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Old 07-31-2013, 01:12 PM   #1
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diagnostic help needed: battery/converter

Hi electrical people out there. I need some help diagnosing a problem I'm having in my new 16' Bambi. It is under warranty, and I will drive it to the dealer if need be, but thought I'd see first if there is an easy fix.

We have been on 4 outings, and everything is working great (except of the unbearably noisy fridge fan, which we have fixed using the solution here). After the last outing, we parked the trailer and got back in it about 2 weeks later (to begin the fridge fan project mentioned above). We found the 12-volt system not working. We have 2 batteries, new and fully charged.

I plugged in the trailer to shore power from the house. Checked the monitor, which indeed read full battery. I went out and unplugged from shore power about 10 minutes later, and the 12-volt worked fine. Next morning, dead again. Nothing running -- no lights, fans or fridge.

Another oddity -- when I plug in to shore power, I hear a humming near the converter, like a fan. It stops when I unplug. It is not the fridge fan or either of the ceiling fans and the furnace and AC are off.
I went into the bathroom to investigate, and when I opened the lid of the toilet, there was some murky bluish water in the bowl. We have never used the toilet, or added any chemicals to the gray/black tank. The gray/black tank was about 1/4 full with gray water after our last trip. Don't know if this is at all related to the humming sound. I noticed that the dump valve is included in one of the circuits -- I had assumed the dump valve was mechanical, not electrical. Is there a vent fan in the tank somewhere?

There are no apparent blown fuses, at least none show a red LED indicator. (An aside -- why is the panel on the converter designed so that you can't grab a blade fuse on both sides to pull it straight out? About 1/3 of the fuse is behind the face plate where you can't grab it. grrrr.)

Any insights/education would be most welcome.

Caroline
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Old 07-31-2013, 01:32 PM   #2
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Last question first: Modern fuses are often difficult to grip because of where they're installed. a "fuse puller" can be handy for this.

The converter-charger has a cooling fan built into it, which may be the source of your humming.

When the trailer was unplugged for 2 weeks, was the switch in the "Store" mode so that most of the systems weren't powered? The refrigerator has a 12v control board in it, and the propane detector gets 12v power even with the switch in the "Store" position usually, etc. If the batteries were discharged because of something like that, they'll need way more than 10 minutes plugged in to get fully charged, no matter what the monitor says.

Another possibility is that the use/store switch is still in the "Store" mode, so nothing works until you plug in, everything works fine while plugged in, but it's back to "Store" mode when you unplug.

I don't see how the water in the toilet could have anything to do with the problem you describe with the lights/fans/etc.
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Old 07-31-2013, 01:35 PM   #3
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Quote:
Originally Posted by Seecue View Post
I plugged in the trailer to shore power from the house. Checked the monitor, which indeed read full battery. I went out and unplugged from shore power about 10 minutes later, and the 12-volt worked fine. Next morning, dead again. Nothing running -- no lights, fans or fridge.
I strongly suspect that, when you've got shore power plugged in, your monitor is not showing battery voltage, it's showing charging voltage. Battery could be dead, but as long as you've got shore power, it will show good voltage.

My guess is, you've got a parasitic electrical power user that drew down the batteries over the two weeks it was in storage, then you didn't have it plugged in long enough to fully recharge. You don't say, but you might have accidentally left the store/use switch in the "use" position while it was in storage.

Quote:
Another oddity -- when I plug in to shore power, I hear a humming near the converter, like a fan. It stops when I unplug. It is not the fridge fan or either of the ceiling fans and the furnace and AC are off.
The converter has a fan built in, to keep it from overheating, so if you're plugged in and charging, you should hear a fan.

Quote:
I went into the bathroom to investigate, and when I opened the lid of the toilet, there was some murky bluish water in the bowl. We have never used the toilet, or added any chemicals to the gray/black tank. The gray/black tank was about 1/4 full with gray water after our last trip. Don't know if this is at all related to the humming sound.
Probably not related. Side note, after four outings you haven't used the toilet, you guys must have bladders of stainless steel!
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Old 07-31-2013, 02:49 PM   #4
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Bladders of steel haha!

Thanks so much for the quick replies. Glad to know about the converter fan, mystery solved there.

And, yes, thank you for the tip -- the monitor shows low battery when not plugged in.

We never switched the battery to the store position. So even though nothing was running, the parasitic power usage can drain 2 batteries in 2 weeks? Good to know, will make sure we disconnect the battery whenever stored. I assume the battery will still charge from the TV when travelling, even if in "store" mode (just in case we forget to change it back).

A last (for now) question -- about how long does it usually (roughly) take to charge up 2 batteries using shore power from a house?

Again, thanks a million for the education!
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Old 07-31-2013, 03:06 PM   #5
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~~

A last (for now) question -- about how long does it usually (roughly) take to charge up 2 batteries using shore power from a house?
~~
With a "smart" charger that will vary the charge rate to take good care of the batteries, it'll probably take a day or so. The battery manufacturers recommend a charge rate little over 5% of the "20 hour amp-hour" rating of the battery, which for a pair of 80 amp-hour deep cycles would come out to around 8 amps, so it would take 20 hours to put in the 160 amp-hours needed.

Now, you never want to have the batteries fully discharged. Really, it's best if you never use much more than 50% of the rated capacity. Hopefully the batteries were low enough not to run the systems but not really FULLY discharged (down into the 11v range) because that can shorten their life.

Leave it plugged into the house overnight and see how the batteries behave after that.
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