DIY switch question

[jbgibson2]

Working on a dual parallel 18650 box, question about switch rating... There are mixed emotions on the web about this subject but a switch rated 3 A at 125VAC what A rating would I have at 4.2 VDC? Any expertise would be thankfully accepted

 

[WKS01]

If there is no DC rating for the switch it would most likely be ok at 3A. Ideally you would want a switch rated for DC.

 

[Izan]

Working on a dual parallel 18650 box, question about switch rating... There are mixed emotions on the web about this subject but a switch rated 3 A at 125VAC what A rating would I have at 4.2 VDC? Any expertise would be thankfully accepted

Welcome!

Amps is Amps. How many will flow through the switch? Best practice would leave 20-25% head room.
Be safe
Cheers
I

 

[tj99959]

If it's a regulated mod the switch should not be wired so that it takes the load that the atomizer takes, so a 3 amp switch should be fine. (if it's wired properly)

If it's a semi mechanical box there is no such thing as a switch that is safe that would fit in the box. Parallel 18650s have the potential of 100 amps. (30 amp continues batteries can do 50 amps pulse each)

 

[jblack741]

I read somewhere that for an unregulated mod any switch rated for at least 3A / 220VAC is good... more than enough to handle dual 18650's. If regulated most NO off-(on) SPST switch will work since it does not carry the load.

One of the mods I'm considering building is the OKR

 

[QBass]

Switches rated for AC only can very easily short in DC situations due to the arc created by the DC as the switch is engaged/disengaged. This can be very dangerous in a mech mod, as the switch can fuse in the on position and cause a runaway in the batteries if not noticed in time. AC is only at full voltage for a short period and cycles through 0v, thus minimizing the risk of an arc doing damage.

 

[WKS01]

I read somewhere that for an unregulated mod any switch rated for at least 3A / 220VAC is good... more than enough to handle dual 18650's.

No, they are not "more than enough" to handle dual 18650s in an unregulated device. Best case scenario a switch rated at 3A/220VAC and is also rated at 6A/125VAC would roughly translate to 6A/25-30VDC. Changing ratings from AC to DC is not entirely accurate and again it is best practice to find a switch rated for DC voltage. Using any switch in an unregulated device and pulling more current than the switch is rated for is a disaster waiting to happen. Plenty of people will tell you how there switch has worked for X amount of time and never gets hot. That does not mean the switch is not degrading and that every other switch will work as long as under the same circumstances. When a switch is used over its ratings it is a matter of time when it will fail. Best case it fails in the open position, worst case contacts weld closed and batteries vent.