LiPo Testing and Comparison Data
 

For the last year and a half Ive been testing LiPos using testing equipment in order to be able to run repeatable identical tests and capturing the data using a data logger. Ive compiled the results in an excel spread sheet so the results can be filtered for comparisons. Im still continuing my work so this is just the beginning but Ive already tested well over 50 different LiPos. If this is something that interests you you can check out my work HERE. I explain all of whys, hows, and details of what Im doing. Please keep the comments and questions constructive. Thanks :)

It feels a bit strange to link to another forum so if thats an issue with anyone then I apologize. Im just trying to share my work without having to post things over and over and try to keep up with it in multiple different forums.

I would love to see a manufacturer code of the cells on the case. Like with CDR and DVDR there are only a few manufacturers and many brands. The Media code on the disk is referring to the original manufacturer with which a true list of quality can be made.

With LiPo's you buy a box with a nice RC brand label on it but no info of what is placed inside so today it can be "cheese" and tomorrow it can be "pinut butter". (in a way of saying)
Also there can be a difference if the battery comes directly from production of was just waiting 6 months in a warehouse for a buyer.

This isnt related to the big battery thread on RCgroups is it? Doesnt look like it. But if you haven't seen it, also an interesting read.

Thanks for sharing! Awesome job

I used to make discharge graphs as well, but what I found was that over time almost all brands of batteries were comparable to an extent where I later discovered that IR was more valuable in detecting battery health and performance so I stopped making discharge graphs. Here's an example of a graph where age of pack makes a significant difference in the readings:

https://live.staticflickr.com/8002/6...c371129e_b.jpg


Before I stopped making graphs I made sure packs were fairly close to new and would compare to older data when I bought a new pack to see how it compered to other brands when they were new, ultimately the rA was fairly uniform across all the brands I tested at the time and that proved to be worthy enough to the point in stock racing where 100C packs became a law of diminishing return and IR was the only thing that mattered and why I only charge at 40A to this day:

https://live.staticflickr.com/8102/8...8e2d9cc2_b.jpg

While I find that an intriguing idea, Im not sure it would be of much use since the same manufacturer may make cells for 20 different battery companies but those cells can all be made to differing specs for each company so there still wouldnt necessarily be any consistency there unless the manufacturing code also had stats about the cells specific specs also. Battery companies generally order cells with certain specifications so unless a brand changes their specs on their cell orders the cells of a particular brand and model of battery should be roughly the same. Im actually starting to test multiples of the same packs in order to make sure that is indeed the case. Its a bit early in to that aspect of my testing to speak definitively but so far what Im seeing supports that statement.

It is not related but Ive been aware of his work for a long time. His work focuses on EDFs though and Im mostly only in to ground kits so I thought Id do some testing of my own :)

Thanks, I hope it helps :)

I agree that IR is very important which is why my testing encompasses not only mAh and Voltage under load but IRs as well.

Could you explain a bit more here? Im not sure I understand what you are saying exactly. Im also not familiar with the rA nomenclature. All of the packs I test are brand new and Ive recently started testing identical packs to make sure that results for a given brand/model of LiPo are within a certain tolerance. So far the duplicates have been very very similar to the original packs. Please expand on the diminishing returns and why you only charge at 40A now. Im intrigued.

With racing most rules say that heating the cells is not allowed. Heating cells will lower the IR, that is why there is a lot of talk about the iChargers which can charge and discharge with high rates. Weird enough high discharge/charge to heat the cell from the inside is allowed.

I love this type of stuff. I do my own battery testing but nothing as comprehensive as this.

When did you take the IR measurements? I didn't see that documented in your procedures.

In regards to your comments about the cell voltages being way off after the test, that's probably because you are discharging them too far. I didn't see in your data logs the cell voltages, only the total pack charge. Are you stopping when a cell reaches 3.0v or when the 2s pack reaches 6v?

Also don't know if you've tested anything other than full size 2S batteries, but if you do low profile or shorty packs, that information would be helpful in the spreadsheet.

rA = Relative Amps which is simply the C rating times the Capacity where a 100C - 5000mAh pack = 100C x 5Ah = 500rA

Generally most brands are fairly accurate with their rA ratings, the only brand I know which is known to overstate their rA is MaxAmps, more info here:
https://www.rcgroups.com/forums/show...0#post42146361

Early on when LiPo's were first introduced they were typically 20C packs and that rating slowly improved to the point where they have peaked to around 150C in general.... if you have a true 150C pack then it can easily handle 40A charge rate without breaking a sweat and if you cycle the battery then you will get the lowest possible IR and highest respective rA regardless of the brand you buy.

The diminishing return is two packs side by side with identical rA spec but the budget brand pack may not perform exactly as well as the name brand in similar fashion to the MaxAmps thread I linked above... at that point it's just wasting money to buy the more expensive brand when you get nearly identical performance with the budget brand.

For stock racing, I won't race a pack unless both cells are below 1mΩ and there are plenty of budget brand batteries offering this level of performance, though they are mostly rated for 2C charge rates, if you are nervous and want peace of mind charging 40A then you can't go wrong with the Trinity White Carbon series, more info here:

https://www.youtube.com/watch?v=blWFtoiqEaE

I mostly run mod now and only care if the IR goes farther than 2mΩ apart where I will race pack up to 7mΩ for mod before I retire a pack, more info here:
https://www.rcgroups.com/forums/show...0#post43510433

IRs are taken right after charging @ 1C with an ambient room temp of approx 71F.

Discharges are done down to 3.2V/C with the exception of the 1C discharges to test mAh which are discharged down to 3.0V/C. I noted the variance in the cell voltages because those were happening at 1C and 2C discharges and is not something Id seen in other lipos at those discharge rates. I have since acquired another identical LiPo to that one for a retest to see if it had any bearing on actual performance.

I have tested a few shorty packs, they are noted on the spreadsheet as either a "Shorty" or a "no-prep" pack where applicable.



While Im onboard with what you are saying here in terms of IRs, I cant agree with the statement "Generally most brands are fairly accurate with their rA ratings" and the talk of true c ratings of 150C. Its been demonstrated by people far more educated than I am (including the US Military) that with the current materials, manufacturing processes, and technologies available no LiPo battery is capable of more than a true C Rating of about 50C. Out of the LiPos Ive personally tested the best true C ratings, which are generally found on the no prep packs, top out around 35 true C rating. So if the C ratings arent correct then the rA ratings cant be correct either since that value is derived in part from the C rating. Heres a couple of links that support what Im saying. Just my .02

https://www.rctech.net/forum/radio-e...s-invalid.html

https://www.rcgroups.com/forums/show...st-Comparisons

I don't know of a hobby grade LiPo that could handle 500 amps. Even if the internal cells could, the solder tabs or the internal wiring (usually around 12awg) wouldn't handle it. I've got a 10,000mAh 150C battery, there's absolutely no way that will handle 1500 amps. Highest I've pushed it is 150A and it sags about 30% of the voltage when it does. C ratings are grossly inflated across pretty much every brand.

I was doing my best to explain what I meant by "diminishing returns", I agree that anything above 50C is subjective but what I find the single most important factor in stock racing is to get the lowest possible IR in order to get the highest possible rA.


Charging at 1C will not yield the full potential in your test results and there are many other variables like manufactured date, materials used and quality of pack assembly which will effect performance. My solution is to charge every pack at 40A and if that particular brand of battery can't handle it, then I ditch the brand and move on to the next. In my findings pretty much all brands (with stated specs of 100C+) perform about the same in stock racing if you cycle the battery at 40A before a race of the handful of brands I've raced with over the past few years.


Another factor since COVID is the ability to get any brand of battery in stock on a regular basis which left me scouring the ends of the earth to get something decent to race with.


Also note this information is only important for stock racing, when running mod classes, I don't cycle those packs but I still charge at 40A where I find it convenient to have my batteries charged in less than 10 min which is no different than the amount of stress placed on the battery because we're discharging at the same rate during a race. I find this to be relatively comparable to cycling anyway with my IR readings throughout a given race day.


I almost always see IR fade at about the same time pack swelling begins to occur. Packs labeled under 100C have always deteriorated faster than the packs labeled higher than 100C in what I've observed,


For my mod classes I run Zeee and for stock I run Trinity White Carbon which are my respective go to brands as of late. What I like about the White Carbon packs is they are hard to get which means the manufactured date is always fresh, the Zeee packs are always easy to get so you're taking a risk on buying a stale pack which may not perform as well but that's okay for mod classes :)

Newest updated spreadsheet is out. Im starting to test more and more duplicate and triplicate packs to make sure that the results are within a certain tolerance. This is important to establish that cells used by a specific company for a specific model of LiPo are all similar and not producing widely varying results.

Tested a second CNHL G+ Series 6200mAh 30C and a second Lectron Pro 5200mAh 50C pack.

Latest updated spread sheet is out. Tested a second pair of Liperior 5000mAh 50C and Turnigy 5000mAh 40C batteries. Ill be testing more duplicate batteries as I go to see how quality control is with some of the better scoring batteries.

I have updated my Lipo testing thread with a new spin off series of testing geared toward people that race. I also updated my NiMH AA document too. Check out the latest info HERE