Electrical questions: 12V on shore power, input current

[geobeck]

I have a 2004 Fleetwood Prowler 28BH that I bought used a couple of years ago.

Q1: When I'm on shore power, does the 12-volt circuit still run through the battery, or does it switch over to a transformer? In either case, will shore power keep my battery charged, or should I put it on a maintainer?

Q2: The external power cord terminates with a 15 amp plug. Is this normal for some trailers this size, or is it likely that a previous owner modified it? 15 amps won't run much, especially if the AC is running... and the presence of AC makes me think my input should be 30 amps. Any ideas on this?

[tuffr2]

Typically trailers with one A/C unit will be 30 amp. 2 A/C units will be 50 amp. There is no trailer I know of that is 15 amp. Your are right that will not run much. Residental Microwaves are 20 amp for example.

Sounds like you need a 30 amp cable on both ends. Now just an fyi - there are all kinds of electrical adapters to go from 30amp at the trailer to 15 amp to plug into a house outlet.

I hope the above answers question #2


Question #1 - keeping the trailer plugged in to a house outlet will keep your battery charged. No need for a battery tender.

Yes, all 12v things like the lights, radio, refrigerator on propane, water pump, water heater on propane all need a battery.

[geobeck]

Thanks for your response. My camper is currently in an RV park, so it's plugged into a 30 amp socket using an adapter. I guess the next thing I need to confirm is how much current I'm actually drawing.

I assume the adapter includes a circuit that limits the current so people can't fry un under-sized power cord. My cord is a heavy-duty outdoor cord, but I have no idea what it's rated for, so once I get to the bottom of this, I'll probably replace the whole thing. When I get back to it, the first thing I'll check is the rating on my main breaker.

[Old-Biscuit]

Originally Posted by geobeck

Thanks for your response. My camper is currently in an RV park, so it's plugged into a 30 amp socket using an adapter. I guess the next thing I need to confirm is how much current I'm actually drawing.

I assume the adapter includes a circuit that limits the current so people can't fry un under-sized power cord. My cord is a heavy-duty outdoor cord, but I have no idea what it's rated for, so once I get to the bottom of this, I'll probably replace the whole thing. When I get back to it, the first thing I'll check is the rating on my main breaker.

So you have a power cord with a standard household 3 prong plug like an extension cord??
And you have an adapter that goes from that 15A plug to a 30A plug which is plugged into a CG power pedestal 30A outlet?

NEMA 5-15 Plug


30A Male to 15A Female Adapter



Nothing in adapters to prevent overloading
30A Breaker at CG Pedestal and your RV Main 30A Breaker are the protection devices

Your power cord if OEM is 30A rated
The 15A replacement plug is rated for 15A
**But with 30A #10 wiring it probably will surfice
Check for HEATING at plug while using

REPLACE with a RV 30A Plug ASAP

[happy2rv]

Is the cord hard wired to the trailer or does it detach? If it detaches, the socket on the trailer should have a cover that indicates the power ratings. Either 50A or 30A. If it's detachable, you should be able to get a whole new cord fairly easily.


With regards to the adapters, they typically do not have any current limiting devices other than the fact that the plugs and internal wiring aren't designed to carry that much current. In other words, the adapters will allow you draw as much current as the breaker on the outlet you're plugged into will provide up to the point that the adapter or an undersized cord it is connected to catches fire.



With regards to keeping the batteries charged, opinions vary considerably. Keeping the RV plugged in will keep the batteries charged. Some of the converter/chargers have a tendency to overcharge and boil batteries dry others aren't as susceptible to that. My personal preference is to disconnect the batteries by means of a battery disconnect switch and use a dedicated "smart" battery maintainer to keep the batteries up while in storage. Some prefer to keep the RV plugged in to allow use of its facilities. So it may depend on how you "store" it.

[tuffr2]

I want to say the thicker outdoor extension cord is good for 20 amps.

It does not make too much sense to have put a 15amp plug on a 30amp trailer cable unless at one time it was plugged into a 15amp outlet permanently. Actually that makes little sense since an adapter should have been used and the original trailer electric cord should have been left alone.

With the current set up you can not use the A/C and the microwave at the same time. You can buy a new expensive 30amp trailer cable if you want full use of electric appliances.

[YC1]

Put a voltmeter across your batteries when plugged into shoreline, then unplug and measure again.

It should start out at about 13.5 and then unplugged it will drop under load. Download a battery voltage chart for specifics but it should hold at 12.5-12.5 basically.

Generally later model rv's do not flip from battery to converter when plugged in but there are those that do.

We had an RV that only charged about three amps when the generator was running or hooked to shoreline. It isolated the battery but this took forNever to charge the battery when it was down.

A picture of your power cord would be helpful. Previous owner must not have needed the full 30 amp capability.

[Persistent]

Some good advice above. Rules of thumb are a good start, but measuring voltage at the battery bank terminal tells all.

Old RV chargers need a battery to stabilize the voltage. Recent designs all work to provide 12 volts DC without a battery just fine. Post make and model of the charger or look it up in the operator's manual. If it is called a converter/charger, it does not need a battery.

Measure battery bank voltage. Deeply discharged batteries will have a voltage below 12.0 volts. Fully charged batteries will have voltage higher than 12.7 volts. Measure when batteries are not being charged or discharged for at least 3 hours. (This is called "static" voltage.)

Plug in to shore power. Voltage should slowly raise. It may take a few minutes. It may take a few hours depending on the charger capability. 13.2 volts is ideal for long term storage plugged in. 13.6 volts is OK. 14.4 volts is only OK for a few hours. It should drop back to 13.6 or less after 4 or 5 hours.

Recheck the voltage in a week or so. Fully recharge the battery bank for 14 to 18 hours for storage before the voltage drops below 12.4 volts. This is necessary for long life of the batteries.

The same rules apply to battery maintainers, battery chargers, or built in RV converter/chargers. Recharge before 12.4 volts even applies if storing disconnected. Always store lead acid batteries fully charged.

I wish you good luck and happy trails ahead!

[Persistent]

Originally Posted by geobeck

...

Q2: The external power cord terminates with a 15 amp plug. Is this normal for some trailers this size, or is it likely that a previous owner modified it? 15 amps won't run much, especially if the AC is running... and the presence of AC makes me think my input should be 30 amps. Any ideas on this?

It is definitely not normal. Since it has been modified by someone, there is no telling what has been done. Please post a picture of the 15 amp plug and cord. Post a picture of each end of the cord.

A 25 foot 30 amp 120 volt RV cable needs at least 10 gauge wire. There would be 3 wires in the cable. One hot, one neutral, one ground.

Your cable may have a 15 amp adapter from the 30 amp 120 volt plug to a 15 amp plug, or it may be a 15 amp plug added to a 30 amp cord, or it may be a 15 amp cord with a 15 amp plug. In all cases, the 15 amp parts are not capable of supporting 30 amps.

Plugging 15 amp parts into a 30 amp outlet is not protected. Plugging into a 15 amp outlet is protected.

I recommend you do not plug a 15 amp plug into a 30 amp outlet using an adapter. At least do not leave it unattended. Keep a look out for smoke or melting parts. It is possible the adapter has a fuse or circuit breaker that would protect the 15 amp parts, but it is unlikely. You would be able to see the fuse holder or circuit breaker.

The RV end of the cable may be hard wired (passes through the wall to the interior) or it may have a plug mounted on the wall and the cable has a socket. If it has a plug and socket, it will probably be 3 pins or blades. You can probably buy a replacement 30 amp 120 volt cable at a hardware store or at Walmart.

A 4 pin socket and 4 wire cable would be for 50 amps 240 volts AC. The wire would need to be at least 8 gauge.

If you post good pictures, we may be able to recognize what you have and give better advice.

[Atlee]

Originally Posted by tuffr2

I want to say the thicker outdoor extension cord is good for 20 amps.

It does not make too much sense to have put a 15amp plug on a 30amp trailer cable unless at one time it was plugged into a 15amp outlet permanently. Actually that makes little sense since an adapter should have been used and the original trailer electric cord should have been left alone.

With the current set up you can not use the A/C and the microwave at the same time. You can buy a new expensive 30amp trailer cable if you want full use of electric appliances.

Or buy a replacement 30amp end plug for the current trailer cord.

[Bill Nourse]

Are you sure you do not have one of these adaptors on the end of your cable? sometimes when connected, they look like they are part of the cable. https://www.lowes.com/pl/Southwire--...ent=4294961321