Key switch for 85V and 10A

Sparfuchs · Feb 14, 2021

Hello EV friends,

i have a 20s6p battery pack on my e bike and bought a transformer to 12V and 10A to power lights, horns and usb chargers.
I'd like to use a key switch between battery pack and transformer to make sure no one plays around with my stuff and to save battery because its switched of when i don't need the transformer. Unfortunately i couldn't find a key switch that can handle up to DC 85V and 10A. Do you have an idea what i have to look for or where to find it ? Or do you have another solution ? Or is a 10A trafo just way more than i'll ever need and i should buy a weaker one ?
Thanks for your help.

Best regard
Sparfuchs

amberwolf · Feb 14, 2021

Sparfuchs said:
i have a 20s6p battery pack on my e bike and bought a transformer to 12V and 10A to power lights, horns and usb chargers.
I'd like to use a key switch between battery pack and transformer to make sure no one plays around with my stuff and to save battery because its switched of when i don't need the transformer. Unfortunately i couldn't find a key switch that can handle up to DC 85V and 10A.

If the "transformer" is actually a DC-DC converter, and is 12v 10A out, then it's input at 85v won't need anywhere near 10A on the input. Proportionally, it would be 12v / 85v * 10A = 1.4A; since it's not 100% efficient it might take up to 2A, maybe 3 worst case.

So...if you are already using a keyswitch or other switch) on your bike to turn the controller on and off, just wire the DC-DC to be powered by the output of that, connecting ot the same point as the controller keyswitch/ignition/doorlock wire.

If the amp and volt ratings on teh DC-DC are something other than what I guess above, you'll need to post the exact details.

John in CR · Feb 15, 2021

I've used cheap motorcycle keyswitches on all my ebikes since 2008 without issue, most with max voltages of 83V or 87V but some with 128V fresh off the chargers. Something like this https://www.amazon.com/QAZAKY-Ignit...rcycle+Ignition+Switch&qid=1613409955&sr=8-21 Like AW said they're carrying low current at the high voltage, and they have no problem at all with 2-3A and the contacts seem to hold up well despite being made for 12V systems. In addition to being cheap, the thing I like about them is that when switched on the key is locked in, so it can't fall out on the road. Plus most have the 4 wire set up so one pair gets continuity in the on position and the other in the off position, so you can use that to activate an anti-theft system.

Sparfuchs · Feb 15, 2021

amberwolf said:
Sparfuchs said:

i have a 20s6p battery pack on my e bike and bought a transformer to 12V and 10A to power lights, horns and usb chargers.
I'd like to use a key switch between battery pack and transformer to make sure no one plays around with my stuff and to save battery because its switched of when i don't need the transformer. Unfortunately i couldn't find a key switch that can handle up to DC 85V and 10A.

Click to expand...

If the "transformer" is actually a DC-DC converter, and is 12v 10A out, then it's input at 85v won't need anywhere near 10A on the input. Proportionally, it would be 12v / 85v * 10A = 1.4A; since it's not 100% efficient it might take up to 2A, maybe 3 worst case.

So...if you are already using a keyswitch or other switch) on your bike to turn the controller on and off, just wire the DC-DC to be powered by the output of that, connecting ot the same point as the controller keyswitch/ignition/doorlock wire.

If the amp and volt ratings on teh DC-DC are something other than what I guess above, you'll need to post the exact details.

Thanks a lot for your reply amberwolf,
your information helped a lot. I've one of those throttles witch a little voltage display and a ignition lock. So as the 85v battery voltage goes through the lock anyway i could connect a wire parallel to the output of the key and connect it to the transformer ?

Sparfuchs · Feb 15, 2021

John in CR said:
I've used cheap motorcycle keyswitches on all my ebikes since 2008 without issue, most with max voltages of 83V or 87V but some with 128V fresh off the chargers. Something like this https://www.amazon.com/QAZAKY-Ignit...rcycle+Ignition+Switch&qid=1613409955&sr=8-21 Like AW said they're carrying low current at the high voltage, and they have no problem at all with 2-3A and the contacts seem to hold up well despite being made for 12V systems. In addition to being cheap, the thing I like about them is that when switched on the key is locked in, so it can't fall out on the road. Plus most have the 4 wire set up so one pair gets continuity in the on position and the other in the off position, so you can use that to activate an anti-theft system.

Thanks a lot for your reply john in cr,
i didn't really get the thing with the anti theft. I bought a anti theft system for e bikes but my sabvoton 72150 doesn't have a anti theft connection... but i'll post my question about that in a new topic, so other users might benefit of the solutions

amberwolf · Feb 15, 2021

Sparfuchs said:
I've one of those throttles witch a little voltage display and a ignition lock. So as the 85v battery voltage goes through the lock anyway i could connect a wire parallel to the output of the key and connect it to the transformer ?

Unless the switch is a realy really tiny one not capable of more than the few hundred mA the controller KSI line is likely to draw, then there shouldn't be any problems with this. (I doubt it is that small)

amberwolf · Feb 15, 2021

Sparfuchs said:
i didn't really get the thing with the anti theft.

If the antitheft is only supposed to be powered when you want it to protect the bike, and not when you're riding, you'd connect it to the key position that is only powered when the bike is "off", if it has one. (like some of the On-Off-On switches, also called SP3T or 1P3T, or SPDT/1P2T-center-off).

John in CR · Feb 16, 2021

I never use those ebike key switches integrated with the throttle, because I personally don't like running pack voltage up to the handlebars. Plus while those wires may be capable of the 200mA or less needed to turn the controller on, I doubt the wire gauge going to that switch is capable of handling the power to your DC/DC converter. Compare the wire gauge of the 2 to be sure.

Key switch for 85V and 10A

Sparfuchs

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amberwolf

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John in CR

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Sparfuchs

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Sparfuchs

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amberwolf

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amberwolf

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John in CR

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