How to run Airstream on Shore Power indefinitely?

[GT73]

I have a 1973 Globetrotter that I plan to use as a guest house on my property.

Currently dealing with some electrical issues and plan to fully update the system. The current Univolt is for 30 amps, and I'm not seeing 30 amp inverters online. Can I replace this Univolt with a PD2160 (60 amps)? Will that fry my system or is this similar to upgrading an electrical panel?

Additionally, once I upgrade the inverter, can I run on shore power indefinitely? I read somewhere there are ways to bypass the battery so the airstream runs more like a house than a boat.

Have never worked with a 12V system before, so a bit of a newbie.

[Dingo Girl]

Unless you have solar you won't need an "inverter" only a convertor.
I used Progressive dynamics 45 Amp converter.

[jeffb831]

You don't need a inverter - that converts 12V battery power to 120V "house" power.

What you may need is a converter - which converts 120V "house" to charge the 12V batteries.

But if you are building a permanently attached/non-mobile trailer you don't even need to deal with a 12V system and can wire everything with a standard home distribution panel, ROMEX wiring, and outlets.

[Fungus]

Some devices need 12V to run. So if you eliminated all 12V you’d need to replace those devices. Fridge. Furnace. Power awning. Anything that can operate when not on shore power.

[richard5933]

Agree with the others - you need a converter, not inverter. The Progressive Dynamics 45-amp is a good unit. I believe that it can be used without a battery in the system, but double check the latest information on their website and manual to be certain.

[CBWELL]

12 volts is required to run A/C, fridge, (unless replaced with a 120 volt only house type) lights, furnace fan, and some water heaters. Also required for vent fans. The PD9245 converter is a very good replacement for the Univolt. Suggest that a battery be kept.

[azflycaster]

An original 1973 trailer has only a few 12 volt items. Refrigerator, AC and water heater are not on the list unless they were replaced with more modern appliances. Heater, lights and water pump definitely need 12 volts. I would go for the PD 45 amp converter and a new battery, plug it in and forget about it. An AGM battery would not need to be checked for water level and some of the 70s trailers had the battery in a very hard to get to area.

[uncle_bob]

Hi

How long term a use is this?

If you are looking at a more or less permanent "guest house", then updating the appliances to 120V is probably a good idea. It gets cold enough in the northeast that running a propane furnace might become a hassle. Same thing with the 12V specific stuff.

Bob

[Hermes]

Depending on your converter, since it's job is to supply power to the 12V circuit which feeds many things in your trailer, it's not wise to leave your batteries connected to the circuit, or they will get cooked by being fed something like 13.6V on a continuous basis.

When connected to shore power, I switch my Use/Store switch to Store and let my intelligent solar system take care of gently topping-up the batteries, not the converter.

In recent years, JC has changed the converter model and installed solar, so it may be different now. You need to check this.

[azflycaster]

Originally Posted by Hermes

Depending on your converter, since it's job is to supply power to the 12V circuit which feeds many things in your trailer, it's not wise to leave your batteries connected to the circuit, or they will get cooked by being fed something like 13.6V on a continuous basis.

When connected to shore power, I switch my Use/Store switch to Store and let my intelligent solar system take care of gently topping-up the batteries, not the converter.

In recent years, JC has changed the converter model and installed solar, so it may be different now. You need to check this.

Cooking a battery is not an issue with a quality multi stage converter.

[Boxite]

Our AS is stored inside a metal bldg (aircraft hangar) at the end of our home and it remains plugged in to a 30A RV outlet year-round.

The refrigerator is not used out there during storage so is simply turned ‘off” and the door propped open for ventilation. The fresh water tank is full (treated with a bit of bleach for sanitary reasons during long-term storage since we are on a well and no water treatment except particle filtration here at home and no danger of freezing in the hangar) and the rare occasion we have more guests than bedrooms in the house….the AS has been used for sleeping quarters and the toilet, while available for use, has not been used by guests….(so far)…but if it were I’d simply move the AS out of the hangar after guests leave and fully service the unit.

When we plan for a trip, I drain and flush the fresh water tank and refill it with our accustomed home-well water…and if the trip is a long one we are not opposed to refilling it with public water supply.

I do disconnect the AS main battery during long term storage using the On/Off factory switch, and reconnect it to refresh its’ charge every other month for a week. It’s a regular lead-acid deep cycle and our World 55A converter is smart enough not to boil it anyway.

Hope this helps.

[richard5933]

Originally Posted by azflycaster

Cooking a battery is not an issue with a quality multi stage converter.

Agree. Modern multistage converters have a float voltage low enough to for long-term use without problems.

[cbburke]

It also depends on the age of the remaining appliances. In particular the furnace. The original furnace was made by Suburban. When asked they will tell you your furnace is past it's service life and must be replaced for safety reasons. The heat exchanger box was make of steel and will rust and perforate over timed. This will allow carbon monoxide into the coach putting the occupants at risk. There are instance of death resulting from operating an old furnace.

[uncle_bob]

Hi

Not to get too crazy here, but the "fine old" converters from a decade or two back had the same float voltage as the fancy modern stuff. The Univolts from the 1960's are in crazy enough shape by now that who knows what they put out ( = they are way past time for replacement ).

Bob

[Hermes]

Originally Posted by richard5933

Agree. Modern multistage converters have a float voltage low enough to for long-term use without problems.

If a converter is to feed the trailer's 12V circuit with a steady voltage, required to operate the appliances and lights, how can it shift into float mode to protect the batteries at the same time? They have a controller on the connection to the batteries? Just asking.

[Boxite]

Originally Posted by Hermes

If a converter is to feed the trailer's 12V circuit with a steady voltage, required to operate the appliances and lights, how can it shift into float mode to protect the batteries at the same time? They have a controller on the connection to the batteries? Just asking.

The WFCO 55 in my AS monitors the battery separately from the 12v appliance demands and has a separate battery-charge circuit. (i only disconnect the battery occasionally for drill…. for the first 5 years we owned it I left it connected full time with no problem.)
This converter is not particularly “high tech” but it’s adequate, inexpensive, and easily replaced. (I actually did replace it in ‘18 while on a 3-mo trip when it refused to allow my generator on-line to provide AC power. It had some sort of microchip failure. I got on Amazon, ordered it to be delivered to the closest drop box (Whole Foods in Colorado Springs) and it came in the next day. It was a simple screwdriver remove the old board install the new board…been working fine ever since, now going on 5 years. Cost was around $100 when local RV dealers wanted 3 times as much and two weeks “backorder”.
Bull! Fixed next day myself.

[richard5933]

Originally Posted by Hermes

If a converter is to feed the trailer's 12V circuit with a steady voltage, required to operate the appliances and lights, how can it shift into float mode to protect the batteries at the same time? They have a controller on the connection to the batteries? Just asking.

Modern converters monitor both voltage and current flow. If you watch a shunt-based monitor while doing like you're saying, you'll see that the amperage is automatically adjusted to keep up with the devices in use, but the voltage will remain at the float voltage.

After a short time at float, fully charged batteries will show 0.0 amps on the monitor. Turn on a few lamps, and the monitor will show -X.X, with the actual number varying depending on what you turned on. After a few minutes, the converter will recognize the new load and adjust the current flow to bring it back to 0.0. If you turn off the lights, it will rise to +X.X, and then slowly return to 0.0 just like when you turned them on. The goal of the converter is to maintain 0.0 amp flow in/out of your batteries with a steady float voltage.

High voltage is what ruins batteries and causes the water loss. At proper float voltage (read your battery's manual to define this) water loss and off-gassing is minimal, which is why float voltage is used.

When we had lead acid batteries and a Progressive Dynamics multistage converter, once the batteries were charged voltage would go down to 13.2v and stay there. Once a day for 15 minutes it would go back up to 14.4v to prevent damage to the plates, and then return to float.

All that said, if you really turn on enough devices and cause the batteries voltage to drop enough doing it, the converter will raise the voltage back up and charge the batteries. When it senses a fully charged battery, it's back to float voltage again.

[Hermes]

Originally Posted by richard5933

Modern converters monitor both voltage and current flow. If you watch a shunt-based monitor while doing like you're saying, you'll see that the amperage is automatically adjusted to keep up with the devices in use, but the voltage will remain at the float voltage.

After a short time at float, fully charged batteries will show 0.0 amps on the monitor. Turn on a few lamps, and the monitor will show -X.X, with the actual number varying depending on what you turned on. After a few minutes, the converter will recognize the new load and adjust the current flow to bring it back to 0.0. If you turn off the lights, it will rise to +X.X, and then slowly return to 0.0 just like when you turned them on. The goal of the converter is to maintain 0.0 amp flow in/out of your batteries with a steady float voltage.

High voltage is what ruins batteries and causes the water loss. At proper float voltage (read your battery's manual to define this) water loss and off-gassing is minimal, which is why float voltage is used.

When we had lead acid batteries and a Progressive Dynamics multistage converter, once the batteries were charged voltage would go down to 13.2v and stay there. Once a day for 15 minutes it would go back up to 14.4v to prevent damage to the plates, and then return to float.

All that said, if you really turn on enough devices and cause the batteries voltage to drop enough doing it, the converter will raise the voltage back up and charge the batteries. When it senses a fully charged battery, it's back to float voltage again.

Thanks, so from your explanation I am to understand that the trailer's 12V circuit is fed from the batteries and the converter takes care of the batteries. So no batteries, no power on the 12V circuit. That's correct?

With older non-intelligent converters like the one I have, I can disconnect the batteries and if we are on shore power the 12V circuit is powered by the converter and all is well. Which is why when on shore power I disconnect the batteries (put Use/Store switch in Store mode) to protect the batteries (and let the intelligent solar system MPPT controller take of them; it's been 4 years and haven't had to add water yet).

[richard5933]

Originally Posted by Hermes

Thanks, so from your explanation I am to understand that the trailer's 12V circuit is fed from the batteries and the converter takes care of the batteries. So no batteries, no power on the 12V circuit. That's correct?

With older non-intelligent converters like the one I have, I can disconnect the batteries and if we are on shore power the 12V circuit is powered by the converter and all is well. Which is why when on shore power I disconnect the batteries (put Use/Store switch in Store mode) to protect the batteries (and let the intelligent solar system MPPT controller take of them; it's been 4 years and haven't had to add water yet).

Yes and no.

The 12v electrical system is powered by your batteries and the converter's job is to tend to the batteries. That is true.

But whether or not you can remove the batteries is another thing. Some converters are designed to be used with or without batteries, some aren't. Doesn't matter if they are old or new converters - you need to check the manual to see if things will be okay without batteries.

Sounds like your system is set up so that when you flip the use/store switch you're disconnecting the converter from the batteries but not the solar charge converter. If that's working for you then keep doing it. Not all trailers are connected the same in this regard, so there's no telling if this would work for another.

[dsluyk]

You really don't need anything except a battery charger with over voltage protection.
I keep my 1960 Tradewind on shore power all the time at home and camping.
I only have one regular 12V car battery and keep a charger plugged in all the time, so my refrigerator, Fantastic fan, and the four 12V lights can be used. My battery is over five years old!

I can even dry camp on a fully charged single battery for 3-4 days if I don't keep the lights on too much and don't keep the fan on.