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Thread: eneloop vs. Kodak Pre-Charged Voltage Maintenance

  1. #61

    Arrow Re: eneloop vs. Kodak Pre-Charged Voltage Maintenance

    Quote Originally Posted by UnknownVT View Post
    Even though it is inconvenient - I'll persist with this set of KP-C - just to see how many shots I can squeeze out of them until final shut Off (ie: turning Off and On will not resuscitate).
    Well impatience got the better of me.

    I was using the dSLR today - for what I thought was non-demanding (ie: no flash and under normal bright conditions) and the camera shut-down on me in the middle of the session - so I won't persist further as it would be too just inconvenient - so have finally given up on this set of KP-C - final total shot count? just 347!!! - this is WAY lower than the 671 shots I managed to get from the KP-C set - when they were more recently charged (however, to be fair, this is still "repectable" - easily within the specs of the K100D for regular 2500mAh NiMH)

    This is relatively "disappointing" for me - as the KP-C do not match the eneloops, after more than about 3 months -

    However it is NOT actual loss of capacity from storage - but lower operating voltage under load - which is the very thing that gives the Pentax K100D dSLR its notorious reputation for being very battery fussy.

    To prove this for myself I took two of the KP-C from the set and and used them on High (in general mode - not Turbo) in the same Fenix L1D-Q5 used in the crude runtime test previously in Post #27 - they both managed just over about ~55 mins until very low/no light - compared to the ~125 mins when the KP-C was freshly charged - this shows the used KP-C still had quite substantial charge left in them - may be as much as 44% left -
    IF the K100D had been able to utilize the remaining capacity - that probably would have resulted in a "theoretical" shot count closer to 631! - which is in the ballpark of the previous set of KP-C (when more recently charged) and the eneloops.

    I know this seems to be beating a dead horse - but I can finally prove (to myself at least) that eneloops do maintain a higher operating voltage under load and do show a practical advantage when used in voltage level sensitive devices (like the Pentax K100D dSLR) - for me the eneloops have to be the choice for use in this camera -

    The Kodak Pre-Charged although do perform well, and managed to keep up with eneloops - will not do so after about 3 months storage - not that they lose capacity (they did not) but because they have lower operating voltage under load at that point......
    ie: KP-C do not maintain their operating voltage under load as well as eneloops.

  2. #62

    Arrow Re: eneloop vs. Kodak Pre-Charged Voltage Maintenance


    remember those eneloops that I charged back on April 27? (see post #38 in this thread)

    I put them in the Pentax K100D dSLR on Sept/22 (see post #61 ) - so almost 5 months after charge (although one of the eneloops was used for the internal resistance test so was recharged on May/16 - so over 4 months for just that one) and those managed 837 shots before giving up on Nov/20 - that's almost 7 months after charge (6 months for one).

    Most of the shots were without flash - but 837 is huge for the Pentax K100D - especially for batteries that were charged almost 5 months before then used for almost 2 months.

    This performance is WAY better than the Kodak Pre-Charged that I considered "disappointing" (post #61 ) when used 3 months after charge managed only 347 shots with several shut-downs.

    As reasoned previously it was not that the Kodak Pre-Charged had lost more charge than the eneloops - it is literally the eneloops were able to maintain higher operating voltage under the demanding load of the Pentax dSLR - whereas under the load the KP-C operating voltage would dip below the cut-off threshold of the dSLR - causing low battery signal and shut-down.

    (see post #61 there was a lot of remaining charge in the KP-C which the dSLR was not able to utilize - the KP-C managed to power a Fenix L1D-Q5 on High for 55 mins = ~44% remaining charge)

  3. #63

    Exclamation Re: eneloop vs. Kodak Pre-Charged Voltage Maintenance

    In August I bought a set of DuraLoops (Duracell Pre-Charged LSD = confirmed re-bafged eneloops) - charged them up on 8/23/08.

    Put them in the Pentax K100D dSLR on 11/20/08 - almost 3 months after charge.

    I depleted them tonight to the point where the camera shutdown -
    so that's almost 4 months after charge .....

    BUT the shot count was a whopping 1,169!!! - some, but mostly without flash - but this count for me is bordering on the unbelievably good.

    Look back at Post #35 where I show the shot count specs of the Pentax K100D for various battery types - the spec for 2500mAh NiMH was 430 shots no flash - DuraLoop = 1,169 = 272%!!

    and the best figures were for lithium CR-V3 batteries at 730 shots, or lithium AA's at 660 shots without flash -
    here are the DuraLoops exceeded both those - achieving 1,169 shots with a few flash shots -
    that's some 60% better than spec for lithium CR-V3
    or 77% better than lithium AA's

    I am most impressed with these DuraLoops (re-badged eneloop-R)

  4. #64

    Arrow Re: eneloop vs. Kodak Pre-Charged Voltage Maintenance

    I just did this and thought it was worth posting here -

    I speculate/suspect that Kodak Pre-Charged may be re-badged GP ReCyko? -

    Here's an animated GIF comparing the discharge curves at various current rates for 3 LSD batteries (note these were produced by SilverFox in his threads - NiMh Battery Shoot Out and Eneloop Self Discharge study - CandlePowerForums )


    I've also drawn a horizontal red line at approx 1.19V the cutoff threshold voltage for the Pentax K100D
    (Ref: Post #49 (link) in thread - K100D - "Low-Battery" Problem gives details of the meter voltage levels)

    One can see that there are more curves above the red line for the eneloop than the other two LSD batteries -
    although this may seem minor, I think this is very significant for the battery fussy/voltage sensitive K100D and *ist D family of Pentax dSLR.

    So although I have Kodak Pre-Charged LSD (which are otherwise excellent - I suspect these are re-badged GP ReCyko) - I use eneloops and confirmed re-badged eneloops in my K100D over any other batteries.

    To get over 1,100 shots out of a set of DuraLoops is simply incredible to me.

  5. #65
    Flashaholic* Black Rose's Avatar
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    Default Re: eneloop vs. Kodak Pre-Charged Voltage Maintenance

    These real world usage tests are great.

    Keep up the good work Vincent.

  6. #66

    Arrow Re: eneloop vs. Kodak Pre-Charged Voltage Maintenance

    Quote Originally Posted by Black Rose View Post
    These real world usage tests are great.
    You're very kind Black Rose....

    Just slightly OT but still on voltage maintenance - as the Pentax dSLRs using AA batteries are very voltage sensitive - the relatively newly announced (now available as Quantaray - from Ritz and Wolf cameras) may be useful -

    Nickel-Zinc (NiZn - Wikipedia)

    CPF thread - Nickel-Zinc to hit the streets end of April

    enGadget link , and the manufacturer - PowerGenix link

    according to the NiZn AA pdf spec sheet - the nominal voltage is 1.65V.

    This is good news as the discharge curve -

    shows that the battery remains above 1.19V (Pentax dSLR cutoff threshold) for the tested currents up to 1C = 1.5A - until it's truly depleted - so it may be capable of delivering all of its rated capacity before the Pentax dSLR shuts down

    The not quite as good news, is the capacity - typical 1500mAh with a minimum of 1350mAh (compared to 2000mAh typical and 1900mAh min for eneloops)


    in a kind of mitigation - because it maintains higher voltage it appears that the batteries may be able to deliver its full capacity before Pentax dSLRs shuts down.

    Some have said that the self-discharge rate is supposed to be about the same as typical (non LSD) NiMH.......

    The other problem is that because of the higher nominal voltage chargers have to be different - one cannot use existing NiMH chargers.

  7. #67

    Wink2 Re: eneloop vs. Kodak Pre-Charged Voltage Maintenance

    For those who are still interested -
    on Dec/19/08 I put a set of eneloops (charged on Aug/31/08) in my Pentax K100D dSLR -
    so that's ~3.6 months after charge.

    I did not quite deplete them last night at a New Years Eve gig -
    although the dSLR was showing mostly low battery signal
    (but would also occassionally bounce back to half empty signal too)
    it never shutdown.

    I changed them out between acts so that I would not have to worry about the camera shutting down
    (there is only so much I am willing to do.... or being bl**dy minded )

    However at the point when I swapped them out they had already taken 1,123 shots - a few flash shots - but mostly without flash - this is an amazing performance - considering the eneloops were charged some 3.6 months before and the Pentax K100D dSLR has been notorious for being battery/voltage sensitive - remember the Kodak Pre-Charged under similar conditions only managed 347 shots with several camera shutdowns....

    So it looks like eneloops (and re-badges like DuraLoops) have "tamed" this notoriously battery/voltage fussy dSLR - over any other LSD battery.

  8. #68
    Flashaholic* Hitthespot's Avatar
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    Default Re: eneloop vs. Kodak Pre-Charged Voltage Maintenance

    Good stuff Vince. It would be interesting to throw a set of PowerEx LSD's in that camera just to see how they do compared to the Eneloops and rebadges.

    Enjoyed this thread. Good work.

    Bill
    "The difference between genius and stupidity is that genius has its limits."
    Albert Einstein

  9. #69
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    Default Re: eneloop vs. Kodak Pre-Charged Voltage Maintenance

    Hello Vincent.

    Thanks for all information in this thread.

    It is very good to know everything you found here.

    Anders

  10. #70

    Arrow Re: eneloop vs. Kodak Pre-Charged Voltage Maintenance

    Quote Originally Posted by Hitthespot View Post
    It would be interesting to throw a set of PowerEx LSD's in that camera just to see how they do compared to the Eneloops and rebadges.

    Enjoyed this thread. Good work.

    Bill
    Quote Originally Posted by Anders View Post
    Thanks for all information in this thread.

    It is very good to know everything you found here.

    Anders
    Bill & Anders - thank you for your kind encouragement -
    I almost thought I was talking to myself -
    and feeling embarrassed for doing updates to this thread

    Bill -
    I would try Imedion PowerEX LSDs in the Pentax K100D if I had any...
    I already have more than I actually need in LSDs - and since the eneloops (and DuraLoops) have now solved my problems with the battery fussy camera ..... there is probably less incentive for me to get another brand.

    Although I do acknowledge that the Imedions tested out well and seem to have more capacity than eneloops - but so did the Kodak Pre-Charged - but one can see after about 3 months' storage the voltage level maintenance made my dSLR shutdown prematurely, when there was still plenty of charge left in them

  11. #71
    Flashaholic* Hitthespot's Avatar
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    Default Re: eneloop vs. Kodak Pre-Charged Voltage Maintenance

    Quote Originally Posted by UnknownVT View Post
    Although I do acknowledge that the Imedions tested out well and seem to have more capacity than eneloops - but so did the Kodak Pre-Charged - but one can see after about 3 months' storage the voltage level maintenance made my dSLR shutdown prematurely, when there was still plenty of charge left in them
    Exactly what I was thinking. I was wondering about the storage factor and if the Imedions would have the voltage dip in the camera. It is amazing how the Eneloops just plain perform. Like you I have a number of Eneloops. I just bought the Maha C9000 Charger and my first 2 4packs of the PowerEX 2700 cells. I bought the cells because I figured I could use them in power hungry devices like my GPS and Fuji S6000fd digital camera. With the extra $ spent on the batteries I got free shipping. I'm just wondering if I shouldn't of went a head and bought the Imedions if they perform as good as the Eneloops.

    Bill
    "The difference between genius and stupidity is that genius has its limits."
    Albert Einstein

  12. #72

    Default Re: eneloop vs. Kodak-> R_int Calculation

    Quote Originally Posted by UnknownVT View Post
    .
    .
    .
    For example I report on voltages - but they are open-circuit readings which are obviously not as useful or meaningful as the actual operating voltage under load.
    .
    .
    .
    I wanted to be able to determine the operating voltage under load for the Kodak Pre-Charged and eneloop to see if there was a difference.

    So I thought of a pretty simple somewhat artificial method, but should be easily controlled and reproducible -
    just get a 1 ohm resistor and read the voltage when the resistor was loaded across the battery terminals.

    .
    .
    .
    Open-Circuit readings -
    eneloop #1: ... 1.454V; FA=11.6A; 1.436V
    Kodak P-C #1: 1.423V; FA=10.4A; 1.409V

    1 ohm load readings -
    ene = 1.388V @ 1.25A (= 1.735watts)
    KPC = 1.336V @ 1.22A (= 1.630watts)

    End of test o-c readings
    ene = 1.440V
    KPC = 1.412V
    .
    .
    .
    The discharge graph can be simplified to two numbers by using a vertical cutline of the graph taken at some point during the discharge curves. In this example, the output characteristic past the 1/2 way point was used:





    The slope of the line in the figure below is equal to the internal resistance "Ro" and the unloaded operating point by "Vo". Lower internal resistance will result in tighter spacing of the discharge curves for different current loads.



    Batteries are very close to "ideal voltage sources" and can be represented by an equivalent circuit. The drop in output voltage (Vt) when loaded is determine by the "output series resistance" or "internal resistance" called R_o . You would a great electrical engineer gauged by your thought process. For people without access to anything more than a DMM, adding a low value load resistor (2 Watt rating for 1 ohm) to your toolbox would allow you to constuct a poor man's ZTS tester.

    With just the unloaded voltage (Vo) and loaded voltages and knowledge of the load resistor value the "intenal resistance" can be estimated. The lower it is, the better. Once known, you can use it to predict the output voltage for different loads that draw more current (or less).

    The series resistance is given by :

    R_int= (Vo - Vload)/ I_load [Equation 1]
    But I_load is known exactly due to the relationship between the "load resistor" value and loaded voltage:

    I_load= Vt/R_load = Vload/R_load [Equation 2]
    Combining Equation 1 and 2:

    R_int = (Vo-V_load)/(I_load)
    = (Vo-V_load)/(Vload/R_load)
    = (Vo/Vload - 1) * R_load
    Example the eneloop:


    Rint=(1.440/1.388-1) * 1 ohm =0.037 ohms (correction pointed out by Cemoi)
    PeAK
    Last edited by PeAK; 02-08-2009 at 10:35 AM.

  13. #73
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    Default Re: eneloop vs. Kodak-> R_int Calculation

    Quote Originally Posted by PeAK View Post
    R_int = (Vo-V_load)/(I_load)
    = (Vo-V_load)/(Vload/R_load)
    = (Vo/Vload - 1) * R_load
    Example the eneloop:
    R_int=(1.440-1.388)* 1 ohm = 0.052 ohms
    Shouldn't the numerical example look like "(1.xxx/1.yyy - 1) * 1 =..."?

    A voltage difference multiplied by a resistance is not a resistance.

    On the other hand, I'm surprised at the value you get. I've tested several of my AA NiMH (including brand new Maha Powerex 2700), and found values in the 0.28 - 0.65 ohm range, i.e. about ten times your value.

  14. #74
    *Flashaholic* PlayboyJoeShmoe's Avatar
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    Default Re: eneloop vs. Kodak-> R_int Calculation

    Extremely interesting thread!

    I mostly use LSD Nimh 2 at a time in my GPS. I started doing that when 2500mAh batteries charged Sunday night would not run the GPS a full day on Wednesday!

    ANY of the LSD NimH I have including Eneloop, Hybrid, Hybrio and Kodak will in fact run the GPS all day at least a couple weeks after charging.

    While thinking about this post I checked a bunch of my older cells like Duracell White Rechargeable Accu 2050 and Lenmar No-Mem Pro 2000 and found them all at 1.27V after 2 to 3 months.

    I plan to charge up 4 of each and try them this week.

    My other use is as flashlight batteries and again I haven't found any of the first four I mentioned lacking in any way.

    That camera sounds like a picky b*tch!

    Anyhow I have not seen Eneloops for sale since I found the 4 I have with a charger at Wallyworld.

    I do have access to Hybrid, Hybrio, Kodak and Duraloop. Of those four which ones should I concentrate on getting more of?
    http://img32.imageshack.us/img32/2640/usflaghalfmastmdwht.gif

    PBJS



  15. #75

    Default Re: eneloop vs. Kodak-> R_int Calculation

    Quote Originally Posted by Cemoi View Post
    Shouldn't the numerical example look like "(1.xxx/1.yyy - 1) * 1 =..."?

    A voltage difference multiplied by a resistance is not a resistance.

    On the other hand, I'm surprised at the value you get. I've tested several of my AA NiMH (including brand new Maha Powerex 2700), and found values in the 0.28 - 0.65 ohm range, i.e. about ten times your value.
    You're absolutely correct about my typo. I'll go back and correct the post. I'm pretty shure about the numbers I came up with using a 2 ohm load. The best batteries were some older Energizers 1700mA-hr (0.04 ohms) which I heard were made for them by Sanyo in the early days of a brand name Alkaline battery manufacturer entering the rechargeable scene. Later day Energizer 2500 were much worse at 0.16 ohms.
    Last edited by PeAK; 02-08-2009 at 08:58 PM.

  16. #76

    Default Re: eneloop vs. Kodak-> R_int Calculation

    Quote Originally Posted by PlayboyJoeShmoe View Post
    Extremely interesting thread!
    .
    .
    .
    I do have access to Hybrid, Hybrio, Kodak and Duraloop. Of those four which ones should I concentrate on getting more of?
    Hello PBJoe,
    In another thread related to NiMh overcharging issues, I was led to the Saitek (aka CCrane) charger thread posted back about 5 years ago by you.

    This seem to be the state of the art charger back then before Lacrosse and Maha got into the game with more modern packaging and better marketing. One on those posts had a link (from Mr Happy) that suggested a scheme (1994) proposed by an SGS application note that would use the change in the slope of the voltage curve was zero. Some refer to this as the inflection point or second derivative voltage slope termination scheme.

    It would seem that in posts discussing the CCrane Quickcharger (aka Saitek SmartCharger or RadioShack 23-410) did not suffer overcharging issues due to the use of the the above scheme and lead to increases in the internal resistance.did not suffer from overcharge issues

    Are you still using that charger , and if so, are you still happy with it ? It might the one charger that will not cook the NiMh batteries due to the use of negative delta-V terminations. It seems as if the new LSD eneloops might heat up quite a bit using NDV.

    PeAK
    Last edited by PeAK; 02-08-2009 at 11:12 AM.

  17. #77
    *Flashaholic* PlayboyJoeShmoe's Avatar
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    Default Re: eneloop vs. Kodak-> R_int Calculation

    Yes, funny you should mention the C Crane.

    It took it a pretty good while starting at 1.27V to hit bottom and start charging the Duracell ACCUs.

    Just changed to the Lenmars now.1.24v on the way down.
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  18. #78

    Arrow Re: eneloop vs. Kodak-> R_int Calculation

    Quote Originally Posted by PeAK View Post
    The discharge graph can be simplified to two numbers by using a vertical cutline of the graph taken at some point during the discharge curves. In this example, the output characteristic past the 1/2 way point was used
    The slope of the line in the figure below is equal to the internal resistance "Ro" and the unloaded operating point by "Vo". Lower internal resistance will result in tighter spacing of the discharge curves for different current loads.
    Example the eneloop:

    Rint=(1.440/1.388-1) * 1 ohm =0.037 ohms (correction pointed out by Cemoi)
    PeAK
    Thank you so much for responding to this thread PeAK.

    I assume since you were responding to my post #41 above that you saw the many calculations of internal resistance of both the eneloop and Kodak Pre-Charged in the immediately following posts started bt Mr Happt - Post #42 - then followed by #44 #45 #46 #47

    I got (with Mr Happy's help in the calculations, ene=eneloop; KPC=Kodak Pre-Charged) -

    Using 1 ohm fixed resistor and the open-circuit voltage -
    ene Rb = (1.294-1.247)/1.17 = 0.040 ohms
    KPC Rb = (1.267-1.220)/1.14 = 0.041 ohms

    and using readings from 0.5 & 2 ohms fixed resistors -
    ene Rb= (1.266-1.224)/(2.09-0.60) = 0.028 ohms
    KPC Rb= (1.243-1.176)/(2.01-0.59) = 0.047 ohms

    We used -

    Internal resistance = (V1 - V2) / (I2 - I1)

    and for the special case of using a single resistor and the Open-Circuit voltage

    Rb = (V1 - V2) / (I2 - I1) = (Vs - V) / (I - 0)

  19. #79

    Arrow Re: eneloop vs. Kodak-> R_int Calculation

    Quote Originally Posted by PlayboyJoeShmoe View Post
    I do have access to Hybrid, Hybrio, Kodak and Duraloop. Of those four which ones should I concentrate on getting more of?
    For me - I have convinced myself that eneloops are superior for maintaining higher operating voltage under load than any other LSD or NiMH. This is from my own "testing" (flaws and all) and from my numerous reading about LSD batteries.

    So, for now it is the eneloop, or any confirmed re-badged eneloop -
    like DuraLoop (must be made in Japan with white tops - Duracell Pre-Charged Rechargeables - Buyer Advisory ...)
    or perhaps the HybrioLoops (as described by Mr Happy in Uniross Hybrios are Eneloops...? - but beware of When is a Hybrio not a Hybrio?).

    But since DuraLoops are now so prevalent - I tend to get those on sale.

    But please remember mine is still a special case of a very battery fussy dSLR -
    as I have shown in flashlights - voltage maintanence does not seem to be a major issue,
    in fact the Kodak Pre-Charged seemed to outperform eneloops when recently charged -
    BUT I cannot say for sure if the voltage maintance would become an issue if stored beyond 3 months -
    reasoning - please see Post #61 and #62 above.

  20. #80

    Default Re: eneloop vs. Kodak-> R_int Calculation

    Quote Originally Posted by UnknownVT View Post
    .
    .
    I assume since you...saw the many calculations of internal resistance of both the eneloop and Kodak Pre-Charged
    .
    .
    Using 1 ohm fixed resistor and the open-circuit voltage -
    ene Rb = (1.294-1.247)/1.17 = 0.040 ohms
    KPC Rb = (1.267-1.220)/1.14 = 0.041 ohms

    and using readings from 0.5 & 2 ohms fixed resistors -
    ene Rb= (1.266-1.224)/(2.09-0.60) = 0.028 ohms
    KPC Rb= (1.243-1.176)/(2.01-0.59) = 0.047 ohms
    Hi Vincent,
    I saw the many numbers that you reported. The variation in the resistance reflects the fact that the "straight line"/linear equations used to describe the V-I characteristic (V-I, hereafter) do account for a curvature in characteristic with smaller loads and increasing currents. To back up a bit, a model needs only to be as accurate/complex to get the job done: In this case, we just want to roughly grade batteries unloaded and loaded. We also want to be able to distinguish differences between batteries with the same unloaded performance (open circuit voltage) but with different voltages when loaded. These 2 conditions allow us to "pin" down the values of 2 variables (Vo and Rb) to describe this condition. If it sounds like algebra, IT IS.

    Mathematical Notation is just a shortcut language to convey a trend in something that we observe. To make the connection stronger, it is sometimes simpler to initially forgo the math/numbers and look at the trend directly with the aid of a graph. A read battery would have the following characteristic:



    The currents I1, I2 and I3 correpond to currents when R=2ohm, R=1ohm and R=0.5ohms are attached, respectively. Immediately we can that drawing a straight line between (I3,V3) and (I2,V2) combination generateds the steepest line (i.e. largers Rb value). Any other combination of points will have a lower value. Using Currents I1 and I3 will generate a smaller value of Rb that the previous case and helps explains some of the trends you saw in your data.

    I like mesuring the point on the curve (Io,Vo)=(0,Vo) after measuring the output voltage loaded so that the battery is preconditioned a bit prior to making the open circuit voltage. It also minimizes time delays between measurements which can impart an error due to the internals of the battery settling out after generating output.




    Quote Originally Posted by UnknownVT
    We used -

    Internal resistance = (V1 - V2) / (I2 - I1)

    and for the special case of using a single resistor and the Open-Circuit voltage

    Rb = (V1 - V2) / (I2 - I1) = (Vs - V) / (I - 0)
    [/quote]

    The form (V2-V1)/(I2-I1) give the slope, so since
    Rb=-slope, we get the equation that you have been using.

    If you really want to capture the curvature, then you can use a quadratic equation that will fit a line through all the dots. A more complicated model
    V=a * i^2+b * i+c
    but not so good at conveying the slope information.

    Compare that to V = Vo - Rb * i
    Using higher currents to determine Rb will result generally in larger values of Rb
    and less optimistic values of "V" for higher resistance loads.It may seem obtuse for now but the best model is the simplest model that you can live with. A complicated model is only worth it if you can manage the complexity to gain more insight.

    PeAK
    Last edited by PeAK; 02-09-2009 at 12:37 PM.

  21. #81

    Arrow Re: eneloop vs. Kodak-> R_int Calculation

    Quote Originally Posted by PeAK View Post
    The form (V2-V1)/(I2-I1) give the slope, so since
    Rb=-slope, we get the equation that you have been using.
    If you really want to capture the curvature, then you can use a quadratic equation that will fit a line through all the dots. A more complicated model
    V=a * i^2+b * i+c
    Compare that to V = Vo - Rb * i
    Using higher currents to determine Rb will result generally in larger values of Rb
    Thanks PeAK - we were basically using the same equation(s) I only listed them so that others can be sure what Mr Happy and I were calculating.

    However I prefer the version without using the R(load) - as there is no way I can measure the resistance accurately - mine is only a cheapo DMM which seems to show 0.6ohms when the leads are shorted on the 200ohm scale (the lowest) - readings for both 1 ohm resistors show 1.6 ohms - so one could say they are 1 ohm allowing for the 0.6 ohm offset....
    - but that is really crude. Also the package rating/specs are 1 ohm +/- 10% so strictly speaking the resistor(s) used could be 0.9 to 1.1ohm - too much margin of error to use in the calcuations - using actual measured voltages and current(s) drawn probably has a better resolution on that cheapo DMM - even then it was liken to hitting a moving target - I just took the "best" measurements I could - it would probably be slightly different on another day/hour.....

    Nevertheless I ended up with 3 sets of results for 0.5, 1, 2 ohm loads plus the open-circuit (no load) voltage which allowed 6 calculations for the internal resistance - and the general trend, not surprisingly, was that the internal resistance increased with increasing current draw (decreasing resistance)
    this was enough to give reasonable "confidence" in the figures -
    although there were slight variences -
    there did not seem to be anything that stuck out to show possible major errors.

    The increments for the resistive load were 0.5,1, and 2 ohms so pretty close to approximate the "curve" and in the common/practical range for flashlight usage (ie: in the range of about 0.6 to 2.4 Amps)

    So the calculated internal resistances probably are good enough for an indication for both eneloops and Kodak Pre-Charged.
    Not forgetting, of course, this is strictly limited to the samples of one of each of the batteries I used.

  22. #82
    *Flashaholic* Mr Happy's Avatar
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    Default Re: eneloop vs. Kodak-> R_int Calculation

    Quote Originally Posted by UnknownVT View Post
    even then it was liken to hitting a moving target - I just took the "best" measurements I could - it would probably be slightly different on another day/hour
    A way to deal with this is to alternate back and forth between the loaded and unloaded state about once a second or so until the readings stabilize.

  23. #83

    Thumbs up Re: eneloop vs. Kodak-> R_int Calculation

    Quote Originally Posted by Mr Happy View Post
    A way to deal with this is to alternate back and forth between the loaded and unloaded state about once a second or so until the readings stabilize.
    Thanks, yes, I waited until the readings seemed to stabilize - but I only have the one DMM which meant making and breaking the circuit each time I changed from voltage to current - so it was still pretty crude.

    Like I said the resultant calculations seemed good enough as an indication
    - considering all the limitations - especially the sample size....

  24. #84
    *Flashaholic* PlayboyJoeShmoe's Avatar
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    Default Re: eneloop vs. Kodak-> R_int Calculation

    One pair of Lenmar NoMEM Pro 2000mAh batteries failed miserably to run my GPS all day on monday.

    Both pairs of Duracell Rechargeable ACCUs 2050mAh DID run the GPS just fine yesterday and today.

    Both types are some of my earliest nimhs.

    The Duracells may be the first of the Hybrid/Hybrio type batteries.

    Shame I only have 4.

    edit for INTERESTING fact: The Lenmars that died during the day on monday show 1.27 and 1.24. The Duracells that lasted until I shut the GPS down at home show 1.25ea for Wed and 1.23 and 1.24 for todays.

    AHA! one of the monday lenmars has 3.5FA and the other 1.5. The Duracells are all over 4 except one almost 4.

    That explains things nicely!
    Last edited by PlayboyJoeShmoe; 02-12-2009 at 07:12 PM.
    http://img32.imageshack.us/img32/2640/usflaghalfmastmdwht.gif

    PBJS



  25. #85

    Arrow Re: eneloop vs. Kodak Pre-Charged Voltage Maintenance

    I depleted a set of eneloops (my #1-4) in the Pentax K100D dSLR - the camera shut down during a test shoot - by turning it off and back on, the eneloops managed to shoot some more - but after about twice - even turning off then on failed to power the dSLR - so I consider this as low as one could drain the eneloops for all practical purposes. The final shot count for this set was 989 mostly without flash.

    Since I now have a Maha C-9000 charger I thought I'd see how much charge was left in these eneloops - discharge current set at 0.2C = 400mA

    eneloops -
    #1 151mAh 25mins
    #2 151mAh 25mins
    #3 151mAh 25mins
    #4 159mAh 27mins

    pretty consistent with only #4 showing very slightly higher.

    That's about 8% remaining charge - if the dSLR could actually take the batteries down to 0.9V (which it doesn't).

    So this is pretty good considering how notorious the Pentax K100D dSLR is for being battery fussy and requiring higher operating voltage under load - my estimate is the DSLR is utilizing just over 90% of the eneloop capacity.

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