Post #2298958
2026-04-14 12:19 UTC
@thunfisch@chaos.social Ye, that big tube thingy is the contactor. A Gigavac GV200, 500A 800V DC contactor to be exact.
It will conduct the main current between battery + and motor controller +.
But because motor controllers have quite beefy and low ESR input capacitors, if the contactor would simply make the connection when the input caps are empty, there would be many kiloamps flowing through not-quite-mated switch contacts, trying to charge the caps rapidly.
Replies (2)
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@LeoDJ@chaos.social 2026-04-14 12:19
That's where the FETs come in. They pre-charge the input caps slowly and only then the contactor will be engaged. The MCU is there to oversee that process. I.e. not engaging the contactor when it still senses a voltage difference that's too great, etc.
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@karotte@chaos.social 2026-04-14 21:04
@LeoDJ@chaos.social @thunfisch@chaos.social In EVs this is conventionally done with two set of contactors, one with a resistor in series for precharge and the main contactor that can carry the full current. Tesla apparently did away with the precharge contactor by running the LV battery charger in reverse to charge the inverter input caps to battery voltage. One part less!