RV Electricity – Troubleshooting 101: Over-current testing

Mike,
I have a question but, as I said at the RVillage Rally, it’s a little long. What would cause a pair of 2kW generators to overload when charging my batteries? Looking for your guidance in what actions I need to do to either the generators or the trailer to allow me to charge my batteries with the generators. 
 
Problem: I tried to charge my batteries with a pair of 2kW Champions with a 30-amp parallel operations kit. Generators would run for a few minutes then something would kick in and the generators would over rev, meaning the trailer would pull too many amps from the generators and charging would shut down. This has happened a few times. 
 
History (background): 
 1. I have my 5th wheel set up for 50 amps. My 5th also has solar on the roof and 8 lithium batteries. It has a switch that will automatically switch from shore power to solar, based on being plugged in or not. Except for overhead lights, water pump and maybe something else that constantly runs off batteries. 
 
2. I have two 2k Champions (with inverters) with a parallel operations kit. Knowing I can only get around 3700 Watts.  And knowing I can run only 1A/C (but this not part of the question). 
 
Thanks in advance for whatever advice you can offer. –Robert

Robert,
Good to see you in Elkhart, and sorry I couldn’t answer your question directly at the campground. But when dinner calls and others are waiting, you gotta go. So here are a few suggestions about how to troubleshoot your problem.

The key to any complex troubleshooting is monitoring and repeatability of the fault. That is, if you can find something that will trigger the fault on a regular basis, then you’re halfway there. But it’s just as important to have a way to monitor what’s actually going on in the system.

While the final outcome is your generators shutting down, that’s really not enough information to suggest a possible cause on the failure. I would suggest you get an AC/DC clamp ammeter like the Southwire 21050T and set it up to monitor AC amperage between your generators and the shore power inlet on your RV. Now realize that you just can’t clamp the jaws of an ammeter around the entire extension cord. That’s because there’s current going in opposite directions (hot wire current going out, and neutral wire current returning) and they cancel each other. So you need to split the hot and neutral wire out of the extension cord and clamp the meter jaws only around the hot/black wire. Here’s a video I made a while ago showing how this works.

Now you can monitor the current coming from your generators while you try to make them trip out. So get someone else to turn every light on and off. Gently tap on the case of the inverter, transfer switch, converter, and anything else connected to incoming AC power. You might notice when you flex the cover of the transfer switch that there’s a little “bump” in the current being drawn from your generators. If so, it could be something as simple as a loose wire or screw making contact with the chassis, or maybe a pinched wire, etc. After that it’s an easy fix.

In any event, all troubleshooting relies on the basic steps of being able to cause the fault to occur at will, and having a monitoring system that measures what’s going on. And sometimes the best monitoring is simply your own eyes and ears. Training yourself to be observant of EVERYTHING while you’re trying to make the system fail is very useful. I often just keep scanning for anything out of the ordinary that happens just before the failure occurs. And that’s usually all the hint I need to focus in on the offending piece of gear.

Good luck, and please let me know what you find out….

FYI: I just found out that another name for troubleshooting is dépanneuring. So now I have to use it in conversation three times today. Dépanneuring, dépanneuring, dépanneuring….

Email me at mike (at) noshockzone.org with your questions.

Let’s play safe out there….

 

Mike Sokol is an electrical and professional sound expert with 40 years in the industry. Visit NoShockZone.org for more electrical safety tips. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.

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2 Thoughts to “RV Electricity – Troubleshooting 101: Over-current testing”

  1. Fred

    If Robert has an inverter/charger in the fifth wheel, It may be trying to charge at 30 amps in the bulk charging stage. His generators will only handle about 27-29 amps continuous charging rate even though they will handle higher amperage for a short time. His inverter may have an adjustable charging rate where he can set it to charge at 25 amp or 20 amp rate, as mine does. This solved the same problem I had with my Honda 2000 generators in parallel. At 30 amps charging rate, the gens “kicked out” after a minute, but when I lower the charge rate to 25 amps with nothing else running, or even 20 amps when I have the tv, computer, etc running, the generators charge just fine. I have a Xantrex sw3012, 3000 watt pure sine inverter with a remote panel that allows me to change many of the parameters.

    1. Mike Sokol

      That’s my initial guess as well. But to really know what’s happening with current draw you need to monitor it somehow. And a clamp meter will tell you a lot about what’s going on with any electrical system.

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