Continue to use battery disconnect solenoid after RV upgrade?

[barnz333]

Admins: I did get the warning asking “Is this already being discussed”, but the original thread really just focused on Aux Start functionality. It makes sense that the Battery Disconnect conversation should have its own dedicated thread.

I just bought a new to me 2021 Jayco Melbourne prestige, and I am looking to upgrade to lithium batteries, solar input, bigger inverter, and a DC2DC charger. At this point the game, I believe I have everything figured out except for how to integrate battery disconnect functionality into the new system. The big question is… can I easily use a new On-Off switch like many modern upgrade wiring diagrams show, or should I stick with the existing solenoid-wired connections? My big concern is that it may be difficult to get some of the existing wired connection functionality to work from a simple on-off switch.

All that said, I’m thinking that keeping the existing battery disconnect solenoid/switch setup is the way to go. It will be valuable to learn if you folks feel the same way!

First, let me start by pointing out the newly discovered schematic that I just uploaded. It really shows some of the connections that I believe the earlier schematic I uploaded is missing. On page 7, it shows pathways to/from some fused connections and isolator studs that I’m finding very helpful.

My first drawing describes some of the connections that page 7 confirms. Here’s a quick question about that: Should all of those ‘direct-to-battery’ connections continue to bypass the battery disconnect solenoid? I don’t know if there were ‘valid’ reasons for bypassing the disconnect function, or not.
- i’m thinking that since the converter will now be part of a combo inverter-converter-charger, it would be hard to isolate just that functionality for direct connection. I’m thinking that should now go through the disconnect and new Victron Lynx distributor, like many other components that have connectivity to/from the house batteries. Issues?
- I’m also thinking that the alternator charging pathway should route through the disconnect and links as well. Issues?

My second drawing is more of a reference. It is a high-level view of the existing (original) wiring set up, and for the most part should align with the schematics. We are currently sharing. Most of the components in the lower right hand side are currently housed towards the front of my RV, and the components depicted at left are located in the back… most hidden under the bed.

The third and final drawing shows my proposed system after mods are done. For the most part, the majority of the components will stay about where they are. The big change is moving the (new lithium) house batteries to the back of the RV, where they will be closer to all of those main battery-powered-hungry components. The separate inverter & converter chargers will now be combined into a combo unit, the DC2DCcharger will be moved back there, and the solar input will come through the roof near the house batteries as well.

I believe having everything connect to/from the new house batteries through the existing battery disconnect solenoid & the Lynx distributor (glorified buss bar) will allow the battery disconnect switch to really shut down the majority of electrified functionality easily. I believe the only remaining components that would continue to have access to battery power (even though the disconnect is in play) are the levelers, generator start and refrigerator connections.

While moving the battery disconnect solenoid to the back of the RV does create a few new long wire paths, I don’t think that’s going to be a problem. The ones to the auxiliary start switch and diode will be small gauge wire. The new auxiliary start to DC2DC charger is basically replacing the battery disconnect solenoid to back-of-camper pathways… So that seems like a wash. And then some of the existing pathways will be shorter.

I guess my biggest question remaining is, does anyone see any glaring issues with this proposed set up?

A huge thank you in advance to you folks for pointing out potential issues in staring me down the right path. Much appreciated!

 

[barnz333]

OK, I think I see a big issue. If what ChatGPT is correct, the battery disconnect solenoid is unlike the aux start solenoid in that the prior only allows one-way current flow. If that is correct, my 'proposed system' will not work because I have current flowing both ways through the solenoid.

What if split the design... the 'current FROM battery' components continue to go through the disconnect solenoid (as they do today ), and 'current TO battery' components (converter charging, solar charging, alternator charging) now come through a new on-off switch. A quick representation of that is in the new diagram.

The other wires off the solenoid can continue to exist (as they do today). Since my inverter and converter functions are both together in a combo unit, I routed that through the on-off switch (because it will need to have current flowing both ways to/from the batteries.

I know its a lot wading through my posts/questions/diagrams, but I do appreciate it. If this works, I would just wonder if the existing 'direct-to-battery' connections (genstart, Levelers) SHOULD come from the battery directly, or from the solenoid (so they are also shutdown with the battery disconnect solenoid. Guessing those small REFR wires will still come directly off the battery.

 

[barnz333]

I’ve got cash for helpers

 

[barnz333]

Hoping someone can look at this in the next day or two? Thanks!

 

[craigav]

Hi Barnz333, my time is limited this time of year but I am happy to answer any questions as I can.

My professional advice would be not to change anything that you don't have a specific requirement to do so. If for example you want to move your battery(s) to a new location then simply run a couple large gauge wires for them to the new location and then connect them back to the original location.

Similar for the inverter, if you desire to install a larger one, then find the best location and run new wires of the appropriate size and wire it in as it is documented to be connected.

Same concept for installing Solar.

It is rarely a good idea to make a lot of changes at the same time as that can lead to confusion and damaging or dangerous mistakes and in part is why I suggested to create a new thread for the battery disconnect solenoid vs the aux start solenoid because they both have different purposes and what applies to one doesn't necessarily apply to the other (at least not completely).

"KISS" is the principal I suggest whenever possible and with that it is certainly appropriate to have a large picture of what you desire as the end result, but for accomplishing the larger goal it is best to break down the larger goal into smaller pieces and take one step at a time.

Regarding ChatGPT, don't rely on it for answers to any question that is important such as with the electrical question you asked it regarding the solenoids, as electricity can certainly flow through a solenoid (relay) in either direction.

I will try to take a look at your attachments perhaps this weekend, they are not easy to read here as the two you drew by hand are upside down here. ~CA

 

[barnz333]

Much appreciated. I’ll see if I can get those diagrams spun around.

 

[Ann-Marie]

I recently did exactly that upgrade. Managed to fit one 300 AH Lithium in the space of the 2 old lead-acids so battery wiring was unchanged. Left everything else including the solenoid switch as-is except adding a shunt to the negative to monitor battery charging/discharging status.
Didn't need a DC/DC for engine charging, just installed a Smart Shore Marine Combiner 200 Lithium version. It is bi-directional so 12 volt charging on house also maintains the starting battery.

 

[barnz333]

Much appreciated. I’ll see if I can get those diagrams spun around.

Much appreciated. I’ll see if I can get those diagrams spun around.

here are the two diagrams that were upside down. They depict the existing/original setup and my initial proposal (before I realized the solenoid was not bi-directional, and my solution as drawn wouldn’t work).

 

[barnz333]

I recently did exactly that upgrade. Managed to fit one 300 AH Lithium in the space of the 2 old lead-acids so battery wiring was unchanged. Left everything else including the solenoid switch as-is except adding a shunt to the negative to monitor battery charging/discharging status.
Didn't need a DC/DC for engine charging, just installed a Smart Shore Marine Combiner 200 Lithium version. It is bi-directional so 12 volt charging on house also maintains the starting battery.

That sounds great! My wife and I will be doing quite a bit of below freezing camping, and we didn’t want to have to deal with lithium batteries in that cold exposed location under the step. Of course, once I moved the battery location, that’s when I started running into potential issues ha ha!

 

[craigav]

Much appreciated. I’ll see if I can get those diagrams spun around.

here are the two diagrams that were upside down. They depict the existing/original setup and my initial proposal (before I realized the solenoid was not bi-directional, and my solution as drawn wouldn’t work).

I took a look at your diagrams a but further and have a couple of questions, what is the LYNX device and while I don't see any issues, I am not sure why your new diagram shows new wires from the aux start relay to the battery disconnect relay, is there a reason the wires already in place need replacing? If you do run new wires be sure to include fuses or self resetting breakers. ~CA

 

[barnz333]

I took a look at your diagrams a but further and have a couple of questions, what is the LYNX device and while I don't see any issues, I am not sure why your new diagram shows new wires from the aux start relay to the battery disconnect relay, is there a reason the wires already in place need replacing? If you do run new wires be sure to include fuses or self resetting breakers. ~CA

The Lynx is just a gloried buss bar from Victron. It allows you to buss up positive, negative and fuses in one small box. The 'new' wires aren't actually new... it was more a reference that these were now long wire runs (10')... no longer short runs (2-3'). Thanks for taking a look!