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Need 48v Low Amp Switches

HRTKD

HRTKD

Boondocker
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I need a couple of switches to enable/disable circuits going to a set of cooling fans. They're 48 volt but very low amps, less than 2 amps. Switches for batteries are huge overkill and wouldn't fit anyhow.

I already have the circuits fused so a breaker isn't appropriate. I'm not sure a fast blow breaker is even available.

The switches won't be used that often, only to take them down for maintenance. The fans are activated by other means.
 
I would do a simple test. Connect and disconnect using two copper wires and see what the arc potential is. I doubt it is much. A brushes motor will have a back EMF which reduces the differential voltage on the switch to a reasonable value. Brushless motors will have an internal capacitor which also keeps differential voltage small. You can always connect a couple uF oil capacitor across the switch if it is a major arc. I think any 120V AC switch will work fine. The test is just to satisfy your mind and let you sleep. This is not a critical circuit. Having switch stick on would not be a safety issue.
 
The fuse in the circuit does show a spark when inserting it. That's without the fans on. The PWM controller is between the PWM fans and the fuse.
 
Everything sparks a little. The concern is when it opens. Does it look like a hot spark that will sustain?
 
ricardocello

Post in thread 'low power DC switches; amp to volt curve'

The DC voltage/current rating of a switch is entirely dependent on the gap distance inside the switch and the materials used, because DC will arc over internally at higher voltages. In general, switches rated over 48VDC do not get high current ratings.

Here is a really beefy old-school switch, but even it maxes out at 3A 6A at 125VDC.
What we don’t know is its rating at 48 or 53V DC. More than 3A? probably, but we don’t know.


IMG_6933.jpeg
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ricardocello said:
ricardocello

Post in thread 'low power DC switches; amp to volt curve'

The DC voltage/current rating of a switch is entirely dependent on the gap distance inside the switch and the materials used, because DC will arc over internally at higher voltages. In general, switches rated over 48VDC do not get high current ratings.

Here is a really beefy old-school switch, but even it maxes out at 3A 6A at 125VDC.
What we don’t know is its rating at 48 or 53V DC. More than 3A? probably, but we don’t know.


IMG_6933.jpeg
  • Like
Click to expand...

That's what I'm looking for! But dang, those are expensive. I expected it to cost more than simple 12 volt switches, but $13+ each on backorder at Mouser is more than I expected. I found a seller on Amazon for ~$11 each and put in an order for the 110-S-73 model. That's a single pole, 3a 250v/6a 125v, AC/DC switch with screw terminals.

As I've told other forum members, if you want to play in the 48 volt space, it's going to cost you a lot more money.

I really appreciate the link. It will work great for my use case.
 
HRTKD said:
That's what I'm looking for! But dang, those are expensive. I expected it to cost more than simple 12 volt switches, but $13+ each on backorder at Mouser is more than I expected. I found a seller on Amazon for ~$11 each and put in an order for the 110-S-73 model. That's a single pole, 3a 250v/6a 125v, AC/DC switch with screw terminals.

As I've told other forum members, if you want to play in the 48 volt space, it's going to cost you a lot more money.

I really appreciate the link. It will work great for my use case.
Click to expand...
As I said in the thread, I’ve never used those switches (but they are littelfuse/carling).
I would expect a big monster click clack sound out of them. :)

iirc, I did a parametric search for DC rated switches above 48V, and there were not that many to choose from for higher currents.
So of course, they would be expensive. Glad you found them on Amazon cheaper.
 
HRTKD said:
That's what I'm looking for! But dang, those are expensive. I expected it to cost more than simple 12 volt switches, but $13+ each on backorder at Mouser is more than I expected. I found a seller on Amazon for ~$11 each and put in an order for the 110-S-73 model. That's a single pole, 3a 250v/6a 125v, AC/DC switch with screw terminals.

As I've told other forum members, if you want to play in the 48 volt space, it's going to cost you a lot more money.

I really appreciate the link. It will work great for my use case.
Click to expand...

110-S-73 - Toggle Switch, On-Off, SPST, Non Illuminated, 110 Series, 3 A, (Pack of 10): Amazon.com: Industrial & Scientific

110-S-73 - Toggle Switch, On-Off, SPST, Non Illuminated, 110 Series, 3 A, (Pack of 10): Amazon.com: Industrial & Scientific
www.amazon.com
$15 for a 10-pack, much better!
 
Last edited:
The fans probably won't cause much arcing problem.
Just put an RC snubber across contacts to prevent burning.

Gotta figure out which leg you want to switch, unless you use DPST.
Normally switching hot would be the thing to do if negative side grounded.
But these could be connected to 48V all the time, because low side switch easier. I suppose you could still just switch high side, controlled low side doesn't matter.
 
Business Name: Changchunshihanghuimaoyryouxiangongsi

Well that just rolls off the tongue 😎
 
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