Determine the Actual C Rating of a LiPo Battery, Formula Exposed!

[@christiannasca3520]

Besides the inflated nature of the C rating. Why is there a C rating anyway, if the actual current in Amps, a battery is capable delivering, depends on the capacity? While, what really matters for the application is the current only! What I mean is: A 5000mAh battery with 50C could technically deliver 250A. A 2500mAh battery would need a 100C rating to provide the same 250A. A 2500mAh battery with the same 50C as the first example, would only be able to deliver 125A! So what good is it to require a 50C or a 100C rating for a given application, if that figure still doesn't tell us, how much current the battery will be able to provide, without throwing the capacity into the equation as well? What they should print on the battery label instead, is simply the current, which the battery can deliver! After all that is what an ESC bears on its label as a technical requirement for it to operate! 🧐

[@RCexplained]

Absolutely agree. I think a C rating leaves the answer a bit cloudy and easier to inflate. Inflating the max continuous discharge current would not be easy. That's my take.

[@christiannasca3520]

@@RCexplained Absolutely correct! Inflating a precise Amp rating on a battery label would come closer to a blatant scam, as if inflating the voltage and claiming an actual 2S battery to be a 3S. Nobody would accept such a blatant scam. But, as you often mentioned, there is no definitive standard to even measure the C rating, which is a perfect setup to get creative...

[@RCexplained]

Yep, exactly, and this is why I buy lots of LiPo's to test their performance and share the results!

[@pepegac9999]

we should convince the goverments that the C rating certification is acualy really needed and it wouldn't be hard since we use them everywhere to power everything and you often see dangeruess uses of batteries that lead to catastrophies just cause of the manifacturer that lied

[@sdy5001]

I hope that people actually take the time to run some of their batteries and post them, ideally with the Brand as well, so we can maybe begin to start to come up with a list of batteries/manufacturers worth giving our money to. I will be posting at least 3 or 4 later on when I get to my shop!

[@TheKjelmo]

You can find that right here: www.rcgroups.com/forums/showthread.php?1767093-Battery-Load-Test-Comparisons

[@yodad4776]

Hello from NZ I'm LOVING this channel and your data points on your topics ..it's GREAT ..cheers ..just subscribed ..keep them coming

[@RCexplained]

Welcome aboard! TY for the sub

[@CharlesGarnierRC]

Hi, On your website, I understand the formula but how do you come up with the Maximum Contiunus Current inn Amps? What's the formula for that? Thank you!

[@solarsynapse]

For a real world test use a volt/amp/watt meter in series with a high draw motor wide open. Divide your amp draw by your capacity and that is exactly what the pack is providing at that moment. 100A draw divided by a 5A pack is 20C. If you have it and your meter can handle it, try a higher power ESC and Motor. I have an HRB that can deliver around 65A and a Roaring Top that can deliver 100A with the same load. The voltage drop of the HRB is severe and the higher internal resistance makes the pack hot. I have a 6 year old Power Hobby pack that can do 80A.

[@RCexplained]

Yep, I did that on Zeee batteries on the channel. But more recently and quite a few packs I've tested, I've looked at IR and loaded power @ ~105A

[@rickyaditya]

Hi Ryan, How do we determine the IR value from the charger? As you know the IR value will be fluctuate as the charging process occurs. On 5:08 the battery almost fully charged when you took the IR value.

[@dannyvonduck659]

Hi I have a question about 4 new batteries I just purchased - these are rated 7,6V HV 2s2p lipo's rated as 140C - 5c Charging - your website doesn't seem to be able calculate with this. However if I use the 120C which is an option on your website I come to shocking results. The measured IR at 1.5 A charge is 3,6 mΩ for these 5800 mAh batteries - When I enter those numbers on your website these batteries should be rated as 17,3C ---thats a really big difference compared to the advertised 140C. Am I doing something wrong? These are the - Abisma Competition Lipo Shorty 5800mAh 140C 2S2P HV Batteries

[@motorbreathjz]

he explained the formula.. you have to divide the constant use of 2500 by the square root of your batteries Mah capacity X the internal resistance on your worse cell.. Mah x IR =???? then square that number and divide it by 2500. that will give you your C rating

[@colin1992]

Ryan i just got myself another infraction, feels good to be shredding tires again, at some point ill convert it to an off road rig

[@RCexplained]

Excellent!

[@luisfelipeortega9411]

I just want to make shure if it´s right, but why considering just 1 cell for internal resistance instead of total pack cells internal resistance? Do you have the formula oficial source?

[@KasprGoodman]

His math is not correct. You need total IR if using total capacity. If not you need to consider how many cells and how they are internally connected in determining how you calculate. His principle is right but this math is wrong. You don't just ignore a load and heat source because it isn't as big. If a 2s pack it experiences a 2 cell total output resistance due to being connected in series. Throw some parallels in there and it gets a little more tricky but not bad.

[@markdellebovi5171]

How are you coming up with this formula? Are you using Ohms Law: V x IR or P = I^2 x R? Formula is very suspect without some sort of explanation as to how you come up with formula and 2500 constant. "Extensive Data collection" doesn't really do it for me.

[@RCexplained]

Yes, it was done with extensive data collection. All data points were plotted on a graph, and a regression analysis was employed to determine the line of best fit. Electrical theory wasn't utilized in this process. Although the formula still tends to overestimate the actual c rating, it gets significantly closer than any specification you'll find on a battery label. Additionally, I've shared battery test results, along with the methodology I employed to get the true C rating of a battery. These battery test videos are unpopular but there are several I've uploaded. Only one video shows me getting the true C rating through a loaded run.

[@jaycullen9901]

Where does the equation you show come from? Also, you are using the manufacturer's rating as part of the equation, but that number may just be made up. Also, when measuring the battery internal resistance, shouldn't a test current be specified such as 1C? Some of these internal resistance measuring devices use a very low test current and get an unrealistic low internal resistance measurement. It would be good to determine a C rating from internal resistance and also maybe temperature rise. Finally, thank you very much for trying to address this sticky industry problem and making such a great video.

[@RCexplained]

The equation comes from a lot of testing and number crunching. You can see the battery tests we do on the channel. I've found a batteries true internal resistance by loading it at that value and making certain it doesn't get over temp. I may have missed saying it in this video, we use 1.5C on the channel.

[@solarsynapse]

A good quality new pack (like Roaring Top) will struggle to provide half of the rated C. The junk packs (like HRB) may only be about a fifth.

[@rhorn3017]

Omg... The companies aren't telling the truth?? 🤔

[@solarsynapse]

Exodus 20:7

[@fazekasgabor4143]

Hello! Does this formula (2500/sqrt(capacity*IR)) applies to li-ion batteries as well?

[@fazekasgabor4143]

I've salvaged some batteries from an old Lenovo battery pack, and according to this formula it gives a maximum current of around 25A. Is that possible?

[@RCexplained]

The formula is untested for Liion batteries. You can cross reference specs on the cells to find max current.

[@edmundblanchard4744]

Great video Ryan! I'm just getting back into the hobby from 30 years ago. I have a WL Toys144001 car that came with 2s 2200 mah 25c, brushed 550 motor. I'm preparing for an upgrade my 144001 to brushless. Planning to us a 3650 - 5900kv with the Quicrun 10BL120 ESC for Speed Runs and general parking lot driving. I'm trying to match the best lipo mah and c rating for this setup. Are you able to recommend lipo to work with this setup? I've watched a lot of your videos but still somewhat confused. Here are the motor Specs: Specification: 3650 - 5900kv Material: Metal + Magnet Weight: 204g Item Name: 3650/3T Motor Watts: 900 Max Voltage:

[@RCexplained]

If your priority is speed. Largest pack in terms of capacity and c rating is best.

[@edmundblanchard4744]

@@RCexplained Thank you Ryan for returning my question. 👊😎👍

[@khrisyeet8022]

Love the content and love the channel. With that being said maybe this could be the Debbie Downer channel. I always get the wind taken out of my sails from these videos.

[@benjoseph4723]

Would this also work with a larger LifePo4 batter? 30Ah Rated C in description: 5C max continuous 3-5 milliohm I got a calculation of 7.2168 Would that be right?

[@RCexplained]

Theoretically yes it should. I have not experimented with packs larger than 8000mAh however.

[@juliosibarani6527]

Hello, i wanna ask, how do we know the number of internal resistance ? Thank you for the video

[@RCexplained]

This comes from many chargers through the charge cycle.

[@martins2657]

Thank so much for content you are making. This is what helps me understand, why my new battery is so hot.

[@philiplewis957]

Have you changed the formula on the website that calculates the C rating? I put the formula that appears in the video at 3:50 into Excel and I'm getting similar but different figures, if it has been changed can you share the new formula? Sorry to be a pain but I like to really get into the formula to understand it fully, thanks in advance. Great video though, a lot of food for thought for many.

[@RCexplained]

No it's the same formula.

[@relaxingmusic7301]

@@RCexplained where does it come from ? I mean have you a demo or something to explain it ? I know i'm a bit penible maybe but i like to really understand from where things and formula come. sorry for my bad english I m french ^^ Anyway I love your videos, it's really cool that you show some calculs and explanation for all the rc stuff !! Thank you so much

[@motorbreathjz]

the formula is at 3:40 Total Mah x IR squared. then divide that number by 2500.. if this forumula is accurate then you have a simple easy way to see you C rating

[@danmartinrc]

I ran a bunch of my batteries with a 1.5c charge rate on a Spektrum S2100 charger and took the first internal resistance reading that popped up after about a minute. This is what I got: Spektrum 4s 5000 100c ir=5.8 c=14.7 4s 5000 100c ir=4.0 c=17.7 4s 2200 100c ir=15.5 c=13.5 4s 2200 50c ir=15.6 c=13.5 4s 2200 50c it=14.7 c=13.9 3s 2200 50c ir=10.9 c=16.3 3s 2200 30c ir=14.7 c=13.9 Venom 3s 5000 35c ir=5.8 c=14.7 Gens Ace Tattu 3s 1300 45c ir=19.4 c=15.6 None were anywhere close to their advertised C rating and there was almost no difference between 30c, 50c, and 100c packs. It makes me a little suspicious of the formula or how the resistance is measured. Or is there really no difference between a 100c and 30c pack from the same manufacture?

[@RCexplained]

Definitely strange that they all work out to similar values here. Formula is hard to argue with but the measuring tool could be a source of error. If 5.8 milliohm is true on the 5000mAh pack, this would have a hard time dealing with the power system installed in the recent EDF Jet video doing 249km/h that I posted. Just for reference, I use 4000mAh 45C packs and they have an average cell resistance on the charger of 3.2 milliohm. This is measured at a 1.5C charge rate 1 minute after starting the charge from 3.80V per cell. Make sure the cell resistance is measured quickly after initiating the charge and it's best to start the charge around 3.80V. Temp should be room temperature. Lots of resistance influencers here.

[@roberttruesdell6151]

If those are your IR numbers you need new packs. But you are suppose to get your ir numbers with a pack at storage and room temp. And then charge. And take the ir reading when it’s close to finished

[@Mr.Wednesday.]

What about lihv graphene, no différence?

[@RandomloserDK]

Was the calculator on the site get updated? When I used it some time ago, I got a result saying something like "Less than 20".

[@RCexplained]

yes, a much more simple formula is used.

[@RandomloserDK]

@@RCexplained You should consider writing the calculator in JavaScript, so you don't have to reload the page every time. As the load/response time on the server seems slow.

[@jankowalski-tu7zg]

Could someone please expain me this, I have spektrum 6s 6800mah 120C g2 smart pack and according to the formula from the site in order to get out a 120c from this pack the internal resistance shoul be around 0,06 miliohm ( yes the coma is where it should be)

[@RCexplained]

Yes, 0.06 milliohm shows you that manufactures have no business putting a 120C rating on a LiPo battery in 2023. To test this further, place an 820A load on the pack until it fully discharges and see what happens.

[@Cwimpee84]

I know a bunch of people that are sad rite now lol. But really this is so true. Great point to bring up also. I can name atleast 3 pretty big name lipos that definitely are not what the say they are. As usual, great detailed video ..

[@RCexplained]

Thanks for sharing!!

[@hansdampf3576]

Lipo Brands hate these tricks…

[@CUBEoneVX]

So what does this tells us about Traxxas 25c on all lipo batteries? are those real 25c?

[@RCexplained]

I need a couple traxxas packs and could let you know.

[@Innvctus]

Had some issues calculating mine. Website won’t let me choose higher than 120c. My battery is a SMC 3s 8600mah 250c. I don’t have a way to calculate my resistance of the cells though. I can’t find anyone else who has tested this battery and if it’s C rating is true.

[@solarsynapse]

That would be 2,150 Amps, so not gonna happen. Your wires and connector would liquefy. Even 80C would be 688 Amps. The wire feeding your house from the power company the diameter of your thumb is for 200 Amps.

[@ashraz1709]

is the c rating determines what esc to use?

[@RCexplained]

no

[@ashraz1709]

@@RCexplained tq

[@electricpowa5002]

really nice video thanks

[@RCexplained]

So nice of you!

[@MrKuztumpainterz]

Is there a way(s) to lower the IR’s?

[@RCexplained]

Is this what you are asking about? kzbin.info/www/bejne/fJKYlmxmlrWbjtU

[@nocknock4832]

Where is the numerator of "True C Rating", 2500 derived from?

[@RCexplained]

Statistical analysis

[@yellock1]

So if it say your pack is 26c do multiply it by the cells seeing that ur only calculating one cell? Example 26c X 4s = 104c total c

[@RCexplained]

no, cell count is irrelevant.

[@yellock1]

@@RCexplained how is that accurate if your only measuring 1 cell

[@RCexplained]

cell count or voltage does not come in to the equation. The formula is C Rating x Capacity = Max Discharge Rate.

[@FirstLast-tx3yj]

@@RCexplained have you tested the internal resistance of zeee 9000mah cells? They claim 100C while the red one claimed 120C And I want to know the true C rating without buying So please let me know the true C rating of zeee just in the ballpark please

[@ET-ve3wb]

This has to be true, I think the calculation only accounts for 1 cell not all. I think depending on the cells you have you would get the C end result calculation and times it by how many cells the battery has. It doesn't make sense for a 4s 100c 6000mah lipo to only have a C rating of 24c" I wish there was a Cell Count option in the calculator. More cells equal more Cs 🤣

[@ИванКозьяков-ф9т]

Super easy! I love your videos!

[@RogallaMarineRC]

Very cool great info!

[@1976Nyquil]

According to your calculator it is telling me that my battery is only putting out 183 continuous amps but how is my recorded data from my castle esc saying that I'm drawing way more amps than that on my speed runs. I know it has bursts but what I'm seeing is way different than what your calculator is telling me. My esc would catch on fire all the time for what this calculator is telling me

[@RCexplained]

You can't compare continuous current draw to your 5 second full throttle pass. Continuous means for the entire duration of your battery. I'm sure you are no where close to this. Your battery could possibly support well over one thousand amps for one millisecond. As loaded time duration increases, current in amps decrease until you get to the continuous rated specification.

[@1976Nyquil]

@RCexplained but if my 5 second burst is showing over 600 amps would my constant be at 300 amps then if burst rate is double

[@RCexplained]

The 2 to 1 factor is a general rule of thumb. A short couple second burst will be more than 2 to 1. A few microseconds could easily be more than 1000A.

[@motorbreathjz]

@@1976Nyquil everything your saying is true.. for a 5 second pass.. lol.. thats not the same as a average or general use application

[@ConditionZero76]

so I have a 2s 6400 MAH lipo with 120C rating. if I multiply 6400 Xs 120 that = 772,800 How does this tell me what C value to charge it at? everybody says charge around 1 to 2 C & never higher than 5c, how does 772 thousand tell me how many C to charge at? Thanks

[@motorbreathjz]

your all over the place.. you need to find your internal resistance first to get your C amp discharge. and the charge c raiting for a 6800 mah battery is 6.8 amps... 2c would be 13.6 amps.. most people stick with 1c charge ..its hard to trust a company.. better off just doing 1c max charge...

[@mohdkhairulhidayatabdulrah4157]

Good video for sharing. 👍🏻👍🏻

[@nigelthompson874]

Not sure you understand c rating? Are you suggesting only zero 0hm I.R. will be correct as labeled? Maybe. However a 100 C falsely labeled and a 20 C correctly labeled battery each with say 3 Ohm cells will come up as close to correct. Don’t think so!

[@RCexplained]

I don't follow what your point is. Not sure what you mean by zero ohm IR either. No electric component can hit a true zero ohms.

[@motorbreathjz]

the whole point of this video is to tell you the printed C rating is most of the time a lie.. it has nothing to do with c rating in a mathmatical/science sense being true or not..

[@motorbreathjz]

this is cool and all but what about the batteries that have no C raiting on the label or paperwork

[@RCexplained]

What do you mean? The C rating is calculated based on IR.

[@motorbreathjz]

@@RCexplained ok i took more time studying this video because my brains slow. i see your formula.. 2500 divided by batteries capacity square root X highest internal resistance. with that aside i cant for the life of me figure out how your website came up with 36.1C on a battery with 4000mah and 1.2 mOhm internal resistance. with your formula.. 2500 divided by 63.24 (square root of 4000) X 1.2 = 47.43C X4 Ah = 189.7 max continuous amps i am now totally baffled on how to find the c rating for my batteries

[@RCexplained]

@@motorbreathjz you are changing the formula by taking only the capacity under the square root. Put both terms under the square root.

[@motorbreathjz]

@@RCexplained you are right. i thought the formula was square root of Mah.. and then separately from that i would divide by 2500 and multiple the IR which is wrong for anyone reading this in the future tho OP shows you the formula it is easily missunderstood when you have a slow brain. the formula is exactly as shown your batteries total Mah x internal resistance (highest resistance cell for safety and common sense reasons) and then square that number and then divide by 2500. thank you RCexplained and im sorry to burden you with stupidity.

[@RCexplained]

I'm hear to help, glad you got it sorted out.

[@paulmartin8051]

yes but what is the actual formula rather than using a website with an invisible formula?

[@RCexplained]

Wait what? I'm very confused.

[@superdriver777]

3:47 there you go!

[@UpInSmoke54]

I bought a 3S 5000mA battery from Sequre for my spot welder and they advertise 100c, the battery is not performing as it should at all, I put the battery on the charger and got 8-2-1 milliohms!!!!! Edit Brand is Zop Power and it's cheap at $35us maybe that's why its performing poorly...🤣

[@JoyGadang]

more video more learning i have

[@tomgreysk]

When i dont know C reating?

[@bobadingo]

C rating and capacity are bogus numbers which mean absolutely "NOTHING " The ONLY thing that matters is how high of run voltage you have under The maximum load! and it is very beneficial to do it with telemetry for a particular application. The higher the Volts output under load, the greater the output power!!.. .

[@MrZamz84]

Mantap

[@FratDede]

Page and also video not explains where this formula comes. Very unlogical unfortunately..

[@RCexplained]

The formula comes from a lot of hard work and data collection.

[@FratDede]

@@RCexplained I am sure it comes from hard work. But still no explanation? where this 2500 constant comes? Or when i enter milliohm value how it decides to C rate? normally V = I x R and 4.2v per cell with milliohm resistances not giving your values. Because of that i am saying it is unsupported work.

[@motorbreathjz]

@@FratDede the formula is at 3:40 my man..

[@overbuiltautomotive1299]

The number one resion not to buy into their claim made in chiny just the way it is sadly