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Lipo C Rating...variable ratings???

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Lipo C Rating...variable ratings???

Old 08-09-2008, 11:12 PM
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VVRC
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Default Lipo C Rating...variable ratings???

Okay so I was looking at the Zippy's (Lipos 3S1P) and one says Zippy-H which is 20C ~ 30C...which means that it varies from pack to pack...hmmm. Then I see the Zippy-R's which are 25C right on, except they say 25C (minimum)...??? Minimum of what 25C ~ 35C??

https://www.unitedhobbies.com/UNITED...idProduct=6350

https://www.unitedhobbies.com/UNITED...idProduct=7240

So my question is: First off what the heck are they talking about for one, and I am trying to get a battery to use in my Traxxas Slash. and eventually in my race truck (haven't decided yet)...anyway, if I were to buy 2 or 3 of the Zippy-H's that have a variable rate....does that mean one battery will perform better than the other of the same brand. Or would one battery be faster (per say) then the other batteries I ordered?

But, then again the Zippy-R's say 25C minimum.....so same thing apply here too?
Old 08-10-2008, 04:16 AM
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mrasmm
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Default RE: Lipo C Rating...variable ratings???

There are variances in mfg process that account for some variability. Ask any engineer about it and you'll probably get an ear full =P When they say C rating they are talking about max discharge rate while holding a specific voltage without causing the pack to heat up excessively or otherwise be damaged.

For C just thing of capacity, so if it's a 25C pack on a 3500mAh or 3.5Ah pack, you can continuously discharge at 25 times 3.5A or 87.5A

Most likely on the first one it is 20C cont discharge with a 30C burst (which is what they can put out for a short amount of time, mfg's have various burst time ratings too and so they should specify for how long), so that's the same as a 20C pack, or at least that is my guess. Higher C is generally better, but as far as the C rating goes, you can really only compare that number to the same brand of packs. There is no standard for testing C ratings, so mfg's sometimes pump up results with different methods to get better ratings so they can sell more packs. There are some guys that have done their own discharge curve graphs of various packs and C ratings. If you can find one of those for the packs you are looking at they are going to be the be your best way to compare packs side by side.

Generally speaking with electronics you want a good safety margin, this is true with lipo's. They will run cooler and probably last longer and perform better. Find out what the max dishage rate is with a watt meter (or get the info online or something if someone else has the same setup as you) divide that # by .8 for about a 20% margin, round up to the nearest C rating on battery packs and go with that C rating or better.

So for example say your truck has a max discharge of 67A, 67 / .8 = 83.75, say you want a 3500mAh pack, 83.75 / 3.5 = 23.92, so the closest C rating you can get rounding up would be a 25C pack, so you would need to get at least a 25C 3500mAh pack.
Old 08-10-2008, 06:05 AM
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Default RE: Lipo C Rating...variable ratings???

He's right, that means sustained and burst. Some mfg C ratings are on the generous side, quality packs like Flight Power are probably conservatively rated.

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