Post #1377274
2026-04-14 11:22 UTC
Replies (5)
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@LeoDJ@chaos.social 2026-04-14 11:22
My planned approach is using a P-FET with a RC network at its gate so it does the pre-charging over a few 100ms in its linear region. What do you think? I've simulated it in LTSpice and it seems to work ok and stay in the safe operating area of the given MOSFET. (I've chosen a similar FET in LTSpice for a good model)
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@thunfisch@chaos.social 2026-04-14 11:37
@LeoDJ@chaos.social I felt my butt clench a bit while reading 48V/500A. That's some serious current. Not sure I understand it correctly though - Is that full 500A current running through Q1 and Q2, or is that big tube thingy the contactor, and Q1 and Q2 are just required to provide enough switching juice for the contactor? I'm totally out of my depths here, but the labelling around Q1 and Q2 suggested to me that all of the current flows through them. And the PCB traces do not look 500A capable to me :D
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@tyzbit@toot.now 2026-04-14 12:12
@LeoDJ@chaos.social the electric too big cannot hold the electric please stop
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@poleguy@mastodon.social 2026-04-14 13:00
@LeoDJ@chaos.social you can't just run a fat pre-charge resistor in parallel with the contactor? That's what we do on our #ppprs karts, but we have a manual contactor switch and wait for many seconds to watch the voltage meter go in to range. And we don't care about parasitic loss because we pull the batteries between races.
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@jakob@mastodon.chaosfield.at 2026-04-14 14:56
@LeoDJ@chaos.social that looks very elegant :D The common approach in formula student is a smaller precharge relay and a PTC resistor but there the rules forbid switching using semiconductors and we are running 600V ^^'