Traditional motor vehicles are dangerous things when they’re in motion, but they’re relatively safe at standstill as long as you don’t set them on fire. EVs pose unique risks, and thus workshops that intend to deal with them must take certain precautions. Chief among them is keeping a big yellow hook on hand, and today, we’ll explore why.
This is no mere superstition. Known as “rescue hooks,” they have a design that might remind you of the medieval concept of the man catcher. Indeed, it’s function is not so different!
Rescue hooks are designed for saving workers in an electric shock scenario while protecting the rescuer in the process. They typically consist of a large hook on the end of a long non-conductive pole.
The problem with electric shocks is that they can instantly incapacitate someone. They often cause muscle spasms, which in the worst cases can lead to the body remaining in prolonged contact with a high voltage source. In these scenarios, it’s not safe to directly try and pull the person away to safety, as the rescuer would receive an electric shock in turn. Hence, the proper technique is to use a stout hook on the end of a non-conductive pole to drag the person to safety.
The hook can also be used in another way. A person who has been shocked may be lying on the ground, for example, in contact or near a high-voltage cable. In these cases, the hook can be used to lift and move the cable a safe distance away, ideally after an attempt has been made to shut the current off.
It also bears noting that these hooks only make up one small part of a workshop’s total EV safety precautions. Others include using personal protective equipment like insulating gloves, safety boots, and non-conductive tools for working on or near high-voltage connectors.
EV batteries typically start in the 400-volt range, with 800-volt examples becoming more common. While it’s not strictly voltage that kills, higher voltages do pose greater risks than lower voltages. Combine that with the fact that EV batteries can deliver plenty of current, and you can see why they pose a genuine risk to anyone working on them.
As an aside, you might have heard typical cliches that current kills, not voltage. However, this is really an oversimplification. As per Ohm’s Law, the current flowing through a given resistance is determined by a simple formula: I= V/R. That is, the current in amps equals the voltage in volts divided by the resistance in ohms. Let’s create a pretend scenario where a human body has a resistance of 1,000 ohms. When we apply 10 volts with a big battery, the body would see a current of roughly 0.01 amps, or 10 milliamps. This would be painful, but would not be debilitating under typical conditions. However, do the same experiment with a battery at 800 volts, and the body would see a current of 0.8 amps, or 800 milliamps. This would likely cause burns, muscle contractions, and come with a high chance of death.
It’s worth noting that the resistance of the human body can vary greatly depending on method of contact and various other factors; these numbers are just a guide. As per the National Institute for Occupational Safety and Health, high voltages can also quickly break down human skin, massively dropping the body’s resistance as low as 500 ohms. This greatly elevates the risk of harmful electric shock.
Rescue hooks were not exclusively invented for use during EV repairs. After all, workers have been dealing with high voltages in the electrical trades for a long time before EVs became mainstream. In fact, most rescue hook demos online show workers being rescued from faux shock scenarios while working on switchboards or high-voltage transmission lines.
Grid infrastructure and industrial installations often operate in the tens of thousands of volts. These situations require rescue hooks rated to be safe at higher voltages. Rescuers may also wear arc flash protection gear, including full overalls and flash hoods, to avoid getting injured themselves. A rescue hook may even be held around a worker as a preventative measure, so in the event something happens, they can be instantly pulled away.
Rescue hook and high voltage detector
byu/toolgifs intoolgifs
It would really suck waiting for your colleague to slowly jog over to fetch the rescue hook in a situation like this one.
The sticks can range in price from a few hundred dollars to a few thousand dollars. This depends on their voltage rating, length, and certification level, among other things. In the grand scheme of things, they’re not a major expense for a workshop, but an important tool to have on hand.
So now you know why EV workshops have big hooks hanging on the walls. Hopefully, you’ll never see one used, but it’s good to know they’re there when they’re needed.
Image credits: via Amazon, Lewin Day, Grade A Tools, Nissan; top graphic base image WavebreakmediaMicro/stock.adobe.com
Used to work on mass spectrometers with 50 kV power supplies that unwitting users could get their hands on, if they worked at it. We had a couple of very long wooden poles that could have been used to roughly shove someone off of a piece of equipment. A hook would have been much better, but we never had to find that out. I did see a guy knocked six feet back and momentarily unconscious once, though.
I actually went to an OEM manufacturers EV training class. We had to practice with the pole and the gloves and all that. But the reality of it actually working on the cars is once you pull the disconnect on the battery pack, there is nothing to worry about.
Careless techs and future engineers will find a way.
Eh, as someone who got the “warning tingles” on some home wiring, I can tell you what happens.
You’re going through some diagnostics, but you’re doing multiple things as once where you may be having to restore and remove power repeatedly. Since you’re doing multiple things instead of just one thing, is you forget whether you’ve disconnected, and you’re so tunnel visioned on the current setup that… yep. There you go.
It comes down to checklists (and following them religiously), serializing tasks (don’t try to do multiple things at once), and ALWAYS test before you touch anything, and test again if for some reason you switched anything back on, or honestly, even if you left what you were working on for more than a few seconds.
Making it hard to make mistakes is huge, and then always ensuring you still didn’t make a mistake is just as important.
Using a breaker lockout and carrying the lock itself on your belt loop is handy check: if the lock is on you, it’s live. I do this precisely because of the conditions you talked about: it’s quite easy to be distracted/ over-focused on minutia.
Or, when working on a unit where I can’t see the disconnect, I’ll ziptie it off. When I cut the zip tie, I bring it back around to the controls and set it in my line of vision.
Breaker lockouts purchased!
Never assume you are safe. After shutting down the breakers and main breakers in a brand new development to service their path lights, I got hit with my feet in wet soil. Turns out someone had mistakenly tapped into the neighbors pathlight conduit and the two houses were inter-wired across a single 15A breaker in each house. I jerked free but it totally exploded my sidecutters. After that, I check every wire every time.
I still intend to always test with non-conductive testers, as I did when I got the “warning tingles” (where I didn’t, because I lost track of what I was doing by doing too many things at once), but the breaker lockouts are yet another safety tool to make doing the wrong thing harder.
I think all workers in these shops need to wear belts as something to hook the hook onto.
Worker is on the floor, so how otherwise do you drag them out? By the eye socket??
Butthole of course.
So the hook isn’t just for bad acts on Vaudeville anymore?
Powers systems class in uni schooled me well on high voltage. I was always leery of electrical system
When I was a kid, my dad had to do some work on a live circuit (not sure why). He had me stand nearby with a wooden handled broom in case something went awry.
30 years later, I still carry that memory with me so I’m sure it didn’t cause any low-level trauma.
My dad held a 2×4 while I did the work
My dad would tell me to “hold these wires” and after I yelped he’d tell me “now you know that phone cords carry voltage.” Or he’d tell me to “hand me that condenser” and after I yelped he’d tell me “now you know that a condenser can hold a charge even when it’s unplugged”.
I swear, he could have just told me taught me these lessons orally, I didn’t need the practical demonstrations.
Which is weird, because I fixing the sink
When I worked offshore they had a “Medium Voltage” room full of equipment. Some of that equipment talked to my system so I occasionally had to go in there. I hated that room. You’re probably wondering how many volts is “medium” anyways, and that’s a good question because that term medium is relative. Anyways, the medium voltage room started at 20,000 volts. The electricians would always try to reassure me with “it’s not the volts that kill you” and I know all about that but when “E” is 20,000 “I” doesn’t have to be very big at all before “P” = 10001010 pops like a hotdog in a microwave.
I’m perfectly happy dealing with my 5v and 12v systems thank you very much.
I’ll DIY 120V and 240V household stuff. It’s pretty safe with basic precautions. Maybe 277V as well, but that’s generally something where a pro’s needed anyways.
Not going anywhere near anything higher than that, though. Above 400V is getting into the territory of “being nearby the problem is dangerous even if you’re not touching it” and 20,000 is “high chance of molten metal shrapnel” and “that thing you thought was an insulator… isn’t anymore”. Absolutely not.
Now it occurs to me that a hook probably would reduce secondary injuries substantially compared to hitting someone with a board. Good job, OSHA!
Yeah, no kidding about the importance of safety protocols and paying attention. After all, that’s why they say “there’s no such thing as a dumb *old* electrician.”
Regular ol’ cars have their share of electrical hazards. One of my trade school instructors told of how in his early days of working in a repair shop, in the 1970s, he saw firsthand a co-worker getting his hand stuck between a positive battery terminal and some ground point while the car was running so that his gold wedding ring melted (keep in mind that gold is one of the most electrically conductive materials out there.) So, for obvious reasons, he always insisted on his students removing all jewelry before working on cars (even ones with the battery removed, just for consistency’s sake.) Wise advice, indeed.
We often joke about safety, but establishing protocols and always following them maximizes your chances of making it home at the end of the day
When assembling the battery pack on my Triumph GT6 EV conversion, I removed everything metallic from me. Watch, glasses, steel gloves(long story, but used for venomous snake handling), ect. I didn’t fancy the idea of having my glasses get melted into my face while tightening down some nordlocks on some copper bus bars. I also insulated the end of the ratchet drive I was using, just in case I dropped it.
steel gloves(long story, but used for venomous snake handling),
For fun or for profit?
For pets.
I prefer my pets less lethal. To me anyway.
People keep dogs, which have a higher rate of killing people. Basically keeping a wolf in their home, except bred to look less intimidating. All of its instincts and faculties remain intact, no matter how friendly. Same applies to anything else kept.
My rattlesnake not once struck at anyone. It also seemed to like being pet and more than once came over to me on its own. But no matter how tame, it was still a rattlesnake, with fangs and venom glands intact. You wouldn’t be able to pull one directly out of the wild and start handling or petting it without spending time working with it, and even then, it may never become tame.
People keep dogs, which have a higher rate of killing people
Are there really enough folks who keep pet venomous snakes to have accurate stats on that?
Basically keeping a wolf in their home, except bred to look less intimidating. All of its instincts and faculties remain intact, no matter how friendly.
Tiny, yappy dogs the world over agree with you! Despite their insistence to the contrary I’d pretty certain your chances of being mauled or killed by a Chihuahua is much less than by a Presa Canario. Or an actual wolf.
An intact rattlesnake OTOH… I hope you have a stock of antivenom handy.
Ya know, the more we learn about you, the more I think Toecutter is too subtle of a name for you. You seem to be a Character. The Weird Uncle. That Guy. At least when you go, people can say you led one heck of an interesting life.
“that’s why they say ‘there’s no such thing as a dumb *old* electrician.'”
Fun fact: it used to be considered acceptable practice to bridge conductors of live circuits with one hand and note the sensation to determine the voltage. If it tingled, it was 120V. If it hurt, it was 240V.
Egad. Presumably this was this in the days of post-and-tube wiring? Ha, yeah, shades of ElectroBOOM! (For those of you who may not know, ElectroBoom is a Canadian electrical engineer who has a highly entertaining and informative YouTube channel where he frequently gets shocked though I’m not altogether clear whether the shocks are just kayfabe or for real or indeed a combination of both.)
Yeah, there can be a weird margin of safety in electricity, like with post-and-tube wiring, if in good fettle, actually being acceptable in some places. One of my siblings bought a lovely old house in the 1990s and found the electrical system to be post-and-tube and still functioning fine after nearly a century. However, he took some night classes for home electricians and used what he learned to replace and update the old system, a most prudent course of action to take.
I had a retired Navy chief as a professor in tech school. He used to say, “There are old electricians and bold electricians, but no old and bold electricians.”
I’m glad it mentions other protective equipment as well. My uncle works in a plant that deals with very high voltage equipment and a few years ago a transformer blew. He was wearing his safety glasses and still was essentially flash banged but recovered. Two of his coworkers who were not wearing their PPE were blinded permanently.
I’ve seen both these and discharge sticks referred to as Jesus sticks. If you don’t have them when you need, you’re meeting Jesus
I have this sneaking suspicion that if I were to be a mechanic at one of these EV shops, my nickname would be sparky (and for good reason).
Better than Crispy
Every electrician in Australia is a Sparky.
Everyone else on the building site is a Tradie.
Traditional motor vehicles are dangerous things when they’re in motion, but they’re relatively safe at standstill as long as you don’t set them on fire.
Traction Engines are exempt from from this rule partly because they are on fire.
I just had to buy two of these for work to keep people from sizzling on the corona discharge treater. There’s loads of interlocks on the thing, and only qualified personnel should be working on it, but it was still a necessary purchase just in case. The damn things aren’t cheap either.
Corona discharge treater sounds like something a nerdy taqueria would name their restrooms.
Nah. Just a high voltage plasma generator that changes the surface properties of materials sent through it.
Ah… that ‘just’ all it is… got it! LOL
For some fun reading, look up NFPA 70E. It used to be a major part of my life when I was a facility and corporate electrical engineer for manufacturing and chemical facilities. I’ve witnessed more than enough arc flashes in my life to appreciate that I’m now far enough in my career that I no longer touch equipment on a daily basis. I still shudder thinking about some of the things I’ve seen over the decades…
I used to love playing with fire as a kid. Then I discovered what electricity can do, which was one factor that nudged me into becoming an electrical engineer. My main motivation was wanting to work on electric vehicles, but there are other things I like pertaining to the subject. Substation arc flashes are the best!
I started my path fixing electronics, then electrical devices, then engineering. I mostly like low voltage stuff, but the medium and high voltage stuff comes with the job sometimes. Arc flash events are always exciting, what with the plasma flying all about. Having worked with a lot of folks who personally experienced arc flash events, I am one of those engineers who gives great deference to quality electricians.
The first electronics I fixed were broken videogame consoles and broken TV remote controls. I put together custom electronics from kits or parts purchased from Radioshack before that. At 13 I modded my PS1 to play pirated games copied onto blank CDs. In spite of starting from such a young age, my soldering skills are still shit. I didn’t know how to PROPERLY tin solder until about 5 years ago, in fact, even though I’d been using a soldering iron for almost 3 decades prior. My soldering has always been atrocious, but barely functional.
As for arc flash events:
https://www.youtube.com/shorts/ucMJhP_Y3q0
I never get tired of that video
Ooo pretty! And only 100% lethal!
“Substation arc flashes are the best!”
Sure, as long as YOU aren’t the conductor!
My boss used to keep me grounded by saying I had no potential.
“I used to love playing with fire as a kid. Then I discovered what electricity can do”
I always thought I liked the cut of your jib. Now I know I like the cut of your jib.
He needs a new name. “Most Interesting Man Alive”? “The Wizard of Autopian”?
Totally unrelated to this but can I ask about your EV build, specifically what are you using for the steering and brakes?
Which EV build? I have three of them, and another vehicle that will eventually become an EV.
-1969 Triumph GT6 converted to electric
-Custom-built electric velomobile
-DB mountainbike conversion
-Milan SL velomobile (not yet converted)
The custom velomobile.
For the front brakes, I have a set of custom brake calipers using parts from ebikes, ATVs, and motorcycles. They are hydraulic and use DOT3 fluid. The fluid reservoir is build into the brake lever like a motorcycle. The disc rotors are from an ATV, and sized so that in theory, they will provide enough material to allow the vehicle to come to a complete stop from 100 mph without overheating(they have never been tested above 60 mph). Lightly pulling this lever also activates regen in the rear wheel hub motor(and once front hub motors are installed, will activate regen in the front motors as well).
The rear brake uses an Avid BB7 cable-pull system as both a parking brake and an emergency brake.
The steering is an Ackermann setup using steering bars where you grip one bar in each hand, with each bar attaching to the left or right side spindle, and they are connected with a tie rod. This is a direct steering system. I have the tie-rod adjusted so that the front wheels have 1/16″ toe-in.
Thank you, this was exactly what I needed and more (I hadn’t thought of the parking brake yet)
The guy in the training videos had those subsection numbers memorized perfectly, five layers deep. I always respected that.
You should take the 70E training directly from the NFPA. The guy who taught the training in 2014 had the entire 70 and 70E books practically memorized. No sense of humor, though.
I used to do a lot of work on poles and we were trained in ‘aerial rescue’, essentially getting someone down who may have been electrocuted and is now strapped onto a pole or ‘midspan’ (hanging from the guy wire).
Also when I was a kid my dad stuck a knife in an outlet and got stuck to it, and then my aunt tried to pull him off and got stuck to HIM. My grandma had to boot them both away from the wall with a well placed kick, but they got really lucky.
The moral is check the voltage, and if you’re not sure, check a known voltage and then check again!
I always remember the scene from Running Scared where Billy Crystal and Gregory Hines are driving on the train tracks, and there’s this dialog:
Try not to scrape the third rail, OK? There’s about 600 volts in there.
It’s not the voltage that gets you. It’s the amps.
How many amps are in there?
Enough to move a train.
From my HV vehicle training these are the effects of DC current (like the AC chart in the article but more relevant for EVs):
5mA barely perceptible.
76mA maximum to still “let go”.
90mA severe pain, respiratory arrest.
500mA ventricular fibrillation threshold. Risk of death.
“What is your favorite color?”- DC current
“Blue..no! Arrrrrrrghhhh….” -Sir Galahad of Camelot
Hey! Something relevant to me.
We’re currently switching our entire transit bus fleet to EV (not my idea) and my team takes care of training. Workplace electrical safety is part of that.
Our electrical process involves the “buddy system” any time you’re in a level 2 de-energization situation and have high voltage work directly. One person working, another there in case things go wrong. We have arc flash suits up to 12cal and both rescue hooks and AEDs in every bay that works on them. (we only have 4 EV buses, but that’ll be up to 26 by next year, eventually over 400).
I’m interested in what you can share about the reasoning, and the “not my idea” disclaimer.
My local city transit has a number of EV busses, but they seem to be transitioning slowly, as older gas busses go out of service, they’re replaced with EVs, which I thought made sense. Why throw away a good bus when you’re only paying gas/maintenance vs a new large capital outlay?
I always thought that EVs seemed like a really good idea for fixed-route local services like busses, local delivery, etc. But I’m curious if there was another factor that you saw that made you more skeptical.
Thanks!
Interesting and useful info.
Not to put a down note here, but don’t those rescuers all suited up and wielding their hooks kinda look like the Grim Reaper?
The Angel of Death and the Angel of Life are not so different after all.
Fun fact: even those suits are not capable of protecting you from everything. At a certain point likelihood of survival/mitigation of grievous bodily harm is the best you can do or ask for. Arc flashes will vaporize metal, and it turns out gaseous copper is pretty rough on the ol everything it touches.
Yeesh!
Yeah that lovely copper its almost instantly over 2,600 degrees centigrade, do not be anywhere near it when it does that. Do not get it on anything you want to keep.
Copper snot never fails to look interesting at least.
Good to see these. I often work with 480V 3-phase. There have been times when we would find a dry 2×4 for one person to stand by with in case the other got ‘hooked’ by current. A former tech once had the current grab & hold him such that the only way he got loose was to smash his face into the compressor housing. Lost a couple teeth & broke some facial bones, but he’s still alive. He had 20 years experience: it can get anybody. You ALWAYS double-check even when you locked that breaker out yourself.
We often joke about this stuff, but it can & will kill you. You have to clear your mind: being the least bit distracted can kill you—and they might not find you for hours
Tales like these from pros make me feel more justified in my usual paranoia when doing boring-to-you-guys household stuff. I’m always checking the circuit a couple ways, usually putting big tape Xs over the open breaker, and sternly telling anyone else around to NOT go anyway near it.
The lockout locks for breakers aren’t that expensive, and adds that extra layer of safety for you.
Did not know those existed for home panels, thanks. I’ve only ever seen big ones in factories and have always thought they seemed like a good idea.
my first big purchase as a lowly helper was a good sniffer. I start my day by checking it on live & disabled circuits. Then I confirm with my meter.
>> always remember that a unit can be fed by more than one circuit!
Today I’m at an old facility that has this in many of the almost 500 pieces of equipment here. The old permanent guy here had an amazing ‘waffle’ scar on his upper arm from just such a situation: he locked out the motors, but the heater was powered separately. If another tech hadn’t been nearby & seen him kicking, he wouldn’t have made it.
watch your ass, people: you want to go home to loved ones
Btw, Southwire sells a ‘sniffer’ at Lowe’s for about $17. I always check around with a sniffer, then confirm with a meter. The sniffers are nice because you don’t have to touch anything: get near live AC and they beep, flash, or vibrate.
-I know I’m peppering this article with comments, but this stuff is serious
As serious as life or death, so we appreciate the advice.
My fancy dancy Fluke does that, too. I love that thing. I got used to using it at work a couple jobs ago. While I didn’t spring for the 87V, I also got to the point that I didn’t and shouldn’t trust the ones I got for literal actual free from harbor freight. I treated myself to a 117.
It’s just such an absolute unit of a device, the yellow standard. When it matters, it’s money well spent.
I’m with you. Decent equipment makes a huge impact. ‘Little’ stuff, like having a swiveling amp-clamp, and reading & storing inrush current help a lot. I’m safer and I have more diagnostic data—also it doesn’t burst into pieces if it falls 10 inches like the HF ones.