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How to test Converter voltage

dunawayk
Explorer
Explorer

I'm having trouble with my heater shutting off after about 20 minutes and the battery appears to be draining quickly when I look at the the central control panel in my RV.  I think the two are related so I'm trying to determine if my battery is being charged by my converter.  I can't really access my converter because it's so far behind the fuse box. So I want to test the voltage that's coming from it by testing the wires near the battery.  If I test the voltage of the battery cables when they're disconnected from the battery, does that tell me how much voltage I'm getting from my converter?  

6 REPLIES 6

StirCrazy
Nomad III
Nomad III

https://www.google.ca/search?q=how+to+test+my+wfco+converter&sca_esv=590909283&sxsrf=AM9HkKlTL7fMVDh... 

if it is a different brand you just need to search on that brand but the method is the same you just have to confirm what the reading should be.  you cant do it with a battery onboard as when a battery is hooked up the voltage will vary depending on the state of charge of the battery.  

2014 F350 6.7 Platinum
2016 Cougar 330RBK
1991 Slumberqueen WS100

YC_1
Nomad
Nomad

Check the battery voltage at the terminals with the heater running. Should be around 13.5..

If the converter can't keep up the voltage will be down. Not all converters can run without a battery but yours might. 

This is not complicated. Battery charge voltage should stay up with the furnace running. If it does not and your battery is old, replace it and begin over. Batteries are not purchased, they are just rented. 

Sure you can test the voltage from the converter with it disconnected but you could get false readings from a simple digital meter. Batteries often are the filters for crappy DC current and without a good filter (battery) attached, you may read high or low. 

Trying to keep this very simple. 

And if your battery cables are corroded, start by taking pictures and then carefully disconnect wires from the negative side and begin cleaning them up. Follow the negative wires to wherever they are connected to the frame and disconnect and clean that area too. 

H/R Endeavor 2008
Ford F150 toad >Full Timers
Certified Senior Electronic Technician, Telecommunications Engineer, Telecommunications repair Service Center Owner, Original owner HR 2008

steveMc
Explorer
Explorer

Hi!

Checking the voltage on the battery cables, even when they are disconnected from the battery, can give you an idea of what voltage is coming from the converter. However, please note that this may not give the full picture since the converter may have built-in voltage regulation and you will not get the exact voltage that the converter supplies to the output.
Use a multimeter to measure voltage.
Disconnect the cables from the battery, set up the multimeter, set the multimeter to DC voltage (DCV) mode, connect the multimeter to the cables, turn on the converter, or turn on the power system.
The voltage on the multimeter will indicate how much power is being supplied from the inverter.

JBarca
Nomad II
Nomad II

Hi,

From your description, you may have a bad battery, a bad converter, or both.

If your camper uses a 12-volt lead acid battery, these would be the voltages you can look for.  Ideally, you need a digital voltmeter with at least 1, but 2 decimal places are better.  Yes, you have to look for at least one decimal place.  There is not a lot of voltage change, but you can see differences to tell what is going on. 

Assuming the camper has been plugged in and the converter was on, you can start here.  

Unhook the battery negative wire, or turn off the battery disconnect, or unplug shore power to remove the power converter from the battery.  Test the battery terminals with the meter.  What is that voltage?    This is a starting place.  Since the power converter was on, the battery may have a surface charge on it. More on this surface charge later. 

Now, hook battery the back up, or turn on the disconnect, or plug in the shore power.  Now test at the battery terminals.   These voltages should be in this range.

13.25 VDC = float charge. (if your converter has float mode)

13.65 VDC = standard charge.

14.4 VDC =  boost charge. (if your converter has 3 stage charging)

The readings may be +/- 0.10 approx. from the above target points. They should not be lower then 13.0/12.9 or a lot more then 14.5/14.6 VDC,  if they are lower or higher, there is a problem.   

After testing the above, here is a battery test. Unhook the battery from the converter by what means you have the easiest way.  Take a battery voltage test at the terminal.  Record the number.   Then wait, over night or at least 8 hours, take another battery voltage test.  Record the number.  Waiting the 8 hrs lets any surface charge drain off and then the battery is at rest.  Here is a few voltages for a battery at rest for a lead acid battery.

12.73 VDC = 100% state of charge

12.10 VDC = 50% state of charge

11.81 VDC = 30% state of charge

As you can see, you need the decimal place as 1 volt is a lot of change.   Your battery might read above 12.73 VDC (13.0 plus volts) when it just came off the power converter, but that higher voltage will drift down over the 8 hours of non battery use and you get the battery at rest voltage which is what you are after.  

See this link to the Trojan battery maintenance for a complete chart on voltage.  Scroll to the "II Open Circuit Voltage Test" https://www.trojanbattery.com/resources/battery-maintenance 

A power converter going bad, can fail in a few ways, it goes high voltage and boils out the battery killing the battery. It stops working all together and no longer charges the battery. It goes low voltage, this then hurts the battery draining it below its fully charged state.   When the power converter goes bad,  it can kill a good battery.    And a bad battery,  may or may not hurt a good working converter. 

If you tell us the brand and model converter, the year and make of the camper, the voltage readings from above, we can help better. And confirm what battery type you have.

Hope this helps

John

2005 Ford F350 Super Duty, 4x4; 6.8L V10 with 4.10 RA, 21,000 GCWR, 11,000 GVWR, upgraded 2 1/2" Towbeast Receiver. Hitched with a 1,700# Reese HP WD, HP Dual Cam to a 2004 Sunline Solaris T310R travel trailer.

StirCrazy
Nomad III
Nomad III

to find out if your converter is working properly yes you disconect the battery and see what the open voltage the converter is putting out.  but you have to look up your modle of converter and see what the manufacture says the open voltage should be.  some times they have a little bit of a rage sometimes they are pretty spicific.  

2014 F350 6.7 Platinum
2016 Cougar 330RBK
1991 Slumberqueen WS100

JOHNBURKE
Explorer II
Explorer II

Easiest way would be to unplug from shore power, put your voltmeter on the battery check the voltage. Plug back into shore power, check the battery voltage, should come up if the converter is working.