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I am working on a high-powered e-bike project. I would like to start the bike using an Arduino. The bike runs on a 60V dc battery with a peak current draw of 40A.

I have looked at various relays, particularly of the latching type as I just want to use the Arduino to switch on the bike and allow the power to flow through. However, I can't find a relay with the correct amp limits. I do find high current relays (>100A) rated for 250v AC. Will this work? Any suggestions as to how I can get this system built would be greatly appreciated!!

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closed as unclear what you're asking by Chris Stratton, laptop2d, PeterJ, brhans, pipe Jun 5 '17 at 3:45

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • \$\begingroup\$ It's more like a starter solenoid but they run hot after a few minutes. There is no simple solution that does not involve using < 1mOhm parallel MOSFET's with heatsinks. Relay "Contactors" are big and bulky. Only simple way around it, I can think of is 2 stage relay/ Solenoid, so solenoid relay does all the ON OFF arcing and a small 50A Relay Holds the current with suitable timing such as motorcycle starter solenoid.. or small car \$\endgroup\$ – Sunnyskyguy EE75 Nov 4 '16 at 12:15
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    \$\begingroup\$ This approach is in essence fundamentally mistaken. You should not be trying to switch power to the e-bike's systems, rather you should be working with the existing motor controller, which already does so. \$\endgroup\$ – Chris Stratton May 29 '17 at 23:19
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Yes, you can always use a relay rated for a HIGHER voltage. However, switching DC is different from switching AC, so relays are typically rated for a lower current when switching DC vs. switching AC.

Note, however, that modern electric vehicle designs commonly use transistors to switch the motor power, not old-school mechanical relays. It is not difficult to find transistors (or combinations of transistors) that will easily handle 100A or more. It would be prudent to use transistors rated for at least 2X the motor current (or more). You may need to use an intermediate stage, a "driver" between the logic-level out of the Arduino and what the big switching transistor needs to control it.

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