Electical Confusion

[Skins44]

Dealer provided a starting battery when i bought the camper last March. I didn't realize it until recently (had no reasons to check). Had some strange power issue recently, that is when i realized i didn't have a deep cell. Dealer is going to give me one.

on to my point...while my battery is disconnected and i am plugged into my home shore power, my camper lights do not work. CO alarm light is not on. The only 2 items that i see have power are the microwave and the TV.

Is this normal without the battery connected? Or, do i possibly have an issue with the converter?

[mohead1]

Battery is part of the inverter circuit.....when battery disconnected the 12v equip doesnt come on

[JimQ]

Short answer is yes: you need a battery connected as your lights and other items work only on the 12v system. When your on shore power, the lights are still powered by your battery which is constantly being charged by your shore power going thru the converter. Hope this helps you.

[Skins44]

phew! that helps, thanks for clarifying mohead and Jim. Glad i don't have to investigate the converter. At least for now.

Appreciate the quick responses.

[Steveo57]

You should have 12 volts provided by the converter without a battery. I would check the converter breaker is on and check the output of the converter.

What kind of strange power issues did you have?

[Brentw]

Yep, you should have 12 volt available from the convertor. Is it possible when you disconnected the battery you shorted the cables. There are fuses on the discharge side of the convertor.

The convertor will provide 12 VDC to the trailer as well as charge the battery.

[chuckster57]

You should have 12 volts provided by the converter without a battery. I would check the converter breaker is on and check the output of the converter.

What kind of strange power issues did you have?



Yup!! No battery, plugged into shore power, all 12V stuff in trailer will operate with a working converter.

[JimQ]

Ooops! Sorry I provided some bad information. That's how I understood the 12v system worked.

[Skins44]

Thanks all, no worries Jim.

Steveo, i keep my camper plugged into a 20 amp outlet while its in my driveway at home. Sometimes when i go into the camper, the lights are very dim. When i check my battery charge level, it shows 0 charge. the next day, i go back in the camper and the lights are bright and my battery level is back at full charge.

As i mentioned, the dealer provided me with a starting battery, not a deep cell. I will be picking up the deep cell today to replace. I don't know if that is where the issues lies, or if something went wrong with my converter along the way. I checked my converter fuses and they appear to be fine.

[Steveo57]

Thanks all, no worries Jim.

Steveo, i keep my camper plugged into a 20 amp outlet while its in my driveway at home. Sometimes when i go into the camper, the lights are very dim. When i check my battery charge level, it shows 0 charge. the next day, i go back in the camper and the lights are bright and my battery level is back at full charge.

As i mentioned, the dealer provided me with a starting battery, not a deep cell. I will be picking up the deep cell today to replace. I don't know if that is where the issues lies, or if something went wrong with my converter along the way. I checked my converter fuses and they appear to be fine.When you change out the battery a quick test of the converter would be to check that the lights and other 12 volt loads work when the battery is disconnected.

[JRTJH]

Two things to consider:

First, BE SURE, ABSOLUTELY SURE that you don't connect the battery in reverse. If you do, you'll be looking for two "hard to find 40 amp" reverse polarity fuses !!!!!

Second, if your RV is a 50 amp model, depending on the 20 amp/50 amp adapter you're using, you may only be powering one side of the 50 amp main breaker panel. If so, and IF your converter is on "the non-powered side", then in reality, you're not powering up your converter.... All 30 amp breaker boxes only have "one side" so any 20 amp adapter will power the whole system. With 50 amp adapters, some do, some do NOT, so be sure that what you're using actually provides power to both sides of the circuit breaker box.

[Skins44]

JRTJH i assume by "in reverse" you mean black to red and red to black.

Also, my rig is 30 amp

I wish i could put my finger on it. now i am thinking more likely a converter issue. Or, perhaps the 30 amp to 15 amp adapter that i use to connect to my garage outlet? However, as i mentioned, when connected to house power (with no battery connected), my microwave and TV lights are on and lights are extremely dim. My house power should take over at that point as i understand.

[JRTJH]

"Should take over" is correct. The question is, "Does the house power actually take over" ??? There may be "hidden draws" on your 15 amp circuit that are pulling down the available voltage. Check to be sure your water heater is off, that the refrigerator is on propane, etc. That "should" allow sufficient available power from the limited source to power the converter. You might want to compare performance when in a campground on a 30 amp plug and how that performance differs from your "15/20 amp" home plug.

[Skins44]

good point JRTJH. I had my fridge on electric while at home. Add that with the amperage requirements of the converter, CO detector, TV idle lights, microwave idle lights and anything else and i could be at or exceeding my 15 amp house outlet.

Appreciate the feedback. Hopefully i can connect the dots later today/weekend to resolve the issue. I will keep you posted.

[Steveo57]

I put together this basic one line drawing of the typical AC and DC power system. This might help you understand how everything works.

See the attached PDF file.

[chuckster57]

Can’t really trust colors anymore. Used to be white was 12V NEGATIVE at battery. Red or black was 12V POSITIVE.

When I install a battery now, I physically trace the ground to the frame, I’ve seen white and black used for ground.

[Skins44]

Replaced the battery yesterday with a deep cell
- measured the battery volts at about 12.6 with house power OFF
- Connected house power and reading jumped to 13.6
(I assume this means the converter is charging the battery, which is good)

What i still do not understand is why, when the battery is disconnected, i did not get any DC dependent items (lights) to work. Which, if I understand correctly, should work by the the converter converting 120 to DC. Keep in mind, i have not tested this since connecting the new battery, but don't see how/why that would make a difference.

drawing is great, nice job. Visio?

[Steveo57]

Replaced the battery yesterday with a deep cell
- measured the battery volts at about 12.6 with house power OFF
- Connected house power and reading jumped to 13.6
(I assume this means the converter is charging the battery, which is good)

What i still do not understand is why, when the battery is disconnected, i did not get any DC dependent items (lights) to work. Which, if I understand correctly, should work by the the converter converting 120 to DC. Keep in mind, i have not tested this since connecting the new battery, but don't see how/why that would make a difference.

drawing is great, nice job. Visio?Yep sounds like it's good. Can't explain why the converter isn't picking up the DC loads when the battery is disconnected. Do you have a battery disconnect switch? Quick test would be to disconnect the battery with the switch and see what happens.

What kind of converter do you have?

It might be wise to unplug the power and disconnect the battery then check all the connections in the power panel and make sure there's nothing loose in there.


I cobbled together the drawing in Excel then saved it out as a PDF file.

[Skins44]

*Update
After a day of my new battery connected, i disconnected the battery and went into my camper to check if my DC dependent items worked and they did! lights worked with battery disconnected, so the converter was doing its job. Happy everything seems to be back to normal, just wish i understood the anomalies. Another weird thing was my batter level showed full when the battery was disconnected. Perhaps that reading comes from the converter?

at the end of the day, looks like all is well (fingers crossed).

[Steveo57]

Sound's like you had a bad battery or an intermittent connection. The battery monitor is really just looking at the DC voltage. It always reads full when you are plugged in.

[JRTJH]

Yes, that reading comes from the converter. Any time you're plugged into shore power, the "battery status indicator" will show all light illuminated. The only time it will give you a "battery only reading" is when you are disconnected from shore power and ONLY the battery is providing voltage to the 12 VDC system.

If you are connected to shore power or to a generator, then all the wiring in the 12VDC system will be at 13.6 VDC provided by the converter, so the "battery status indicator" will interpret that as "fully charged battery" and light all the lights.

[Skins44]

def a bad battery
1. it was marked as demo, so dealer either forgot to put a new one in when i purchased or they tried to pull a fast one.
2. it wasn't even a deep cell battery. It was a starting battery.

having a used, starting battery certainly created some odd issues. I didn't stand a chance with that scenario. Appreciate all of your feedback!

[14george]

Glad you found out what caused it

[Harrishome2005]

I have a 2017 Montana and I have had trouble keeping my batteries charged during the storage season. This year I thought I would kind out why batteries keep losing a charge with I have the switch off in the service area. My batteries are completely shot after 2 years of owner ship, and I purchased it new. After investigation, it was determined that the switch only turned off power to part of the fuse panel only and there were other parts of the electrical system on trailer that was still powered.
I took the all of your advice and installed a on/off switch to completely turn all of the power when it is stored. This situation has cost me 2 batteries, labor to install the switch, and trouble shooting cost.
Thank you Skin44 for starting this thread.

[Skins44]

Glad you resolved the issue Harrishome. Misery loves company! this forum has been a huge help for me so far in my <1 year of camper ownership. I have had a few issues and made a few mistakes, but in the end i love it.

Enjoy my friend!