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AlotOfReadinglast Wednesday at 10:40 PM3 repliesview on HN

Automotive transients can be wild. I did a bringup with a board that had specified 100+v range specified for transients and finicky quality requirements on the output. The power supplies took up most of the (very large) board.


Replies

mixduplast Wednesday at 11:27 PM

14v is not a transient, if your voltage was 12v with the car running, there's something wrong with the charging system (DC-to-DC in an EV, alternator/generator in an ICE)

13-14v is normal in all 12v automotive systems as the charging voltage

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hatsunearuyesterday at 8:19 PM

Yeah, this is normal. When the battery suddenly disconnects (for example of the lugs pop off) the alternator's momentum will send a massive, long-standing transient on the bus up to 100V. This is called a load dump.

jeffreygoestoyesterday at 6:27 AM

Saw up to 800A on units like the FSD for the short time until the caps were full. Slow starting a SoC is a software problem, slow starting the Cs and keeping the impedance low at the same time a non-trivial hardware problem.