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-   -   Dead capacitors (https://www.rctech.net/forum/radio-electronics/1011600-dead-capacitors.html)

stuffandthat 02-25-2018 02:21 AM

Dead capacitors
 
Hey guys, did something a bit dumb today. I accidently connected the the battery around the wrong way which caused a lot smoke and maybe a little flame from the capacitors of my Pico ESC. I'm hoping only caps have died. I'm going to order a new capacitor module but the only supplier here in Australia has the 3 capacitor module that's on the MMax Pro, where the Pico only has two caps. Will this work with the Pico?

Roelof 02-25-2018 02:47 AM

It will work, a capacitor bank is just acting as a buffer and a high frequency filter.

But why searching for a specific RC capacitor bank, go to an electronic component shop and you can find the capacitors in all sizes and values.

But you have to fear the ESC is toasted, you can still try it w/o the capacitor bank.

stuffandthat 02-25-2018 03:11 AM


Originally Posted by Roelof (Post 15167447)
But you have to fear the ESC is toasted, you can still try it w/o the capacitor bank.

There's a good chance it will be toasted, but I will check it. It will run without the capacitors?! What do they do exactly?

gigaplex 02-25-2018 03:18 AM


Originally Posted by stuffandthat (Post 15167450)
There's a good chance it will be toasted, but I will check it. It will run without the capacitors?! What do they do exactly?

They smooth out the voltage when the current flow changes abruptly, which helps protect the ESC and can potentially give you a bit more punch.

Don't run the ESC normally without them, but it's fine to test if the ESC is functional without them.

the rc guy 02-25-2018 04:53 AM

stuff so you reversed the polarity on the esc and poof caps went.. esc is toast..caps on esc don't work as a high freq filter .not wired in that way.. they do help voltage sags only when wired like they are on your esc.

chuck_thehammer 02-25-2018 05:18 AM

.
good thing the 'caps' did not explode... they can.. when powered backwards..but they do have a pressure release body
electrolytic capacitors ... they store and release power...
they are not high frequency filter capacitors..

test the ESC.. but the 'fet's' hate that.. big time.

stuffandthat 02-25-2018 12:17 PM


Originally Posted by chuck_thehammer (Post 15167487)
test the ESC.. but the 'fet's' hate that.. big time.

I reckon it's probably dead but how should I test it? Cut the capacitor module off and connect the battery and see if it runs?

chuck_thehammer 02-25-2018 01:19 PM


Originally Posted by stuffandthat (Post 15167799)
I reckon it's probably dead but how should I test it? Cut the capacitor module off and connect the battery and see if it runs?

yes,,, see if it drives a motor.. and check and see if bec works a servo.

faqcya 02-25-2018 01:25 PM


Originally Posted by stuffandthat (Post 15167799)
I reckon it's probably dead but how should I test it? Cut the capacitor module off and connect the battery and see if it runs?

You could always go to your local electronics store and buy a 4700uf 16v capacitor for cheap then wire it in place of your existing cap bank and see if the esc still works.

stuffandthat 02-25-2018 01:31 PM


Originally Posted by faqcya (Post 15167852)
You could always go to your local electronics store and buy a 4700uf 16v capacitor for cheap then wire it in place of your existing cap bank and see if the esc still works.

Will the ESC still power on without a capacitor?

chuck_thehammer 02-25-2018 01:37 PM


Originally Posted by stuffandthat (Post 15167858)
Will the ESC still power on without a capacitor?

YES, its main function is to prevent a low voltage issue at Full power starts...
like a run-away.. or shudder..

for testing it is fine..

Roelof 02-25-2018 01:44 PM

Yes, the capacitors are parallel connected to the battery wires, they only provide a more stable voltage, not only as a voltage buffer but also as an high frequency filter to damp the high frequency ripple on the power lines.

Without them a normal ESC will still work but the ESC can become hotter if you still want to use it to drive a car.

stuffandthat 02-25-2018 02:06 PM

Thanks guys. Will give it a test tonight and see what happens. If it's dead I'll send it in for repair. Probably going to be a costly mistake!

faqcya 02-25-2018 02:46 PM


Originally Posted by stuffandthat (Post 15167888)
Thanks guys. Will give it a test tonight and see what happens. If it's dead I'll send it in for repair. Probably going to be a costly mistake!

Have you ever had a high power car stereo? It's easy to see at night when stereo is cranked up and the bass booms, the car headlights will dim. That's because the amplifier is pulling more amps then the battery can deliver. One solution is to add a capacitor inline to the amp. That's the same thing these capacitors are doing. When you pull full throttle from a dead stop the motor will pull a lot of current causing ripples in the battery voltage which can cause problems for the esc's fets.
You can still test the esc though to see if it's fried simply by disconnecting the pinion connecting the battery and squeezing the trigger once. If it turns the esc is good if not it's fried. CAUTION you don't want to do a lot of free spinning of the motor it's not good for it, but one quick test won't hurt anything.

faqcya 02-25-2018 02:49 PM


Originally Posted by stuffandthat (Post 15167888)
Thanks guys. Will give it a test tonight and see what happens. If it's dead I'll send it in for repair. Probably going to be a costly mistake!

If you fried it a manufacturer won't cover it. They don't cover esc's that were hooked up reverse polarity. And it's possible that it's not fried I accidentally hooked one up backwards once and got lucky.


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