Wierd voltage affecting battery chargers?

[jaggedben]

What would cause a receptacle to read 120V hot-to-neutral but a varying voltage between 20-50V hot-to-ground? I would assume a high impedance connection to ground, but could it be something else?

Even more mysterious to me was that my power tool battery chargers (Makita 18V) would not operate properly when plugged into this receptacle. :blink: Both of them gave 'bad battery' indications. When it happened with two different chargers and two different batteries I realized it was something about the supply from the receptacle. The chargers worked fine later on at a different site. The battery charges do not have a third prong, and it does not seem right that a bad ground connection would affect them. What would the relationship be, if any, between the voltage readings and the battery chargers not operating correctly? :?

Thanks in advance for your speculations.

 

[ptonsparky]

Were the tests done with load or no load?
Type of tester?

 

[jaggedben]

No load at that receptacle, can't speak to the rest of the branch circuit. Fluke 322.

 

[hurk27]

was the power utility, generator, or inverter?

some of these chargers can be very finicky with how clean and the type of sign wave it is, my dewalt does not like square wave sources, or generators running too slow or just dirty power

 

[mike_kilroy]

my assumption is you are in the US where neutral and ground are tied at the main cb panel.

my speculation is that since you already have a loose or corroded connection back at the cb panel between nuetral and ground to cause the 20-50v rather than 0v, you too have a loose or corroded connection on the nuetral itself feeding that receptacle; hence your high impedance meter reads 120v but anything plugged in loads it down to a lower voltage.

to test this theory simply plug the charger (or better yet, a 1000watt hair dryer) in to one receptacle of the duplex outlet and measure the volts with your meter in the other one AT THE SAME TIME IT IS LOADED THIS WAY.

 

[hillbilly1]

Is this at your residence? Or at work? Sounds like XO is not bonded if it is not a loose ground connection. Check other circuits out of the same panel.

 

[jaggedben]

This was a jobsite. The receptacle was not part of the job, I just needed to charge batteries. I will probably not be going back to this site, but just wanted to get advice in case I do end up going back, or if I run into something similar in the future.

Of course the receptacle happened to be only a single, with a light switch in the other spot, so I couldn't test voltage at that spot while the charger was plugged in. Otherwise I would probably have done that.

Not sure why the chargers should read 'bad battery' instead of something else when they don't get voltage, but maybe they just aren't designed to allow for this situation, and the resistance of the battery looks too high when the supply voltage is low?