2nd battery powering AC side of my trailer.

[Pass me]

Hi folks, I'm wanting to connect my stand alone 2000W Inverter to the AC side of the distribution panel, it will be powered by a 12 V100Ah LiFePO4 battery. I will leave my factory LAB system as is (PD 9130/no TCMS).
The lithium battery will be isolated in a closet and I'll recharge it with a Genius10 powered by my generator/extension cord. This way I can use my AC receptacles while boondocking. The problem is when I connect to shore power via the 30A cord.
Do I have to isolate the Inverter from the panel when on shore power? I
could simply unplug the extension cord(s) from the Inverter (that are wired to the chosen [ not all] AC plugs of the trailer) but would these male ends now be live?
While on shore power Can I power the Genius10 charger from any 120AC receptacle inside my trailer without isolating my Inverter?
My hunch is to wire in an on/off switch between the AC panel circuits and my converter to allow easy isolation while on shore power but I'm wondering about the implications if I don't.
This is in the "thinking out loud"
stage by the way but I think it's a dandy (and inexpensive) way to this Lithium battery.
1998 Aerolite 21RDB travel trailer.
As per always all input/warnings and suggestions are most welcome and graciously accepted.

 

[Gary RV_Wizard]

You must insure that the inverter can never attempt to power any circuit where shore power can be active at the same time. There will be smoke, loud noises, and maybe flames if that ever happens, and equipment will be destroyed. Relying on humans to never activate the two at the same time is high risk - people simply forget or fail to check when they get busy or are detracted.

The safest method is some sort of transfer switch that connects one or the other to the panel but never both together. Basically a double-pole, double-throw switch with the panel connection on the center poles and inverter on one side and shore cord the other.

 

[solarman]

A simple transfer switch will do the job, either power from shore or inverter, NEVER both..

red flag here is 2000W from 12Volts.

at full load you will be drawing approx. 183 Amps.. not a good thing to do to a battery that small.
additionally, the BMS "MAY" have a current limit of 100 Amps.
depends on the battery.
if you keep loads small to less than 1000W then you should be ok.

quote - " I will leave my factory LAB system as is"

a LAB is a dog isn't it ? LOL

customary way to describe lead acid battery is "FLA" = "flooded lead acid"

 

[HueyPilotVN]

I can offer a little advice as I have a system that does something similar.

My system consist of two independent battery banks. One is the traditional 12 volt power supply for the normal 12 volt needs.

The second system is designed to provide 120 volts AC from a large battery bank to the main distribution panel. This system uses a Invertor/charger with a pass thru function to supply the 30 amps either from the battery bank or from the incoming AC from either the generator or shore power.

This system does not require any intervention to seamlessly and automatically pass thru the AC or supply the AC power to the entire panel from the battery bank.

It does power the entire distribution panel rather than just some circuits.

This is a basic snap shot of the system and if you want more detail than you might want to read you can go to this thread.

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[Pass me]

“There will be smoke, loud noises, and maybe flames if that ever happens”.
Ain’t gonna happen gentlemen, thank you for the quick reply’s.
Can you recommend a simple transfer switch? Amazon quick search brought this up. I connect shore power to “A”, my Lithium battery to “B” and the switch output side to ….. the AC side of the distribution panel? I’ll google a wiring schematic for this panel & go from there. Warning there may be questions….lol

 

[Ray-IN]

Pass me; that is limited to 15A, That means 30A shore power may let out the smoke. You need a 30A ATS.

 

[John From Detroit]

One of the things I like about Inverter/Chargers like my Xantrex Freedom XC 2000 watt is they have the transfer switch built in. On shore power or not days "Mains" power it charges the batteries. and runs some radio gear.. If mains fails. I drop an extension cord to the kitchen and the Refrigerator keeps refrigerating (If I did sme rewiring this would be automatic but I do not own the building) and the radios keep working along with some other stuff plugged into it.

What I don't like about this SPECIFIC inverter/charger is the 120 volt power connections. But that's a different matter. others will have better connections.

 

[Pass me]

Thanks for this a dandy example of what can be achieved by the boondock set. My needs are super simple as this ‘98 Aerolite 21’ RDB hard wall of mine is primarily my fishing shack. The lithium battery and Inverter will be held together in an aluminium frame which will be mounted in a closet. Directly below said closet is the house battery, the PD 9130 & the distribution panel. My learning curve is the electrical connections involved.
Starting today on this project, 1st I’ll note existing wiring and go from there. But I’ll need advice on how to tie my Inverter into the AC side of the distribution Center property safely.

You must insure that the inverter can never attempt to power any circuit where shore power can be active at the same time. There will be smoke, loud noises, and maybe flames if that ever happens, and equipment will be destroyed. Relying on humans to never activate the two at the same time is high risk - people simply forget or fail to check when they get busy or are detracted.

The safest method is some sort of transfer switch that connects one or the other to the panel but never both together. Basically a double-pole, double-throw switch with the panel connection on the center poles and inverter on one side and shore cord the other.

You must insure that the inverter can never attempt to power any circuit where shore power can be active at the same time. There will be smoke, loud noises, and maybe flames if that ever happens, and equipment will be destroyed. Relying on humans to never activate the two at the same time is high risk - people simply forget or fail to check when they get busy or are detracted.

The safest method is some sort of transfer switch that connects one or the other to the panel but never both together. Basically a double-pole, double-throw switch with the panel connection on the center poles and inverter on one side and shore cord the other.

You must insure that the inverter can never attempt to power any circuit where shore power can be active at the same time. There will be smoke, loud noises, and maybe flames if that ever happens, and equipment will be destroyed. Relying on humans to never activate the two at the same time is high risk - people simply forget or fail to check when they get busy or are detracted.

The safest method is some sort of transfer switch that connects one or the other to the panel but never both together. Basically a double-pole, double-throw switch with the panel connection on the center poles and inverter on one side and shore cord the other.

Thanks Gary, I will include a 30A automatic transfer switch into this project. I’ve googled the wiring schematic of a typical travel trailer but just how to complete this safely remains a mystery to me. I will be tracing the wiring today and would appreciate sharing the results with you.

red flag here is 2000W from 12Volts.

at full load you will be drawing approx. 183 Amps.. not a good thing to do to a battery that small.
additionally, the BMS "MAY" have a current limit of 100 Amps.
depends on the battery.
if you keep loads small to less than 1000W then you should be ok.

quote - " I will leave my factory LAB system as is"

a LAB is a dog isn't it ? LOL

customary way to describe lead acid battery is "FLA" = "flooded lead acid"

 

[Pass me]

Hey folks, update here. There is no easy access to my system unfortunately. I’m debating cutting out the 1/8” vaneer flooring in this closet to access the Progressive Dynamics PD 9130 and the back of the Distribution Panel. As it is it’s next to impossible to trace the wiring.
Before I proceed this is what I know re electrical, please jump in with any corrections.
Shore power 30A cord connects to AC side of the panel. This then feeds all 120V outlets. One of these plug-ins powers the PD 9130. This then is wired to the 12V side of my panel. I think it’s also connected directly to my FLA house battery but again my limited view makes it hard to confirm.
My 2nd 120V source will be my 2000W stand alone Inverter powered by a 100Ahr lithium battery.
I will install a 30A auto switch with two input lugs, connect shore 30A wire to “A” and my 120V/15A Inverter wire to “B”. Then connect 30A wire to AC side of Distribution Panel.
But how do I prevent the lithium battery from charging the house battery while boondocking or should I try? The PD 9130 converter draws 500W/4.2A.My power consumption is minimal.
AC side will be my Bose radio, tablet, cell phone charger and a mid size fan at times. The Keurig coffee maker will only get used on particularly groggy mornings, lol. And then only once.
The 12V draw includes furnace(3.1A/37W per hr), Dometic RM2510 fridge on propane(? 12V draw but it can’t be much), some LED lights, roof vent fan, CO2 detector and water pump.
I will put a battery monitor w shunt (recommended brands/types most welcome!) in the lithium battery + lead feeding my inverter to tell me it’s time to plug the shore power cord into my generator.
And I can count on the auto transfer switch to choose this power source over my Inverter source? If true I will power my Genius10 charger (plugged into a dedicated 120V receptical) to recharge my Lithium battery as well as the house FLA via the PD 9130.
What do you think?

 

[Gary RV_Wizard]

But how do I prevent the lithium battery from charging the house battery while boondocking or should I try? The PD 9130 converter draws 500W/4.2A.My power consumption is minimal.

That's not a minimal draw from a single battery. 500W @ 12v = 42 amps! If the converter is on it's own circuit, flip the breaker off. If not, install a manual switch on its 120vac feeder. Better yet, put a "normally closed" solenoid relay on that feeder and activate it with a control signal from the inverter output. That way when the inverter is ON the power to the converter is automatically shut OFF.

 

[Pass me]

That's not a minimal draw from a single battery. 500W @ 12v = 42 amps! If the converter is on it's own circuit, flip the breaker off. If not, install a manual switch on its 120vac feeder. Better yet, put a "normally closed" solenoid relay on that feeder and activate it with a control signal from the inverter output. That way when the inverter is ON the power to the converter is automatically shut OFF.

I have to remember the 10x factor when considering 120V and 12V! Your right of course and I can and will trip the converter breaker FIRST and then unplug the 30A shore power cord. What I am pleased about though is my grasp of the interaction between 120V and 12V in my RV. If I didn’t factor in the Converter draw I would have realized pretty quick via the battery monitor or my quickly depleted LiFePO4 battery. All the more reason to install a monitor w low voltage alarm. But the wiring sequence from 30A AC in to 13.6V DC charging the house battery is basically correct?
I have cut the floor out of this closet and am tracing the wiring (shore power unplugged!) and share what I find. I think your auto solonoid suggestion is the safest solution here but I have to learn about this device. Your help continues to be greatly appreciated Gary.

 

[Pass me]

Good morning, I've exposed the wiring compartment (there's now a trap door in this closet bottom) & wow, crowded! I'm gonna shelve this aforementioned project for now but have a question re my 2nd stand alone battery powering my stand alone Inverter. Can I connect this 2nd battery to the house FLA battery while boondocking to boost mt 12V system? I'll install an inline disconnect switch to accomidate shore power times. And is there a type of 12V auto switch to do this for me?
Thx for any input sir.

 

[Gary RV_Wizard]

Yes you can. It's not ideal to mix battery types in the same bank, but it's not a disaster either. Disconnecting when not in use helps to reduce the downside.

 

[WME]

$$$$ answer to a $$ problem
https://www.etrailer.com/RV-Transfer-Switch/Go-Power/342GPTS.html

 

[Pass me]

The auto switch is a little pricey for my needs and thank you for showing this as an option.
I'll connect the two batteries in parallel running the + through a battery on/off switch. This will be used only when the house battery is down 50%+ to get me to the afternoon. I'll isolate the batteries, plug the 30A cord into the portable genny and recharge both batteries, house via the PD9130 & the LiFePO4's via the Genius10 powered by a convenient kitchen 120V outlet.
I'd like to acknowledge Gary & WME for their continued support here, as my license plate (PASSME) suggests my fast lane days are behind me, I will take the time to confirm I'm doing things correctly re RV electrical.