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Author Topic: Calculated or Stated Battery Capacity  (Read 8847 times)

Offline Fred Underwood

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Calculated or Stated Battery Capacity
« on: November 13, 2015, 08:14:47 PM »
Comparison of batteries seems useful and desirable.  Zippy 2700 mah packs are about 1/4 of the cost of ThunderPower 2700 and most others fall between.  Of course the recent TP sale cut that difference in half, and other sales have been about 1/3 off.  A comparison of capacity and useful battery cycles would be useful.  Of course the guarantee and customer service is better at TP, if needed.  
 
Actual battery capacity may not be stated battery capacity.  Battery capacity is self rated by the supplier.  Safe usage is about 80% of the actual capacity often observed and calculated by charge replacement.  Battery percent from voltage is not a very accurate number and may not prove very useful. More than one voltage vs. percent capacity remaining plots are used. If similar calculations and curves are used, it seems that battery capacity may be compared.  
 
http://www.helifreak.com/showthread.php?t=333661
 
However, hopefully some useful information can be gained when comparing batteries using similar methods, and therefore similar voltage vs. percentage curves/calculations.  Usage numbers were obtained with a FMA PL8 charger with reported percent remaining as a basis to help determine capacity.  Hopefully while the percentage may not be an absolute number, the comparisons may be made using the PL8 as a standard.  Similar tests may be done on another chargers comparing various brand batteries, using that charger as a standard, but it seems that similar equipment is needed to compare.  
 
Capacity is then [(charge in mah) / (% charge increase)]   x  100%
 
For example
 
Battery usage based on replacement mah was about 1835 mah/ flight with about 25% left, so 75% increase back to full charge.  Capacity is then (1835 mah/75%) x 100% or 2446 mah.  
 
And the same batteries on another plane, about 1950 mah/flight with about 22% remaining, so (1950 mah/78%) x 100%  is 2500 mah.
 
Very similar numbers were found when using the values from storage to full charge and then that % charge increase, in the PL8, almost always about 50 – 52% storage charges when allowed to sit overnight.  That calculation gives (1225 mah/50%) x 100% equaling 2450 mah.
 
Those numbers were very consistent over the summer with 4 packs and many flights suggesting that Zippy 2700 mah batteries may have closer to 2450 – 2500 mah.  That may suggest that if you routinely need 2100+ mah per flight, that the Zippy batteries may prove inadequate and may low volt out before a flight is over by set timer duration.  Or they may work for a while but have less usable cycles.
 
In my use Zippy compact 2700 mah 6S packs were good for about 115 – 125 cycles each, something like 25 cents per “tank.”  Weight of my 6S packs average 369 - 370 gms.  Most charges were 1C at home and 2 – 2.5C in the field.  Discharges were about 1900mah/5 min 20 second average rate.  Because the ZIppy capacity seems about 2500 mah, I did not have room to undercharge.  Undercharge could have resulted in over discharge since 1900 mah  used.
 
Zippy 2700 mah 5S packs were used the prior year, with appropriate change in line length and props, and yielded essentially the same capacity calculation of about 2450 – 2500 mah for the 2700 mah packs.  Of course the cells are similar, so as expected.
 
A good resource article is listed below about extending battery life by undercharging to less than 4.2v, selecting the correct charge current termination (C/X), avoiding high charge and discharge rates for the given battery, avoiding deep discharges, and avoid over heating.
 
http://lancair.net/lists/lml/Message/56976-02-B/Li-Ion%2520Battery%2520Life.pdf
 
and, pardon the drone reference, but there is some useful battery information following.
 
http://www.dronethusiast.com/ultimate-drone-battery-care/
 
I believe that FMA PL8 and PL6 both have similar % charge determinations and could be used as a comparator to calculate battery capacity and compare brands.  Actual useful number of battery cycles would also be useful.
 
Another popular battery is the ThunderPower Prolite 2700 mah 25C.  Does anyone have similar information to compare and estimate actual capacity of the TP’s?  Also, what is the weight of a 6S pack.  TP says 351 gms, but actual weights with wires and battery plug would be useful information.


« Last Edit: February 06, 2016, 07:05:47 PM by Fred Underwood »
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Offline John Cralley

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Re: Calculated or Stated Battery Capacity
« Reply #1 on: November 14, 2015, 07:23:08 AM »
Interesting Fred,

I have no actual data but I can say that I have managed to puff Zippy batteries in just a relatively few cycles assuming that the capacity is what is stated. From your data I suspect I pushed them near their actual capacity. I only thought that they were cheap and thus poor quality. They probably would work fine if you only used 60% of the stated capacity.

I have switched to Thunder Power batteries (buying them on the 1/2 price sales) and have had no problems with them.
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Offline Motorman

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Re: Calculated or Stated Battery Capacity
« Reply #2 on: November 14, 2015, 09:34:27 AM »
So you're trying to determine what 100% mah is by subtracting after flight voltage from full charge voltage then dividing by mah used?


MM

Offline Fred Underwood

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Re: Calculated or Stated Battery Capacity
« Reply #3 on: November 14, 2015, 10:55:11 AM »
John, what capacity batteries and do you know mah used or recharged.  If I understand your post, the TP's and Zippy's were of the same stated capacity and TP tolerated the same amount of mah output that puffed the Zippy batteries. 


MM, the attempt is to calculate or estimate the useful capacity by extrapolating from known % charge to 100% charge and the mah it takes to get there.  If you have a battery at 50% charge and take it to 100% with 1250 mah, then it seems the battery would hold 2500 mah.  Voltage is not used directly though there are tables or calculators to turn voltage into percent charge.  unfortunately there is not a single standard voltage to % charge standard.  It is an easy calculation for comparisons however, and could make sense if we use the same 5 calculator, in my case, the PL8 charger.  Similarly, it could be estimated if all used the Hyperion type battery checkers, but there are many clones and I am not sure of calibration and standard.  If batteries were discharged to say 3.75 volts, which is close to 75% use, comparison of mah back to 4.2 volts would give similar results.  The purpose is not to justify use of % charge or to get a firm capacity number, but to be able to compare and understand capacity of different brands.

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Offline Fred Underwood

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Re: Calculated or Stated Battery Capacity
« Reply #4 on: November 14, 2015, 10:56:47 AM »

Perhaps the information would be more plentiful, perhaps less comparable, as follows (for 2700 mah batteries to begin) with Zippy 2700 as an example:

battery brand       low % where charge begins      high % where charge ends         input in mah
  Zippy                         22                                              99-100                                   1950
Fred
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Offline Motorman

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Re: Calculated or Stated Battery Capacity
« Reply #5 on: November 14, 2015, 12:12:36 PM »
MM, the attempt is to calculate or estimate the useful capacity by extrapolating from known % charge

Yes, but you don't know the full mah capacity of the battery beyond what it says on the label. How do you know if it's at 50% charge or 25% charge if you don't know what 100% mah is? Voltage drop vs mah used is the only reference and, from what I read, it varies greatly from brand to brand depending on chemistry ect.

MM

Offline Tim Wescott

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Re: Calculated or Stated Battery Capacity
« Reply #6 on: November 14, 2015, 12:19:15 PM »
Yes, but you don't know the full mah capacity of the battery beyond what it says on the label. How do you know if it's at 50% charge or 25% charge if you don't know what 100% mah is? Voltage is the only reference and, from what I read, it varies greatly from brand to brand.

MM

There's a distinctive knee in the voltage vs. charge curve at the 'almost entirely discharged' end.  If you brought a pack down to that level it'd be pretty obvious, and it shouldn't shorten the life of the pack too much to do it once.

This is what battery reviews are for...
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Offline Fred Underwood

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Re: Calculated or Stated Battery Capacity
« Reply #7 on: November 14, 2015, 01:06:08 PM »
Yes, but you don't know the full mah capacity of the battery beyond what it says on the label. How do you know if it's at 50% charge or 25% charge if you don't know what 100% mah is? Voltage drop vs mah used is the only reference and, from what I read, it varies greatly from brand to brand depending on chemistry ect.

MM



MM, I mentioned that and suggested that a comparison of capacities might still work, not absolute numbers.  That comparison would be best done on same/similar chargers, and the FMA PL6 and PL8 give both % and voltage.  The charger charges or discharges to storage at about 50%, and I believe that it does it by voltage.  It still takes more mah to go from storage to full when comparing cells of different capacity.  I have another inexpensive charger that does storage a bit lower and always adds about 1500 mah from storage to full for the same Zippy 2700's thus my reasoning for values coming for similar equipment.  A friend has the same inexpensive charger and gets very similar numbers on it.  It does not give %, but one can get similar comparison values of different cells by using storage to full.  Apart from the actual capacity, I would be happy to know if TP has more than Zippy, and by what percent.  The other number useful for comparison is number of charge cycles one has obtained from different batteries used in the same plane and same circumstances.  If my understanding is not correct, perhaps no value.  If correct, it may help determine bang for buck, and explain the deep discharge by voltage or percentage of some 2700 mah cells as they give up 2100 - 2150 mah.

Hopefully if some numbers are posted, the information may sort itself.



Battery percent from voltage is not a very accurate number and may not prove very useful. More than one voltage vs. percent capacity remaining plots are used. If similar calculations and curves are used, it seems that battery capacity may be compared.   
 
However, hopefully some useful information can be gained when comparing batteries using similar methods, and therefore similar voltage vs. percentage curves/calculations.  Usage numbers were obtained with a FMA PL8 charger with reported percent remaining as a basis to help determine capacity.  Hopefully while the percentage may not be an absolute number, the comparisons may be made using the PL8 as a standard.  Similar tests may be done on another chargers comparing various brand batteries, using that charger as a standard, but it seems that similar equipment is needed to compare. 
 

Fred
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Offline Fred Underwood

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Re: Calculated or Stated Battery Capacity
« Reply #8 on: November 14, 2015, 01:35:38 PM »
Another way to compare brands, for those with more than one brand of the same stated capacity, would be to put the batteries at storage on your charger and then to see how many mah it takes to fully charge each.  Since the charger has a set voltage for storage that point would be the same for both batteries. Any difference in mah to full charge would reflect a difference in capacity.

Perhaps if storage to full mah is posted for 2700 mah packs, and charger brand and model noted, the comparison can be made using data from different battery brands done on same charger brand/models.  Assuming enough interest that there will be posts.  Capacities can be noted as % each other, not absolutes.
« Last Edit: November 14, 2015, 02:13:54 PM by Fred Underwood »
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Offline Keith Renecle

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Re: Calculated or Stated Battery Capacity
« Reply #9 on: November 14, 2015, 09:58:05 PM »
Hi Fred,

In case you missed it in a few other threads, the Battery University website is a good place to look. Here is the link http://batteryuniversity.com/ The section that is particularly good is the one on how to prolong life in lithium batteries http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

On the left side of each page they also have many links to all kinds of batteries and so much data that is useful. It's not always easy to get good comparisons between the different makes because some times the quality control is not consistent. Some I know have had much more good cycles out of cheap batteries than Thunder Power, but basically if you use these batteries without pushing their limits either way, you can get many cycles out of batteries like the Zippy's.

Keith R
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Offline Fred Underwood

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Re: Calculated or Stated Battery Capacity
« Reply #10 on: November 16, 2015, 10:01:37 PM »
Keith, thanks for the additional reference.  You note “if you use these batteries without pushing their limits either way, you can get many cycles out of batteries like the Zippy's.”  The “limit” is the very reason that it would help to know if the capacity ratings are realistic.  From my limited observation Zippy’s 2700’s seem to have less than the stated capacity. I would like information on other brands to help know the limits, so that are not pushed. I am not trying to say any battery is better or worse, just trying to get realistic capacities.  My Zippy’s worked well when about 1900 mah used.  In “list your setup above,” a few users of 2700’s note about 2100 mah replaced, and when specified, I see TP’s and not Zippy’s. My Zippy’s would have been at less than 20% remaining. 

Just trying to learn, and to spend money for batteries wisely.
Fred
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Offline Howard Rush

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Re: Calculated or Stated Battery Capacity
« Reply #11 on: November 16, 2015, 10:45:21 PM »
Also, what is the weight of a 6S pack.  TP says 351 gms, but actual weights with wires and battery plug would be useful information.

Old Thunder Power G8 25C 2700 mAhr battery weighs 370.6 grams with Deans connector; new one that came today (hence delay in providing this answer) is 366.1 grams with Deans connector.  That's for a sample of one each.
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Offline Fred Underwood

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Re: Calculated or Stated Battery Capacity
« Reply #12 on: November 17, 2015, 08:33:10 PM »
Thanks Howard, it will be interesting to see how the new Prolite's stack up against the old G8's.  Most of the data I've seen seems to be on the G8's. 
Fred
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Offline Fred Underwood

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Re: Calculated or Stated Battery Capacity
« Reply #13 on: February 06, 2016, 07:48:13 PM »
Finally some better weather and some more "field research," or flying.

Data reported is from FMA Cellpro 8 charger, Charge in mah, and % charge.

My Prolite 2700 mah 6 cell packs with Deans are 369.5 gms average and the comparable Zippie 6 cell packs, 370 gms.

Several flights on a few different days have required about 1925 mah "refill" as did the Zippy packs.  The Zippy packs used from 99% full down to 22% full or 77% for 1925 mah and the TPs used only 70% for the same 1925 mah. 

So Zippy full capacity is 1925mah/77% X 100% equals 2500 mah.
The TP pack capacity is 1925mah/70% x 100% equals  2750 mah.

Since I have needed only 1925 mah for the current plane, I have started using a lower charge cutoff, now down to about 4.17 with a C/5 finish rate and then rechecked and had 94% starting charge and finished with 24 and 25% charge on various packs.  Will drop that a little bit and shoot for 92% and 22 - 23%.  Lowering the top charge is supposed to give more cycles over all as noted in early references.  As long as my need is in the 1900 - 1950 mah range/flight that should work.  Of course if 2100 - 2150 is needed, then it will take a full charge and down to about 20% remaining.  Or 79 - 80% of 2700mah is 2160 mah.

At the end of the Zippy life I found what happens as a single cell begins to fade.  The battery really didn't like the overhead 8's.  Apparently use a bit of power and are late in the pattern.  I would experience a subtle softness and loss of line tension and then the battery would seem to recover and finish the pattern.  At flight end, I usually get a slowing and then 1 lap speed up, KR timer, and there was no speed up on that pack.  I got slowing and back to normal speed, no speed up.  On the charger, that pack had one cell with high internal resistance and low voltage, though the charger could "balance" it, so not easily found unless the charger is capable and you are looking.  I tried it a couple of times being very careful, and perhaps not very bright, but in cool minimal wind days and reproduced that finding a few times. It would have been a disaster if unexpected, up high, and in the wind.  On the other hand the Zippy cells were very reliable for over 100 cycles as long as they were used as if the capacity was 2500 mah.  If over used, over discharged, that cell failing may occur without warning and early in the cell life.

Hope that this useful if you are pondering how to spend your battery money.
Fred
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Offline Mark Scarborough

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Re: Calculated or Stated Battery Capacity
« Reply #14 on: February 06, 2016, 11:30:23 PM »
I Have seen simialer results with the Zippy packs. I had 8, my current airframe is a bit heavier than it needed to be, I am on longer lines as a result ( it flies well, but I am at full length lines and cranking the rpm to hold 5.2 lap times)
I put 2100 and on cold days a bit more. My packs are showing wear, well three of them have lost a cell.
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Offline Fred Underwood

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Re: Calculated or Stated Battery Capacity
« Reply #15 on: February 07, 2016, 02:27:30 PM »
Mark, are they all Zippy 6 cell?  Do you know how many cycles/pack, or guestimate?
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Offline Mark Scarborough

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Re: Calculated or Stated Battery Capacity
« Reply #16 on: February 07, 2016, 02:41:18 PM »
Mark, are they all Zippy 6 cell?  Do you know how many cycles/pack, or guestimate?
they are  the Zippy compact, 6S. The ones I have had the most problems with have been all from the same batch of 4 I bought, I guess they are at 20 to 25 cycles each. SO I am having , or wanting to fly at a higher airspeed to maintain the lap times on longer lines which is driving my packs  to hard. I never really thought before about the perspective of them being "less than rated Mah" that would have been important to think about. Hopefully my new build will be light enough to allow me to fly at a slower lap speed, and shorter lines so I dont drive them as hard. I cant afford new packs every 20 flights.
I am looking at dissasembling the packs with bad cells and trying to rebuild them matching the remaining cells. but thats new territory
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Offline Tim Wescott

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Re: Calculated or Stated Battery Capacity
« Reply #17 on: February 07, 2016, 04:20:45 PM »
I never really thought before about the perspective of them being "less than rated Mah" that would have been important to think about.

Batteries in general, and LiPo cells in particular, are "soft" around their rated values.  Meaning, they'll pretty much all let you squeeze more out of them a few times than is really good for them, and they'll all respond favorably to never being fully discharged or overcharged.

LiPo cells are just ever much more so.

The only honest way to rate a LiPo cell (or any cell, really) would be to give a certain capacity rating for a certain number of charge/discharge cycles.  That's not done, so you're left at the mercy of the battery vendor. 

I've done a very little bit of product design using LiPo cells, and when you start trying to pin manufacturers to the wall on number of cycles vs. capacity, they pretty much tell you what we already know: (A) don't discharge the cell down to rated capacity if you want it to live a long time, and (B) don't charge it all the way and leave it.  (The vendor, BTW, was Tenergy.  If you need to buy lots of LiPos for a product, try them first -- they're nice, knowledgeable and helpful and they hire guys who speak fluent English.)

I think the big difference between Zippy and "better" brands is that because there's no industry standard, Zippy can and does push the specifications harder than, say, Thunderpower.  I would suspect that they also use cells that aren't manufactured to as tight of tolerances.  The upshot is that you get what you pay for -- cheaper cells don't work as well as spendy ones.
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Offline Fred Underwood

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Re: Calculated or Stated Battery Capacity
« Reply #18 on: February 11, 2016, 07:31:07 PM »
I have acquired a few more cycles and have now undercharged to about only 92% and about 4.12 to 4.13v.  Charger set to 4.15v cut off and C/5 and after about 15 minutes post charge settles to about 92 - 93%.  I use about 1900 - 1925 mah and end at 22 - 23%, so again the TP's calculate to about 2750 mah capacity.

The upshot is that you get what you pay for -- cheaper cells don't work as well as spendy ones.

That may be true generally, but if you need 1900 mah or less, then the Zippy 2700s may be good.  I have used 5 and 6 cell packs without difficulty and a friend has used several 5 cell packs.  I am not sure if the TP's that beat cycles/dollar if you only need a 2500 mah cell.  OTOH, it seems that if you need 2100 mah output, then you will have trouble with Zippy 2700 packs.  The problem then is not only less cycles, but an unpredictably short number of cycles. Failure may be at the top of the hemisphere where you lose more than a battery.  If I had a light airplane and knew that I stayed well within the usage parameters of less than 80% use and not over drawn, then inexpensive cells may be fine.  The other positive of the TP's is the compact size that give a better chance of weight shift and balance.
Fred
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Offline Rogerio Fiorotti

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Re: Calculated or Stated Battery Capacity
« Reply #19 on: February 12, 2016, 08:51:28 AM »
Fred

Usin them already batteries TP 5S 2700mA 25C with flight fear in 5:20 using 2000mAh and using Hyperion meter remaining 20%, we can say that in reality the battery provides only 2500mAh, correct?

The same battery discharging using Hyperion EOS0730i charger discharge 2,7A (1C) provided exactly 2700mAh.

I'm currently using Hyperion 2800mA HV 30C 5S same weight as the Thunder Power batteries, but use 4,25V per cell charging and remains the same 20% on the same flight conditions.

Weights: Thuder Power 315gr with connector - Hyperion 311gr with connector
Prices: Thunder Power U $ 98.00 - Hyperion U $ 54.00

Rogerio.

Offline Crist Rigotti

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Re: Calculated or Stated Battery Capacity
« Reply #20 on: February 12, 2016, 11:18:32 AM »
Rogerio,
Good information.  Thanks.
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Offline Fred Underwood

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Re: Calculated or Stated Battery Capacity
« Reply #21 on: February 12, 2016, 12:15:39 PM »

Usin them already batteries TP 5S 2700mA 25C with flight fear in 5:20 using 2000mAh and using Hyperion meter remaining 20%, we can say that in reality the battery provides only 2500mAh, correct?

The same battery discharging using Hyperion EOS0730i charger discharge 2,7A (1C) provided exactly 2700mAh.

I'm currently using Hyperion 2800mA HV 30C 5S same weight as the Thunder Power batteries, but use 4,25V per cell charging and remains the same 20% on the same flight conditions.


For the purpose of comparison and capacity calculations, I use a before and after measurement of %, and on the same meter, and after a "rest," not immediately after charge of discharge.  If I charge to 4.15V with a C/5 finish, the charger may show that it stopped at 99%. If I wait 15 minutes and then hook back up to the charger/meter it will then read say about 95%.  After flight and a short rest, the reading will be about 25% for a usage or 70%.  You seem to get a different capacity for use of 2000 mah, and discharging on the Hyperion.  That may be due to different cut off values and discharge rates.  It would be nice to get similar values of capacity, or use the same method for comparison.  If the Hyperion meter read 97% before flight and 20% after, then 2000 mah was 77% and the capacity calculates to 2597 mah.


I'm currently using Hyperion 2800mA HV 30C 5S same weight as the Thunder Power batteries, but use 4,25V per cell charging and remains the same 20% on the same flight conditions.


If you have only 20% left, then is the capacity also only 2500?  What was starting voltage and %?  Of course the meters may not be set up to give accurate % of HV top voltages???

The price of the Hyperion HV 2700 6S and the Sale price 50% off TP's are about the same, about $60. 

Useful information Rogerio, thanks for the post.
Fred
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Offline Fred Underwood

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Re: Calculated or Stated Battery Capacity
« Reply #22 on: June 23, 2016, 09:34:30 PM »
Just got a recent update from Thunderpower.  The 2700 cells have been replaced with 2800 mah cells and at a much better price.  My batteries are fairly new, so I won't be testing these soon.  If someone starts using them, the recharge mah and % left will be interesting.

http://www.thunderpowerrc.com/Products/2800-mAh

« Last Edit: June 23, 2016, 10:41:21 PM by Fred Underwood »
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Offline Crist Rigotti

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Re: Calculated or Stated Battery Capacity
« Reply #23 on: June 24, 2016, 07:13:41 AM »
Just got a recent update from Thunderpower.  The 2700 cells have been replaced with 2800 mah cells and at a much better price.  My batteries are fairly new, so I won't be testing these soon.  If someone starts using them, the recharge mah and % left will be interesting.

http://www.thunderpowerrc.com/Products/2800-mAh



Nice batteries!  Much better price too.
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Offline Fred Underwood

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Re: Calculated or Stated Battery Capacity
« Reply #24 on: June 26, 2016, 02:28:53 PM »
In the opening post there is a link to % left vs. voltage. 

http://www.helifreak.com/showthread.php?t=333661

Three different plots are shown, meaning that not everyone agrees on how voltage of a battery converts to % remaining.  That's a big part of the problem in looking at % remaining.  % remaining may be useful when you begin using new plane, prop, line length....  At that point you need some guestimate of battery use so that you don't overdraw and ruin batteries.  OTOH, a simple and perhaps better way to get that information is to fly for a shorter period, say an easy number like 3 minutes, and get the usage in mah/minute by recharging at the field and then multiply that by your flight time in minutes.

Another problem of "% remaining" is that it is often done very shortly after the plane lands. The battery voltage has not bounced back and stabilized.  When I check % remaining it is at home with all batteries stabilized for over an hour, or for pickup and drive home time. If I check voltage during flight, via datalog, the voltage may be about 3.5v/cell.  At landing I get somewhere between 3.5 and 3.78, and rising.  At home, usually about 3.78V.  Since voltage and % are related by some manufacturer equation or algorithm, estimated % will also change.

The % remaining can be read on the PL8 charger, and I use that number when I am interested, but that is well after flying the packs.
Fred
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Offline Fred Underwood

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Re: Calculated or Stated Battery Capacity
« Reply #25 on: September 30, 2016, 09:04:26 PM »
My original TP 2700 6S Prolites now have about 60 - 70 cycles and while the IR has remained about constant, the capacity has not.  Now for comparison, there is a replacement battery of the same model as original, and a new 2800 ProliteX 6S.

One flight on each battery is about 1925 ma and according to the PL8 charger, this took 75 - 76% on the old 2700's.

The new 2800 only took about 72 - 73%, and the new 2700 took 71 - 72% of capacity.

That calculates to a capacity of 2520 mah for the older used 2700s, and they were 2700+mah new, above. The new TP Prolite 2700 @ 2710 mah and the new 2800 ProliteX at 2675.

The new TP 2800s are stated to be 351 gm for 6S and mine weigh 362.2 with the Deans.  351 gms must before the electrons were added!
The new TP 2700 replacement is 362.8, and the old ones about 368 gms.

The new batteries have about 1/2" shorter battery leads which may account for the weight difference.

Hmmm, the old used Zippy 2700s had a capacity of about 2500 mah calculated and the used TP 2700s about the same....  I don't have a comparative number for new Zippy 2700s.
The new TP 2800s seem about the same as the older 2700s, though only one tested.  The price is better.
Fred
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Offline Mark Scarborough

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Re: Calculated or Stated Battery Capacity
« Reply #26 on: October 01, 2016, 12:22:23 AM »
Good stuff Fred, thanks for taking the time to document this,
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Offline Fred Underwood

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Re: Calculated or Stated Battery Capacity
« Reply #27 on: February 20, 2018, 04:08:38 PM »
A little update on capacity with the finding that the individual cells of the TP 2800 packs are labeled 2700.  When the TP 2800s are new, I get a calculated value of about 2750+ mah, and this drops with usage.  Seems close to the 2700 TP, and a little better than on the single pack previously tested, above.  I recently decommissioned a 6S 2800 pack and found the cells marked at 2700 as others have noted.  Not really what I wanted to see, but the cells seemed to have a bit more capacity than the TP 2700s that I originally had.  I had a couple 2700 cell packs that seemed as good as the 2800s, perhaps the same cells?  Still, more capacity than Zippy 2700s which quickly are closer to 2500 mah in my use.  Both follow a similar degradation curve with use, but the TPs start on a slightly higher capacity curve.

Stated capacity is somewhat subject and left to the manufacturer.  TP and Zippy both probably have some data to support their capacity claims, but is up to the users to find practical values for our use of the cells, and realize that capacities fall and IRs go up with use.  Hotter temperatures and poor cooling likely accelerate that.  Stated values aren't available for long, and perhaps never, except in fairly ideal test conditions.

The good news is that the packs are reasonably priced on a 40 - 50% off sale, then comparable to Zippy packs. 

I wonder what the "matched cell" claim means.  Also, not sure that matching is currently claimed, I didn't find a recent statement.  Interesting but old thread here

http://www.tjinguytech.com/reviews/tp-experience

It seems that the cells come from TP at less than normal storage charge, and not nearly as matched in IR as they become with a couple of break-in cycles.  Capacity goes up after a couple break-in cycles and IR goes down, and mine usually then match well.  This may be true of most cell brands. 

Not meant as a complaint, just my observations and musing.


Fred
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