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Old 07-25-2014, 05:35 AM   #1
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Default why are lipos rated the way they are

Why cant the be rated by cca or some useful realistic # it aquires thru a test?

like how many amps a battery can flow without droping below say 7.4v from a fully charged state?
then also include it Mah info? Would this # be much more referable than just a C rating thats bs?
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Old 07-25-2014, 06:45 AM   #2
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I never found CCA to be a useful number.

Lead acid motive power batteries (like a deep cycle battery for a trolling motor, or a electric forklift battery) are rated in amp hours. RC batteries are rated in miliamp hours.

For one, I always look at the charger and watch how many maH the battery takes when I charge it. Occasionally I'll even cycle a battery to see what it's condition is.

I always thought the C rating indicated a maximum charge rate, but I'm not sure anyone pays attention to them anymore. Some of those guys who fly competition gliders will dump a 10s battery to 0 volts in 30 seconds. They charge at 80 amps.
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Old 07-25-2014, 08:27 AM   #3
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Mah and Ah, are ratings for capacity. How many amps can the battery put out for how long. A group 31 battery and a 8D battery will have the same 1100 amps CCA rating, but the 8D battery will last 5 times longer on a charge.

CCA is the instantaneous power output of the battery. A John Deere 6068TF150 likes a battery with more than 800 CCA. Even though the starter only requires about 200 amps. The higher the CCA, the less voltage drop during cranking. Less CCA will lead to slower cranking and hard starting, and the voltage drop can upset some of todays electronics.

C rating is similar, but is relative to the mah rating. 5000 mah battery is 5amps. 5 x C Rating = how much the battery can output. But I don't think there is a spec for how long.

Why is the C rating relative to capacity in Lipos? Because they're sloppy goo, not lead acid cells. Bigger lipo cells flow power through the goo better.

A 5000mah, 50c battery can output 250 amps? Not for long.
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Old 07-25-2014, 10:38 AM   #4
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Thats where my logic comes into play .
If that 5000/50c is rated to put out 250a how many amps can it deliver for a constant (but short) period of time with out dropping below a given voltage (say 7.4)?
example: (i make these # up,for referance only)

5000/50c
90a for 10sec =7.4
7200/80c
120a for 10sec =7.4
6000/90c
100a for 10sec =7.4
my thinking it would show how good a battery can flow the current ,which to me would help me figure out which battery to pic to run a given class.
but of course weight and mah are 2 other factors i consider in purchasing packs.
so if 2...equal mah/weight packs supply different amps you would know which is better (by having better power delivery)
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Old 07-25-2014, 11:10 AM   #5
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Quote:
Originally Posted by jlfx car audio View Post
Thats where my logic comes into play .
If that 5000/50c is rated to put out 250a how many amps can it deliver for a constant (but short) period of time with out dropping below a given voltage (say 7.4)?
example: (i make these # up,for referance only)

5000/50c
90a for 10sec =7.4
7200/80c
120a for 10sec =7.4
6000/90c
100a for 10sec =7.4
my thinking it would show how good a battery can flow the current ,which to me would help me figure out which battery to pic to run a given class.
but of course weight and mah are 2 other factors i consider in purchasing packs.
so if 2...equal mah/weight packs supply different amps you would know which is better (by having better power delivery)
Why would lipo sellers want honest numbers on their cells? If that happened no one would pay top dollar for big name cells as we'd all know that BrandX or whatever has the same performance for half the cost.

Only the small number of sellers doing top spec cells for a low price (such as SMC) would be in business under such a system, and they couldn't cope with the demand.

So bullshit made-up numbers are here to stay.
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Old 07-25-2014, 11:23 AM   #6
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Ding ding think you figured it out. Lol
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Old 07-25-2014, 11:43 PM   #7
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The Rc business is no different than other businesses out there....
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Old 07-26-2014, 08:59 AM   #8
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Part of the problem is that there are multiple manufacturers- red cases, orange cases, black cases, etc. in the NiCd/Mh days there was only one or two, and the matchers/vendors had to duke it out with each other. If your numbers weren't accurate, news got out quick. Now that mfg's use "C" ratings instead of voltage and runtime, matchers are hamstrung. C rating is just for advertising.
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Old 07-26-2014, 09:29 AM   #9
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Quote:
Originally Posted by BadSign View Post
Part of the problem is that there are multiple manufacturers- red cases, orange cases, black cases, etc. in the NiCd/Mh days there was only one or two, and the matchers/vendors had to duke it out with each other. If your numbers weren't accurate, news got out quick. Now that mfg's use "C" ratings instead of voltage and runtime, matchers are hamstrung. C rating is just for advertising.

There's only two manufacturers of Lipo batteries as well, but they sell raw cells to many companies and don't have their own brands sold directly to the public, so third parties can do whatever they want. For instance sell gobledygook to suckers.

As for maximum discharge rates, the manufacturers rate and limit our Lipos to no more than 50A for safety reasons so no, you won't get 250A out of a Lipo even for a wink and even if you blew crystal meth up its arse.
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Old 07-26-2014, 09:34 AM   #10
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the C rating is it's power delivery. you can tell a big difference in 2 batteries of the same size and brand that have 2 different C ratings. the more c it has the better it is.

I have a few lower c rated batteries and a few higher. the higher ones deliver noticeably better punch and higher speeds than the lower ones. it's not a BS #
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Old 07-26-2014, 11:16 AM   #11
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Quote:
Originally Posted by mtpocketsracing View Post
the C rating is it's power delivery. you can tell a big difference in 2 batteries of the same size and brand that have 2 different C ratings. the more c it has the better it is.

I have a few lower c rated batteries and a few higher. the higher ones deliver noticeably better punch and higher speeds than the lower ones. it's not a BS #
I think that's what the different vendors would like us to believe but there's no hard data to support this. There is some connection between C ratings and battery current delivery, but not obvious in the sense above. As I explained, batteries are limited in current delivery because otherwise they would go into avalanche discharge and would explode. Our batteries can tolerate momentarily higher currents, but this is not quantified in any way. We just know they are capable of short bursts, but not how short we are talking about. 1 second? 1/10 of a second? Either way, it's not in the (multiple) seconds, that's for sure.

Another unknown which confuses things further is that nobody knows how rapidly the battery can ramp up the current. Some may be better than others, but again, we only have soft data ("feel"). This can not be part of a serious rating, no matter what the manufacturer (vendor) tells us.
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Old 07-26-2014, 02:03 PM   #12
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Matching used to be the core of the RC battery business. That business has died in the LiPo era... apparently for no good reason...

...or perhaps the good reason is that all the cells are virtually identical and that matching would offer no competitive advantage any more.

It's probably easier to sell cells off the back of a bit of mythology than hard data.
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Old 07-26-2014, 02:42 PM   #13
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I guess every racer needs to develop their own personal benchmark testing either on or off the track, but it would have been nice if the industry had developed some sort of standard... Until then, it will be thunderpower for life. as far as I am concerned: thunderpower balanced electricity + thunderpower power supply + thunderpower charger + thunderpower battery= TQ and WIN !!!!!!! LOL!!!!!!!
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the C rating is it's power delivery. you can tell a big difference in 2 batteries of the same size and brand that have 2 different C ratings. the more c it has the better it is.

I have a few lower c rated batteries and a few higher. the higher ones deliver noticeably better punch and higher speeds than the lower ones. it's not a BS #
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Old 07-26-2014, 03:17 PM   #14
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Here in south Germany the Reedy 7000mAh LiPos have the reputation to have a little more punch for the first three minutes before falling to a normal level. Orion and other brands seem to be a little on the backfoot here. As user of the mentioned Reedy battery I would underline this. If there are only two manufacturers there should only be two battery levels...
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Old 07-26-2014, 04:01 PM   #15
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Quote:
Originally Posted by wtcc View Post
Here in south Germany the Reedy 7000mAh LiPos have the reputation to have a little more punch for the first three minutes before falling to a normal level. Orion and other brands seem to be a little on the backfoot here. As user of the mentioned Reedy battery I would underline this. If there are only two manufacturers there should only be two battery levels...
There are a lot more than just two battery manufactures. And within each manufacture you can get different "grades" of cells in your packs. Some choose the cheaper cells to make more $$ and some use the higher grade cells for better performing packs. Just all up to how much each company wants to spend on their packs.

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