Inverter “automatic” transfer switch.

[lwebb]

I'm restoring a 1950 Vagabond. I want to add a 12volt yo 110 inverter. I'd like the 110 output of the inverter wired directly into the camper 110 line so if the power goes out, the 12volt battery will kick in and keep the clock etc., running. I'm told I will need an “automatic” transfer switch. I have no idea what that is or how to use it.
Any advice?
Lanny

[DR60]

I got an inverter with a 20 amp 120 v pass through circuit. This lets 20 amps of 120 volt power pass through the inverter automatically when there is shore power available.
The inverter cost a little more but I did not have to buy an ATS [ Auto Transfer Switch] . And the wiring was very straight forward. It only needed Pos and Neg 12 v wires, and a 120 v wire to the inputs and the three output 120v wires going to the trailer.
Good luck with this. DR

[Arch Hoagland]

Does your 1950 Vagabond have gas lamps? Just curious.

[lwebb]

No all my fixtures on the Vagabond were 110. I’m converting them to 12 volt.
Ok I already have a 5500 watt inverter. I’ll be using a LiFePo4 lithium battery with a converter to switch the 110 to 12v and supply 110 to the outlets. I want to wire the 110 output from the Inverter directly into the 110 line but I don’t want to have to throw a switch to go from the land line 110 to the inverter 110.

[Argosy]

Look for "pass through" in the description of the inverter. What brand is it?


Do you intend to add a generator?

[Persistent]

Originally Posted by lwebb

No all my fixtures on the Vagabond were 110. I’m converting them to 12 volt.
Ok I already have a 5500 watt inverter. I’ll be using a LiFePo4 lithium battery with a converter to switch the 110 to 12v and supply 110 to the outlets. I want to wire the 110 output from the Inverter directly into the 110 line but I don’t want to have to throw a switch to go from the land line 110 to the inverter 110.

Generally speaking, inverter output does not work well with shore power. Thus the need for a transfer switch. The transfer switch can be manual or automatic. Post make and model of inverter and converter/charger.

Many RV's use a combined inverter/charger/converter with built in automatic transfer switch.

Google search for "automatic transfer switch" for options.

There are several things that need to happen when switching from shore power to inverter or back.

1 Keep two AC power sources separate. Double Pole, Double Throw, Disconnect before connect type switch.

2 Disconnect battery charging when shore power is not available. Connect charger when available

3 Connect system ground to neutral when on inverter power. Disconnect when on shore power.

A battery bank sufficient to run a 5000 watt inverter is required. (5000w/12v) + conversion loss = 460 amps at 12 volts approximately. Typically, a 1000 amp hour lead acid battery bank is required.

Many inverters can be used at less than full capacity. A 30 amp 120 volt shore power system can be matched with a 3600 watt inverter.
(3600w/12v) + conversion loss = 330 amps. Typically a 700 amp hour lead acid battery bank is required.

To use a smaller battery bank many users install a 2000 watt inverter and conserve energy while running from batteries. Don't run air conditioners or electric heaters. 180 amps from a 400 amp hour battery bank.

The high current 120 volt devices and battery charger are left on the main circuit breaker panel. Circuits that you wish to run from battery power would go to a new sub-panel. The sub-panel would be powered from a transfer switch that supplies either 30 amp shore power or 16 amp inverter output.

12 volt Side of Life part 1
http://marxrv.com/12volt/12volt.htm
12 volt Side of Life part 2
http://marxrv.com/12volt/12volta.htm

[153stars]

Old school ATS.... well manual MTS is to plug a MH cord into genny outlet. This inverter is not a charger too but just no pass through. So can you chose charge only on inverter. You can chose to which is primary if its powered aka the shore power and it will stay on that ignore inverter. Or visa versa.

[lwebb]

Wow, Paul, that's a very detailed response. Thank you. It took some time for me to go through it and try to figure it out. Unfortunately, I'm afraid much of it was over my head. My brother knows a bit more about electronics so he may be able to help me. He's actually the one who gave me the inverter. It's probably much more than I need. It's certainly larger than I was thinking but a very gracious gift.

The inverter is a TVNIKD 5500 Watt Inverter Power Inverter of Modified sine Wave Truck RV Solar Inverter dc to ac 12V to 110V Inverter for Truck RV.

My plan was to use a Go Power Lithium RV Battery - Deep Cycle - LiFePO4 - Group 31 - 12V - 100 Amp Hours. The specs are :
Capacity: 100 amp hours
Battery group: 31
Voltage:
Nominal: 12.8 V
Maximum charge: 14.6 VAC
Charge cutoff: 14.6 VAC
Discharge cutoff: 8.4 VAC
Charge current:
Recommended: 50 amps
Maximum: 100 amps
Maximum discharge current:
Continuous: 100 amps
30 minutes: 120 amps
5 seconds: 150 amps

With a Progressive Dynamics PD9100L Series Battery Converter Charger w/ BMS - Lithium - 12 Volts - Specs are:
Application: 12V battery systems
Rated power output: 1,000 watts
Amperage output: 60 amps
Voltage:
Input: 105 - 130 VAC
Output: 13.6 - 14.6 VDC.

Unfortunately, I'm afraid this is beyond my skill set.

[153stars]

A single 100ah battery will only supply 1000w to inverter. OAlithium has 100ah with a 200amp BMS. and Bluetooth UL cells , usually have to pay about double to get UL listed cells.
IMHO you would be better off with good used RV inverter charger than cobble a bunch of the bits you're talking about together. I can usually find at least four usable ones within 100 miles of me on FB marketplace. Even if not with LIFEPO4 battery profile,it will charge it to about LIFEPO to about 90%. You get pass through, charger, inverter. A small amount of solar or portable lith charger like NOCO-10 can do occasional cell balance.

[Persistent]

Originally Posted by lwebb

...
The inverter is a TVNIKD 5500 Watt Inverter Power Inverter of Modified sine Wave Truck RV Solar Inverter dc to ac 12V to 110V Inverter for Truck RV.

My plan was to use a Go Power Lithium RV Battery - Deep Cycle - LiFePO4 - Group 31 - 12V - 100 Amp Hours. The specs are :
Capacity: 100 amp hours
Battery group: 31
Voltage:
Nominal: 12.8 V
Maximum charge: 14.6 VAC
Charge cutoff: 14.6 VAC
Discharge cutoff: 8.4 VAC
Charge current:
Recommended: 50 amps
Maximum: 100 amps
Maximum discharge current:
Continuous: 100 amps
30 minutes: 120 amps
5 seconds: 150 amps

With a Progressive Dynamics PD9100L Series Battery Converter Charger w/ BMS - Lithium - 12 Volts - Specs are:
Application: 12V battery systems
Rated power output: 1,000 watts
Amperage output: 60 amps
Voltage:
Input: 105 - 130 VAC
Output: 13.6 - 14.6 VDC.
...

Unfortunately, running a high capacity inverter from a small battery bank is not a practical situation.

First evaluate what appliances you wish to operate and for how long. Choose an inverter sized to meet the need. Choose a battery bank large enough to support the chosen inverter for as long as is required.

The gift is a good thought, but not suitable for your application.

TVNIKD 5500 Watt Inverter Power Inverter is not designed for permanent installation. It has four 120 volt sockets. An inverter designed for full house installation would have screw clamp connectors and cable clamps for 120 volt sheathed cable.

It should be directly and permanently connected to a large 12 volt battery bank. However, appliances need to be plugged directly into the four outlets.

It does not have a built in transfer switch. It is not designed to be used with an automatic one. Anything is possible, but will not work well.

The 5500 watt rating is for peak output. So continuous duty would be limited to substantially less. I could not find a manual for it.

It is way too much to power a clock. It will discharge the battery fast with only the clock working. All inverters consume 12 volt power. High capacity inverters consume substantial power even when idling.

A 100 amp hour Li battery will power the inverter to support a clock, but not for long. Get a 12 volt clock. A 100 amp hour Li battery will power a 12 volt clock for weeks. Some battery powered clocks will run for a year on a pen light battery.

A 100 amp hour Li battery will not support a 5500 watt inverter to power heaters, A/C, coffee pot, microwave, ... any heating device. A minimum 400 amp hour battery bank would be required to run one heating device. A 200 amp hour Li bank may do the job for a very short period.

I recommend you visit a motor coach dealer and get a tour of a motor coach. Get the salesmen to explain the power management and show you the 12 volt house side of the system. You will have to lie and say you are considering buying one. Wear nice clothes. I think this is much more than you are qualified to install.

[shootist]

1) you do not need a transfer switch unless you have a generator. Period. The inverter can be on standby at all times and will seamlessly kick in in case of a power loss. That is the whole purpose of having a pass through relay in the inverter. If yours doesn’t have a pass through. Buy one that does.
2) if your inverter has a battery charger ( which I would be shocked if it didn’t) make sure it can charge lithium batteries, this is critical.

[SteveJ.]

Good reading:
The 12volt Side of Life (Part 1)

There is also a part 2.

BTW, you really don't want to be using a modified sine wave inverter.

[Archer2]

Personally I would be very wary of a 5500W (continuous, 11,000W peak) inverter costing less than $400.

[rffowler55]

As others have said your battery bank size will determine what you are able to run with an inverter and thereby reflects on what size inverter you need. Our 2007 Newmar Bay Star has a battery tray that will only hold 2 12volt batteries ( 6volt batteries are too tall) so we have around 250 12volt amps of storage but at 50% discharge only 125 amp hours available. The 50% discharge limitation is our limit and is not a firm rule but has worked well for us on our large solar power system on our primary home .

Our coach came with a Magnum 700 watt modified sine wave inverter with a built in automatic transfer switch. The inverter received 120volt power from either shore power or the generator as the primary power and when available passed through the inverter to power the Tv outlet, the only outlet powered through the inverter. When shore or generator power was not available the automatic transfer switch selected the secondary power source, which was the batteries and power remained to the tv until the battery drain reached the maximum battery discharge set point.

Having only 2 batteries we were only able to upgrade our system to a Magnum 1000 watt pure sine wave inverter so we could run our refrigerator off the inverter to keep it cold on long trips since the alternator also charges the house batteries. The new Magnum inverter did not have a built in automatic transfer switch so I bought a Magnum stand alone automatic 15 amp transfer switch that has inputs for the shore/generator as primary and a secondary input for the batteries. There is a plug from the transfer switch that goes into the inverter supplying power to the refrigerator.

Our refrigerator is very energy efficient and not extremely large so the max 120 amp pull is 3 to 5 amps well below the 15 amp max.

As you can see there are many variables to take into consideration:

What do you want to power with the inverter, this will be limited by your battery bank size and if you have a way to recharge the batteries other than shore/generator/alternator such as solar. If not, think small since even if you 100% discharge your 120 amps of 12 volt battery capacity is only 10 amps of 120volts of power, 10amps / amps of draw determines how long the item could run. Also, just because you can draw down a lithium battery to 100% discharge does not mean you should since every battery manufacturer expresses a reduction in life expectancy based on level of discharge so know what your manufacturer recommends.