Safety: How hazardous can a 14s be to your life?

elkooo

Member
Joined
Aug 9, 2019
Messages
32
Hey Guys

So far I have only been dealing with 36v systems (which have 42v fully charged).
If Itouch the terminals there, I was clearly able to feel current to flow. How safe is a 14s system (going to nearly 60v fully charged...)? I only have (a little bit) of experience with mains-shocks (been shocked 3times by 220v AC and don't want to do it again! 1st: wet paperstrip on plug when I was 17 or so... 2nd: Broken cable on a hairdryer, one strand of copper sticked out and got me on my hand... 3rd: changing a ceiling lamp :idea: and there was current on the neutral line for some reason...)

I am sure, you might have (accidentally or intentionally) tested what happens if you touch the terminals of a 14s configuration... I would be glad to hear some of your experiences with those packs. I am sure It can be hazardous in many ways but I rather hear your incidents and don't do the same than learn all cases myselfs... :angel: :cool:

Maybe this thread can be sort of a collection of incidents or don't try this at home events?! Or also what your precautions are while working with 14s (or greater) packs.
I really want to be safe and get as much knowledge as I can before starting to assemble my packs.

Looking forward to your answers. :cool:

Best, elkooo
 
60 Volts can kill You, so if You do not know what You are doing, Dont!

60 V DC must be treated with at least the same respect as live Mains, maybe more because DC can cause severe burns.

50 Years ago some places still had DC Mains at 110 Volts and people got killed trying to handle wet laundry in a defective washing machine, or placing a pot on a defective cooker.

Therefore, be careful, use insulated tools and do not touch with moist fingers, use gloves if You are in doubt.

Live long and stay healthy :)

ChrisD
 
12VDC can cause some discomfort if your skin sweaty. Had this plenty of times trying to jump start a vehicle and leaned on the vehicle while connecting the Pos terminal. It has like a pinching/tingling/stinging sensation.

With that said, 60VDC can pack a punch. It's at least 5 times as powerful (maybe more, not sure if it's exponential increase or not). You can safety touch a 48VDC system (which can get up to 60VDC), BUT ONLY with dry hands. HOWEVER, I do NOT recommend touching both terminals to find out. Please wear gloves if needing to touch the live terminals of a charged system.

Continuing on, if you find yourself working on 72VDC system, always wear gloves and preferably long sleeves. As Chris states, 110VDC will definitely kill.

The higher the voltage, the harder it is to pull off of it. DC causes a 100% locking motion of the muscles in contraction of the strongest muscles, with the hands that's latching on. With AC, there is a pulsing latching, which kind of gives you some time, albeit little time, to pull yourself off. Fortunately I've only had contact with AC with the back of hand and never on my palm, so I don't know what that feel likes.

In the end, if you can get away with it, make sure all live wires are clear of each other and you cannot mistakenly touch both at the same time. Wrap tap, put a cloth/sock/something over it, wire nut it, etc if needed. At the very least, if it doesn't kill, it could leave a nasty burn mark (think of how a spot welder works)
 
From what I've read, the code requirements in my jurisdiction (Oregon USA) require 48v to be *in conduit* whereas 12/24 are not required. The reasoning (I read) is that 48v is just high enough to present some cases of physical danger due to shock / current in body leading to serious risk. I presume the code requirements are based on the science of voltage risks - so I take them seriously.
 
I agree OffGrid. However, I think the OP was referring right at the battery bank, so I think conduit is a bit tough to do :p
Buuuut, the need to keep the terminals/bare-wires covered is better understood now. I didn't realize it was code to be in conduit. I'm sure in here in Florida is the same thing. Actually, considering it's NEC, it's nationwide anyways. So yeah, same code here.
I would imagine other countries have the same or similar restrictions
 
@Korishan - Yes, thank you. I was referring to 'transmission' lines i.e. from PV combiner box to Charge Controller and possibly from Charge Controller to Battery bank if long enough. For example, my Charge Controllers are about 10 feet from battery control box (with circuit breakers / shunts) and the Electrician said conduit was required as the wires ran up on the ceiling over to the other side of the room.

Its interesting that the electrician 'waved his hands' in frustration that there was no way to 'conduit' very short distances - like 12 inches from battery control box to the Inverter. However, putting things like shunts and circuit breakers into a box as a terminus for conduit is definitely encouraged. One of the key things about control boxes and conduit is that it protects exposed wire against things 'hitting it' - so protected locations / short distances such as connecting batteries in parallel get 'a pass' as far as conduit, but should be protected.

>Buuuut, the need to keep the terminals/bare-wires covered is better understood now.
Agree 100%. As I work with my larger battery with wrenches to tighten bolts ... its so important to keep + and - covered / separate as much as you can. If you do a design where a 'slip' of the wrench can short + and -, it will be sure to happen eventually :)
 
OffGridInTheCity said:
Its interesting that the electrician 'waved his hands' in frustration that there was no way to 'conduit' very short distances - like 12 inches from battery control box to the Inverter. However, putting things like shunts and circuit breakers into a box as a terminus for conduit is definitely encouraged. One of the key things about control boxes and conduit is that it protects exposed wire against things 'hitting it' - so protected locations / short distances such as connecting batteries in parallel get 'a pass' as far as conduit, but should be protected.

The plastic conduit can easily be cut shorter. I hadn't thought of putting the shunt in a combiner box. That's a good idea. And those boxes come in various different sizes. This also gives the added protection of keeping insects/dust off the connections as well (especially if you keep your gear out of house/garage and in something like a shed (which are usually not environmentally sealed)

OffGridInTheCity said:
>Buuuut, the need to keep the terminals/bare-wires covered is better understood now.
Agree 100%. As I work with my larger battery with wrenches to tighten bolts ... its so important to keep + and - covered / separate as much as you can. If you do a design where a 'slip' of the wrench can short + and -, it will be sure to happen eventually :)

Hahahha take all your metal tools and plasti-dip them ;) no more chances of sparks!

And yeah, Pete had a similar slip-up when a dangling wire got loose and hit his battery pack connection. Sparks!
 
If you just work with everything like it could kill you... you will be fine.

That said, I started having a much greater respect for electricity after it does try and kill you, something you have already experienced OP, which puts you ahead of most. Which is probably why you are asking smart questions.
 
In Qld Aus licencing starts at 50V DC systems, it used to be 100V DC but was reduced in the last couple of years as 50V DC systems were considered safe.

That said, Im very cautious making sure I take the same precautions as I would with a 240V AC system when working on my 48V system
 
i grabbed once in a 12v 30a dc power supply, lucky for me it was grounded, yah, it stings...
I thought it was disconnected from the grid, always check.

In the Netherlands you don't need papers if you are working below 62v.
But this information is 25 years old, things could have changed a bit.
 
treat it as if it is live.
keep 1 hand in your pocket just like you should with any live equipment.
getting hit is bad enough.
getting hit via a path through your heart is deadly.
i work on lots of hv dc stuff.
600v dc bus for vfd units (industrial motor drivers),plate supplies for rf power amplifiers(linears),ect.
 
I asked for what the limit was to work on in the Netherlands: it is still below 62v without papers above you are not allowed to do anything without papers.
But even with dry hands....48v and a 50kwh battery touching both terminals....nah i believe you, in everything you are saying, i am not going to try, or find out.
Put fuses everywhere and be safe please.
Look into one of the videos of this forum founder: hb powerwall.
He had a small mistake with one of his batteries.....
Can not remember exactly which one, but it was a huge spark...we all make mistakes, but we don't say or show.


@kc8adu.
Back in school they always taught me to touch after you make sure everything was safe, with the back of your hand.
And be careful with those thick and long wires cause they could act like a capacitor.
When talking about 10kv lines ac or bigger in those transformer houses, always after shutdown and after the discharge cablethrow your rat to the coils...
Was 30 years ago when they tried to teach me something :rolleyes:, i suspect there are now some sophisticated measurement devices?
I am just curious, sorry

Thanks in advance.

kc8adukc8adukc8adu
 
I think most of you are being overly dramatic.

You'd just about have to try to be injured with anything 50V or lower on AC, let alone DC. Most countries don't even have regulations for anything below 50v.

Most of the time, you could grab 120vdc and it would hurt a bit, but you'd be alright.

AC is far more dangerous than DC because of your body's capacitive coupling.

Do you guys know ElectroBoom? Here's him hooking up 10 car batteries in series (123vdc) and touching it. He gets surprised at first that he can even feel it, but he can touch it without problem. And he's a sweaty kind of guy.


Protect it if you want, but, I wouldn't be overly worried.
 
Wet skin, especially sweaty skin, can and will conduct more current than dry skin. If dry skin and touching 60VDC both lines, then the chances of getting electrocuted is very very low. DC current must "punch" through the skin to the deeper more conductive tissue before it can flow. AC current doesn't need to do this, so lower AC voltage can allow current to flow sooner.
However, at 120VDC wet and especially sweaty skin, current will be able to penetrate the skin and conduct a short circuit through your body. Whether that path goes through your heart or not will determine if you live through the process. Also, duration is a factor. If you let go soon enough, no harm.
120VDC will have a much harder time penetrating callused skin than thinner skin. As Matt is referencing ElectroBoom (whom I find to be very annoying, imho), his hands are not exactly soft. He's got rough hands. Maybe this is why it didn't effect him. I bet if he put the wires under his arm pits, he'd get a nice hot spot if not a burn mark.

We here on SLS in no way advocate or downplay the safety factor of voltage and current. It only takes 2mA of current to kill a person. A single 18650 cell can deliver that much current. However, it's voltage can't penetrate. Scale the voltage up with series connections, and even a 1p setup, could make for a very bad day for someone.
Safety is primary above ALL other things. I personally have been bit by 12VDC, so I "know" that higher voltages has the potential of doing damage if the conditions are right. ALWAYS work with electrical connections with dried hands. NEVER work with wet or sweaty hands. It only takes a slip up to get bit, especially at the higher voltages.

Are we being overly dramatic? Maybe. Are we being cautious so we don't get electrocuted? Most definitely. Electricity has the potential to kill, and kill "very" rapidly if not treated with respect, and this doesn't matter if it's AC or DC.
 
As Matt is referencing ElectroBoom (whom I find to be very annoying, imho), his hands are not exactly soft. He's got rough hands.

Medhi's hands are both abnormally soft and sweaty. I mean, I wasn't on stage touching him during the presentation, so perhaps he made special efforts to dry them, but it was his first public appearance and he was nervous as hell.

He is (well, was, before being a content creator) an engineer, not a welder or fabricator.

It only takes 2mA of current to kill a person. A single 18650 cell can deliver that much current.

Err, suppose that's true, that's still a bit like saying "The world's Strongman winner can lift a paperclip!".

A single 18650 can deliver 20,000x the amount of current required to kill you.

But... 2mA is not a realistic estimate.

See here: https://en.wikipedia.org/wiki/File:IEC_TS_60479-1_electric_shock_graph.svg

Below 500mA, (250x your lethal minimum) effects are reversible for short shocks. Lowest that's fatal is still 15x your minimum, at 30mA. 2mA isn't debateably even reaching the threshold of sensation yet, let alone lethality.

It's common in developing countries to have bad grounds on half your appliances, such that you get zapped a little when you touch them.

However, these are all still practically microscopic amounts to anything a human will encounter. Almost every piece of electronics and every power source ever made aside from maybe the solar cell on your calculator can deliver enough current to murder you.

It's almost not worth talking about current, only voltage.

And yes, most everything else you said is correct.

Even if the odds are 1 in a million, (that poor sap who died from 42vac) you don't want to be the lottery winner. So, to someone who has to ask, the answer to behavior I suppose should almost always be to treat electricity like a loaded firearm. Safety safety safety, use no judgment, make no assumptions, do the safest thing.

But for a reasonable person in most reasonable circumstances, you won't even feel voltage below 50vdc. The world record for fatality, is 42vac. If you keep a consistent level of paranoia (with respect to consistent odds of a behavior being fatal) of your behaviors across all aspects of danger in your life, there are thousands of everyday things you should be avoiding before you should be scared of voltages below 50vdc. Never play a sport. Never move faster than a walk. Never go outside. Never enter a car. Never walk down a street. Never sip a beer. Etc.

We here on SLS in no way advocate or downplay the safety factor of voltage and current.

Genuine question...

Does SLS even have an official voice with the authority as to what "we" advocate or not? I'm not familiar.

My perception is that this is a community, and thus makes no official claims of safety, danger, endorsement, condemnation, or other opinion. It's just a group of people with their own opinions. Bit of a slippery slope to start making official representations of authority on anything, safety or otherwise, lest anyone miss moderating a comment and then be held responsible for the content of what was said unchecked.
 
I dont know what rules in most country's, but here in the Netherlands is max62vdc without papers.
After the ac fuse box you are allowed to do the installation yourself, everything is at your own risk, but it is allowed to do yourself, above 400v ac nope.
 
I has a lot to do with the individual as well, I can sometimes feel the effect of a 12v battery, while friends cant. This is mainly due to the individuals skin resistance and moisture, salt levels and the amount of dead skin.
Dead skin is also a reasonable insulator compared to muscle and nerves.
What really needs to be taken into account is the voltage and resistance of the body and where its being applied, dry skin has a typical resistance of approx 100,000 ohms, wet new skin is approx 1000 ohms, the amount of distance between where the voltage is applied also plays an effect, as well as men having a lower resistance then women too.
A 3.7v battery touching dry skin could cause a current flow of approx 3.7/100,000 = 0.037mA , the same on wet skin is 3.7/1000=3.7mA, however skins dielectric effect also comes into play with DC as mentioned above and negates most of this. Theres lots of variation in all of this of course. Best to be careful over 50v, especially if you have hands that are wet or with soft supple skin :)
 
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