Dissadvantages of using flashlight body as a conductor

So....as title says.....what are real disadvantages off using a flashlight body as a conductor?
Since there are many, especially homemade, flashlights designed to use a tail cap switch, and
a metal (aluminum or titanium) body as a conductor I'm wondering if this can couse problems
of any kind....? ....maybe the electronics in flashlight can be damaged by outher electrical pulse,
or the batteries can be discharged by outher load....?

thank you

It's a bit like how the entire body of your car is used as the -ve electrical path. It can get hit by lightning and suffer no damage.

In alot of ways it may have advantages, nice big path of conductive metal means very low resistance. Aluminum is marginally less conductive than copper but when you have that much of it that difference doesn't really matter.

I saw a picture once of a modded aluminum light someone made. It was bare aluminum and used as a dive light.

Electricity conducting through the body of the light caused some kind of chemical reaction with salt water. Light worked fine, but the outside of the body looked very worn even after just brief use. This was basically just cosmetic though and wouldn't be a problem for anodized aluminum.

Bare aluminum would get pretty rough in saltwater without any current.

mvyrmnd said:

It's a bit like how the entire body of your car is used as the -ve electrical path. It can get hit by lightning and suffer no damage.

Click to expand...

So the flashlight body should work as a faraday cage, and protect sensitive electronics against external influences as EMP ,lightning,....etc....

jezdec said:

So the flashlight body should work as a faraday cage, and protect sensitive electronics against external influences as EMP ,lightning,....etc....

Click to expand...

Until the other effects would probably be more important than a working flashlight, yes.

There are some LEDs with non-neutral thermal contacts. These require care with installation in body-path flashlights, especially in arrays.

AnAppleSnail said:

Until the other effects would probably be more important than a working flashlight, yes.

Click to expand...

Good point. If lightning strikes your flashlight, please don't be holding on to it at the time.

When working with 110 Volts and above I use my non-metal body flashlight, like this one http://www.surefire.com/illumination/flashlights/g2x-pro.html .

mvyrmnd said:

Good point. If lightning strikes your flashlight, please don't be holding on to it at the time.

Click to expand...

OK...I will keep this in my mind....:thumbsup:

BUT...I was thinking more like what happens if the body of such flashlight gets in contact
with another power source...like car battery....would this interfere with driver or kill it or not?

Enabling current from the cell or cells to flow through the body can present problems. Most often, a steel spring in the tail cap is used. This presents issues both at the bottom of the cell contacting the spring and at the point(s) where the spring contacts the body of the light. Oxides, skin oils, contaminants, corrosion or other problems may affect the performance of the light. In the worst case, intermittent or no electrical current flow may occur.

<corrected a typo, added detail>

jezdec said:

OK...I will keep this in my mind....:thumbsup:BUT...I was thinking more like what happens if the body of such flashlight gets in contactwith another power source...like car battery....would this interfere with driver or kill it or not?

Click to expand...

Not usually. Electricity usually flows in and out. If you stick a flashlight, on or off, across a car battery, the 12V will travel through the metal, but not "Wander" around inside. Electricity takes the path of least resistance, from high to low potential.So kilovolts might do interesting things (static electricity), but regular volts won't.