I agree, that resistor you linked to could easily handle the power for that pulse. But that’s a monster resistor you’re recommending!
That 1282W pulse only exists for a couple of mS. After 5mS you can get 600uF of ESC caps charged up to about 65V, significantly lowering the current, and at 10mS the caps are essentially charged.
So that’s a manageable average current level over one second, 1282W / 100 = 12.82W for that 5.5Ω resistor you mentioned. Actually, much less than that since the current plummets very quickly.
I think a pair of small 10Ω 1W resistors in parallel could handle that but going up to 16 Ω would make it easy for a 1W resistor to handle the current. IMO you wouldn’t need a huge aluminum cased one.
Going to that higher resistance would also lower the value of the voltage spike that was generated from the (much lower) inrush. Not a real concern though unless operating very close to or at the ESC’s voltage rating.
After I killed the first AS150 at 20S I switched to 12S for testing. I didn’t have any issue at this voltage using a XT90-S as antispark switch.
I also precise I killed the two AS150 at 20S operating at storage voltage (3.85V per cell).
I don’t really know if I can trust the " Flipsky Anti Spark Switch Aluminum pcb 300A" :
Engineers have thoroughly tested prototypes; however, this is still a new design and a first production run, please exercise extreme caution (as one would normally do with any electric vehicle) when using this device.
I’d rather go with a DIY antispark running a wire in parallel to the main lead with a power resistor.
Yet, I’ve understood choosing the right resistance value is a matter. @Trampa can you help?
4.7Ohm or 2 x 10Ohm in parallel. But the resistor needs to be able to cope with quite some amps for a short period. So the power rating needs to be aligned with the total capacitance in the system.
The XT90S uses a quite small 4.7 ohm if I remember correctly.
Nah it’s a typo, they meant 10 Ohms not 10k Ohms. 2 x 10 Ohms in parallel gives you 5, it’s offered as an alternative because 10 Ohm and 4.7 Ohm are standard resistor value, while 5 Ohms isn’t.
Generally it’s weird to deal with single digit values for Ohms, so rather than find and copy the omega symbol all the time people use K for kilo ohms or M for mega ohms. The symbol denoting order of magnitude also gives you a decimal place and saves space if you need to print it on a circuit or component, so a 10K is 10,000 and a 5K1 is 5,100. There is a standard for single digit values it’s just not super common - we use R because it’s a resistor and R isn’t already “taken” to measure a common parameter on a circuit other than maybe a radius if you were dealing with mixed mechanical and electrical design. So 4R7 is trying 4.7 Ohms, and 10R is 10 Ohms.
In theory you need to worry about capitalisation (lower case m is milli and upper case M is mega) but in real world use cases it’s very weird to see milliohms and megaohms side by side.
There, they know since like 2015 that XT90-S, AS150, QS8 and QS10 antispark connectors are not good when handling more than 12S. They all share almost the same kind of tiny resistor from 5 to 8 ohms.
They usually fail by heating too much at connection because of inrush current.
They advice Jeti AFC Anti-Spark Connectors for such systems :
The Jeti 5,5mm do have about 30 ohm and they work well on my 22s liIon pack. Just stay about 2sec on the “precharge ring” before completely plug them together and you will never see a spark.
Better go with Jeti 5,5mm (36 Ohm) or Jeti 8mm (30 Ohm) for higher current. Their smd resistors should withstand precharge well at higher volts and even don’t get warm.
Jeti AFC Anti-Spark Connectors 5.5mm (150A)
Jeti AFC Anti-Spark Connectors 8mm (300A)
I couldn’t find these connectors elsewhere than US stores.
The Flipsky AS looks good, but is actually rated only 150A continuous. Wires are AWG12, and look tiny for my (supposed) need. I would be concerned it would start a firework inside the ammo box…
I’ve finally chosen the JETI 8 mm AFC connectors. They are great. No spark anymore. Tested several times. I think it’s the way to go for more than 18S.
I’ve also found these 8 mm connectors are very easy to solder with AWG8 wires.
