# Staying alive - electrical safety.



## Woodsmith (Jun 5, 2008)

The last really big pack I worked on. That is 3p51s of 200Ah cells.









All the spanners and other tools were insulated.
Plywood boards were placed over the pack so that only the area we worked on was exposed.
The pack was tested with many fuse links to split the pack into manageable sections.
As the cells were linked in groups of three parallel cells to get 600Ah we needed to make sure the bus bars were installed correctly. This was always done with two people, one fitting and one checking, to make sure the bars went across the right terminals.

When it was installed in the car the same process was used and each row of cells ended with a fuse link which was only put in afterwards. That meant that during installation there was only the voltage of one row.
Before connection of any cells two of us separately checked all the cells were correctly orientated relative to each other and only when we were both satisfied did we get spanners. Then it was two other people to make sure each connection was still right.


----------



## Ziggythewiz (May 16, 2010)

I heatshrinked all my tools after my first such incident (just this month, after nearly 2 years of working/driving). 

Yes, you can touch a single point in the pack, not two. Don't touch one unless you need to, and when connecting things be sure to touch metal to metal first.

Try to size busbars or other connectors so they can't swing and hit another...btw, how did yours turn? busbars are usually connected to two points.

Put insulation on anything where a short could occur, such as a metal strap latch that rests between batteries.

Use mechanical disconnects, and use them whenever you're working around the pack.

Keep the pack covered, in a box or at least by a tarp or similar to keep things clean and safe.


----------



## Tesseract (Sep 27, 2008)

lowcrawler said:


> ...
> Can you touch a positive as long as you are also not touching another battery terminal? Do I ever need to worry about touching ONE point in the high voltage loop?


At a high enough voltage just touching one terminal can shock you - if not electrocute (that is, kill) you - because it can force enough of a current flow through the atmosphere, your clothes, shoes, etc., for you to feel it. In general, we don't work with voltages in an EV high enough to do more than barely tingle if you were to touch one terminal (and polarity, by the way, is irrelevant).

That said, you still don't want to touch *any* terminal which is at traction pack potential just in case there is already a path to "ground" (ie - the vehicle chassis) somewhere else. The two most pervasive cause of such current leaks are dust from the brushes and condensation/spilled electrolyte on top of the batteries.

Use insulated tools and, where possible, try to follow the old electrician's rule of keeping one hand in your pocket when working on even supposedly dead traction pack circuits. 



lowcrawler said:


> ...Most 'centralized' BMS wires, as far as I can tell, carry pack voltage -- how do you keep the dozens of wires that all need to be on terminals 2mm from each other from touching? If they did, what's the real risk?


Assuming the wires have an insulation rating appropriate for the total pack voltage, they can all touch each other.

A centralized BMS that only monitors cell voltage should use - in my *opinion* - teflon insulated wire, which can be purchased for a reasonable price as surplus. If the BMS also actively balances the cells with a shunt then you should add a fuse to the cell-terminal end (said fuse needs to be capable of interrupting the full pack voltage, btw, which can be a tall order for a low-amperage fuse combined with a high pack voltage.



lowcrawler said:


> We shoudl 'wrap' our wrenches and tools in electical tape -- but does that really stop 160V+ or is it just for our own 'feel good'? Is standard "automotive" wire acceptable for low amperage, pack-voltage connections?


Any tape that says it is for electrical applications must actually pass some dielectric strength and flammability tests so, yes, it will stop 160V+ (a typical rating for vinyl electrical tape is 600V per single layer).

Standard "automotive" wire is generally *not* acceptable for carrying pack voltage. Anything rated for "AC wiring" use is going to have much tougher insulation, such as THHN, THWN, MTW, etc. Alternatively, the teflon insulated wire above is my number one choice.


----------



## lowcrawler (Jun 27, 2011)

Good ideas, all. Any others?



Ziggythewiz said:


> Try to size busbars or other connectors so they can't swing and hit another...btw, how did yours turn? busbars are usually connected to two points.


I put the (first) busbar spanning to the next cell , started screwing in the bolt on cell and the bus bar must have caught as I was turning. It turned with the screw 90 degrees before I realized "hey, that's not a good idea" and it started a little spark show. Given that's just the potential from ONE cell, and I've got 48 it really drove home how much deadly power we are messing around with here.

I've since gone through about 3 rolls of electrical tape. 




Ziggythewiz said:


> Yes, you can touch a single point in the pack, not two. Don't touch one unless you need to, and when connecting things be sure to touch metal to metal first.





Tesseract said:


> At a high enough voltage just touching one terminal can shock you - if not electrocute (that is, kill) you - because it can force enough of a current flow through the atmosphere, your clothes, shoes, etc., for you to feel it. In general, we don't work with voltages in an EV high enough to do more than barely tingle if you were to touch one terminal (and polarity, by the way, is irrelevant).
> 
> That said, you still don't want to touch *any* terminal which is at traction pack potential just in case there is already a path to "ground" (ie - the vehicle chassis) somewhere else.


So that brings up the question that kind of was the impetus for this question. We aren't supposed to touch the terminals or anything at traction pack voltages (for me, 150V)... yet we do, in fact, need to assemle these things. How are you connecting the last few batteries if you aren't touching them? Ya know?


----------



## Tesseract (Sep 27, 2008)

lowcrawler said:


> ...So that brings up the question that kind of was the impetus for this question. We aren't supposed to touch the terminals or anything at traction pack voltages (for me, 150V)... yet we do, in fact, need to assemle these things. How are you connecting the last few batteries if you aren't touching them? Ya know?


By wearing gloves?

Seriously. These gloves are good for working on the pack as they are thin enough to allow for good dexterity yet the rubber coating is a pretty dependable insulator.


----------



## lowcrawler (Jun 27, 2011)

Interesting. I've been doing research on this for a year and I've never heard of people advocating the use of electically-insulating gloves before.

Nice.

Are they really required, or are you probably safe at 150V using the 1-hand trick?


----------



## Ziggythewiz (May 16, 2010)

Nothing is required. Just recommended. I don't have any gloves, but don't get shocked too frequently. Also, don't know how anyone does anything one-handed. Almost all my shocks were one-handed.


----------



## Tesseract (Sep 27, 2008)

lowcrawler said:


> ...Are they really required, or are you probably safe at 150V using the 1-hand trick?


Depends. Seb shocks himself all the time working on the battery pack in the Porsche 911 because those new Helwig brushes seem to be throwing off a huge amount of carbon dust. He neither wears gloves nor puts one hand in his pocket and suffers the consequences. Maybe one day he'll depolarize his atrioventricular node and that will be the end of tinkering on that infernal Headway pack for Seb.


----------



## Woodsmith (Jun 5, 2008)

Tesseract said:


> By wearing gloves?
> 
> Seriously. These gloves are good for working on the pack as they are thin enough to allow for good dexterity yet the rubber coating is a pretty dependable insulator.


I use very similar gloves, mostly to keep my hands clean, but also good for working on the pack.

Funny thing though, I work on live 240V ac bare hands and have never had a shock.


----------



## tomofreno (Mar 3, 2009)

If you aren't going to wear gloves, at least cultivate the habit of checking continuity between the pack and chassis ground each time to ensure it is an indefinitely high resistance before doing any work on the pack. Check that the point is a good ground by checking continuity between it and another ground point. 

Also plan out step by step exactly what you are going to do and how you are going to do it, thinking about possibilities for mishaps, then execute those steps carefully. Many times it is after things become routine that we become complacent and make mistakes due to lack of thought.


----------



## aux_man (Feb 2, 2012)

Is there any regulatory admin on EV? Recreational boats have the Coast Guard and ABYC.


----------



## lowcrawler (Jun 27, 2011)

tomofreno said:


> If you aren't going to wear gloves, at least cultivate the habit of checking continuity between the pack and chassis ground each time to ensure it is an indefinitely high resistance before doing any work on the pack.


And how would one do that?


----------



## Ziggythewiz (May 16, 2010)

aux_man said:


> Is there any regulatory admin on EV? Recreational boats have the Coast Guard and ABYC.


It's called DPS or DOT, every state has one, but most probably don't know what EV means.


----------



## mizlplix (May 1, 2011)

Along that line, I use simple vinyl gloves on my hands with common cloth gloves over them. Plenty of di-electric strength and easy to work in.

For more serious things, I have an issue pair of 480 volt certified {but out of date} linemans gloves. Cloth inner, rubber middle and leather over gloves, all kept in the mesh bag.

My only real shocks on an EV have come from supposedly dead circuits.....I assume they were powered by those caps in the controller. They were traction cables to chassis ground with the pack disconnect off.

Just a "tickle" really.

Miz


----------



## tomofreno (Mar 3, 2009)

lowcrawler said:


> And how would one do that?


 With a Digital Volt Meter, DVM. Adjust it to the setting for measuring resistance. Hold one of the probes on the chassis ground point you intend to use to measure resistance between the pack and ground, and the other probe at another chassis ground point. Resistance should read zero. Then hold the second probe at a point on the pack, a bus bar or cell terminal, with the first probe still held at the ground point. Resistance should be off scale, indefinitely high, if the pack is isolated from ground as it should be. Checking continuity means checking if there is a continuous path for current flow between two points.


----------



## PThompson509 (Jul 9, 2009)

When I'm working on my 370v pack, I use nitril gloves. I don't like it, but I REALLY don't like the idea of electrocuting myself on my own car. So sweaty hands are a minor handicap as far as this goes.


----------



## algea07 (Oct 1, 2010)

brace yourselves there is a potentially stupid question coming.

I had thought that people where relatively well insulated, and i had assumed that made us relativity safe at low voltages, and that 3.7v even at high currents couldn't hurt us. 

if this isn't the case that's cool, if this is the case what voltage is it safe to work with. Could you break the pack up into a safe voltage, then use simpler Anderson connectors to conect the harmless low voltage packs to create the high voltage pack? this way you aren't fiddling with bus bars and a spanner on a 300V pack.


----------



## tomofreno (Mar 3, 2009)

algea07 said:


> brace yourselves there is a potentially stupid question coming.
> 
> I had thought that people where relatively well insulated, and i had assumed that made us relativity safe at low voltages, and that 3.7v even at high currents couldn't hurt us.


 That is generally correct. The danger is that you contact different parts of the pack with larger voltage difference, or your pack is not isolated from the chassis and you touch a terminal on the pack while in contact with the chassis. With the potential for thousands of amps to flow, you don't want to explore what amount of voltage is too high though, and skin conductivity is increased if your hands are sweaty. I suppose you could use large Anderson connectors rated for your magnitude of discharge current, but they are another interface so another power loss.


----------



## Ziggythewiz (May 16, 2010)

You'll never get 1000s of amps going through you. Your IR is significantly higher than that of the batteries. It doesn't take a whole lot though, if the voltage is high enough to push it across your chest.


----------



## mizlplix (May 1, 2011)

I believe that the fire department is more concerned about electric vehicles than the state DOT or DMV here in Arizona.

I have had several conversations with firemen at Hot Rod functions and they all tell the same story. Inconsistent construction among "home builts"

Factory cars are somewhat engineered. They are more numerous and can be trained for easier.

Home builts are generally all different. Other than all having batteries and electric motors, they are different from each other in component placement, battery mounting and safety features. 

The fire Department teaches their personnel to cut the main pack cables if any smoke exists. They use standard safety gear,cable cutters and rubber gloves.

They are taught to not spray on anything if possible, use CO2 as second choice, foam as third choice then to simply stand back and wait for it to stop reacting.

Their biggest complaint is no standard disconnect placement. The NHRA requires one on the rear/center of the cars external body work. Clearly marked and RED. I would add it to be up higher than bumper height and out of the "crash" zones for street car use.

Or maybe an extra contactor mounted mid-pack. Have it connected to an inertial switch like all cars have when using high pressure fuel injection. When a large enough crash happens, it cuts the pack circuit, but is instantly reset-able if it is safe to do so {it seems to work on ICE vehicles}.

Miz


----------



## GizmoEV (Nov 28, 2009)

mizlplix said:


> Their biggest complaint is no standard disconnect placement. The NHRA requires one on the rear/center of the cars external body work. Clearly marked and RED. I would add it to be up higher than bumper height and out of the "crash" zones for street car use.


My concern with an externally visible disconnect is "vandalism" if that is what it could be called. It would be readily accessible to just reach out and kill it as someone walks by. How do you place such a device where it can be used in an emergency but passers-by won't know it is there?



> Or maybe an extra contactor mounted mid-pack. Have it connected to an inertial switch like all cars have when using high pressure fuel injection. When a large enough crash happens, it cuts the pack circuit, but is instantly reset-able if it is safe to do so {it seems to work on ICE vehicles}.


I remember seeing on a Tesla Roadster that there was a loop of small wire, under the hood IIRC, that had a label that said something to the effect of "cut wire for pack disconnect." I assume it was for such a contactor.

I guess for a mid pack contactor to be a reliable disconnect it would have to be energized by the pack, maybe with its own DC-DC, so that when the inertia switch tripped it would open up. The problem is, how to initiate the initial closing of the contactor? Are there contactors which have a manual enable option but which need power to remain energized? Maybe use a shorting bar across the main posts to get started.

As I think about this more one could have several places through out the vehicle where the coil wire could go with loops which could be cut in an emergency, much like on the Tesla Roadster, in addition to the inertia switch. For manual disconnect just pull out the fuse operating the contactor.


----------



## Ziggythewiz (May 16, 2010)

GizmoEV said:


> I remember seeing on a Tesla Roadster that there was a loop of small wire, under the hood IIRC, that had a label that said something to the effect of "cut wire for pack disconnect." I assume it was for such a contactor.


So there is an unplugged storage mode!


----------



## PThompson509 (Jul 9, 2009)

Are there examples of "standard" cutoff switches that we could see? I'd prefer to have a standard in use than a non-standard that the firemen didn't know about.

Cheers,
Peter


----------



## Ziggythewiz (May 16, 2010)

Mine looks like this. It's pretty much a a worldwide standard that a round red button stops stuff. Mine's mounted on the left of the instrument panel, easily to the driver or from outside (once door is opened).

I like what was mentioned above though, about cutting wires with isolated tools, etc. People seem to freak out about it alot, but I'm pretty sure most 1st responders aren't cutting cars open with their bare hands.


----------



## PThompson509 (Jul 9, 2009)

Ah, yes, I've seen a similar button. However, in order for the first responders to be absolutely sure, they need a button on the outside.

The first responders are actually being trained on how to cut The Big Wires, and when to just let the car burn. I was a volunteer fireman for 6 years, and we got training in just that sorta stuff. Lots of fun. 

I guess I'll go mouse around and find out what the NTSB and others are looking for us to have.

Cheers,
Peter



Ziggythewiz said:


> Mine looks like this. It's pretty much a a worldwide standard that a round red button stops stuff. Mine's mounted on the left of the instrument panel, easily to the driver or from outside (once door is opened).
> 
> I like what was mentioned above though, about cutting wires with isolated tools, etc. People seem to freak out about it alot, but I'm pretty sure most 1st responders aren't cutting cars open with their bare hands.


----------



## Ziggythewiz (May 16, 2010)

Outside a racing application, I can't imagine ever having a disconnect, either button or large cable, on the outside. That's just rediculous.


----------



## MN Driver (Sep 29, 2009)

PThompson509 said:


> Ah, yes, I've seen a similar button. However, in order for the first responders to be absolutely sure, they need a button on the outside.
> 
> The first responders are actually being trained on how to cut The Big Wires, and when to just let the car burn. I was a volunteer fireman for 6 years, and we got training in just that sorta stuff. Lots of fun.
> 
> ...


No, not on the outside. ..and first responders are trained to NOT cut orange wires.
Please read this before you say that first responders are trained to cut "The Big Wires"!!!
21 automotive manufacturers resources for fighting a fire, cutting the car, and rescuing a vehicle when submerged in water.
http://www.evsafetytraining.org/Resources.aspx

Based on what I've read there, I think there should be a big orange sticker under the hood nearby the high voltage wires indicating how the high voltage contactor should be disabled. This is the one place where a firefighter is most likely to get themselves killed if they make a mistake. I'll have mine orange with 'Emergency Responders' and that indicates to shut off the ignition and I'll have a mid-pack contactor that splits the pack in half and another disconnect accessible nearby where Honda already has it on my car. Since I'm converting a hybrid, the idea is that I am doing a SEVERE disservice to not duplicate EVERY safety measure that my car already has so I need all high voltage wiring outside of the battery enclosure dead with the ignition off. I'm also going to add a high voltage neon 'on' bulb under the hood near my Emergency Responders sticker.


----------



## MN Driver (Sep 29, 2009)

Ziggythewiz said:


> So there is an unplugged storage mode!


2008 Tesla Roadster you do this.
1. Press trunk release button or turn the key counter-clockwise to open the trunk.
2. Remove SRS(airbag) and HV safety cover.
3. Cut black loop between the two arrows.

2009+ Roadster
1. Open hood using release to the left of steering wheel.
2. If you can, insert prop rod to hold the hood up.
3. Cut yellow loop at the arrow to safely disable SRS(airbag) and HV.

It doesn't look like you could easily splice these back together either, they are thick cable and a very short loop. It looks like once you've severed it you'll be calling up Tesla.


----------



## mizlplix (May 1, 2011)

After doing some research, I have found some interesting things.....

Most OEM disconnect switches or controls are orange, not red.

Most OEM built cars have the disconnect switches or controls in the trunk areas.

Many have external markings along the HV current cable paths.

Most all have a combined system to shut off low and high voltage as well as gasoline flow on a large impact.

http://evsafetytraining.org/Resources/Auto-Manufacturer-Resources/Tesla-Motors.aspx

This link leads to almost all electric or hybrid car safety systems in PDF form.

Miz


----------



## lowcrawler (Jun 27, 2011)

So this thread seems to have taking a turn into the typical 'safety' discussions we have here -- first responder, fuses, cutoffs, etc.

Does that mean we've exhausted all discussion on how to BUILD your pack without killing yourself? Just put on some nitrile gloves and hope? That doesn't sound right...


----------



## Duncan (Dec 8, 2008)

Hi Lowcrawler

I have the bits for my pack but I haven't yet assembled it

My pack is 88 Headway 16Ah cells 44S2P (little pack for short range)
It is split into two halves with an Anderson connector 
The full pack voltage goes to an old forklift connector thing

Assembly
Cells in support structure
square copper connectors bolted onto the bottom, the rest of the bottom structure is screwed on - pretty safe so far

square copper connectors bolted onto the top - definitely need safety glasses for this step - don't think I can electrocute myself but a carelessness could result in a spark
Rest of the top structure is screwed on

The battery box is now compete and safe until I plug in the Anderson connector

I can make the car safe by removing the Anderson connector and doubly safe by undoing the fork lift connector


----------



## Ziggythewiz (May 16, 2010)

lowcrawler said:


> So this thread seems to have taking a turn into the typical 'safety' discussions we have here -- first responder, fuses, cutoffs, etc.
> 
> Does that mean we've exhausted all discussion on how to BUILD your pack without killing yourself? Just put on some nitrile gloves and hope? That doesn't sound right...


There were quite a few other suggestions beyond the use of gloves. I suggest you re-read.


----------



## lowcrawler (Jun 27, 2011)

Ziggythewiz said:


> There were quite a few other suggestions beyond the use of gloves. I suggest you re-read.


No, you are right.

I was just frustrated because it seems every 'safety' thread turns into "emergency responder" stuff. Almost like we are more interested with buying more stuff and accessories than talking about being safe with the stuff we have...

Sorry, I was sick and my patience was thin.


----------



## PThompson509 (Jul 9, 2009)

I understand the frustration, but seriously - most of the precautions are what should be common sense (yeah, yeah, I know it *isn't* common. 

I'll try to summarize:

Work rules:
1) Don't wear jewelry.
2) Wear anti-conductive gloves.
3) Use tools that have anti-conductive coatings.
4) Cover areas you aren't working on with non-conductive covers.
5) Use one hand at a time if possible.

Battery and Connector rules:
1) Always have a fuse inline with your pack. 
1a) More fuses are fine as long as they don't have too much resistance.
2) Always have a safety disconnect.
3) Invest in an intertial breaker to shut off your contactor.
4) Make sure your batteries are someplace that doesn't get wet.
5) Make sure your batteries are someplace that people can't easily get into.

I'm sure there are more, but those seem to be pretty good ones to me. 

Cheers,
Peter


----------



## mizlplix (May 1, 2011)

There have been so many common sense but good tips on pack building, it could really fill a book.

For my own part, After I receive my cells, I plan to equalize them, then assemble them into 5 cell units. These 5 cell units fit into the space of 1-6 volt golf cart battery. I must make 6 of them, then 2- 4 cell units, giving me 38 cells on a 120 Volt pack.

My plan is to use 1/8" aluminum plates at each end with 3- 3/8" plastic shipping bands around them. This stuff is strong. I use it every day and it still amazing at the strength. 

At this point I plan to put the cell electrical straps on the 5 cell units, then install into car before installing the inter connecting straps. This gives me only about 18 volts to work around during the bulk of the hand work.

After all units are installed in the battery boxes, I can inter connect them, still leaving the contactor, main disconnect and inter-pack disconnect open {off}.

If I have any reservations, I can simply lay an old blanket over the cells in the battery box and work through a hole, like surgeons do when they operate {except the majority dont use an old blanket}

If you want to complicate things, lets talk about adding capacitors to the pack and charging them....Batteries are pretty straight forward if you remember that they are a little more than an old flash light.

I see no real reason to get crazy if routine precautions are observed. Then again, years ago, I used to work as a powder monkey and you develop decent safety habits....static grounds...non sparking tools...Etc.

Miz


----------



## lowcrawler (Jun 27, 2011)

Tess said:


> Standard "automotive" wire is generally *not* acceptable for carrying pack voltage. Anything rated for "AC wiring" use is going to have much tougher insulation, such as THHN, THWN, MTW, etc. Alternatively, the teflon insulated wire above is my number one choice.


This page recommends auto wire and specifically says not to use thhn.... thoughts?


http://www.austinev.org/evinfo/build/eva-safetyfirst.html


----------



## lowcrawler (Jun 27, 2011)

Is the any concerns about dangerous arc faults at DIY EV power levels? 

My research reading shows 120v*ac* is the lower end of where you cease to have to concern yourself with arc faults or massive explosion type stuff... but i'm having no luck finding comforting info on DC stuff. (not because I'm finding _bad_ stuff -- it's just the main computational method of arc fault protections for AC involve things DC doesn't have.

(Better to be over safe thab under - never assume anything)


----------



## Tesseract (Sep 27, 2008)

lowcrawler said:


> This page recommends auto wire and specifically says not to use thhn.... thoughts?
> 
> 
> http://www.austinev.org/evinfo/build/eva-safetyfirst.html


There are lots of good tips on that site, but the author of that page did not specify *why* the insulation on THHN, etc. might eventually crack; my suspicion is he (she?) is concerned that extreme vibration or repeated flexing of the wire will crack the insulation.*

I suppose that is a valid concern, but my counterargument would be that you can take steps to minimize the amount of flexing, abrasion, etc., that your wiring must endure, but you can't do anything to minimize the voltage it will have to carry. 


* - more specifically, it is the nylon outer jacket on THHN wire that tends to get damaged from mechanical abuse. Indeed, the nylon overcoat is routinely damaged when pulling the wire through conduits (aiding such pulling is the purpose of the overcoat) but as long as the main insulating layer of PVC underneath is unharmed the installation is code-acceptable.


----------



## lowcrawler (Jun 27, 2011)

Thanks for the quick answer. Any thoughts on Arc Faults or other electrical explosions at all?


I also wonder about fuses -- the Soliton Jr in my car can peak to 600A... yet I was recommended to get a 400A fuse. First, this makes no sense to me... but when you are in the theoretical stage and haven't seen dozens of videos of firey electrical explosions you just take it as a given that what other say is okay with very little need for 'supporting evidence' or understanding it yourself. From what I can guess, it appears it's simply a 'time delay' type thing... This "fuse opening time" section on this page seems to support that theory.

Given that's the case... and in an arc-fault or other plasma-inducing situation (think: car accident) wouldn't you want a fuse that popped IMMEDIATELY once over a level you know your car should NEVER pull? 
For instance --- have your normal 400A A30QS as everyone recommends, (which if what I read is correct (please correct me if I'm wrong), can pull up to 1500A for a tenth of a second (times 150V is a heck of a lot of energy... no?) ) and then something like a fuse that blows IMMEDIATELY if seeing anything over 700A (for a 600A soliton jr-based system)? Does a fuse like that exist? Is it a worthwhile concept?

Given most of us have two main fuses anyway (a main and then a backup 'mid-pack' one... why not try to meet both these goals? Any how?)


----------



## Tesseract (Sep 27, 2008)

lowcrawler said:


> Thanks for the quick answer. Any thoughts on Arc Faults or other electrical explosions at all?


This is too open-ended of a question; please be more specific. 



lowcrawler said:


> I also wonder about fuses -- the Soliton Jr in my car can peak to 600A... yet I was recommended to get a 400A fuse. First, this makes no sense to me.......


I give a very brief explanation as to why I recommend a 400A fuse in the battery circuit on page 7 of our manual. To recap for those too lazy to read it: the fuse is there to protect the insulation on the wiring from melting due to prolonged overcurrent, it is not there to protect the controller or motor. For example, this datasheet shows a 300V rated 400A Class-T fuse from Mersen will pass 1000A for 10 seconds before blowing; a 600V version of that fuse will pass 1000A for *50* seconds before blowing.

NOW do you see why a 400A fuse on the battery side is fine for even a Soliton1 installation? If you are pulling 1000A of battery current for 10 seconds then I guarantee you just cooked your motor, and unless you have 4/0 cable, you probably cooked the high power wiring, too.



lowcrawler said:


> Given that's the case... and in an arc-fault or other plasma-inducing situation (think: car accident) wouldn't you want a fuse that popped IMMEDIATELY once over a level you know your car should NEVER pull?


There is no such fuse; only an electronic circuit can respond to an overcurrent that fast.


----------



## Ziggythewiz (May 16, 2010)

You need to consider the source of arc faults or explosions. An arc fault would mean a spark gap that is insufficient for the voltage you're using, so use stuff that's rated for your voltage. An explosion requires explosive materials, typically gasses, so don't have sparks around flooded batteries. Also don't tax your electronics.

For the fuse, most use a slow blow type fuse, that means it's designed to allow a variable amount of overcurrent depending on the time. In a full on short it would blow pretty quick.

There are quick blow fuses, but they would probably be expensive, and say you have one of those sparky events, do you really want to have to replace a very expensive fuse vs just feeling embarrassed?


----------



## lowcrawler (Jun 27, 2011)

Ziggythewiz said:


> You need to consider the source of arc faults or explosions. An arc fault would mean a spark gap that is insufficient for the voltage you're using, so use stuff that's rated for your voltage. An explosion requires explosive materials, typically gasses, so don't have sparks around flooded batteries.


It's my understanding the in an arc fault situation you actually end up vaporizing your 'wire' into an electrically conductive plasma at insanely high temps... it's not a hydrogen explosion, that's tame by comparison. (again, just going by the research I'm doing... looking at gaining insight into exactly why/how things end up safe or not)

A standard 480V three-phase faulting at 20kA is roughly equivalent to .8 pounds of TNT going off. I'm just looking to see if we are in the 120V/125kVA tranformer range (where it doesn't matter) or in the "TNT explosion" area...



Tesseract said:


> This is too open-ended of a question; please be more specific.


Specifically, arc faults in industrial/commercial wiring are extremely dangerous. But in <120V installations with less than 125KVA transformers, it's really not an issue because there isn't enough energy to really create an arc fault or blast that really does damage enough that the explosion/blast causes much damage... thus leaving electrocution/shock as the only real concern.

... but that's AC... not DC. I was wondering if you knew of any guidelines about DC stuff in this regard. I haven't been able to find any yet.




> I give a very brief explanation as to why I recommend a 400A fuse in the battery circuit on page 7 of our manual.


 That was actually the first thing I ever read that gave me reasonable understanding of the issue back in the day. Drives home the idea of 'fuses protect the wires'. Well done.



> There is no such fuse; only an electronic circuit can respond to an overcurrent that fast.


Bummer dude. Just to verify my understanding, however... if one did exist, it would be a reasonable idea, right?

Ziggy -- I think the A30QS is labeled 'quick blow' ... right? am I mis-reading something?


----------



## Ziggythewiz (May 16, 2010)

lowcrawler said:


> A standard 480V three-phase faulting at 20kA is roughly equivalent to .8 pounds of TNT going off. I'm just looking to see if we are in the 120V/125kVA tranformer range (where it doesn't matter) or in the "TNT explosion" area...
> 
> 
> Ziggy -- I think the A30QS is labeled 'quick blow' ... right? am I mis-reading something?


I don't think you need to make comparisons between EVs and 480V @ 20kA. I'm not aware of anyone running a significant fraction of that power. I think the risk is only the shock unless you are manually causing the plasma ball, or in close proximity to a plasma inducing device.


I don't know the details on the A30QS, but most fuses are fast, normal, slow, some are ultrafast. I assume a quick is somewhere between fast and normal, so not that fast. 

For all types speed is relative, so the higher you are over the rating, the faster it blows. In an accident you may have a full on short which will be whatever your pack can put out, which will break most fuses pretty quick.


----------



## palmer_md (Jul 22, 2011)

Here is an interesting read on the subject....

http://www.plasmaboyracing.com/blog/?page_id=10


----------



## DanGT86 (Jan 1, 2011)

Another safety related issue that I encountered with my car was the chassis grounded 12v/110vac wall wart power supply that ran chassis grounded 12v fans and a dash light during charging. AC current was leaking through that power supply and would give me a jolt when I leaned on the chassis. Was 43vac measured between the chassis and the 110v outlet ground. Turns out the ground prong was not connected behind the car's charge port either. Seemed odd to me. I bought the car already converted.

In general I don't like the idea of anything plugged into the AC charging system sharing grounds with the chassis in normal operation. Same goes for pack voltage being chassis grounded. Seems like there would never be reason to chassis ground the pack. 

Shortly after I got the car the controller blew up. Because the controller body was not isolated from the chassis and the 12v cooling fans were grounded to the controller body, I was getting pack voltage 155vdc in all kinds of random places. It was a nightmare.

The safety precautions that seem redundant or unnecessary under normal conditions become very important when things go wrong. In my case I couldn't trust any part of the car not to have dangerous current.

Watch out for cheap wall warts.


----------

