Weird Voltage

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adas
adas Solar Expert Posts: 136 ✭✭✭✭✭
in General Solar Power Topics #1
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
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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #2
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    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
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
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  • adas
    adas Solar Expert Posts: 136 ✭✭✭✭✭
    #3
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    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
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  • System2
    System2 Posts: 6,290 admin
    #4
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    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
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  • adas
    adas Solar Expert Posts: 136 ✭✭✭✭✭
    #5
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    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
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #6
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    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.
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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #7
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    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
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
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  • newenergy
    newenergy Solar Expert Posts: 291 ✭✭✭✭✭✭
    #8
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    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?
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #9
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    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]
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • newenergy
    newenergy Solar Expert Posts: 291 ✭✭✭✭✭✭
    #10
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    Re: Weird Voltage

    Yeah, don't try to measure the current and treat everything as hot until you figure it out.
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  • mikeo
    mikeo Solar Expert Posts: 386 ✭✭✭
    #11
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    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.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #12
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    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.
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  • adas
    adas Solar Expert Posts: 136 ✭✭✭✭✭
    #13
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    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.
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  • newenergy
    newenergy Solar Expert Posts: 291 ✭✭✭✭✭✭
    #14
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    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?
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  • mikeo
    mikeo Solar Expert Posts: 386 ✭✭✭
    #15
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    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
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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #16
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    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
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #17
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    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.
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