Personally, I find things spontaneously welding themselves together until whatever solder joint is weakest decides to peace out, or the whole thing lighting on fire a far scarier possibility than the frame somehow ending up at the positive battery voltage but otherwise isolated. If the frame is at negative battery voltage all the time and a positive battery conductor touches it, you get welding, fire, and all kinds of bad things that I want to avoid. If the frame is isolated and that happens, then there is a possibility that you will shock yourself if you somehow also touch another conductor, but otherwise, nothing should happen. I would hope that would be caught before another conductor also starts contacting the frame and the welding and fire and whatnot occur. I also hope it is something that would be noticed before going digging in the electronics and touching a negative battery lead or something connected to one while touching the frame.
I guess if youâre more concerned about the shocking potential, you could argue the short circuit disaster is better than a small chance of shock. I certainly wouldnât, though. And I would also argue the other ways that it makes the likelihood of a shock go up, by making it far easier to accidentally touch something connected to a battery lead, more than negates that.
Yeah fair, Iâve had connectors just blow open circuit not to much other than a little ooh shit moment. Regardless the way itâs wired the way we hot swap and get a visual on whatâs going on in the enclosure and then store disconnected itâs not something Iâve lost sleep about.
For your AC house appliances and wiring. All Y wound AC systems are tied to earth ground, from the source generation through the transmission towers to the distribition lines through the house wiring and into your appliances including yes, your water plumbing.
In order for Y A/C to work it needs to have a return to the source generation. That would be through earth ground.
Anytime you touch your stove/ toaster or sink your are at earth ground potential. If you are statically charged at a different potential and touch a grounded appliance you get zapped. If you come between the source potential and ground you get zapped.
Every metal appliance and faucet in your house is grounded to earth ground. The neutral wire in your house is also attatched to earth ground. In the event you find yourself inbetween source and ground the hope is that your source is protected through a Ground fault interrupt. Electricity is lazy. It will always find the shortest path back to source. A GFI unit uses the earth ground and house neutral to detect a foult. GFI then opens potential source before a load can be produced across the fault. At the speed of light it saves from damage and possible loss of life.
Coming between an ungrounded energized appliance and ground can lead to shock. Once again electricity is lazy. If you are the shortest return to source path, it will take it.
If you touch your ungrounded toaster and your grounded stove the potential is there.
With either DC or Y wound A/C it is all about not making yourself a conductor when you are handeling it. Understanding what harm potential can have 12v or 100v, high amp or low amp is mitigated through work practices and knowledge. You need to know the rules before you handle any potential.
50v is where DC voltage can seriously shock anyone when put inbetween source and return. 50v can leave an entry and exit wound. As little as 50miliamps can stop a human heart.
The likelihood of touching an exposed wire and coming in contact with a chassis ground is definitely there. Same as touching your toaster and your stove with a ground missing on one or the other. Or touching an exposed hot wire in yoir house while touching the faucet or apiliance. The Potential is there.
Running a DC two wire system is as easy as running a chassis ground. The provisions are built into Both the GTA spine and V-6 if the end user so chooses to run a two wire system. If two wire makes more sense that will work just fine.
Keep in mind that the motors and ESC are already connected on this chassis potential and coulld also make a return path if faulted.
The important part is to understand the potential you are working with, always wear appropriate personal protective equipment (mainly gloves) when handling any potential that can harm you.
Voltage and current are a serious business and should never be handled without knowing the rules. We should have more discussions on potential to have a better general awareness of the risks involved when working around it.
It is important to use good connectors thar are properly shielded and isolated from touch. Hazard Mitigation is always the best approach.
Fusing or current breakering is a good idea.
Having a projected or accidental ground on the chassis would be an unknown. In my line of work, thats how people unintentionally get hurt. Knowing the potentials and rules is the best way of hazard Mitigation.
With All source potentials A/C or D/C, the sources job is to find a path back to itself. Weather it be through ground, the neutral, or the negative, includes anything bonded or shorted to it.
If you become the shortest path back to the source you become a difference in potential. Once you complete the path is where you fond trouble. Dont put yourself inbetween a conductor. It is simple rule to follow but an unknown ground or projected ground would be a much bigger hazard to work with than a known common ground.
There is no less danger putting yourself in series with a neutral, ground or negative. In DC voltage as well as AC. If there is a difference in potential there is a risk if you put yourself between it.
Iâm sorry Moe, but youâre just simply wrong about this.
I think some of your confusion is coming from the difference between âearth groundâ as itâs used in AC home electrical systems, and âGNDâ as itâs used in DC electrical systems. Itâs confusing that they are both called âground,â but I assure you they are referring to two very different things.
Earth ground in an AC system can act as a return path for voltage/current (only in a short circuit fault scenario, see @Pecos below), youâre correct about that. However, that has absolutely nothing to do with a fully isolated DC system on a skateboard.
We often call the lowest voltage point in a DC system âgroundâ or âGNDâ but thatâs just a convention. It is not equivalent to earth ground in an AC system, and youâve clearly drawn some faulty conclusions by conflating them.
And thatâs exactly the problem that @glyphiks and many others are trying to point out. By bonding your battery negative terminal to your chassis, you have effectively made the entire chassis the battery negative terminal. You are introducing a massive risk that literally no other production esk8 has. Youâre dramatically reducing the overall safety of your skateboard, for no apparent benefit. It would be like stripping the insulation off half the wires in your esk8.
Except itâs not the same at all. The average user of a home electrical system is not expected to regularly handle a hot wire every time they use the system. On this skateboard you have designed, youâre asking the user to handle a hot wire every time they touch a metal part on the board.
And your response to that danger you are passing on to your customers is basically âskill issue.â
Thatâs really shitty behavior in my opinion. I think you should reconsider this.
Dude, buddy, pal, my guy, are you seriously equating someone using your skateboard as itâs designed to someone sticking their hand into a live toaster? And you think thatâs a point in your defense???
Unfortunately, there is simply so much male ego at stake in this hobby that electrical engineers from NASA could enter this discussion, and no one would concede their point. Thatâs been demonstrated elsewhere when speaking to people like this, and itâs just the reality.
This is wrong, you are both wrong. this isnât meant to be insulting but i need yall to take one step back and be careful because you can set yourself up to let the magic smoke out of people if you arenât careful here.
GroundED and groundING conductors are separate and isolated. This is a common mistake as this makes them sound so similar but they provide a very different and isolated purpose in the circuit. the change happened when panels went from fused systems (knob and tube type installations) and circuit breaker protected systems. for a circuit breaker to function and interrupt a short circuit there must be a low impedance path from the point of the short to the bond at the panel board.
grounded conductor= neutral conductor = Often white or grey in the US. this is bonded at the point of distribution as well as at the y of a three phase transformer. where to bond gets complicated so ill leave this short. there is no measured voltage potential at this conductor because it is bonded to earth grounding conductor and is therefore at equal potential i.e 0vac
Grounding conductor= ground conductor = usually green or green with yellow in the us or bare uninsulated. this is the short circuit path and all equipment not double insulated must be bonded to the service grounded conductor in order for circuit breakers to function.
Current can not be placed on the grounding conductor during normal operation. this is in the definitions in the NEC. Article 100.
NEC.250.6.A Objectionable current
âThe grounding and bonding of electrical systems, circuit conductors, surge arresters, surge-protective devices, and conductive normally non-current-carrying metal parts of equipment shall be installed and arranged in a manner that will prevent objectionable current.â
NEC.250.24.B load side GROUNDING connections âA GROUNDED conductor shat NOT be connected to normally non-current-carrying metal parts of equipment, to equipment GROUNDING conductor(s), or be reconnected to ground on the load side of the service disconnection means except as otherwise permitted in this articleâ
there are no exceptions to allow for current on the GROUNDING connections btw ONLY that they may be bonded at separately derived systems which isnât applicable here.
Sause: teach and practice as a sparkie and Iâve been at it for two decades.
ha, rad. didnt realize you were a sparkie @MoeStooge. this chat is getting kinda intense if you wanna id love to go over what my concerns are over dm? lmk
If you have expertise that would explain whatâs going on in a battery operated DC electrical system (like a PEV, here) shouldnât it all continue in this public discussion?
Otherwise itâs like those Reddit threads you find where someone else has the issue youâre experiencing, and someone says they solved it and no one ever posts about how.
yes but: personal conversations that arnt on display get people on the same page faster. talking vs text and all that. it also helps to get people speaking the same language as the terminology here is very specific and important and if there is just one typo it can get blown out of context and get things messy. like grounding, grounded, bonding, grounding electrode conductor, grounded electrode conductor, chassis ground, chassis wiring, chassis current rating, rating of chassis as return path. super easy to get into the weeds here and not solve the issues
Normally Iâd agree, since youâre correct about all that.
But this has been a whole big public spat where the parties involved arguing are ones with influence on members of this small niche community, and at least one of them continues to position themself as a leader and figurehead of essentially an entire sport.
Itâs poor form for that all to be foundation of a technical argument where people are arguing safety, people have obviously shared opinion, and thereâs not just a lack of understanding of terms, but a lack of accountability of their own expertise.
Itâll probably happen anyway, and folks will go back to pretending to be buddy buddy and no one will actually care because usually no one actually does.
But, all the big posturing happened here already, so itâs silly to then have the resolution be private.
Would you ever run a wire with no insulation jacket (just bare exposed copper wire) from the battery negative to the ESCs?
That seems like an absurd risk to take if there is no appreciable benefit.
Thatâs basically what you are doing by grounding the battery negative to the chassis.
Youâre making it very easy to short the pack, where very little risk previously existed.
Iâve shorted a pack before and I got lucky that I didnât damage myself. Have you ever seen an Allen key turn into a quick blow fuse? Iâd recommend avoiding that.
Fair, i donât have much sway in racing or eskate so ill play along nicely. i donât think callouts are as helpful as discussions to get people on the same page though as people get up in their feefees (me included). @MoeStooge none of this is meant to accuse you of intentionally creating a dangerous product but i think there have been some updates to the NEC and best practices around DC systems with EVs in mind that you might have gotten the wrong info about. its just to lay out the situation as i understand it (edit)
My position is that 50vdc plus systems, like Moe said, should be treated like AC systems. they are inherently more dangerous to people and property because the potential for shock and short circuits is much higher.
traditional ICE vehicles use the frame as a return path for the 12vdc system in order to save wire. using the chassis as a return path is fine here and doesnât pose any serious safety hazard. it is fused to prevent fires and this is all good. EV systems that operate over 60vdc are required to be isolated from the vehicle chassis for safety reason mentioned above. there is required to be at least 500ohm per volt of insulation per volt of potential in the system.
NEC requires that the maximum leakage current that could flow between hv system and the chassis is below 5 milliamps because that is the threshold of a harmful or fatal shock. a 12v system just cant provide that kind of shock without getting stabbed by a battery.
ohmâs law is simple here, E=I x R
lets go with 12s so max so 50v for simplicity. this voltage on the frame of a vehicle. a dry person is about a meg ohm and a sweaty person is about 1000 ohm as an example
getting into the circuit at a meg ohm is going to put .05 milliamps into someone. thatâs fine but you will feel it. if you are sweaty that puts you at 54mA which can be fatal.
now if we jump to 20s it gets a bit more sketch: lets call it 84vdc
dry you are fine still at .084mA but sweaty you are getting hot at 84ma.
not a big difference but even 12s is an order of magnitude over the potential fatal shock threshold. which is somewhere between absolutely dry and sweaty as fuck. somewhere i live lol - always moist
I donât have a thread. Iâve only just learnt to quote for a reply, and my recycled 18650 batteries arenât anywhere as good looking as the folksâ here.
In the next few weeks, construction of a new double garage with workshop starts. Iâll probably spend the year out getting stormwater, driveway, and fitting out the garage with linings and whatnot. But Iâd like to think Iâll build something with pride in 2026 once I start filling the new space with things useful for building some boards which arenât upcycled evolve GTâs.
AC is not my expertise (i know just enough to get in trouble) so I appreciate you setting us straight!