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Can discharge rate be too high?

Old 09-26-2022, 01:34 AM
  #1  
boodaghost
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Default Can discharge rate be too high?

Getting back into this hobby after an 11 or 12-year hiatus. The thing I'm noticing is the discharge rate on lipos is way higher than what it used to be. If it was 35 on an 11.1 2200mah battery, that was considered high. That is, at least, the way I recall it.
Can the discharge rate be too high when flying say, a 400 size brushless or something similar? Can it fry components? I've got all kinds of decade old HH electrics and it's already bad enough that if I crash one, parts are scarce are completely unavailable all together.
Thanks for the help!
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Old 09-26-2022, 09:44 PM
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ron_van_sommeren
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No worries, battery discharge rating a.k.a. C-rating cannot be too high. It is a maximum rating, not the actual current, batteries (and controllers) don't force feed the motor with a certain current.
Each fuse in the fuse box of my apartment can handle 16A, but that does not mean 16A flowing all the time.
Pitch, voltage≤, velocity konstant Kv≥ and prop-diameter⁴ determine actual current, not the battery (unless rating is way too low), not the ESC.

Apart from the above, there's lies, big lies ... and C-ratings. I would at least half a/any specced C-rating. Your batteries will love you for it.

About C-ratings, discharge rates, stickertuning and other 'optimistic' ... eeeh ... 'marketing'.
Using uniform tests, getting published/refered in opening posts:
Battery Load Test Comparisons - RCG

From the link posted by JohnCT, this well help, some excellent battery info
LiPo best care practices - post#8346 - RCG
Contents
  • Maximizing Cycle Life and Performance
  • Storage Facts
  • Fun Facts
  • Nerd Facts a.k.a Solid-Electrolyte Interphase (SEI) layer
  • Thermal Runaway
  • Results, Comparisons, and Lies exposed in opening posts

And there's this post#198 by Frank Siegert, about (yet) another advantage of heating a battery to body temperature, through and through, for about one hour. Before using and before charging. Not only voltage is higher and battery wear lower, but also ...
Short flight time is killing me - post#198

Want more background info?
Lithium Polymer Battery Technology - RCG
An introduction, with special consideration of RC model lithium batteries.
By dipl.-ing. Frank Siegert, a.k.a. RCG user bzfrank.

Last edited by ron_van_sommeren; 09-28-2022 at 02:58 PM.
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Old 09-27-2022, 08:11 AM
  #3  
boodaghost
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Thanks! I saw this post when I was searching the forum but it didn't answer my question directly as you have here. Really appreciate. Like I said, I'm getting back into this hobby after several years. Doesn't hurt to know more.
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Old 09-28-2022, 01:33 AM
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ron_van_sommeren
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Originally Posted by RCModelReviews
...a lot of the time, C stands for crap...
Have you ever wondered how a 100C battery gets away with an XT60 connector that is only rated for 60A? If you use lipo batteries in your RC planes, helis or drones then you need to watch this video and learn why the C rating of your batteries might not be what you think it is. There's also some other lipo info in this video that hopefully everyone will find interesting and of some value.
www.liporatings.com
www.rcmodelreviews.com
www.youtube.com/user/RCModelReviews/videos

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Old 09-28-2022, 11:33 AM
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quorneng
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boodaghost
Also be aware that LiPo c rating can be subject to "marketing" influences.
I have found LiPo with claimed 150c continuous rating. That would be a current giving a full discharge in just 24 seconds!.
They do not say what would happen to the LiPo if you did!
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Old 09-29-2022, 12:41 AM
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Wildflyer
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The only thing I have ever seen was a racing battery for cars I think with an extreme C rating, The company said in the ad that the battery must be used or drained down within 20 minutes after full charge, It was something like 200 C
I don't know what would happen if left too long, this was several years ago, so maybe even that doesn't matter now.
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