A Call for Revolution: Supercapacitors in Airsoft

[Sewdhull]

You can measure or calculate IR using voltsdrop as you have, apply an oscillating signal using a meter to measure it or a small and larger current to get a better idea of the IR.

 

I'm curious as to what could raise the inrush current then drop it as spring rates rise, then raise it again as the spring rate rises again.. My thoughts are that it's a limitation of instrumentation, but I don't know why that would be.

This happens for the non specna motors..

The other currents rise with increased loads on all the motors.

 

https://www.benzoenergy.com/blog/post/battery-internal-resistance-and-its-measuring-method.html/

 

There's a description the AC measurements there.

Edited December 20, 2023 by Sewdhull

[Egon_247]

I have come to the conclusion that years of drugs/drink/women has destroyed my knowledge of most things capacitor based other than how to charge up a big one with the legs bent round and chuck it to your mate...

😂

So, my hat is off to you sir, much respect for getting this far and good luck. Hope it pays off for you. 👍

[Pseudotectonic]

@kadamski I agree with more testing with LiPo. In actual fact, rather than me buying a bunch of LiPo and just simply measuring the trigger response in milliseconds, it would be more economical and informative for me to make another unit and simply send it to you to be tested with your LiPo and looking at the currents and voltages with the scope, if you don't mind the work and sharing the results of course. That will be more insightful than me measuring with Audacity.

 

In fact the offer is up for anyone happy to test it, the condition is you need to have a scope to look at the currents and voltages (with LiPo) and share the results. (I will pay for postage and everything)

 

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And btw, I have uncovered the ancient texts from the "Airsoft Mechanics" website (2005) somehow stored on the Internet Archive. There is an article and some forum posts which some interesting discussions that somewhat mirror the discussions here...

 

https://web.archive.org/web/20110511090621/http://www.airsoftmechanics.com:80/home/content/view/16/30/1/0/

https://web.archive.org/web/20090726234228/http://forums.airsoftmechanics.com/index.php?topic=78. (sadly only the first page was saved)

 

In the article they say they tested with some salvaged PC motherboard "2200mFD 10V" capacitors which I think is a mislabelling on their part. Because a 2200 mF or 2.2 F 10 V capacitor would be firmly in the realm of a supercapacitor (rather than a normal capacitor) but I don't think you can find these on PC motherboards. Also looking at their small picture it seems to be rather a 2200 uF (which is 0.0022 F) capacitor which is more plausible coming from a PC motherboard. In their text they refer to "microfarads" instead of "millifarads".

 

Although their caps were in the millifarad territory, which I don't think would work, somehow they say they have improved ROF by around 3% and an unknown amount of reduced voltage drop (I think their image is missing).

 

I don't know what to make of this. Maybe it is down to the fact they were using some 8.4 NiCd on some TM motor. The forum did confirm the OP didn't improve trigger response, although another person say it did but with unknown capacitors. All without any actual numbers so I don't think it means anything other than confirming my maths about they need more farad than a few millifarads to actually improve trigger response.

 

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And for the sake of continuity here is the Reddit post for future reference: https://redd.it/18k2324

 

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Also semi-relevant: https://www.youtube.com/watch?v=tKki89sq0XY

 

Edited December 21, 2023 by Pseudotectonic
correction 2200 uF = 0.0022 F

[kadamski]

13 hours ago, Pseudotectonic said:

@kadamski I agree with more testing with LiPo. In actual fact, rather than me buying a bunch of LiPo and just simply measuring the trigger response in milliseconds, it would be more economical and informative for me to make another unit and simply send it to you to be tested with your LiPo and looking at the currents and voltages with the scope, if you don't mind the work and sharing the results of course. That will be more insightful than me measuring with Audacity.

I will try to check if I can setup a measurement environment next week. I'm not entirely sure if shipping the unit to me would be the most economical option, maybe it would be simpler if I build one myself. You didn't specify which exact supercaps you use, though. Or I missed it?

[Pseudotectonic]

The ones I'm using are PTV-6R0V305-R

https://www.digikey.co.uk/en/products/detail/eaton-electronics-division/PTV-6R0V305-R/13404670

(They are 3Fs)

 

Resistor is https://www.digikey.co.uk/en/products/detail/yageo/FMP100JT-52-2K2/9107445

 

LED is https://www.digikey.co.uk/en/products/detail/broadcom-limited/HLMP-1601/637567

 

Wire is 16 awg

 

Deans is deans

 

Btw I'm studying the pros/cons of omitting the resistor because the LED alone draw more than enough milliamps to function as draining resistor (with its built-in resistor), perhaps this is something you can try

[Sewdhull]

I think if you have a supplementary power source, esp something like capacitors, you will take some of the load off the primary power source.

 

Those smaller caps are likely to have much lower esr than the larger ones and may be able to supply a burst to help the battery whose voltage is sagging which is significant. Getting enough energy out of them to matter would be the issue.

 

There are some some fairly standard caps of 47000uF 16v with 13mOhm ESR. Sadly they would only give you 47mA for a msec for each volt they were above battery voltage, but could supply 77A. getting the right cap for the job, esp given what is available its tricky and you may have found the best cap already for the task.