Stargate Logo  Secured by phpPhobos

Smurphtools   
  Login  - No Account?  Create One   
Search 
Tuesday, 11 December 2018  -
News FeedRSS Feed
rss rdf  
  Home 
  Authentication 
 Documentation 
    Site Documentation 
    About me 
  Legal Notice 
 Applications 
    Web Links 
 RC Models 
    RC Models 
    RC Batteries 
 Modules 
    Downloads 
    Weblinks 
 Blacklists 
    Blacklist 
    Blockout 
    DNS Blacklist 
 Registered Bloggers 
  Blog de Maiwenn 
  Blog de Morgane 
  Joerg's Blog 
 Gallery [Listing]
  > Indy travels 
  > Steampunk 
  > FPV Drones 
  > RC Planes 
 FAQ  [ Topics  ]
 Common Linux problem... 
 Routerboard RBxxxAH 
 Apple Mac-mini 
 PHP Phobos 
 Stargate's Backup sc... 
 eBook Reader / PRS-5... 
 RC Models 
 Server in SolLan 
 System Stats [ Index ]
 Router
  > Gateway 
 Server
  > Stargate 
 Client
  > RemPi 
Stargate's FAQ   [  Topics  | Groups  | Last  | Expand  | Search  | Print  | Documentation ]
Folder open  RC Models [ Expand ]
  Question ?  RC Batteries: Status   
  Question ?  Common connectors for LiPo batteries   
  Question ?  FOM: Figure of Merit   
  Question ?  RC Batteries: Battery life cycle listing   
  Question ?  LiPo Battery internal resistance measurement   
  Question ?  Max I: Maximum recommended average current draw   
  Question ?  MP: Manufacturers Promise   
spacer line
Folder open  Answers
spacer line
Question ? RC Batteries: Status   [
View DetailsView details
|
Print ViewPrint view
]

 The Status in RC Batteries gives a very fast overview on the actual real health of the LiPo pack. To make understanding easier, the explanation will be based on a real example - as shown below.

Battery: 1300mAh 3S1P 45C HobbyKing Nano-Tech
Status: FOM1.15, MP0.72, IR ~7mΩ σ2mΩ 

We have here 4 values, FOM, MP, IR ~ and IR σ.
FOM tells us that from the expected 30C, we have more than expected. Good. 30C is a fictive value from experience. It is not linked to what the manufacturer promised us.
MP tells us that from the "promised" 45C we get only 72%. Bad
IR ~ average shows us 7mΩ per cell. There are way better cells out there. OK, but not excellent either.
IR σ is the Variance, telling us how many mΩ apart the individual cells are. Remember that the worst cell defines the overall state of the pack. In general, the smaller the σ value the better.

Warning

FOM0.02, MP0.06, IR ~111mΩ σ253

In case the IR ~/ IR σ are displayed in red color - it means the variance between the cells is higher than the cell average. This is an indication that one cell of the pack is way worse than all others and that this pack can explode if not charged using a Balancer-capable charger. Best would be to retire this pack ASAP!

More detailed explanation on each information type:

  • FOM: Figure of Merit is a calculation that uses measured cell internal resistance and normalizes it to cell capacity. It is very useful when comparing packs of different sizes and from different manufacturers
    The meaning is as below, taking into account that a FOM=1 means a 30C Cell able to deliver 30C based on the cell with the highest IR.

    • FOM < 1: below average < 30C capable
    • FOM == 1: average - 30C capable
    • FOM > 1: good - More than 30C capable
    • FOM >> 1: outstanding - much more than 30C capable

  • MP: Manufacturer's Promise is there to tell us if the C-Rating of the LiPo pack is actually accurate.
    Based on what the Manufacturer claims the pack is capable to deliver, we calculate the actual C-Rate based on the worst cell's Internal resistance.
    The relative number out of there tells us how good the C-Rating statement of the Manufacturer is.

    • MP == 1: Very good. The proclaimed rating matches the mesured one
    • MP < 0 : No good. The LiPo pack delivers less than claimed
    • MP > 1 : Excellent - The LiPo pack delivers more than claimed

  • IR ~: This is the Average Internal Resistance of all cells. Average value is taking into account how the cells are arranged (Serial or Parallel) and computes an overall average. In the battery details view, the color will change accordingly depending on the overall IR of the pack.

    • Green: IR < = 6mOhm : Excellent
    • Yellow: 6mOhm < IR < = 12mOhm: Good/Reasonable
    • Orange: 12mOhm < IR < = 20mOhm: Aging signs
    • Red: 20mOhm < IR : Read for retirement

  • IR σ: The variance of the Internal Resistance tells us how similar the cells internal resistance actually is. The smaller the IR σ, the better. The bigger the difference, and the older the cells probably are. Remember that the overall LiPo pack capability is defined by the worst cell in that same pack!
    The danger of the IR difference is that cells will be discharged differently. The worst cell will generate most heat that needs dissipation in the pack, and reach lower voltage levels first. Also - if charged without balancer control the worst cell can very fast be overcharged which can cause an explosion of that cell.

 

Entered by smurphy on Wednesday, 08 June 2016 @ 10:33:44  
Electronics - RC Models, # Hits: 13762
spacer line
Question ? Common connectors for LiPo batteries   [
View DetailsView details
|
Print ViewPrint view
]

 Check out the nice page on LiPo batteries explaining all details about them A Guide to Understanding LiPo Batteries


  • B1 - Deans (T) type main connector - Female & Male. Used for main connection to speed controllers and motors. Used for medium to high current draw. HOBBYWING chooses this connection mainly
  • B2 - JST / BEC type main connector - Female & Male. Used for main connection to speed controllers and motors. Used for low current draw
  • B3 - Tamiya main battery plug usually used on Car and Boat batteries (NiCd / NiMh) - Female & Male
  • B4 - Bullet Connectors - Female & Male. Single wire connectors, available in a range of different sizes to suit current draw / load requirements from 2mm to 8mm
  • B5 - HXT Connectors - Female & Male. Available in 3.5mm and 4.00mm sizes. Used for main battery connectors for medium / high power applications
  • B6 - Traxxas Connectors - Male & Female. Mainly used on high current draw car and boat batteries
  • B7 - XT60 Connectors - Male & Female. Used for high current draw battery connections
  • B8 - EC3 Connectors - Male & Female. Used for high current draw battery connections
  • B9 - Flight Power / Thunder Power (FP / TP) LiPo Balance Charger plug - Female & Male
  • B10 - Hyperion / PolyQuest (HP / PQ) LiPo Balance Charger plug - Female & Male
  • B11 - JST-XHR (XH) LiPo Balance Charger plug - Female & Male
  • B12 - JST-EHR (EH) LiPo Balance Charger plug - Female & Male

Check the below picture and list for an overview (kindly taken from Hobbywing - for having a local archive). 

Entered by admin on Thursday, 26 May 2016 @ 09:21:55  
Electronics - RC Models, # Hits: 13542

Attach   Battery connectors  [ 41,037 bytes - image/jpeg ]
spacer line
Question ? FOM: Figure of Merit   [
View DetailsView details
|
Print ViewPrint view
]

 Figure of Merit is a calculation that uses measured cell internal resistance and normalizes it to cell capacity. It is very useful when comparing packs of different sizes and from different manufacturers. The larger the calculated FOM, the better.

The meaning is as below, taking into account that a FOM=1 means a 30C Cell (able to deliver 30C based on it's internal cell witrh the highest IR.

  • FOM < 1: below average < 30C capable
  • FOM == 1: average - 30C capable
  • FOM > 1: good - More than 30C capable
  • FOM >> 1: outstanding - much more than 30C capable

Example calculator is here.
For more background information on FOM, go here: RC Groups Forum

Example calculation of FOM and its meaning from the rc-forum:

I calc C this way, C=370mV/capacity/IR, where 370mV is 1/10 of a lipo
 cell's nominal voltage. 

as an example my Turnigy 6S5000 has an IR of 2.4mohms/cell.
so it's C=370/5/2.4=30.8C.

or, 370000/5000/2.4=30.8

divide left & right by 30.8, 

that's exactly 12000/5000/2.4=1. 

It means a FOM=1 cell IS a 30C cell. a FOM=0.5 cell is a 15C cell....

 

Entered by admin on Saturday, 04 June 2016 @ 15:20:14  
Electronics - RC Models, # Hits: 13211
spacer line
Question ? RC Batteries: Battery life cycle listing   [
View DetailsView details
|
Print ViewPrint view
]

 The Status in RC Batteries gives a very fast overview on the actual real health of the LiPo pack. To make understanding easier, the explanation will be based on a real example - as shown below. Note that not all data is always entered, so some values may not show up.

Battery: 1300mAh 3S1P 45C HobbyKing Nano-Tech
Status: FOM 1.15 @ 39 chrgs | Max I: 32A | chrg. 1.00C | IR ~7.00mΩ | IR σ 2mΩ @ 21°C | Real 32.53C | cap. 100.77%

- FOM tells us that from the expected 30C, we have more than expected. Good.
- 39 charge cycles so far
- Max recommended continuous current draw is 32A
- Battery has been charged with 1C
- IR ~ average shows us 7mΩ per cell. There are way better cells out there. OK, but not excellent either.
- IR σ is the Variance, telling us how many mΩ apart the individual cells are. Remember that the worst cell defines the overall state of the pack. In general, the smaller the σ value the better. Note the temperature at which the IR measurement has been taken is recorded
- Real C is the calculated real C Rating based on the worst cell IR of the pack. - 100.77% of the current that has been charged into the pack has been discharged. usually a higher value than 100% is due to temperature change of the pack during the process


Warning

FOM0.02, MP0.06, IR ~111mΩ σ253

In case the IR ~/ IR σ are displayed in red color - it means the variance between the cells is higher than the cell average. This is an indication that one cell of the pack is way worse than all others and that this pack can explode if not charged using a Balancer-capable charger. Best would be to retire this pack ASAP!

More detailed explanation on each information type:

  • chrgs.: Actuall number of charge/discharge cycles of the Pack. In other words, how many times has this Pack been used.

  • FOM: Figure of Merit is a calculation that uses measured cell internal resistance and normalizes it to cell capacity. It is very useful when comparing packs of different sizes and from different manufacturers
    The meaning is as below, taking into account that a FOM=1 means a 30C Cell (able to deliver 30C based on it's internal cell witrh the highest IR.

    • FOM < 1: below average < 30C capable
    • FOM == 1: average - 30C capable
    • FOM > 1: good - More than 30C capable
    • FOM >> 1: outstanding - much more than 30C capable


  • MAX I: Regarding the estimate of the "Maximum recommended average current draw to prevent pack damage" - the max current is the square root of (6*capacity/IR)

    The calculation of the FOM/Current draw were developed by Mark Forsyth and Wayne Giles. As always we emphasise that this is just a pragmatic rule of thumb based on extensive practical battery testing that seems to reflect practice fairly well over a wide range of LiPos and capacities - although some recent cells like the Turnigy Graphines do better than predicted. It has some theoretical basis in a maximum allowable % of energy dissipated internally (6 Watts/AmpHr) but we don't rely on a theoretical explanation. It is a purely empirical observation that has been surprisingly useful to date.

  • Real: Computed value of the Real discharge capability of the pack using the IR of the worst cell in the pack. This is the real discharge capability of the pack.
    Note: In case Real C Value is displayed in orange, it just means that this pack can be used above the recommended Max I!

  • cap: percentage of capacity charged and extracted later. This is usually done doing charge/discharge cycles. Around 100% and the pack provides the same amount of capacity as has been put inside.

  • chrg: Current used to charge the cells. 1C means that a pack with 1000mAh has been changed using 1A

  • IR ~: This is the Average Internal Resistance of all cells. Average value is taking into account how the cells are arranges (Serial or Parallel) and computes an overall average. In the battery details view, the color will change accordingly depending on the overall IR of the pack.

    • Green: IR < = 6mOhm : Excellent
    • Yellow: 6mOhm < IR < = 12mOhm: Good/Reasonable
    • Orange: 12mOhm < IR < = 20mOhm: Aging signs
    • Red: 20mOhm < IR : Read for retirement


  • IR σ: The variance of the Internal Resistance tells us how similar the cells internal resistance actually is. The smaller the IR σ, the better. The bigger the difference, and the older the cells probably are. Remember that the overall LiPo pack capability is defined by the worst cell in that same pack!

 

Entered by smurphy on Wednesday, 08 June 2016 @ 12:04:03  
Electronics - RC Models, # Hits: 13156
spacer line
Question ? LiPo Battery internal resistance measurement   [
View DetailsView details
|
Print ViewPrint view
]

 The optimal environment for LiPo batteries depends on what you do with them.

  • Optimal performance: 50°C to 60°C. This also means that this is the temperature at which the cell Internal Resistance (IR) is the lowest.
  • Storage temperature: 10°C to 20°C. At 10°C or below, do not charge the cells at more than 4.1V/Cell

The problem now is - as we can't heat up the cells to 50°C for our testings - to find the coefficient to apply to the temperature at the moment of measuring the cells.

Quote found on the internet of someone having spent quite some time with this topic:
My personal internal resistance number for high performance cells is 12000 / cell capacity, when measured after stabilization at room temp (~21C) for 1 hour minimum.. Anything around or below this number I consider to be outstanding performance.

See the attached Graph for an idea on what influence temperatures have. Also - this graph was taken from the following thread

This is what the Computation will be based on, after applying the correction factor for the temperature.

The discussion can be found here

A very good article around RC LiPo can be found here: Understanding RC LiPo Batteries 

Entered by smurphy on Wednesday, 01 June 2016 @ 14:22:01  
Electronics - RC Models, # Hits: 13033

Attach   LiPo IR Temp curve  [ 151,028 bytes - image/png ]
spacer line
Question ? Max I: Maximum recommended average current draw   [
View DetailsView details
|
Print ViewPrint view
]

 Regarding the estimate of the "Maximum recommended average current draw to prevent pack damage" - the max current is the square root of (6*capacity/IR)

The calculation of the FOM/Current draw were developed by Mark Forsyth and Wayne Giles. As always we emphasise that this is just a pragmatic rule of thumb based on extensive practical battery testing that seems to reflect practice fairly well over a wide range of LiPos and capacities - although some recent cells like the Turnigy Graphines do better than predicted. It has some theoretical basis in a maximum allowable % of energy dissipated internally (6 Watts/AmpHr) but we don't rely on a theoretical explanation. It is a purely empirical observation that has been surprisingly useful to date.  

Entered by admin on Saturday, 04 June 2016 @ 15:17:37  
Electronics - RC Models, # Hits: 12960
spacer line
Question ? MP: Manufacturers Promise   [
View DetailsView details
|
Print ViewPrint view
]

 Manufacturer's Promise is there to tell us if the C-Rating of the LiPo pack is actually accurate.
Based on what the Manufacturer claims the pack is capable to deliver, we calculate the actual C-Rate based on the worst cell's Internal resistance.
The relative number out of there tells us how good the C-Rating of the Manufacturer is.

  • MP == 1: Very good. The proclaimed rating matches the mesured one
  • MP < 0 : No good. The LiPo pack delivers less than claimed
  • MP > 1 : Excellent - The LiPo pack delivers more than claimed

 

Entered by admin on Tuesday, 07 June 2016 @ 15:28:54  
Electronics - RC Models, # Hits: 12943
 
Problems to  admin(-AT-)solsys(-DOT-)org  - best viewed @ 1920bpp
This site is powered by phpPhobos v2.0b446
© J. Mertin smurphy(-AT-)solsys(-DOT-)org 
Icons - Copyright Breeze artists GPL 2+