Precharge resistor values

[Bigbondo007]

The use of a precharge resistor is common knowledge to me but my question is why would a lower amperage controller require a different value resistor over a higher amp controller I.E. Alltrax requires a 470 ohm for 600 and up and standard 240 for smaller controllers.

[klanel]

I'll take a wag at it. The larger amperage controllers may have larger farad capacitors. If so, more inrush current would be present to charge the capacitors. A higher resistance value would lessen the inrush current. In contrast if the capacitors in the smaller amperage are smaller, there would be less in-rush current and a lower resistance value might be used. As prefaced, just a wag. Alltrax could answer for sure.

[Bigbondo007]

Thanks klanel, been trying to get in touch with alltrax for a few days with no luck

[tag50]

Don't quote me but I believe the resistor also helps reduce the arcing of the contacts in the solenoid. Higher amperage=bigger arcing=bigger resistor.


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[Old vic]

When I installed my new Alltrac XCT 400 IQ controller the Alltrex customer service rep said neither the diode nor resister is needed for the solenoid. The controller is designed to operate without either.

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[scottyb]

Originally Posted by Old vic

When I installed my new Alltrac XCT 400 IQ controller the Alltrex customer service rep said neither the diode nor resister is needed for the solenoid. The controller is designed to operate without either.

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The SR control requires both the pre-charge resistor and the voltage suppression diode.

The XCT requires neither of these as both the pre-charge resistor and the voltage suppression diode are built in to the controller.

[Old vic]

Thanks for the clarification Scottyb!

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