frame ghost voltage

[kgsc]

Your electrifying personality?

Jb, my ghost actually was messing with my Alltrax to the point it was throwing an error saying it was too cold to operate. Called Alltrax and they said either the controller was toast or frame voltage. I had just wired everything so I knew that possibly couldn't be it so I unhooked pack mains and any other wire going to pack then tested. Yep, voltage.

[JohnnieB]

Originally Posted by yurtle

................. How come I get zapped when I touch a battery post when standing on a concrete floor barefooted?

1. Might be psychosomatic. You know there is voltage there, so you feel it.
I'm not being facetious or disparaging, it can and does happen, and is more common than many people realize.

2. Your threshold of perception for DC current may be exceptionally low. For adult males the average for random, sudden onset, DC current flow is about 1mA. It is typically lower if the test subject knows when it is coming and higher when the onset is gradual.

3. Your transcutaneous impedance is low (IE: sweating or recent shower/bath), so the instantaneous peak current is high.

4. Your cart's tires contain a lot of carbon black, or the neighborhood dogs are mistaking them for fire hydrants and your garage has some drainage issues causing a damp (conductive) floor.

Whatever the reason, you can measure the amount of current by holding onto one test probe of a Milli-ammeter with one hand and touching the battery post with the other probe while standing barefooted on the garage floor. If it is over 1mA or so, you might want to find and eliminate (reduce) the phantom current path.

Also, when the charger is connected, a high(?) impedance DC path to Earth ground exists.

[JohnnieB]

Originally Posted by kgsc

Your electrifying personality?

Jb, my ghost actually was messing with my Alltrax to the point it was throwing an error saying it was too cold to operate. Called Alltrax and they said either the controller was toast or frame voltage. I had just wired everything so I knew that possibly couldn't be it so I unhooked pack mains and any other wire going to pack then tested. Yep, voltage.

Which Alltrax controller (AXE - DCX - SPM) and what did you do to eliminate the frame voltage?

I was being too cavalier when I said I just accept that it exists.
I have had ghost voltages cause some issues in complex electronic devices, but the root cause was circuit design rather than ghost voltage. More correctly, the engineer that designed the circuit did not take the inevitable existence of ghost voltage into consideration and harden the circuit against it.

[kgsc]

It was a dcx300. I put on some thick paint and just to test it put some slices of inner tube between the battery and rack. Numbers went to 0 or very low. Changed the batteries out like 3 months later.

[radioman]

Ghost current.

[yurtle]

I get .2 ma from both + and - to the concrete floor with charger plugged in. 0 with charger unplugged from cart.

[JohnnieB]

Originally Posted by yurtle

I get .2 ma from both + and - to the concrete floor with charger plugged in. 0 with charger unplugged from cart.

What was the contact area of the floor electrode?

If it was just the test lead probe, the current density was high, so the mA reading probably was low.

When measuring the conductivity of floors in surgical suites and other flammable gas areas, I used 5 pound weights whose bottom was 2.5" in diameter and covered with tinfoil, as specified by NAPA-99.

Clip the test lead to a 3" square of Sn or Al foil, place a flat wood 2x4 on top of it and stand on the 2x4. That should give you about 8 or 9 square inches of contact area and more or less eliminate current density as a factor.

Also, measure both the AC and DC current.

If you only get zapped when the charger is plugged in, you may be feeling AC leakage from the charger.

[yurtle]

I wet the concrete about the size of one of my feet. My hands feet are usually covered in sweat, and sweat has lots of salts, so...

I may play with it some more, and see what the AC and DC currents are while charging and on float. I'll also check frame voltage and current. It's quite possible that I was leaning or somehow touching the frame when I got zapped.

I generally get zapped by bumping my hand into something by accident, so I doubt it's psychosomatic. I've been getting zapped since I was in second grade, so I'm pretty familiar with the feeling, and have no phobias about working on circuits while they're hot.

I usually put on my sandals and unplug the charger when I'm working on any cables, and don't get zapped. I also don't wear jewelry or appliances.

[JohnnieB]

If it is AC, check the grounding in the AC outlet, to main panel in house (Station ground) if possible.

I did an electrical safety inspection on a new addition to a hospital I was working for and found all the outlet grounds in the new rooms were within ~0.1 Ohms, but there was ~25 Ohms of resistance between them and the station ground. I didn't get a Christmas Card for the contractor that year.

I don't know what the cost was, but the contractor had to run several hundred feet of heavy gauge copper and bore a bunch of holes through poured concrete walls to fix the problem so it was more than just chicken feed.

I also don't know exactly what they did, I was persona non grata in the construction area after that since I was a third party non-union consultant.

[yurtle]

I know the ground to the breaker panel is good, since I installed it. Could be the house ground isn't good, which is 40' away. Over the years, I've seen numerous ground rods that either hit rock or very hard soil, and were cut short.