23 replies to this topic

[Sticky]

The main xenon headlight bulb has gone on the wife's Volvo XC90 and there are warnings all over the place about risk of electricution etc.

 

Is there anything I should be careful of when changing the bulb or is it just sensitive Swedish types hoping I'll go to a dealer for them to do the work?

[chris_uk]

Just change it.. Its only a 12v battery.

[fezzasus]

I'd guess about 50 % of the cars here have retrofitted xenon bulbs so the risk is taken fairly regularly here, do it after the car has sat for a while to allow any residual voltage stored by capacitors in the ballast to dissipate and you should be fine.

 

 

Just change it.. Its only a 12v battery.

 

Except the ballast takes the voltage provided to the bulbs up to 23,000 v

Edited by fezzasus, 26 September 2013 - 07:28 AM.

[chris_uk]

Are they not a completely sealed unit tho.. Anyway its the amps which kills you not the volts. What amps is it?

[Claws]

You will be fine if the lights are switched off, take extra care to not touch the glass.

[fezzasus]

Are they not a completely sealed unit tho.. Anyway its the amps which kills you not the volts. What amps is it?

 

No, they're not completely sealed. The ballast is always separate to the bulb, the only thing that changes is the position of the ignitor, sometimes part of the ballast, sometimes part of the bulb.

 

And no, it's not just current that kills. There's a reason defibrillators operate at 1000 v

[chris_uk]

Its the transfer of current which will kill you, you could have a million volts and 0.0000001 amps and you will be safe. 20v at 1 amp and your dead.

[fezzasus]

Its the transfer of current which will kill you, you could have a million volts and 0.0000001 amps and you will be safe. 20v at 1 amp and your dead.

 

While that's generally the case it's not something that should be followed as if it were law. The body reacts in different ways to the way a charge is delivered. High current and low voltage causes localised burns, while high voltage and low current can stop electrical transfers, in some cases stopping the heart (hence my defibrillator example).

 

In this case we are looking at a ignition voltage of 23,000 v and operating voltage of about 100-200 v at 2.5 a, so it's certainly got enough poke to kill you.

[chris_uk]

Ive been done god knows how many times by house wiring, 240v with a 13amp fuse (put my hand on an exposed plug) the fuse didnt pop so im not sure how many amps it was lol. BAck on topic... Why dont you just disconnect the battery if your unsure?

[vocky]

if changing the bulb doesn't kill you the cost of the new bulb will

[Sticky]

if changing the bulb doesn't kill you the cost of the new bulb will

 I'm going to invite Chris and Fezz round to help

[ghand]

Ive been done god knows how many times by house wiring, 240v with a 13amp fuse (put my hand on an exposed plug) the fuse didnt pop so im not sure how many amps it was lol. BAck on topic... Why dont you just disconnect the battery if your unsure?

Most die on 240 because they get hold of something live, the muscles go into spasm and they can't let go.if your lucky you just touch and the shock throws you off and you just feel the pain. Thats why its bred into us sparks to lightly touch a bare cabe even if you know it's dead, it a habit you soon get into after a zap or two Nothing electrical on the car will kill you unless you get a belt, shout fcuk and jump back, fall over you tool box and split your head open.

[-Dab-of-Oppo-]

Nothing electrical on the car will kill you

 

Not strictly true if you should have a pacemaker or other underlying condition some things could be enough to tip you over the edge. But generally yes at worst you'll get a nasty jolt like this -

 

[-Dab-of-Oppo-]

do it after the car has sat for a while to allow any residual voltage stored by capacitors in the ballast to dissipate and you should be fine.

 

It's all needlessly erring on the side of extreme caution but I wouldn't count on any reasonable amount of time simply being enough to fully discharge them.  I remember as a kid making a tazer out of the flash capacitor from a disposable camera, once filled they seemed to hold their charge pretty much indefinitely until shorted across some flesh. Delivered enough of a short sharp whack to leave burns and you wanting a sit down if you hadn't already hit the floor.   Surprising for something half the size of a matchbox!

 

Depending on exactly how they operate maybe a more effective approach would be to disconnect the power with the circuit still open? Should mean more of the accumulated stored energy is used up right up to the point where there is insufficient amounts left to power them?

[Claws]

Ive been done god knows how many times by house wiring, 240v with a 13amp fuse (put my hand on an exposed plug) the fuse didnt pop so im not sure how many amps it was lol. BAck on topic... Why dont you just disconnect the battery if your unsure?

Most die on 240 because they get hold of something live, the muscles go into spasm and they can't let go.if your lucky you just touch and the shock throws you off and you just feel the pain. Thats why its bred into us sparks to lightly touch a bare cabe even if you know it's dead, it a habit you soon get into after a zap or two

Spot on! 240v at 50hz feels funky! You can certainly feel that in the chest 110v is a bit funnier Can remember an engineer in work telling me he was doing some work in the house, decided to try and strip some telephone wire with his teeth as his wire strippers weren't to hand... 50vDC, like putting your tongue on about 6 9v square batteries!

[Goosenka]

Sure there was something in the Profanisaurus about licking batteries

[turbobob]

 

Ive been done god knows how many times by house wiring, 240v with a 13amp fuse (put my hand on an exposed plug) the fuse didnt pop so im not sure how many amps it was lol. BAck on topic... Why dont you just disconnect the battery if your unsure?

Most die on 240 because they get hold of something live, the muscles go into spasm and they can't let go.if your lucky you just touch and the shock throws you off and you just feel the pain. Thats why its bred into us sparks to lightly touch a bare cabe even if you know it's dead, it a habit you soon get into after a zap or two Nothing electrical on the car will kill you unless you get a belt, shout fcuk and jump back, fall over you tool box and split your head open.

 

It's DC voltage that causes you not to be able to let go. AC you'll let go of pretty quickly. DC basically turns your muscles on so you can't let go. AC are turning them on and off quickly so you can let go.

 

And Chris is mostly correct. It is current that kills you. I believe it's either 10 or 20 milli amps across the heart that will kill you. You can apply a high voltage and current across two points on one arm and whilst it will hurt or even burn, it's not across the chest so unless you have a condition that is likely to be triggered, it won't kill you. The main danger is across the chest e.g. from one hand to the other.

 

As for the ballast / bulb. Changing it is fine providing the lights are turned off. If you want to be certain, then just remove the 12v into the ballast and allow a few minutes for any residual charge in the ballast to dissipate.

[myles]

Sure there was something in the Profanisaurus about licking batteries

 

 

I think the joke went along the lines of:-

 

What have your girlfirends arsehole and a 9v battery got in common?

 

You know its wrong, but you always end up putting your tongue on it.

 

 

I got a bolt off some leakage on my old Golf distributor. That was interesting!

[ghand]

 

Ive been done god knows how many times by house wiring, 240v with a 13amp fuse (put my hand on an exposed plug) the fuse didnt pop so im not sure how many amps it was lol. BAck on topic... Why dont you just disconnect the battery if your unsure?

Most die on 240 because they get hold of something live, the muscles go into spasm and they can't let go.if your lucky you just touch and the shock throws you off and you just feel the pain. Thats why its bred into us sparks to lightly touch a bare cabe even if you know it's dead, it a habit you soon get into after a zap or two Nothing electrical on the car will kill you unless you get a belt, shout fcuk and jump back, fall over you tool box and split your head open.  

It's DC voltage that causes you not to be able to let go. AC you'll let go of pretty quickly. DC basically turns your muscles on so you can't let go. AC are turning them on and off quickly so you can let go.   And Chris is mostly correct. It is current that kills you. I believe it's either 10 or 20 milli amps across the heart that will kill you. You can apply a high voltage and current across two points on one arm and whilst it will hurt or even burn, it's not across the chest so unless you have a condition that is likely to be triggered, it won't kill you. The main danger is across the chest e.g. from one hand to the other.   As for the ballast / bulb. Changing it is fine providing the lights are turned off. If you want to be certain, then just remove the 12v into the ballast and allow a few minutes for any residual charge in the ballast to dissipate.

Bob if you grab hold of a live 240v trust me you can't let go. The muscles will go into spasm and just tighten up and generally your dead before you can let go. Unless your fast enough to open your hand and throw away the cable in between each half cycle very few folk have access to DC over a few volts any way. Most deaths certainly domestic are people who have got hold of something live and not just touched it. Like I say I have had my share over the years working in some of the old factory's years back was quite dangerous at times and if you have the choice to lightly touch or get hold off 240v I know which is best.

[turbobob]

Believe me Gordon, I've had my share of mains belts! For the reason I mentioned above is why DC is more dangerous than AC.

 

I hate anything over 12v