Help with Disconnecting my old battery from the DC Distribution Panel (in RV)

[John Frum]

Sounds good. Just wondering about the old battery.... If I disconnect it from the DC Panel but leave it in the engine bay where it is still connected to the chassis and the engine battery, would it interfere with my new battery and system once they are also connected to the chassis?

Only the positive side needs to be disconnected.
Its less than optimal to hall around that old chunk of lead.
Probably even worse to waste gas charging it.
Check with your meter to make sure the panel is energized before you disconnect.
Then check again to make sure its not energized after you cut that positive wire at the battery.

 

[John Frum]

You said you would post new pictures.
I'm sure we all want to see them.

 

[aluchipawa]

ok here are my long awaited pictures. this is what i think you were telling me to do. Just wanting to confirm before making the switch. and of course I will be disconnecting the original battery first but keeping the green wires connected to the chassis

 

[John Frum]

ok here are my long awaited pictures. this is what i think you were telling me to do. Just wanting to confirm before making the switch. and of course I will be disconnecting the original battery first but keeping the green wires connected to the chassis

Looks correct.
For the "ground" lug you want to leave the green wire in place and add your new wire.
You are using 6 awg wire, confirm?

 

[John Frum]

Let me know the results of your tests.

 

[aluchipawa]

4awg is what i am using so it should be good

 

[John Frum]

4awg is what i am using so it should be good

4 awg probably wont fit in the mechanical lug.
The manual says 6 awg max and you also have to keep the green wire in there to boot.

 

[aluchipawa]

4 awg probably wont fit in the mechanical lug.
The manual says 6 awg max and you also have to keep the green wire in there to boot.

The green wire has an additional lug behind the panel which fit my wire and amazingly the positive wire also fit. DC Panel is now working on liFePo! Unfortunately the water pump and propane detector are seperately fused in the engine compartment so I will need to figure out where those wires are going so I can reroute them to the new battery

 

[John Frum]

The green wire has an additional lug behind the panel which fit my wire and amazingly the positive wire also fit. DC Panel is now working on liFePo! Unfortunately the water pump and propane detector are seperately fused in the engine compartment so I will need to figure out where those wires are going so I can reroute them to the new battery

The propane detector should be very low amp draw and should be on all the time if you have propane.
Not sure how much load the water pump is or why it would not terminate in the dc distro panel.
Glad you got it working.
Did you isolate your new system from the old house battery?

 

[aluchipawa]

The propane detector should be very low amp draw and should be on all the time if you have propane.
Not sure how much load the water pump is or why it would not terminate in the dc distro panel.
Glad you got it working.
Did you isolate your new system from the old house battery?

Unfortunately we ran the heater a few too many times and the old house battery is at around 7v which is causing the Propane detector to refuse to open the propane lines. This is why I want to get the Propane detector on the new battery ASAP.

I think the reason the fridge, battery monitor/water pump, water heater and propane detector are all directly connected to the battery rather than run from the DC Panel is because the Panel is way in the back of the RV and the Battery is in the engine bay, so wiring everything to the DC Panel would have added a lot of length to all the wires.

At the house battery I have figured out that there are inline fused wires for the fridge, battery monitor/water pump and the one that used to connect to the DC panel. On the Positive terminal there is also a wire going to the generator, a small mystery wire and one going to a solenoid which then runs a line to the engine battery which has another small mystery wire on the house battery side of the solenoid.

I am guessing one of the small unfused mystery wires go to the propane detector? Then the other mystery line is probably for the waterheater. I also included pictures to help make sense of my explanation. I am planning on disconnecting the fused lines and running them to a DC fuseblock to connect to my battery I also will disconnect the generator positive line and connect it to the new LiFePo Battery. The generator is already grounded to the chassis which is why it just needs a positive line running to it (I think?).

 

[John Frum]

Are you talking about a dc starter circuit for your generator?

 

[12VoltInstalls]

guessing one of the small unfused mystery wires go to the propane detector? Then the other mystery line is probably for the waterheater

Check that they’re on; then disconnect one at a time and prove it out.

 

[aluchipawa]

Check that they’re on; then disconnect one at a time and prove it out.

Turns out both "mystery wires" are for the propane detector and the propane detector turns on if either one is connected.

There is a yellow wire coming in where all the other wires from the RV come in which then travels to somewhere under the dash? I think am guessing it is for the gas tank selector since this RV has 2 gas tanks.

My plan now to to reroute all positive leads to my new LiFePo battery where I will either in-line fuse them or set up a seperate DC Fusebox and leave the green chassis wires connected in the engine bay

Are you talking about a dc starter circuit for your generator?

yes its a huge positive wire from the house battery to gen (probably 0AWG)

 

[12VoltInstalls]

There is a yellow wire coming in where all the other wires from the RV come in which then travels to somewhere under the dash?

Yellow
12V conventions would be an unswitched pos(+) source, a monitor or signal wire, a permanent safety ground - that’s just for starters.

I would have as a first guess it’s an “ignition on” sense wire but it could’ve anything - trace it out and discover it.

 

[John Frum]

Turns out both "mystery wires" are for the propane detector and the propane detector turns on if either one is connected.

There is a yellow wire coming in where all the other wires from the RV come in which then travels to somewhere under the dash? I think am guessing it is for the gas tank selector since this RV has 2 gas tanks.

My plan now to to reroute all positive leads to my new LiFePo battery where I will either in-line fuse them or set up a seperate DC Fusebox and leave the green chassis wires connected in the engine bay


yes its a huge positive wire from the house battery to gen (probably 0AWG)

Its possible/probable that your LFP battery/BMS will not be able to crank the generator.

 

[Geokilroy]

Unfortunately we ran the heater a few too many times and the old house battery is at around 7v which is causing the Propane detector to refuse to open the propane lines. This is why I want to get the Propane detector on the new battery ASAP.

I think the reason the fridge, battery monitor/water pump, water heater and propane detector are all directly connected to the battery rather than run from the DC Panel is because the Panel is way in the back of the RV and the Battery is in the engine bay, so wiring everything to the DC Panel would have added a lot of length to all the wires.

At the house battery I have figured out that there are inline fused wires for the fridge, battery monitor/water pump and the one that used to connect to the DC panel. On the Positive terminal there is also a wire going to the generator, a small mystery wire and one going to a solenoid which then runs a line to the engine battery which has another small mystery wire on the house battery side of the solenoid.

I am guessing one of the small unfused mystery wires go to the propane detector? Then the other mystery line is probably for the waterheater. I also included pictures to help make sense of my explanation. I am planning on disconnecting the fused lines and running them to a DC fuseblock to connect to my battery I also will disconnect the generator positive line and connect it to the new LiFePo Battery. The generator is already grounded to the chassis which is why it just needs a positive line running to it (I think?).
View attachment 71419View attachment 71420View attachment 71421

On my class C the mystery solenoid is for the "Boost" of your engine battery. On mine there is a button in the cab by the drivers knee on the dash used to add the house battery to the engine battery to boost it in case you drain the engine battery while boondocking. This system also allows you to keep the house battery from draining your main battery and allows the alternator to charge your house battery while driving.

 

[aluchipawa]

On my class C the mystery solenoid is for the "Boost" of your engine battery. On mine there is a button in the cab by the drivers knee on the dash used to add the house battery to the engine battery to boost it in case you drain the engine battery while boondocking. This system also allows you to keep the house battery from draining your main battery and allows the alternator to charge your house battery while driving.

Good to know

Its possible/probable that your LFP battery/BMS will not be able to crank the generator.

If I am getting rid of the house battery, should I connect the generator to the engine battery?

Update: I have succesfully hooked up the propane detector and the battery monitor/water pump to the existing DC Panel. I have one more slot available on it where I will hook up the positive DC connection for the fridge, just need to get a 30A fuse for it at the store tomorrow. Following the wires and disconnecting them under the RV was a bit of a pain, but I was glad they were all accessible and not hidden in the walls.

Thanks to everyone that has helped me through this process, especially SmoothJoey! This is my first time setting up a solar system and also my first time integrating a solar system into an existing RV system. Thirdly this is my first time doing anything with electric beyond installing a ceiling fan.

 

[John Frum]

If I am getting rid of the house battery, should I connect the generator to the engine battery?

What are the specs for the old house battery?
What are the specs for the starter battery?

Update: I have succesfully hooked up the propane detector and the battery monitor/water pump to the existing DC Panel. I have one more slot available on it where I will hook up the positive DC connection for the fridge, just need to get a 30A fuse for it at the store tomorrow.

The manual indicates that the dc branch circuits can be fused no higher than 20amps.
Also that little green return wire looked pretty small.
Remember it has to carry the current for the whole dc panel.
Also if memory serves, those duel function propane/dc fridges are consume stupid amounts of power in dc mode.
Do you have a means of current accounting in your system?

 

[12VoltInstalls]

those duel function propane/dc fridges are consume stupid amounts of power in dc mode.

Yes. And some of the newer ones with electronics can use a surprising amount of watts albeit just a little at a time but 24/7. Even at 120V they have to heat the coil to keep the emulsion cooling the fridge unless it’s a compressor fridge.

 

[aluchipawa]

What are the specs for the old house battery?
What are the specs for the starter battery?

The manual indicates that the dc branch circuits can be fused no higher than 20amps.
Also that little green return wire looked pretty small.
Remember it has to carry the current for the whole dc panel.
Also if memory serves, those duel function propane/dc fridges are consume stupid amounts of power in dc mode.
Do you have a means of current accounting in your system?

The old house battery was a NAPA 8302 https://www.napaonline.com/en/p/BAT8302
The starter battery is a NAPA 7534 https://www.napaonline.com/en/p/BAT7534

The starter battery had a negative wire running to the engine block which I think was because it could be charged by alternator? As long as the green wires are attached to the chassis i don't need an additional wire going to the engine block, correct?

Good call on the info from the manual. I will put the fridge on its own 30A fuse coming directly off of the 80A fuse for the DC Circuit.

I don't have an exact current count for the DC Panel but at this point I only added the water pump (Probably 6A? I don't want to test it now since the water tank is empty and the lines are winterized) and the propane detector (which takes about .3A). The panel already had the furnace on it which takes about 5A and then a 15LED lights which are about .3-.5A each and then the water heater pulls about .7A when on.