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Joule

Shocked

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Did an event in Arizona where it rained. Seriously, it rained in Arizona. Dripping wet waiting in queue on second loop about midway through the loop, got a severe jolt in the left hand while soaking glove hand had finger on clutch lever and thumb wrapped around grip. Shock was felt throughout my hand and seemed to exit (enter?) at my thumb. I've done enough work with AC and DC (I'm a sparky), including some medical experiments with DC, that I think this was a real shock event. Meaning I don't think it was some nerve pinch or arthritis related garbage. I've not run an experiment on myself to calibrate sensation vs voltage (I've got some mates who would be happy to help), however the magnitude of effect has me thinking it was the full 50V or so of the battery pack. 

My dealer has been very responsive and said he has had big bike customers report similar shocks of the left hand which were traced down to an inadequately tightened ground wire. My dealer is going to contact EM for more information.

My dilemma: I want to ride. I know the best way to get a Li-ion battery fire is to short the battery. While a loose ground isn't a short, it is a close cousin. The battery is out of the bike while I contemplate my next move. 

I am interested in suggestions on how to proceed. I'll wiggle everything to see if there is a loose connection. I hesitate to dismantle motor less I void warranty? 

Stripped bike photo attached. The more I do with this bike the less interest I have in petrol powered bikes. This electric stuff certainly has a learning curve, but it seems so much more simple. Is it a siren's song?

 

em_Race_stripped.jpg

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Not EM related but a Honda road bike I had in the rain would send a shock through the bars every time it fired.  This was very annoying with soaked gloves and a 15 mile journey home!  I certainly didn't drop off on the ride home!

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In wet weather try this idea. Bolt a wide copper strap to bare metal on bike frame, long enough for it to drag on the ground as you ride it.   Its volts that jolts - Its current that kills--- . I was riding my techno - rode underneath High voltage power lines - 4" cables on the towers-- big time power lines that come from grand coulee dam and feed seattle, wa.   As i went under this tower, my gloved hand with 2 fingers on clutch lever had a shock. Frightful.  Volts that jolt, current that kills--  This is why living things can take a direct lightning hit and live. Millions of volts, but very little current.   Same with sliding your feet across carpeted floor and grabbing a door knob.  approx 40k volts but very little current.

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14 hours ago, Joule said:

The more I do with this bike the less interest I have in petrol powered bikes. This electric stuff certainly has a learning curve, but it seems so much more simple. Is it a siren's song?

 

 

If so, then I am singing the same song! Technology yes, but such a drastic reduction in moving parts makes for elegant simplicity. In your search for the issue, I presume that you removed the orange mesh and checked all the cable connections? Time to break out the multi-meter and go to town!

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Thanks for the suggestion, my riding partners do experience what you describe on occasion at one of our staging areas which sits under some high tension lines. My experience was far from any lines and I immediately expressed to the riders around me did anyone else experience a discharge or see anything...no one else. 

I think I may have traced the culprit, at minimum I am not concerned about operating the bike in dry weather. Attached photo shows the attachment point of the battery +50V terminal. The terminal is one side of an 800A fuse, and the additional wires coming off the terminal are clearly going to melt long before the fuse if there is a short on their side. Point being, I don't think I need to worry about a short induced battery fire. As an aside, one could definitely do some welding in the field with the EM battery...that's got to come at a huge premium price! 

In the picture I've circled a red wire that is on the +50V battery terminal in yellow. If I traced it correctly this wire runs to the LCD display (and I want to believe I traced it correctly because it isn't uncommon for an LCD to need more than +5V logic supply. I'm guessing EM chose to use a step-down converter in the LCD rather than a step-up, keeps wire size down). I'm highly suspicious the jolt I received came from the LCD supply line. I'll be even more convinced if someone can give me a reasonable explanation of the current path...

I think for a long term solution, if it is the LCD line, I want my dealer to find out from EM if the hypothesis is plausible, and if yes, what is the current draw of the +50V line so what value resistor could be placed in line to limit any future shock. Or an inductor...but that could backfire severely if a resonance occurs...both inductor and resistor...

LCD_50V_supply.JPG

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I agree with the suggestion of checking continuity with a meter. For anyone not knowledgeable about ohm meters, please be aware they apply a small amount of energy to make a resistance measurement. If an integrated circuit is not properly designed the ohm meter can destroy it. My hand held DMM applies about 2V when making a resistance measurement.

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22 minutes ago, Joule said:

In the picture I've circled a red wire that is on the +50V battery terminal in yellow. If I traced it correctly this wire runs to the LCD display (and I want to believe I traced it correctly because it isn't uncommon for an LCD to need more than +5V logic supply.

I am a bit taken back by them taking those power taps ahead of the fuse. Running 50v from there, all the way back to the LCD, before stepping down just doesn't sound wise, if that is the case.

Given you felt the shock on the clutch side, I would look closely at the kill switch lanyard button mounted right next door. In addition to the normal kill switch functionality, it lights up as well. No clue what type of power they are sending up to it for that. Should be minimal, but it is still a current path. Wet lanyard around your wrist is a conduction path, as well.

Edited by dgshannon

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40 minutes ago, dgshannon said:

I am a bit taken back by them taking those power taps ahead of the fuse. Running 50v from there, all the way back to the LCD, before stepping down just doesn't sound wise, if that is the case.

I suspect that it is deliberate to leave the electronics live on whatever is left of battery power after the 800A event...it let's them have a diagnostic and maybe a warning message like: "RUN!" or "Please enter next of kin"

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1 hour ago, Joule said:

I'll be even more convinced if someone can give me a reasonable explanation of the current path...

Current path being to the ground via your thumb and feet which i imagine were on the ground when you were stopped. Soaked clothing and boots i imagine would greatly reduce this paths resistance. Where does the lcd negative line go or is it earthed to the bars?

Edited by faussy

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Wow , I think I will be sticking with 2 stroke power ,

all this talk of - 50+volts , 800A fuses, mixed with heavy rain , is not convincing me that electric is the future.

Good luck, I hope its a simple fix

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1 hour ago, faussy said:

Current path being to the ground via your thumb and feet which i imagine were on the ground when you were stopped. Soaked clothing and boots i imagine would greatly reduce this paths resistance. Where does the lcd negative line go or is it earthed to the bars?

It looks like the LCD has a separate return wire. I'm not going to dismantle anything since it has a warranty and I'm satisfied with everything I've seen that the bike is perfectly safe to operate. I am curious about the model of current flow you propose. Are you suggesting current left the positive terminal of the battery, went through me to earth (ground but I literally mean the Earth since I think that is what you are suggesting) and then found a return path from the earth to the negative terminal of the battery? Or are you suggesting the motorcycle acquired a net charge such as someone shuffling their feet on a carpet, hence a potential difference with respect to the earth, which then was able to discharge through me when my resistance to the earth provided a path? Or something I am not imagining? I'm tempted to set up experiments to test your hypothesis, but I don't understand what you are suggesting. I believe if I understood I could instrument the bike and not have to participate in the conduction path. 

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2 hours ago, djr said:

Wow , I think I will be sticking with 2 stroke power ,

all this talk of - 50+volts , 800A fuses, mixed with heavy rain , is not convincing me that electric is the future.

Good luck, I hope its a simple fix

My mistake. It is an 800A fuse holder, the ceramic part, with a 300A fuse. Still enough to do welding. Approximate total peak power is 50V X 300A =15kW or about 20 HP. Pretty impressive...

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On 9/29/2021 at 5:02 AM, Joule said:

My mistake. It is an 800A fuse holder, the ceramic part, with a 300A fuse. Still enough to do welding. Approximate total peak power is 50V X 300A =15kW or about 20 HP. Pretty impressive...

300A is at or close to the point the fuse blows. I doubt the controller would be setup to be pulling close to the ragged edge of the fuse, so I'd think closer to 12kW would be more realistic.

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