Weird Voltage

adas · April 2008

Aloha. continuing the post about not using the same ground for the DC side and AC side of the inverter...... I have been verifying that I do not ground to neutral ANYWHERE and the 24v neg is not grounded, but I have a very confusing problem.

I have an electric forklift used as an elevator that is tied into the PV and whose battery is used as part of my battery banks. Here is the Poser..... I totally disconnect the forklift from the PV charging and it is TOTALLY independant and not touching any PV, inverter, conduit etc.

The battery voltage is 25v AND I get 23v running from the positive terminal of the forklift battery to the conduit of the PV array!!!!! I don't think there is any amperage though, but a constant 2 v lower than the battery voltage. I am tearing out my hair trying to figure out where this voltage is coming from.
HELP!!!

Frank

westbranch · April 2008

Re: Weird Voltage

Frank, Are you SURE that there is nothing connected?

"I totally disconnect the forklift from the PV charging"..."AND I get 23v running from the positive terminal of the forklift battery to the conduit of the PV array!"

SOME THING IS CONNECTED! Somewhere.... no connectivity = no current flow...

Cheers
Eric

adas · April 2008

Re: Weird Voltage

westbranch wrote: »

Frank, Are you SURE that there is nothing connected?

"I totally disconnect the forklift from the PV charging"..."AND I get 23v running from the positive terminal of the forklift battery to the conduit of the PV array!"

SOME THING IS CONNECTED! Somewhere.... no connectivity = no current flow...

Cheers
Eric

NOTHING connected..... I even dug around the forklift in the gravel to be sure there was no rebar or wire, etc. giving us this connection. but here is further info. My office is made out of steel containers that are 8'wide by 40' long and 5 units wide, so there is no wood and typical insulating items you would find in a home. For instance there is continuity throughout the 40' x 40' structure, but the forklift is a good foot away. NO connection.
It is a total mistery.
Frank

System2 · April 2008

Re: Weird Voltage

Is it possible that you are using a very high quality and thus sensitive voltmeter? If so, it might just be reading some slight but harmless leakage to ground through anything the metal of the forklift may be touching. It can be surprising what sensitive meters can sometimes detect.
Even slight leakage down the sides of slightly dirty, or dampish tires.
Wayne

adas · April 2008

Re: Weird Voltage

Wayne from NS Cana wrote: »

Is it possible that you are using a very high quality and thus sensitive voltmeter? If so, it might just be reading some slight but harmless leakage to ground through anything the metal of the forklift may be touching. It can be surprising what sensitive meters can sometimes detect.
Even slight leakage down the sides of slightly dirty, or dampish tires.
Wayne

Tried a expensive down to a Radio Shack VOM's. Nothing metal is touching. Ground is sandy/gravel and dry. But I do not think there is any amperage behind the transient voltage. I am going to ground the containers via ground rod and see if that removes the voltage. I am also about to lift the electric lift by my 12 ton lift to see what is underneath the lift.
frank

niel · April 2008

Re: Weird Voltage

do you have anything in there with a radio transmitter like cordless or cell phones, wireless intercoms, leaky microwave oven, etc.? sometimes a radio signal could be picked up by the meter and give some erroneous voltage measurements especially in a confined metal building like you have. you also didn't say if it was a dc voltage reading or not, but verify there isn't an ac voltage there. you may try to see if there is current flowing and at what level when you get this 23v you site.

westbranch · April 2008

Re: Weird Voltage

Had an experience one foggy day, with an induced charge in a barbed wire fence running parallel with high tension lines... how is your RH ..rel. humidity? is there a possibility that there is a very small distance between the fork tines or ? and the deck of the metal box (floor, walls) where there is a 'leakage'?

just a thought..

Eric

newenergy · April 2008

Re: Weird Voltage

What voltage do you show from the positive battery terminal to something else that is grounded?

What voltage do you show from the pv conduit to something else(?) that is grounded?

mike95490 · April 2008

Re: Weird Voltage

I am also about to lift the electric lift by my 12 ton lift to see what is underneath the lift

Use a car headlight as part of your "wire". Ff there is a lot of current, it will just light, but if you use a wire, something can/will melt. [bad]

newenergy · April 2008

Re: Weird Voltage

Yeah, don't try to measure the current and treat everything as hot until you figure it out.

mikeo · April 2008

Re: Weird Voltage

Didn't he say he was on a Navy Base and couldn't get permission to tap into the 3-phase power system. One thought would be to check out if the Navy still has VLF transmitters operating close by. Look for the antennas that go on forever. They can induce stray currents for long distances, just a thought.

niel · April 2008

Re: Weird Voltage

i agree with you guys that he should take some precautions when it comes to the current, especially if it turns out to be an ac source.
as to the vlf transmitters, i believe they bury the antennas so if there is one below his place he'd never find it. i also think these antennas would be somewhat difficult to place on the islands being as large as the antennas are and the amount of lava rock there, but you never know.

adas · April 2008

Re: Weird Voltage

Aloha, yes it could be anything now.
OK I did a test.
With forklift isolated (disconnected as described before), I get 23.8 volts from Pos+ of battery to adjacent conduit. I hook up a 16Guage wire from Pos+ of battery and touch conduit I get a VERY VERY little spark and the meter goes to "0".
To be sure, I reconnect the battery and try a POS+ (at 24.5v) and total 24v zap to the conduit. (yes mx's were off and the grid was off. and inverter still works).

Frank.

newenergy · April 2008

Re: Weird Voltage

Did you try measuring the voltage between the conduit and things other than the forklift and between the forklift and things other than the conduit?

It does seem like the radio waves or something like that are inducing some current.

What if there is a significant ground fault going on from either the system you are working on or something else in the area?

Could there be some weird single wire earth return system in the area?

mikeo · April 2008

Re: Weird Voltage

This VLF station is apparently active http://en.wikipedia.org/wiki/VLF_transmitter_Lualualei

I don't know which Island adas is located

westbranch · April 2008

Re: Weird Voltage

Frank, another thought...did you take the fork lift out side the container while testing it and then try to measure for conductivity between the lift and the container?

Eric

niel · April 2008

Re: Weird Voltage

if it turns out he has a vlf transmitter nearby he would be getting some free power harvestable by an antenna, a tuned circuit, and a diode rectifier. don't count on it being lots of free power though.
try reversing the polarity of the meter leads to see if it stills shows 23.8v.

Weird Voltage

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