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Mar 06, 2010, 01:27 PM
nsg
nsg
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Discussion

ripple current


Castle folks keep mentioning ripple current as the primary source of spectacular ESC fires. So.. what is acceptable ripple current and what isn't? Specifically, could one (or more, this being a free country) Castle people here comment on the attached pic?

Thanks in advance!
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Mar 06, 2010, 04:36 PM
Put a Quark in it!
nexgen's Avatar
to add to this, what the heck is ripple current anyway? and what does it do to the esc?
Mar 06, 2010, 07:22 PM
A man with too many toys
Quote:
Originally Posted by nexgen
to add to this, what the heck is ripple current anyway? and what does it do to the esc?
If you do a search Patrick discussed this when the ICE first came out. As I recall he did not give any specific recommendations.

Since ripple is available on the data logger it would be nice if CC would give some clue on how to interpret the data. I called Tech Support a long time ago but all they did was ask what the value was and said that I was ok? Why even log ripple if we have no idea if itís good or bad?

Mar 06, 2010, 08:24 PM
MrE
MrE
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Quote:
Originally Posted by RC Man
If you do a search Patrick discussed this when the ICE first came out. As I recall he did not give any specific recommendations.

Since ripple is available on the data logger it would be nice if CC would give some clue on how to interpret the data. I called Tech Support a long time ago but all they did was ask what the value was and said that I was ok? Why even log ripple if we have no idea if itís good or bad?

The closest thing I recall seeing is that "less is better". That still leaves me feeling pretty much in the dark though.
Mar 06, 2010, 09:37 PM
Put a Quark in it!
nexgen's Avatar
Im assuming based on the name of it, that there must be occasions where the current ripples, or jitters, and the esc sees alot of rapidly changing current, or is not able to output it smoothly (?). I assume that the frequency (amount of fluctuations) and the amplitude (diff between low and high) are whats being measured here. and just like a ripple in a pond, less is better. more must mean that the esc has to work harder at making the consistent output.

???????????????????????????
Mar 06, 2010, 09:49 PM
nsg
nsg
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Thread OP
Well, I can assume a number of things, but I'd prefer not to assume...
Mar 06, 2010, 10:09 PM
MrE
MrE
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The input capacitors on the esc are there mostly to smooth out that ripple. Ive been told they have to work harder and get hotter as the ripple current goes up. So it makes sense that less is better.

Id still like some sort of guideline as to how much is too much and how much is good.

Is it some function of the input voltage or the total power draw or how hard your pushing the controller in terms of total watts out or is it a function of how close you are to the peak current draw or the peak voltage or the phases of the moon or ???
Mar 07, 2010, 10:33 AM
nsg
nsg
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Thread OP
Quote:
Originally Posted by RC Man
If you do a search Patrick discussed this when the ICE first came out. As I recall he did not give any specific recommendations.
...
Could you post a link, if you can still find it?

By way of guessing..

ICE logs ripple voltage. I see a curve that looks like a derivative of the throttle - it's maxes out when the throttle is being changed, and it is zero at constant throttle. I would guess the problem is when ripple voltage adds up with the 'normal' battery voltage. If you are already maxed out, that may exceed the voltage the capacitors are rated for, so a capacitor will pop. Now you have a short right between the (combustible) remains of a capacitor. That would cause an open flame fire as described. Interestingly, the model may still be controllable, at least for a few seconds.

If this is correct, the ESC fires should be happening at
1) setups that use max rated voltage: capacitors are close to the rated max to begin with.
2) setups that were logging increased ripple voltage - could be established by examining past logs, if these exist. If the battery came out of the fire alive, ripple currents may be measured on another system
3) soon after takeoff: battery still supplies max voltage

If this is incorrect, there should be reports of ICE fires at 4-5s.

If the above guess is correct, the number to watch for is ripple voltage + max battery voltage. That should be less than what the capacitors are rated for.
Mar 07, 2010, 11:21 AM
A man with too many toys
Quote:
Originally Posted by nsg
Could you post a link, if you can still find it?
https://www.rcgroups.com/forums/show...5&postcount=13



Actually that entire thread has lots of good information.
https://www.rcgroups.com/forums/show....php?t=1101016



Mar 07, 2010, 08:32 PM
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gww528's Avatar
I bought the HV-ICE just to measure ripple current. I was told the ripple current will kill the control board and a 5v ripple voltage was not good. You will get ripple when you ask batteries to supply more amps than they are capable of. I want to test a this with A123 batteries that have a higher internal resistance and see if adding more capacitors will help with the ripple current.
Mar 08, 2010, 06:04 AM
A man with too many toys
Quote:
Originally Posted by gww528
I bought the HV-ICE just to measure ripple current. I was told the ripple current will kill the control board and a 5v ripple voltage was not good. You will get ripple when you ask batteries to supply more amps than they are capable of. I want to test a this with A123 batteries that have a higher internal resistance and see if adding more capacitors will help with the ripple current.
I have done a few tests on A123 and found that they have more than double the ripple of my Turnigy 30C packs. I think that LiPo technology has advanced so much in the last year (now 5c charge) that A123 technology (LiFePO4 chemistry) is becoming obsolete.

Mar 08, 2010, 07:04 AM
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missle's Avatar
Quote:
Originally Posted by gww528
I bought the HV-ICE just to measure ripple current. I was told the ripple current will kill the control board and a 5v ripple voltage was not good. You will get ripple when you ask batteries to supply more amps than they are capable of. I want to test a this with A123 batteries that have a higher internal resistance and see if adding more capacitors will help with the ripple current.
Please post your results here cause I too would like to see if there's benefit to adding extra capacitors.
BTW, anyone knwo off hand what capacitors are on the older HV-85
Mar 08, 2010, 08:53 AM
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gww528's Avatar
Quote:
Originally Posted by RC Man
I have done a few tests on A123 and found that they have more than double the ripple of my Turnigy 30C packs. I think that LiPo technology has advanced so much in the last year (now 5c charge) that A123 technology (LiFePO4 chemistry) is becoming obsolete.

I do agree with you about A123 technology and where Lipo's are heading.
Mar 08, 2010, 08:58 AM
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gww528's Avatar
Quote:
Originally Posted by missle
Please post your results here cause I too would like to see if there's benefit to adding extra capacitors.
BTW, anyone knwo off hand what capacitors are on the older HV-85
The HV-80 ICE is suppose to arrive today. I have already added the extra caps with the HV-85 and they really stabilized the head speed & extended the flight time. Here are the caps I am using...
http://search.digikey.com/scripts/Dk...0-nd&x=14&y=15
Mar 08, 2010, 09:37 AM
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missle's Avatar
Quote:
Originally Posted by gww528
The HV-80 ICE is suppose to arrive today. I have already added the extra caps with the HV-85 and they really stabilized the head speed & extended the flight time. Here are the caps I am using...
http://search.digikey.com/scripts/Dk...0-nd&x=14&y=15
Thanks so much for the link and the info and now I must ask for one more huge favor; Could you post a quick how-to or suggested setup on how you did yours or at least a pic showing exactly where you've located yours. I'd like to install some on mines as I just put one back on my O550 heli. Thanks so much.


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