DC Voltage Drop on Heavy Load

[Sparky_Coog]

Hi All,

Purchased a new Cougar 29BHS last April and have enjoyed many many trips last year. Actually on our first trip of 2022 and 10th overall currently.

Our last trip of the year last year was quite a cold one so we used the propane furnace along with most of the other 12V loads (lights/fridge/etc). When we initially bought the trailer I noticed the battery level in the InCommand system would always show 13.6V and would sometimes jump to 14.4V like in boost mode. No matter how much 12V load I had it would hardly waver from 13.6V

Back to our last trip of last year - I started noticing that with the lights on it was dipping down into 12.4-12.6V. As I turned the furnace on it was drop to 12.0-12.2V. And then when I’d turn the awning lights on it would drop
Even lower to 11.6-11.8V. But it would fluctuate about .2-.4V in those ranges. Just odd. Like the converter wasn’t kicking up into absorption or boost mode. The last night was the coldest so we ran the furnace all night. Sometime in the middle of the night the fridge kicked off on low voltage and iN·command was reading 11.2V.

All of this was plugged into shore power and battery switch was on.

Over the Xmas break I got into troubleshooting the converter. I pulled the battery off and did all the checks recommended on the WFCO 9800 manual. Was getting 13.6 at the battery terminals just fine. I went ahead and replaced the battery and the voltage seemed to stay good testing loads so I left it at that. Although it never reached the voltage levels on the iN·command as when we first purchased it.

Now we’re back camping again and sure enough same problems. Just with a few lights on and fridge and furnace and I’m down to 11.8V.

Any suggestions or help would be appreciated.

[ChuckS]

Yup.. I would do these things to correct your voltage drop since you’ve already properly,tested and verified the converter is working right….

.. remove the battery ground cable at the chassis and scrape the paint off that’s most likely under the connection
.. check all cable feeds from battery to resettable breakers for security
.. remove power center corner and inspect the 12volt DC BUS bar cable connections for the converter and battery feed and torque the screws
.. torque the screw for each 12 volt feed at the power center
Yes.. there is an actual torque value for those screws that hold each 12 volt feed wire in place

For the In Command Display voltage drop observed :
.. locate the BCM and check the 12 volt IN and ground feed wire terminal connections

This should take care of the voltage drop issues you are seeing

[flybouy]

What year is your trailer? Do you're light fixtures have incandescent lamps or LED. What type battery? A group 24 or 27 "marine" starting battery? That will make a difference in battery life and amp capacity even connected to the converter.

Definatly check those battery connections and the ground to frame connection. Look at the cable ends where the ring terminals are connected. If you see grren and or white discoloration replace the cable, simply cleaning the ring terminal won't fix it. Corrosion causes resistance which requires a higher amperage for the same amount of work.

[JRTJH]

Depending on the 12 VDC load you're placing on the trailer, it could be a "undersized wiring issue, internal corrosion on one or more of the DC mini-breakers (contact points inside the little plastic box) or even corrosion on a crimped wire connector on any of the "distribution wiring harness" in the trailer.

I'd start by cleaning the battery terminals, inspect the connectors carefully for corrosion, then inspect the ground connection on the white/red battery cable. Then move to the DC mini-breakers, inspect them carefully and check the connector crimps on those wires.

I believe your trailer is a "travel trailer" not a fifth wheel, so your "giggy box and DC mini-breakers" are probably mounted on the trailer bulkhead located at the rear of your trailer A-frame. They are very likely exposed to rain/road splash when towing and are open to the environment even in storage....

[Sparky_Coog]

All good suggestions and got some things to check now.

For reference I have a 2021 Cougar 29BHS TT bought new last April. Using a Group 24 Marine battery bought from Walmart.

I've replaced the battery and tested the converter per WFCO recommendations so I think ya'll are right time to start with all of the connections and the DC breakers in the junction box on the A-frame.

[chuckster57]

Never assume a new battery is “good”. I’ve had brand new batteries go bad in a week. If it’s not a sealed battery I would do a hydrometer test on each cell. Then continue with the other tests suggested.

[snoobler]

Definitely worth checking all fuses, wires and connections between the converter and battery.

I've had two converters fail, so that's where I am. The genny on my motorhome had a failed regulator, so it was putting out 160VAC unloaded. This effectively "fried" the converter limiting it to about 2A of output. It still worked, but just barely. Our failure was EXACTLY as you describe... progressively lower battery voltage even while on shore power. In order to get through the night, I had to put a separate charger on the 12V.

The other one just petered out during storage.

For the battery to read those voltages with an operating converter, it would have to have an internal short and be gobbling up all the amperage the converter can deliver, and the converter should be running its cooling fan full blast all the time, and the voltage would NEVER recover.

On shore power, the system should work with the battery disconnected, so that's another way to check if your converter is operational - disconnect one terminal of the 12V and see what happens.

I'm not sure of the troubleshooting criteria of the WFCO, but until you verify BOTH voltage and current out of the converter, you can't be confident it's working. I have a Klein CL800 for this reason.

[Sparky_Coog]

I’ve done the WFCO checks and have verified I can operate fridge/lights/water pump on the converter just fine. I don’t believe I can run the slide or the jacks without a battery though and didn’t try as my issues have been during “normal camping operation”.

However, as I had some quiet time today in the camper with the wife and kids gone, I did notice that the fan on the converter would oscillate from low speed to high speed back to low speed and just vary speeds for about 10 minutes or so. Then it would stay on low speed for a bit then kick up to high speed for about 30 minutes or so. No load change. Fridge wasn’t running as it was at temp. No furnace running. Had a few lights on and nothing plugged into the inverter outlets. I looked at the iN·command panel while this was going on and would notice the voltage would change whenever the fan speed on the converter would change as well. As the fan kicked on higher the voltage would jump from 12.5V or so up to 13.2V-13.5V then when it went to low speed it would drop back down to 12.2V-12.5V. I kicked all the lights on and the fan speed wouldn’t change but the voltage would drop to about 11.8-11.9V. about 2-3 minutes later the fan would kick higher and the voltage would jump back up about 1V. Just crazy.

I checked the battery terminals, giggy box and breakers on the frame rail, ground connection on frame rail, and everything behind the distribution panel associated with 12V. Everything looked good and was tight. The only thing I didn’t do was pull the frame rail ground off and grind off some paint to give it a good place to contact on the frame. But it was strapped on pretty good and thought that since this was a “newly” discovered issue that it couldn’t be that connection.

I’m about out of items to check other than taking it to a dealer and letting them diagnose.

[ChuckS]

Part Of OPs Post:
I looked at the iN·command panel while this was going on and would notice the voltage would change whenever the fan speed on the converter would change as well. As the fan kicked on higher the voltage would jump from 12.5V or so up to 13.2V-13.5V then when it went to low speed it would drop back down to 12.2V-12.5V. I kicked all the lights on and the fan speed wouldn’t change but the voltage would drop to about 11.8-11.9V. about 2-3 minutes later the fan would kick higher and the voltage would jump back up about 1V. Just crazy.

These voltage readings are NOT what you should be seeing from your converter..

Disconnect the battery leads and wit shore power plugged in check the output of the converter at the battery terminals.. it SHOULD STAY solid at around 13.4 to 13.6

If it isnt then either you have a loose wire from converter to the power center DC BUS bar or the converter is not operating right..

a voltage reading below 13.2 volts DC with converter running into a KNOWN GOOD AND LOAD TESTED battery means either converter is bad or you have a loose cable off the converter to the BUS, etc

Your In Command Display for voltage output should never drop under 13.2 with a good battery and properly working converter

[jasin1]

Originally Posted by ChuckS

Part Of OPs Post:
I looked at the iN·command panel while this was going on and would notice the voltage would change whenever the fan speed on the converter would change as well. As the fan kicked on higher the voltage would jump from 12.5V or so up to 13.2V-13.5V then when it went to low speed it would drop back down to 12.2V-12.5V. I kicked all the lights on and the fan speed wouldn’t change but the voltage would drop to about 11.8-11.9V. about 2-3 minutes later the fan would kick higher and the voltage would jump back up about 1V. Just crazy.

These voltage readings are NOT what you should be seeing from your converter..

Disconnect the battery leads and wit shore power plugged in check the output of the converter at the battery terminals.. it SHOULD STAY solid at around 13.4 to 13.6

If it isnt then either you have a loose wire from converter to the power center DC BUS bar or the converter is not operating right..

a voltage reading below 13.2 volts DC with converter running into a KNOWN GOOD AND LOAD TESTED battery means either converter is bad or you have a loose cable off the converter to the BUS, etc

Your In Command Display for voltage output should never drop under 13.2 with a good battery and properly working converter

Chuck are the iN·command voltage readings ever wrong? Wondering if he puts a voltmeter on the battery to confirm the readings

Edit: should have read the first post

[ChuckS]

Originally Posted by jasin1

Chuck are the iN·command voltage readings ever wrong? Wondering if he puts a voltmeter on the battery to confirm the readings

Edit: should have read the first post

Most likely NO.. BUT this is why the OP needs to do as I stated.. remove the battery connections off the battery and measure the converter output..

Doing so verifies the "Source" output from the converter is in fact within specs otherwise you will chase your tail till you are dizzy

[jasin1]

Originally Posted by ChuckS

Most likely NO.. BUT this is why the OP needs to do as I stated.. remove the battery connections off the battery and measure the converter output..

Doing so verifies the "Source" output from the converter is in fact within specs otherwise you will chase your tail till you are dizzy

Thanks ..I sometimes have the bad habit of not reading thru all the posts

[Sparky_Coog]

Originally Posted by ChuckS

Most likely NO.. BUT this is why the OP needs to do as I stated.. remove the battery connections off the battery and measure the converter output..

Doing so verifies the "Source" output from the converter is in fact within specs otherwise you will chase your tail till you are dizzy

As stated in my original post I did remove the connections at the battery and measured the output from the converter at those connections per the WFCO manual and I was getting 13.6V at those terminal. However I did NOT test the voltage at those terminals while operating under load. Are you saying I should be getting 13.6V at those terminals, at all times, while adding and removing load on the DC system? (Reading the WFCO manual it doesnt exactly state this but it seems i should right as long as I'm not overloading the system)

[snoobler]

Originally Posted by Sparky_Coog

As stated in my original post I did remove the connections at the battery and measured the output from the converter at those connections per the WFCO manual and I was getting 13.6V at those terminal. However I did NOT test the voltage at those terminals while operating under load. Are you saying I should be getting 13.6V at those terminals, at all times, while adding and removing load on the DC system? (Reading the WFCO manual it doesnt exactly state this but it seems i should right as long as I'm not overloading the system)

Voltage checks tell you very little. Voltage under load can tell you everything.

Your converter has a voltage spec. Common is 14.4-14.6 boost, 13.6-13.8 absorption and 13.2V float. WHATEVER your unit's specs, it should generally not read below the float spec UNLESS:

1) you are pulling a load that is a significant % of the converter's rating.
2) your RV converter to battery wiring is as bad as most, and you have a voltage drop.

Given:

1. No battery connected.
2. I KNOW all the converter and any relevant connections are properly torqued.
3. I KNOW I'm pulling 80-90% of my converter's current rating.
4. Voltage is no less than 1.0V BELOW float voltage
5. Voltage rebounds to 13.XV+ when I reduce the load to a minimum.

Then I would conclude the converter is operating to spec.