Is this safe or risky?

[E-HP]

There is no problem switching 5A at 100V if you have the right switch, domestic switches handle this every day but it doesn't mean that one from ebay for ebikes will work.

I'd be interested in how you calculated the inrush current as being 5A. Can you show how you got to that?

 

[ebike11]

How about this way??..both switchs are independently turning on and off its own converter and the converters are independently wired directly to the battery positiv and negative. Though they are sharing the same battery +/- wires.

How much energy do those converters suck? Could be several watts while idling. Higher voltage = less current for given power. Your switch really should be on the battery<-->converter side if there are thin wires. Less energy loss in that case. But then again, bringing 100V to the handlebar is not good idea. You should put a relay between the battery<-->converter and switch them from the handlqebar.

Hi!
The converters are rated by the seller specs at 20A 240Watts.

Oh that is true that the higher voltage would have less energy loss on the battery to converter side. I just assumed that 100V might be a lot for handlebar switches. I do in fact have a 110~220v rated switch but it is also using the same thin wires as the 12~24v switch.

 

[BobBob]

There is no problem switching 5A at 100V if you have the right switch, domestic switches handle this every day but it doesn't mean that one from ebay for ebikes will work.

I'd be interested in how you calculated the inrush current as being 5A. Can you show how you got to that?

Hi E-HP,
I didn't calculate the inrush current as being 5A. Each buck converter draws 2A nominal so a 16 A mechanical switch for 2 of them is probably going to last a while in my opinion.
Feel free do disagree and provide better estimates
Calculating would require data which we don't have and are unlikely to get
I'm not suggesting a solid state relay which needs better calcs
I suggested that a purely mechanical hardware switch designed for 16 Amps and 110V would probably be ok with the current drawn by 2X cheap 240W buck converter that draws 2A
What do you think? What do you think the failure modes are and how would you advise the OP to spend their hard earned to mitigate? Alway happy to be wrong and corrected. What's your suggestion that is better?
Lots of domestic devices have higher inrush currents than the rated fuse value
If a standard switch fails after 6 months it costs a few $ to replace and so what - failure mode is likely low risk
The use of $5 switches that are designed for 16A provides a 5X engineerign FOS for a system likely to draw 3A
I know this isn't proven but it's better than thin wires and Ebay handlebar switches
If you want a properly designed engineered system then for sure specify that but this is a cheap, sensible, cheap and above all cheap solution
If the 100V switch breaks then the light doesn't go out and you spend $5 replacing it - seems pragmatic
I could give the more detailed, check every component and do a calculation answer but I thought this seemed a cheap n cheerful type approach

 

[E-HP]

There is no problem switching 5A at 100V if you have the right switch, domestic switches handle this every day but it doesn't mean that one from ebay for ebikes will work.

I'd be interested in how you calculated the inrush current as being 5A. Can you show how you got to that?

Hi E-HP,
I didn't calculate the inrush current as being 5A. Each buck converter draws 2A nominal so a 16 A mechanical switch for 2 of them is probably going to last a while in my opinion.
Feel free do disagree and provide better estimates
Calculated would require data which we don't have and are unlikely to get
I'm not suggesting a solid state relay which needs better calcs
I suggested that a purely mechanical hardware switch designed for 16 Amps and 110V would probably be ok with the current drawn by 2X cheap 240W buck converter that draws 2A
What do you think? What do you think the failure modes are and how would you advise the OP to spend their hard earned to mitigate? Alway happy to be wrong and corrected. What's your suggestion that is better?
Lots of domestic devices have higher inrush currents than the rated fuse value
If a standard switch fails after 6 months it costs a few $ to replace and so what - failure mode is likely low risk
The use of $5 switches that are designed for 16A provides a 5X engineerign FOS for a system likely to draw 3A
I know this isn't proven but it's better than thin wires and Ebay handlebar switches
If you want a properly designed engineered system then for sure specify that but this is a cheap, sensible, cheap and above all cheap solution
If the 100V switch breaks then the light doesn't go out and you spend $5 replacing it - seems pragmatic
I could give the more detailed, check every component and do a calculation answer but I thought this seemed a cheap n cheerful type approach

So the 5A is relevant because you feel that's the maximum current for the switch contacts, or is it relevant because it's the only value you can estimate, since you can't estimate the inrush current?

 

[Comrade]

So the 5A is relevant because you feel that's the maximum current for the switch contacts, or is it relevant because it's the only value you can estimate, since you can't estimate the inrush current?

Depends on the size and quality of caps on the input, but probably around 100A. It needs an NTC on the input no matter how it will be switched on, with a relay or a switch. With a properly sized NTC a 5A rated switch will work just fine for a long time.

 

[E-HP]

So the 5A is relevant because you feel that's the maximum current for the switch contacts, or is it relevant because it's the only value you can estimate, since you can't estimate the inrush current?

Depends on the size and quality of caps on the input, but probably around 100A. It needs an NTC on the input no matter how it will be switched on, with a relay or a switch. With a properly sized NTC a 5A rated switch will work just fine for a long time.

yup. cheap protection. $5
https://www.amazon.com/Ametherm-SL32-2R025-Aqua-Rite-Thermistor/dp/B06ZY4W8P4/ref=zg_bs_306526011_2/136-8903534-1598418?pd_rd_i=B06ZY4W8P4&psc=1
Typical ESR for electrolytic capacitors is in milliohms, so way more that 100A, if at 100V, ohm's law. :?

 

[ebike11]

So the 5A is relevant because you feel that's the maximum current for the switch contacts, or is it relevant because it's the only value you can estimate, since you can't estimate the inrush current?

Depends on the size and quality of caps on the input, but probably around 100A. It needs an NTC on the input no matter how it will be switched on, with a relay or a switch. With a properly sized NTC a 5A rated switch will work just fine for a long time.

The converters i believe have 160V caps but stated use is 120v to 12v converter

 

[JackFlorey]

I didn't calculate the inrush current as being 5A.

Should be very easy to measure.

If a standard switch fails after 6 months it costs a few $ to replace and so what - failure mode is likely low risk

Keep in mind that HV DC switch failures can be very ugly (i.e. smoke, fires.) Check out youtube for what happens when people use AC breakers to disconnect DC loads.

 

[BobBob]

There is no problem switching 5A at 100V if you have the right switch, domestic switches handle this every day but it doesn't mean that one from ebay for ebikes will work.

I'd be interested in how you calculated the inrush current as being 5A. Can you show how you got to that?

Hi E-HP,
Each buck converter draws 2.5A nominal so a 16 A mechanical switch for 2 of them is probably going to last a while in my opinion.

So the 5A is relevant because you feel that's the maximum current for the switch contacts, or is it relevant because it's the only value you can estimate, since you can't estimate the inrush current?

5A is the continuous current.
The inrush current will be higher due to the caps, for AC or DC powering a PSU
I'm assuming inrush would be similar for AC or DC - thoughts?

A domestic mains power switch will also have to deal with inrush when connecting to one or more PSUs
I put my clamp meter onto my laptop PSU (12.3A 19.5V) and measured inrush of around 28A at 230V (UK AC)
for a 260W output power Dell, similar to the 240W OP PSU rating.

So the transient from my PSU is nearly 30X the continuous amperage and the switch is rated for 13A continuous
Extrapolating, this switch might have to deal with 400A as a transient if connected to a bunch of computer equipment and other stuff with PSUs as a ballpark

Arcs - hmm
A way to reduce the risk of arcs at switch off, would be switching off at the handlebars before switching off at 100V so there will only be a few milliamps being switched if you remember.

If you forget and switch at full power the you have a 5A but if the arc dissapates some voltage this will drop supply to the PSI so although there is theoretically 500W, this is taken by the PSU and I'd think much less could be generated accross the arc, which I can't see causing much of a problem as far as smoke and flames, it's relatively chunky Copper plus contacts
If the switch fails short circuit it doesn't matter too much, you can still switch off at the bars and disconnect pretty safely.
If it fails open circuit you just replace it.