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Old 10-31-2022, 11:40 AM   #1
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2019 16' Sport
Wimberley , Texas
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Newbie with Electrical Mystery - HELP!

First-time RV owner with 2019 Bambi 16, acquired in September.

Had been keeping on shore power with 15 > 30 adapter. For two months all well. I unplugged it for a couple of weeks, verified that battery at 100% and no electrical items (insofar as I can tell) operational.

After a couple of weeks, monitor is showing 30-50% battery power and fluctuating. Will not show charge above 50% - all inside electricals (did not try AC) working, but not charging.

1. Changed extension cord to 12 guage
2. Verified that red incoming connector is illuminated
3. Verified again that all electricals other than AC and fridge are working
4. Battery is a single Lifeline rig, probably the original battery
5. Monitor is a stock SunExplorer II

Q1 - Why is this happening?
Q2 - Most likely explanation?
Q3 - Most likely resolution?
Q4 - Sequence of things to check?

I am open to the notion that there is something I did that caused this, but I plugged and unplugged it several times within the first month with no anomalies. Still - never underestimate the power of inexperience and ignorance.

Thanks for your advice. S.
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Old 10-31-2022, 12:00 PM   #2
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Can't answer your questions with specifics, but my hunch is your battery needs to be replaced.

Depending on your electrical skills, it would be a good idea to check to make sure that the converter/charger is putting out the correct voltage before dropping in a new battery. The instructions for doing this are on page 5-8 of your manual.
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Old 10-31-2022, 12:04 PM   #3
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If it was me, I would disconnect the battery, take it out, and connect it to a battery charger to see if it will take a charge and keep it. If not, buy a new battery. If OK, scratching my head…hard to diagnose long distance.
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Old 10-31-2022, 12:06 PM   #4
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It sounds like you might have a converter problem. The converter is what "converts" 120 volt AC into 12 volts DC, it is also what charges the battery. Check to make sure it is plugged in, beyond that, it's hard to know what might be wrong. Not sure about the newer trailers, but in the older ones, like mine, the OEM converter was poor prompting many, like me, to replace them.
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Old 10-31-2022, 12:11 PM   #5
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I do agree with Richard. The battery is probably gone. But...you should get a reading of the 12 volt voltage be sure. I use a 12 volt meter that plugs into a 12 volt outlet in the trailer or you could use a multimeter meter where ever you can access a 12 volt circuit. If you get 13 plus volts when plugged into short power the power converter is probably woking and the battery is bad. If you get less than 13 volts unhook the negative on the battery and try again. If still less than 13 your power converter is dead. You can do these readings at the battery with a multimeter since you are probably going to be taking it out anyway.
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Old 10-31-2022, 12:15 PM   #6
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Hi

There are various things on any RV that pull power regardless of what's going on. They are typically called parasitic loads. The propane detector is one often abused example. Things like inverters and subwoofers pull power even when switched off. Just what is or isn't present on this or that trailer .... who knows.

The result of these loads is that you really can't leave the RV unplugged for very long. A month typically is pushing things pretty far. Having the battery at "only" 50% is actually doing quite well after (say) three weeks.

The solution to these issues is to install a full battery disconnect switch. They cost about $30 and go in the negative wiring to the battery. When the switch is "off" nothing is connected to the battery to drain current.

Next up, you don't seem to be charging things. First step is to check the AC breaker that goes to the converter / charger. If it's tripped then reset it and see what happens next. After that, grab a multimeter and look at the voltage on the battery terminals. You will get one number with shore power disconnected. Let's say it's 12.2V. When you plug in the shore power, that voltage should go up. Maybe it goes to 12.6V. The key point is that it goes up.

If it stays at 12.2 then the converter isn't doing its thing. Next check is at the output lugs on the converter / charger. Same pair of measurements. With shore power disconnected you should see what you saw at the battery ( say 12.2V ). Plug in power and the voltage should go up.

You may find the voltage is zero with shore power disconnected, if so there is a fuse / switch / wire disconnecting things. Trace along the wiring between the converter and the battery. Eventually you will find what's broke.

You may find that the voltage does not budge at the converter / charger. Next check would be to see that there is 120V AC on the input. If so, it's a pretty good bet the gizmo has died.

Lots of twists and turns .....

Bob
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Old 10-31-2022, 12:21 PM   #7
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Thanks

What a gold mine is this forum! Thank you all. This will keep me busy today. Good thing I'm retired...

S.
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Old 10-31-2022, 12:46 PM   #8
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If your battery is real low you may have to give it a jolt to get it to take a charge again. Once you get it charged back up have it load tested at a good battery/alternator shop and if it is good you can trouble shoot your AS converter(charger).
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Old 10-31-2022, 02:50 PM   #9
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Yes to the above. It is possible for an AGM to go so low that some chargers will not see it and will not recharge. But at that age I would change the battery anyway. Just make sure the converter is working to save the new battery.
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Old 11-01-2022, 10:24 AM   #10
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Analog Ideas…

Our 1999 Excella’s converter started running all the time. We checked the 2017 batteries every three months, topping them off with distilled water. This time a cell was completely empty. This combination, over-exercising converter and low/no water in a battery cell, was a death diagnosis for the (five-year old) batteries. New, zero maintenance batteries have been flawless, and the converter never has anything to say!

When we close up the Excella (a permanent installation), all 110v devices, except heater and dehumidifier during cold weather, are unplugged to help with energy use. She always remains on shore power.

You will soon speak 12-volt like a pro!
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Old 11-01-2022, 10:36 AM   #11
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One thing that wasn't mentioned is that the USE/STORE switch has to be in USE for the batteries to charge. When the batteries get discharged low enough, the switch will not activate. The fix is to put a separate charger on the batteries to bring them up far enough for the switch to work.

Fluctuating battery percentage, assuming it is measuring the battery voltage is a clue. A likely problem is a shorted cell in a battery. The battery will draw excessive current and get hot but voltage will not come up to par.
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Old 11-01-2022, 11:40 AM   #12
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Quick update:

1. Voltage at battery was 12.0-12.2.
2. I charged at 7 amps overnight - it was very slow to charge, but by the morning showed on the charger as being full capacity.
3. I reconnected power to the trailer, and the meter is now showing at 100% battery capacity, voltage at 13.2.
4. Same reading of 13.2 as measured at the battery with multi-meter.

So...it seems that battery is back up to capacity with the external charge. I will now monitor it with the trailer hooked back up to shore power to see if it stays there.

Does this mean that there is something wrong with my charging circuitry/devices? Shore power was unplugged for 2-3 weeks with everything but parasitic devices OFF. Should my onboard converter have been able to restore the battery to full power without having to resort to the external battery charger?

I am still going to follow the advice of taking the trailer/battery to my local battery shop and have things tested. Given that the battery is probably 3-4 years old, I think I'll go ahead and replace it with a new AGM one.

Thank y'all for your advice so far. Does it seem like I have an onboard charger problem, or is this mostly due to my ignorance and leaving the trailer unplugged for 2-3 weeks?
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Old 11-01-2022, 11:44 AM   #13
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You need to do a voltage check on the converter/charger to know how it's doing. Instructions for checking it are in your owners manual. Just need your multimeter and a few steps to follow. If the converter/charger isn't putting out the correct voltage, I'd suggest giving Best Converters a call.
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Old 11-01-2022, 02:06 PM   #14
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Different types of batteries require different charging profiles. Given the age of your Bambi, there is a chance that your converter charger won't handle an AGM (I figure you are going from standard lead acid to AGM). I didn't see if you have solar on the roof. If so, the solar controller will need to be switched to AGM or replaced.

It looks like you have just about all the "usual experts" in this thread (I'm a fellow newby, so don't listen to me.). Post all the details on your Bambi's electrical system (Solar y/n, model of controller/charger, solar controller, etc.) These people are great, and have incredible depth and breadth of experience. The more information you give them, the better their advice will be.
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Old 11-01-2022, 06:25 PM   #15
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13.2 volts means the converter is probably working. To determine the state of charge as accurately as possible by measuring voltage, disconnect the negative lead from a battery and measure the voltage from the positive post to the negative post several times over an hour or so. 7 amps charge overnight is only about 50-60 Amp-hours which is half the capacity of one battery at 100% efficiency, which you probably didn't get.

I see you have a single (probably AGM) battery, 12 volts is about half capacity. Guessing about 80 Ah of capacity, you used 40. Three weeks and 24 hours per day is 504 hours. 40 amp-hours divided by 504 hours is only 0.079 amps, or 79 milliamps. That could easily be a parasitic device or two coupled with self discharge.
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Old 11-02-2022, 09:36 AM   #16
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Quote:
Originally Posted by NDSinTX View Post
Quick update:

1. Voltage at battery was 12.0-12.2.
2. I charged at 7 amps overnight - it was very slow to charge, but by the morning showed on the charger as being full capacity.
3. I reconnected power to the trailer, and the meter is now showing at 100% battery capacity, voltage at 13.2.
4. Same reading of 13.2 as measured at the battery with multi-meter.

So...it seems that battery is back up to capacity with the external charge. I will now monitor it with the trailer hooked back up to shore power to see if it stays there.

Does this mean that there is something wrong with my charging circuitry/devices? Shore power was unplugged for 2-3 weeks with everything but parasitic devices OFF. Should my onboard converter have been able to restore the battery to full power without having to resort to the external battery charger?

I am still going to follow the advice of taking the trailer/battery to my local battery shop and have things tested. Given that the battery is probably 3-4 years old, I think I'll go ahead and replace it with a new AGM one.

Thank y'all for your advice so far. Does it seem like I have an onboard charger problem, or is this mostly due to my ignorance and leaving the trailer unplugged for 2-3 weeks?
Hi

As noted above, 7A is a mighty small charger for the typical battery setup in an AS. Even the "50A" converter chargers ( that only put out 30A) are a bit challenged by a dead battery.

If you start from "half full" you will get to about 3/4 full fairly quickly. If you have 80 to 100 AH usable and a 7 A charger that will take something in the 5 to 6 hour range. Getting from there to full might take another 20 hours.

The main problem is trying to guess battery charge state from a voltage reading. As the battery charges, the voltage will go to the "full" point very early. If it's cold out, it may read full when it's almost empty. This makes the charge process really crazy.

Best way to do things from voltage: Disconnect all loads and all charging sources. Let the battery sit for a couple hours. Measure the voltage at the posts with a multimeter. Check the battery temperature. Then head off to a chart to guess ( it's still a guess ) what the charge state is.

Yes, this is why folks buy shunt based monitors.

Fun !!!

Bob
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Old 11-02-2022, 03:32 PM   #17
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Today's update:

Luckily for me, the jolt to the battery from what I now know to be a paltry charger (7A) seems to at least allow the display to report a steady 100% of battery. As long as it is plugged into shore power.

That is progress.

It's a good thing, because your inputs, and the manual pages to which I've referred as recommended, have reminded me that electricity of any kind is, and apparently will remain, a total mystery.

I was unable to get past step one on page 5-8 of the manual. I might not have gotten that far. If "confirming 120-volt power is going into converter" means something other than seeing that the red light on the connection to the AS is on, then I have not even done that. Step two says to "disconnect the 12+ wire from the master switch". I have no idea what a 12+ wire is, and there is nothing labeled as such at the fuse box.

The best of the careful analyses and suggestions you have put forward are beyond my ability to benefit from them - my apologies. If anyone can - or wishes to - point me in the direction of a basic understanding of the RV electrical system, I need to begin at RV 101. Otherwise, I realize to my consternation, I am just like the "idiots" who drive cars without being able to change a tire, or check the oil. Any pointers will be appreciated.

And thanks to all who have given me such detailed information and instructions. Sometimes dumb luck is enough to solve a problem, though I hate being in that position.
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Old 11-03-2022, 07:58 AM   #18
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Hi

There's nothing wrong with taking an RV to a service shop. There are things that *all* of us find to be outside our area of interest. Head over and have a tech look at things. Yes, it will cost something. Randomly swapping out bits and pieces ( some of which are 100% ok ) also has a cost .... Making a mistake and doing damage can have a *big* cost.....

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Old 11-03-2022, 08:19 AM   #19
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What is...

Quote:
Originally Posted by uncle_bob View Post
Hi

Yes, this is why folks buy shunt based monitors.

Fun !!!

Bob
...a "shunt-based monitor"?
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Old 11-03-2022, 08:26 AM   #20
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Quote:
Originally Posted by NDSinTX View Post
...a "shunt-based monitor"?
Something like the Victron BMV-712

https://www.victronenergy.com/batter.../bmv-712-smart

These count every amp going into/out of the battery bank and can provide accurate information on the state of your batteries.
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