming from the salesman switch, goes to the generator starter. The one with the yellow sleeve, right side of the solenoid, goes to house batts. Full red one on left side of solenoid goes to chassis batt.

Is the smaller yellow wire, on the center lug of the solenoid, coming from the boost switch? I assume that when this is energized, the solenoid connects house to chassis for boosting. Disconnecting this should disable the solenoid, yes? Follow up to that - where does charging current from the alternator enter the system? That's what I think I really need to disable, in favor of the DC-DC charger.

Next, Would the output of the DC-DC charger go on the right-hard Solenoid connection?

Where does charge current from the converter/charger enter? Is it the small yellow wire on the right side of the solenoid? Or maybe one of the ones entering the salesman switch? Winnebago's drawing is helpful, but not at all complete.

I feel like I'm just missing a couple of details here. Thanks for any guidance.

PS: I will also replace the charger board in my converter/charger to one with a lithium charge profile. It's a WFCO WF-8955PEC. I believe there is a direct, slide in replacement charging board for it.

 

[DonTom]

and installing a DC-DC charger, so as not to burn up my alternator.

I use one of these in my Y2K RV.

-Don- Reno, NV

 

[CharlesinGA]

By all means, remove the wire to disable the boost solenoid. Some people want to remove it but me, I'd leave it and tag it as to why it is disconnected. I think you are correct that the B2B unit needs to connect so it supplies the batteries where you indicate. I have not looked at the wiring diagrams but knowing that almost all WBO units are wired in a similar fashion, you are on the right track. Not sure if the Amp-L-Start will cause any issues or not, but I suspect you will be ok.

Charles

 

[FunSteak]

I use one of these in my Y2K RV.

-Don- Reno, NV

Thanks. This is exactly what I was looking at. Looks like I'm on the right track!

 

[FunSteak]

By all means, remove the wire to disable the boost solenoid. Some people want to remove it but me, I'd leave it and tag it as to why it is disconnected. I think you are correct that the B2B unit needs to connect so it supplies the batteries where you indicate. I have not looked at the wiring diagrams but knowing that almost all WBO units are wired in a similar fashion, you are on the right track. Not sure if the Amp-L-Start will cause any issues or not, but I suspect you will be ok.

Charles

Yes, I'd cap and label it, not remove it altogether. I'd like to keep it easy to return to stock if needed.

My thoughts on the Amp-L-Start are that it's regulated, and therefore shouldn't cause any overloading issues. I welcome a correction if anyone knows why that's not the case.

 

[Lou Schneider]

Be aware adding a DC to DC charger will eliminate the ability to use the boost switch to let the house batteries jump start a dead chassis battery (current won't flow backwards through the DC to DC charger). If you're installing 200 a/h or less of LiFeP04 batteries I'd first try wiring them up without the DC to DC charger and see how much current they draw from the alternator when they're discharged. On my Safari Trek two 100 a/h batteries draw 30-40 amps each, well within the capacity of the engine's 160 amp alternator.

The ability to jump start the engine from the lithium house batteries saved me from being stranded when the starting battery failed in the middle of Nowhere, NV on my first trip after installing the new house batteries. I was able to put off replacing it until I reached the land of inexpensive batteries (a town with a Walmart).

 

[FunSteak]

Be aware adding a DC to DC charger will eliminate the ability to use the boost switch to let the house batteries jump start a dead chassis battery (current won't flow backwards through the DC to DC charger). If you're installing 200 a/h or less of LiFeP04 batteries I'd first try wiring them up without the DC to DC charger and see how much current they draw from the alternator when they're discharged. On my Safari Trek two 100 a/h batteries draw 30-40 amps each, well within the capacity of the engine's 160 amp alternator.

The ability to jump start the engine from the lithium house batteries saved me from being stranded when the starting battery failed in the middle of Nowhere, NV on my first trip after installing the new house batteries. I was able to put off replacing it until I reached the land of inexpensive batteries (a town with a Walmart).

Hmm. I am installing 200AH, and don't know the capacity of my alternator. I was willing to sacrifice the boost switch in favor of greatly improved battery life. Planning to pick up a heavy duty jump pack.

If I don't need to forgo that function, it would be great. I'm sure I can get my alternator specs, but how should I calculate the worst case current draw from the batteries?

 

[DonTom]

The ability to jump start the engine from the lithium house batteries saved me from being stranded when the starting battery failed in the middle

And of course, you would know how to bypass your DC2DCC if you had one anyway if you needed to use your boost switch.

I assume you would have everything required to do such (tools & wire) as I do.

-Don- Reno, NV

 

[FunSteak]

And of course, you would know how to bypass your DC2DCC if you had one anyway if you needed to use your boost switch.

I assume you would have everything required to do such (tools & wire) as I do.

-Don- Reno, NV

Good point. Also, yes, I carry tools and spares at all times.