Battery to Battery charger 2020 Qwest

[JerryP]

I have a 2020 Entegra Qwest 24R. I recently upgraded to two 100 Ah Lithium batteries by Battle Born. I am worried that charging these batteries will burn the alternator on the Sprinter Chassis so want to install a battery to battery charger. The Sprinter has a 220 A smart alternator. My preference is to Install a Victron smart battery charger. Question is do I disable the existing charging system on the sprinter or just install the smart battery charger along side of the Mercedes battery charging? I have been researching this subject and have only found how to install the smart charger on a sprinter that does not have an existing charging system. Any help and direction is greatly appreciated.

[bluztoo]

I am currently trying to figure this out. There is an aux battery solenoid on my Melbourne 24LP. This is not the battery disconnect solenoid which is separate and in the battery compartment. This solenoid on mine is under the passenger seat. It obviously allows power from the house to go to the chassis for starting the engine. However, it does allow power to flow to the house when the engine is on and the alternator is running. Mine pulls about 100 amps to charge the back and I think it is probably too much or at least will want power for too long. My alternator is listed at 225 and may be a "smart" alternator as well. Seems to me that the dc to dc charger goes on to that 4awg cable. I can't get it to work yet and am not sure why. I suspect I should just bypass or jump this solenoid when installing a dc to dc charger. My charger (Victron) comes on when the engine runs, although I have yet to install it. It won't work yet. Can't figure out what that solenoid is doing. Also this charger doesn't allow power to flow from house to chassis, only the reverse. So jumping the solenoid should not matter, except if I want to use my house batteries to start the rig. I figure I can just use my jumper cables if it becomes necessary to start it that way. So today I hope to figure this out. Here's a picture of the aux battery solenoid (which even Jayco does not seem to understand - one tech told me my unit did not have that!). Please let me know of your progress if you get there before me.

[JerryP]

What you have done is what I was going to try. But now it's back to the drawing board. I have the wiring diagram for the Qwest and Melborne if you are interested. I actually have my Victron B2B charger installed in to the chassis battery under the driver's seat. However this means I have two systems charging the house batteries. This is the reason I am worried about my install. One idea I am pursuing is to install a Blue Sea two position battery cut off switch just before going into that selenoid. Attaching the B2B charger to one of the legs and the other led going to the selenoid, this would allow me to switch back and for between the two systems. My problem has been that I have not been able to verify that 1 this will work and two that I won't damage the systems.

[bluztoo]

You might find this thread interesting from the Winnebago forums. https://www.winnieowners.com/forums/...on-361274.html
I am convinced now just to bypass the solenoid in the picture. You absolutely do not want two connections. As for using the house batteries to start the rig - I can just use the jumper cables I carry with me. No big deal.

[bluztoo]

Victory is mine! Finally got it working. Just put the thing in place - output isolated to the battery posts, input directly to the cable coming from the solenoid (but now the solenoid is out of the circuit) and to the chassis ground. Works perfecto. If I ever need to jump my chassis battery from my coach batteries a short jumper cables will do. I've got a victron multiplus that trickle charges my chassis battery. This stuff is a learning curve. The industry is a little behind the technology right now and the dealers and manufacturers don't feel they have incentive for you to be "creative."

[JerryP]

Hi bluztoo,

Glad you got it working. Do you have any pictures? Did you disconnect the wire on the batteries under the step? Do you have a picture of that ? That you could share. I know that I definitely have to disconnect the MBS charging system. Thank you for any help. By the way I have the wiring schematics for our MHs if you want.
By the way what year is your Melbourne?

[bluztoo]

I have a 2021 Melbourne 24LP. Let me know what pictures you need. For now I have relocated my batteries on the drivers side in a storage bin. They'll soon go under my bed although that will take some work. I just ran 4awg cable to the original location of the batteries. As for the dc to dc charger, make sure the output wires go directly to your positive and negative battery connection. The input wire should go to the one coming off the solenoid to under the step - that's the positive. The negative on the input side has to go to ground on the chassis. As for the solenoid - jump the two posts - direct connect. This won't hurt anything if the dc to dc charger is in place. In fact, you need to keep all the smaller connectors on that solenoid working cause it powers other things. I'll take whatever pictures you think would be helpful and share them if you like.

[JerryP]

I found the solenoid under the passenger seat. I disconnected the 4 ga black wire that goes to the battery. I ordered a battery switch that I will connect the black 4 Ga wire to and then to the solenoid. Attached are pictures of the solenoid and screen shots of the B2B App one with the engine off and one with it on. I think I also have this issue solved, what do you think?

[bluztoo]

That looks great. I originally only connected to one side of the solenoid but found that affected a couple of other things. But if yours works you’re fine.

[JerryP]

Originally Posted by bluztoo

That looks great. I originally only connected to one side of the solenoid but found that affected a couple of other things. But if yours works you’re fine.

What didn't work? Did you disconnect the B1 (upper) or B2 (lower) on your first try?

[bluztoo]

I ran out of juice to my power step and my hydraulic levelers. Once I jumped the connection leaving everything in place it worked fine. Ignition was enough so that I did not need a switch.

[Justafordguy]

This is what Battle Born recommends for charging their lithium batteries from the alternator on an RV.

https://battlebornbatteries.com/prod...ation-manager/

Here is their wiring diagram.

https://1t1pye1e13di20waq11old70-wpe...uick-Guide.pdf

[JerryP]

Thank you for your reply. I will be looking at that.

[bluztoo]

JerryP - my installation of the Victron is working perfectly.

[JerryP]

Originally Posted by bluztoo

I ran out of juice to my power step and my hydraulic levelers. Once I jumped the connection leaving everything in place it worked fine. Ignition was enough so that I did not need a switch.

In real life usage I am now finding that my frig is not working on 12V while traveling. Have you tried running your frig on 12 V?

[JerryP]

I resolved the issue. Turns out the 20A fuse on the frig control board had blown once I replaced the fuse it's been working fine.