How safe from electrical shock are you in an electric vehicle?

[slimjim]

When I was an apprentice, we use to use the 70v etcher connected to metal tools strategically placed on the bench, so that anyone borrowing your tools would get a shock, seemed like fun at the time.

 

[Pigeon_Droppings2]

When I was an apprentice, we use to use the 70v etcher connected to metal tools strategically placed on the bench,

As kids we used to reverse wire step down transformers to batteries to zap each other...I remember it being lots of fun....probably get put in prison now for that!

 

[mtt.tr]

I googled which is more dangerous....turns out AC is a lot more dangerous than DC....I can't remember if I knew that!

Causes fibulation easier

 

[Robotstar5]

Causes fibulation easier

I suspect you meant Fibrillation?

 

[eLuSiVeMiTe]

Well like when removing the leads from a 12V battery, I'm assuming that you wouldn't see a spark when disconnecting the negative first.

Umm.
You disconnect negative first to isolate the supply from the chassis.
Other way around any metal touched with the positive lead will complete the circuit.

 

[eLuSiVeMiTe]

Disconnecting earth lead first/reconnecting last has got nothing to do with arcing under load, it's about avoiding the possibility of shorting the spanner to an adjacent metal part as you tighten the battery clamp, or if you're clumsy with the jump lead.

That's only to stop have a live lead loose that can easily arc on any other part of the vehicle

As neutral is at same potential to the chassis no spark

Beat me to it. Teach me for not reading ahead.

 

[outofthefire]

Was the cladding on Grenfell a firewall?

That sounds like a bit of a far stretch of wataboutery if you ask me.

I don't know what wataboutery means, but what I was saying is wooden cladding isn't used on highrises because it's obviously flammable, whereas as most folk assume metal isn't, so is safe to "clad" or use as a "firewall" if the fire gets hot enough ally will catch fire wether its cladding a building or in a car (though granted it will hopefully give you time to get out of the car)

Regarding the 400v battery packs, the problem is that in crashes they can be damaged, but in normal use they are pretty isolated, and there’s no reason for a diyer to have them apart to service a vehicle.

Not to service a vehicle, but as time goes on and the individual cells start to give up the ghost, like they do in a battery power tool. I took my drill battery apart the other week to see if it is a bad cell that's fubared which isn't too scary with 18v and only 3 cells, but you can almost guarantee that some diyer will try the same with one of the 100's or 1000's of cells in an electric car.

 

[mtt.tr]

I suspect you meant Fibrillation?

Indeed. Must have had **** on my mind inlaws just left making the most of my throne time.

 

[slimjim]

I don't know what wataboutery means, but what I was saying is wooden cladding isn't used on highrises because it's obviously flammable, whereas as most folk assume metal isn't, so is safe to "clad" or use as a "firewall" if the fire gets hot enough ally will catch fire wether its cladding a building or in a car (though granted it will hopefully give you time to get out of the car)



Not to service a vehicle, but as time goes on and the individual cells start to give up the ghost, like they do in a battery power tool. I took my drill battery apart the other week to see if it is a bad cell that's fubared which isn't too scary with 18v and only 3 cells, but you can almost guarantee that some diyer will try the same with one of the 100's or 1000's of cells in an electric car.

They aleady do, you can replace individual cells on the leaf and the Toyota hybrids for sure,

It’s not the metal that sets fire it’s the stuff bonded to it, the insulation, though metal will in some circumstances burn, wire wool for instance, or certain metals, of high reaction,

The problem is any vehicle can set on fire and burn, it’s not just electric vehicles but petrol and diesel vehicles, but it’s relatively rare.

 

[WorkshopChris]

I googled which is more dangerous....turns out AC is a lot more dangerous than DC....I can't remember if I knew that!

It's much harder to break a DC load than an AC load, You tend to need to use rotary contacts and more complexed arc shielding.
EDIT> I wrote it back to front

 

[Pigeon_Droppings2]

....am still googling. I quite like this explanation I found although with electric vehicles with 600v batteries maybe the statistics will change.

"Realistically (statistically) speaking, AC is more dangerous that DC. This comes from the fact that 120/240v AC is the voltage that we are most likely to encounter - which can kill us. The DC voltage that we are most likely to encounter is 12 DC (in our vehicles), and it is very unlikely to kill us."

 

[mtt.tr]

It's much harder to break an AC load than a Dc load, You tend to need to use rotary contacts and more complexed arc shielding.

You mean harder to switch dc.

 

[mtt.tr]

....am still googling. I quite like this explanation I found although with electric vehicles with 600v batteries maybe the statistics will change.

"Realistically (statistically) speaking, AC is more dangerous that DC. This comes from the fact that 120/240v AC is the voltage that we are most likely to encounter - which can kill us. The DC voltage that we are most likely to encounter is 12 DC (in our vehicles), and it is very unlikely to kill us."

Nonsense. Neither is safer or more dangerous both kill if you induce enough current and both will burn you internally.

 

[Robotstar5]

It's much harder to break an AC load than a Dc load, You tend to need to use rotary contacts and more complexed arc shielding.

I've always thought DC switching was worse, we nearly lost an apprentice off the bridge of a yard crane at the foundry when the DC magnet contactor opened with the flash hood up, the arc it pulled startled him and he would have gone over the side if one of the sparkies hadn't grabbed him.

 

[Milkybars]

I thought DC grabbed you and AC threw you ..
The 750DC third Rail on the railway is the worst and once in touch you have had it

 

[mtt.tr]

I thought DC grabbed you and AC threw you ..
The 750DC third Rail on the railway is the worst and once in touch you have had it

Nope both cause you to hold on

 

[Pete.]

AC is easier to switch because it crosses zero potential 100 times a second, the arc is killed by the loss of potential. This is the same reason it's easier to get away from a AC shock. My lathe has a DC motor and it has 'blow out' coils on the contactors that create a magnetic field to drag the arc away from the contactor tips to kill the arc as they open.

Many relays have a DC rating and a AC rating, the DC rating is much lower.

 

[outofthefire]

Nonsense. Neither is safer or more dangerous both kill if you induce enough current and both will burn you internally.

I thought historically we use ac domestically because back in the day they decided it was the lesser evil, but i've just googled it and it seems ac was chosen mostly because it can be transmitted over greater distances.

 

[mtt.tr]

I thought historically we use ac domestically because back in the day they decided it was the lesser evil, but i've just googled it and it seems ac was chosen mostly because it can be transmitted over greater distances.

They used ac as they could up the voltage easier, higher voltage lower current thinner cable.

With modern semiconductors they now use dc megalinks its actual more sensible as its easier to convert it to ac and keep it synchronous to the frequency.

 

[R-D-R]

Our i3 mechanically connects the traction battery using the normal 12v ignition circuit (normal 12v car battery). There is a Maintenance option that locks the relays open for working around it. There is a pyrotechnic fuse inside the battery that blows on collision (with airbag deployment) to isolate power to the orange connector and emergency services can then disconnect it if needed. The location and access route to the connector is on the same database as the diagrams for cutting the roof off cars that emergency services have.

to disconnect the connector for maintenance it’s designed to be safe but there is process and Good practice guidelines in the service manual.