High current switch?

[Geoff S]

Not really.  This was high-lighted in an AliExpress email I received this morning and I was curious enough to check it - particularly as it's supplied with XT60 connectors. 

[Simon Chaddock]

I note the switch is actually rated for 15A 250AC. It is not a DC switch.

Yes it would isolate the voltage from a 8s Lipo (30V) but only if no current was flowing. It would likely arc and fail if anything like the maximum amps of the plugs (50.60 or 90 amps) was actually flowing when it tried to break the circuit.

A DC switch has to rapidly move the contacts to beyond the arc distance which at 30V DC is considerable.

With AC the voltage goes to zero at each cycle so any arc is self extinguishing.      

[Geoff S]

Of course if you should (foolishly IMO) choose to fit such a switch in a model it wouldn't actually be switching a large current (just the receiver esc etc stand-by load).  You just need a switch big enough to pass the motor current not to switch it.

[Peter Jenkins]

About a year ago, Jeti used to list 2 genuinely high power switches.  One was rated to 100 A and the other to 200 A.  Both could be operated by the Radio system but they were pretty expensive.  I don't see them advertised any more which tells me that the take up on these products was insufficient to justify commercial production.  As you would imagine, they were primarily to connect and disconnect the drive batteries.  I see they do a separate switch for the Rx and servos for up to 15 A.

[Frank Skilbeck]

1 hour ago, Geoff S said:

Of course if you should (foolishly IMO) choose to fit such a switch in a model it wouldn't actually be switching a large current (just the receiver esc etc stand-by load).  You just need a switch big enough to pass the motor current not to switch it.

Part of the issue is the inrush current to the ESC capacitors, this is what causes the spark when we make the connection, it's basically close to a short circuit until the capacitors charge up. So the problem with this type of switch is the arc that would occur internally as you make the connection.

 

Multiplex do an Antiflash connector rated for 70amps, which basically uses a solid state circuit to limit the inrush current and hence the arcing, this can be fitted with a separate switch.

 

You could I suppose make a 3 position switch, i) off, ii) connected via a resistor (to reduce the inrush current), iii) connected with no resistance.

 

Back in the early days of electric flight it was common for ESCs to be fitted with a separate on/off switch, I've still got a couple of Jeti ESCs with this feature.

[Peter Jenkins]

Jeti also do an anti-spark plug for 4 mm bullet connectors.  I've used them for the past 10 years.  They are excellent.

[Geoff S]

1 hour ago, Frank Skilbeck said:

Part of the issue is the inrush current to the ESC capacitors, this is what causes the spark when we make the connection, it's basically close to a short circuit until the capacitors charge up. So the problem with this type of switch is the arc that would occur internally as you make the connection.

 

Multiplex do an Antiflash connector rated for 70amps, which basically uses a solid state circuit to limit the inrush current and hence the arcing, this can be fitted with a separate switch.

 

You could I suppose make a 3 position switch, i) off, ii) connected via a resistor (to reduce the inrush current), iii) connected with no resistance.

 

Back in the early days of electric flight it was common for ESCs to be fitted with a separate on/off switch, I've still got a couple of Jeti ESCs with this feature.

 

I had a few ESCs with a separate on/off switch, too.  I never trusted it. I think they just disabled the operation of the ESC rather than acted as a true disable switch.  I used to leave them on and bury them in the model.

 

I suppose there may be a use for the switches I was pointed to but it's not in the main battery circuit of an electrically powered model aeroplane

[Frank Skilbeck]

5 hours ago, Geoff S said:

 

I had a few ESCs with a separate on/off switch, too.  I never trusted it. I think they just disabled the operation of the ESC rather than acted as a true disable switch.  I used to leave them on and bury them in the model.

 

 

But a brushless motor won't run unless it's getting the power applied in the correct sequence, so these on off switches isolate the ESC control system effectively disabling it. Never had a problem on any of the ones I had fitted on models, quite useful especially if the battery was difficult to access.

 

7 hours ago, Peter Jenkins said:

Jeti also do an anti-spark plug for 4 mm bullet connectors.  I've used them for the past 10 years.  They are excellent.

 Yep use them on 6s+ systems, but you can only make the system safe by unplugging the battery.

[Martin Harris - Moderator]

7 hours ago, Geoff S said:

 

I had a few ESCs with a separate on/off switch, too.  I never trusted it. I think they just disabled the operation of the ESC rather than acted as a true disable switch.  I used to leave them on and bury them in the model.

 

 

Maybe not the best practice. A clubmate lost a model recently to power loss and after retrieving the wreckage found the ESC inactive. On investigation, it was found that operating the ESC switch (which had been secured with a block to prevent accidental operation) a couple of times cleared the fault so we surmised that the contacts had oxidised from lack of use over the years. 

[Dickw]

If an ESC has a switch I tend to cut it off, then either insulate the two ends or solder them together depending on which way leaves the ESC operational.

 

Dick