Tackling the anti-spark problem (Title by a good friend)

But take care, the guy is a noob and a lot of what he says doesn’t make sense :smiley:

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That sounds promising under his bahookie.:joy:

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2bb1dac154f50aebb991f85eb41830157ecb5d38

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Come on, he is ok :slight_smile: lets say Kanber is the noob one here (for now) :slight_smile:

Most “inrush limiter circuits” fail because they are operating in linear mode during inrush. It’s a design limitation on almost every one.

Imagine a FET is a resistor with a variable resistance. When it’s “off” the resistance is [nearly] infinity and when it’s “on” the resistance is [nearly] zero. That’s all fine and dandy until you add capacitors to the load, like the filter capacitors on VESC and other ESCs. Right when it turns on, it’s effectively a momentary short circuit with [not really…] infinite current because the capacitors are empty. So what the antisparks do is they limit inrush current by turning on not from zero to full blast, but gradually over several milliseconds they ramp from [nearly] infinity to [nearly] zero ohms. It’s this period during the ramp that is the problem, the FET itself is taking almost the entire load due to Ohm’s law because the capacitors have effectively zero resistance to inrush. It’s said to be operating in “linear” or analog mode at this point, as opposed to “digital” mode where everything is either on or off with no in-between. This is extremely stressful to the junctions inside the FET and technically exceeding the design limitations for a very brief period of time. Each time it’s powered-on, it’s taking a tiny bit of damage.

The way to ameliorate this is much the same way a loopkey works – you have a “precharge” circuit where the nonzero inrush-limiting resistance is provided by an actual discrete resistor instead of the FET junction itself. So you have one FET with a heatsinked power resistor in series, that is separate from the one or more FETs on the main power switch.

So in order of operation, you’d have a single FET turn fully on [nearly] instantaneously (digitally) with a resistor in series to charge the filter capacitors, then once the output voltage approached the supply voltage (meaning the capacitors are nearing full charge) then the main FET(s) turn on [nearly] instantaneously (digitally) to supply high-current power to the system. This is never operating in “linear” mode but is “fully digital” and will not suffer the incessant failures that plague the inrush-limiting Vedder design. The power limiting and heating is moved to a discrete resistor instead of burning off the energy inside the FET junction itself, which stays cool during inrush.

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It’s true i don’t even know from esk8. I’m also a terrible person, and mostly ride evolves in traffic and cause accidents. I also hate kids and like to bite babies because they don’t have any teeth so what are they going to do about it. And dogs are stupid, and helping people is communism.

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I don’t want to assume as I wasn’t keeping track with all AS switches but I think only our switch has real pre-charge circuit with beefy resistor. So far the latest iteration didn’t received any negative feedback apart from 0.5W power consumption in off mode.

After all events die down and work will not be more hectic I will spend some time to develop newer design which shouldn’t drain “nothing” in off mode.

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ewwwwwwww… that could be enough to kill a mostly drained pack and creep it into the no-more-charge zone, right?

We’re always looking for the perfect eswitch as well because the unity isn’t for everybody, especially people building rat boards and dirt junkers like we do out of spare parts.

So far the only one that’s been worth a shit consistently is the 300 amp Flier eswitches that you have to order 5 at a time of. Not sure how they’re designed but they haven’t failed us yet.

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@Pryside have designed a Antispark with a real pre-charge curcuit. He wants to sell it, but he is silent as a dead coyote in the last time.
This is his design.

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The @3DServisas is the only “commercially available” one I’ve seen with a precharge circuit. Several others are in the concept/design/prototype phase. Of course there may be others I don’t know about.

The most ideal switch would have roll-to-start and auto poweroff after 15 minutes, not require a button or hole in enclosure, not draw current while “off”, and of course have a robust precharge circuit.

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:slight_smile:

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I think @Gamer43 has something brewing as well.

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Dear friend, have you send your design to the big guys in the comunity for test & review ?

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Failure at power on vs failure during the ride… @longhairedboy which one is more common ? Do “during the ride” failures happen ?

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@b264 Thanks for the detailed info, thanks for your time… Everybody has an antispark sw design I guess… So I told myself " why dont you have one the big noob newbie you !! :slight_smile: "

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When do you got it from him? Looks good.

I got it from him a couple weeks ago.

His switch is available to buy on his website for a long time already. :wink:

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all of the failures we’ve seen on any eswitch we’ve tested so far are the kind where they fail on. They freeze into the on position and stay there. I always figured it was the fets being forced to carry too much current or something, either from regen braking or hard acceleration on hills or something that cooked them and forced them stuck in the on position.

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