Limitless Capacitor Question

[Spoc85]

This is a repost as I had no answers on the last thread.


Does anyone know if the Caps in a Cap pack die after so many runs? The Cap pack I was using was made for 6s by a speed runner and he reckons as long as I don’t use it for anything above 23volts they should be right. After 5 runs I started noticing that there wasn’t a spark like there used to be when I would plug the batteries into the ESC. The Car also started cutting out as you will hear in the first Vid. I texted the bloke and he reckons they should be fine but I don’t know. I swapped it out anyway. The car completed a smoother pass although there was not that much of a difference in speed as you’ll see in the second Vid.
Sorry about the length of the second Vid........... the car got loose down the end there?‍

 

[jondilly1974]

This is a repost as I had no answers on the last thread.


Does anyone know if the Caps in a Cap pack die after so many runs? The Cap pack I was using was made for 6s by a speed runner and he reckons as long as I don’t use it for anything above 23volts they should be right. After 5 runs I started noticing that there wasn’t a spark like there used to be when I would plug the batteries into the ESC. The Car also started cutting out as you will hear in the first Vid. I texted the bloke and he reckons they should be fine but I don’t know. I swapped it out anyway. The car completed a smoother pass although there was not that much of a difference in speed as you’ll see in the second Vid.
Sorry about the length of the second Vid........... the car got loose down the end there?‍

View attachment 105401

Have you tried more lipo packs? Do you have anti spark connectors now?

 

[LibertyMKiii]

The spark when you connect your LiPo is not related to having a cap pack or not.

Capacitors do go bad some times for many reasons. The most common visible indicator is a buldge on the top metal which should be flat.

Residue of any sort like the above image would also be an indicator.

To test the Cap Pack: What you want to do is connect the pack to a battery to charge it (10 seconds or so)
Then connect the cap pack to a multimeter and measure the voltage. I do this when the cap pack is new and measure the time it takes to drop "X" voltage. This way you have a base line to compare against later.

The multimeter has infinite internal resistance so the cap pack will start draining power the moment you connect it to the meter.

 

[Spoc85]

Have you tried more lipo packs? Do you have anti spark connectors now?

After I noticed there was no spark when plugging in the Vant 3s 75c batteries, I plugged in a gensacearespammers 6s 60c..... Same thing no spark.
I’ll look into those anti spark connectors?

 

[LibertyMKiii]

The ESC cutting out is related to the fact that you are right around the amp limitations of the BLX185 esc. They tend to choke when you get in the 90-98 mph range. It appears you are there. Next change would be moving to a castle ESC like the MMX8s or XLX2.

 

[Malice]

https://www.arrmaforum.com/threads/esc-quitting-at-90mph.27547/page-2#post-382047

I can't help but feel like he already knows this...

 

[jkflow]

Cap packs do not go bad by using them, they do go bad by applying reverse voltage, overheating or mechanical stresses. They do diminish over time but not be zero all of a sudden.
Yes, sparks are caused by cap packs but the cap packs do not get damaged by them. No spark at initial plug-in can be a sign of not having capacitance but it's a bad indicator.

Crack your wrapping and look at the caps. Look at the voltage rating and overall state of each capacitor.
Anything puffy or coming out of them is a sign of death.

If you ever applied more than the rated voltage they are as good as dead. If they are rated at 25V and you run on 6S that is already close to damaging them but most likely ok. On 8S they are damaged for good. They typically come in 25V, 35V, 60V etc, only the datasheet or the label will tell you what you have.

Reverse voltage typically ends in a spectacular death and you would know right away, with some bad luck you would have splinters in your face, they will explode.

To check:
The cap pack needs to be disconnected or it will discharge into the ESC (or whatever is connected). You can simply hook up a DMM and measure resistance, leave connected for 10 s and switch over to measure voltage. If you measure the voltage (pending DMM) and it stays stable it's a good pack. Value doesn't matter much but measure for a duration and should stay stable (5-10s), minimal decay is ok. Typical DMM output is ~ 2V i.e. that is what I would expect to read.

Alternative:
You could try as suggested by @LibertyMKiii. You would have the unknown of the drain into the ESC. My guess, you should see a slight voltage decay going to zero but really no idea what it will do in the real world. By all means , do not turn on the ESC for this, no danger, just useless and will prevent you from measuring.

 

[Spoc85]

Thanks for the informative responses?. There’s plenty there for me to chew on so I’ll open it up, test and see what I find.