Olight
Results 1 to 28 of 28

Thread: D-cell Alkaline VS AA nimh

  1. #1

    Default D-cell Alkaline VS AA nimh

    This may sound unfair but here is my situation and concern.
    I've bought a Osram crosser 3-led spotlight a while ago. The light runs off 4 D-cell alkalines. I was under the impression that you can't use D-cell rechargebles in them as they dont have a metal positive that covers the top of the battery like its the case with alkalines. The light has wide springs so to get the positive tab to make contact the springs would require some modding.
    So I've decided to cut everything out and use 4 AA nimh batteries in an adapter. Actually I've got 3 packs to run in parallel for increased runtimes.

    I then thought that since the light only draws about 0.96 amps and the Nimh is only 1.2V against the 1.5V of the D-cells, that the light might be a little less bright now.
    So I went to my father who owns the same light but still in standerd form.

    Now here is my concern, at long last.. My light is twice as bright as my fathers? How can this be possible with 1.2V less, at this relatively low ampdraw? Will this mean that the led's might burn out prematurely?

    I really thought that big D-cell alkalines would sag a lot less under a small load like this

  2. #2

    Default Re: D-cell Alkaline VS AA nimh

    Nimh AAs are not 1.2v, they are "rated" at that voltage but vary from 1.45v off the charger to about 1.1v essentially discharged. Nimh have a lot lower internal resistance so if you had 4 hot off the charger at ~1.4v and put it against alkalines that had been used for awhile sagging to 1.3v or so you would have 0.4v difference. I am thinking your father's light the batteries are nearly depleted and yours are barely used. 0.96A is a decent load for D cell alkalines there would be a little sag on them, more when they get depleted but fresh they probably would closely match nimh off the charger.
    Fenix Split rings 1400+ sent, SWIVELS now available also!
    Psalm 112:4 Light shines in the darkness for the godly. They are generous, compassionate, and righteous.

  3. #3

    Default Re: D-cell Alkaline VS AA nimh

    I got a reading of 5.41V with the pack of 4 Nimh's
    The D-cells were fairly new and all were giving between 1.62 and 1.64V for 6.53V collectively

    Both figures quoted were unloaded figures.

  4. #4

    Default Re: D-cell Alkaline VS AA nimh

    so we have approx. 1.35v for the nimh and 1.63v for the alkaline. You would have to get voltages when operating as I cannot see the alkalines caving in below 1.4v at that voltage normally. Did you try swapping batteries between the lights?
    Fenix Split rings 1400+ sent, SWIVELS now available also!
    Psalm 112:4 Light shines in the darkness for the godly. They are generous, compassionate, and righteous.

  5. #5

    Default Re: D-cell Alkaline VS AA nimh

    I cannot swop bats between the lights as I had to rip out the insides of mine to put in the 4AA battery holders. So mine can't work with D-cells anymore.

  6. #6

    Default Re: D-cell Alkaline VS AA nimh

    Quote Originally Posted by lightseeker2009 View Post
    I cannot swop bats between the lights as I had to rip out the insides of mine to put in the 4AA battery holders. So mine can't work with D-cells anymore.
    I invested in a bunch of clip leads long ago so I can test things outside of their cases.
    Fenix Split rings 1400+ sent, SWIVELS now available also!
    Psalm 112:4 Light shines in the darkness for the godly. They are generous, compassionate, and righteous.

  7. #7

    Default Re: D-cell Alkaline VS AA nimh

    No I can hereby confirm that AA Nimh batteries lights up a led better than D-cell alkalines.
    I have done the following test. I've used a 300 lumen Solarforce drop in (0.8-4.2V) I connected it directly to 2 d-cell batteries, and directly after to 2 AA nimh batteries. The difference is much more than expected. With the AA's its so much brighter that you just wont believe. The resting voltages of the two D-cells are quite a bit more than the voltage recorded for the AA's.

    Simply amazing. Another reason to go green I supose.

  8. #8
    Flashaholic* 45/70's Avatar
    Join Date
    Oct 2005
    Location
    Rural Ohio
    Posts
    2,800

    Default Re: D-cell Alkaline VS AA nimh

    Interesting results, lightseeker. I can't say I'm too surprised though. It is a well known fact that NiMh cells deliver higher voltage under load than alkaline cells, at higher current rates.

    Alkaline cells, are primarily designed to deliver current loads in the <500mA range. Even the "D" size cells are designed in this way, and their larger size is more to extend runtime in devices, rather than to increase the actual power output. That's not to say that a D alkaline isn't able to provide more power (ie. Watts, not Watt/hours) than an AA alkaline, it's bigger so probably does. As I said though, it really doesn't surprise me that an AA NiMh cell can provide more power than a D alkaline. Now, if you were to compare the two cell sizes at a rate such as 50mA, the D size (or maybe even an AA) would most likely do better than the NiMh cell.

    Dave

  9. #9

    Default Re: D-cell Alkaline VS AA nimh

    Quote Originally Posted by 45/70 View Post
    Interesting results, lightseeker. I can't say I'm too surprised though. It is a well known fact that NiMh cells deliver higher voltage under load than alkaline cells, at higher current rates.

    Alkaline cells, are primarily designed to deliver current loads in the <500mA range. Even the "D" size cells are designed in this way, and their larger size is more to extend runtime in devices, rather than to increase the actual power output. That's not to say that a D alkaline isn't able to provide more power (ie. Watts, not Watt/hours) than an AA alkaline, it's bigger so probably does. As I said though, it really doesn't surprise me that an AA NiMh cell can provide more power than a D alkaline. Now, if you were to compare the two cell sizes at a rate such as 50mA, the D size (or maybe even an AA) would most likely do better than the NiMh cell.

    Dave
    I'm sure. The D-cell have a much higher mah rating than AA nimh cells.

    But now that this was established. How will the use of the AA's affect the life of my spotlights led's since they were originally designed to work with alkalines? The Nimh's makes the light output very close to twice as bright, I kid you not!

  10. #10

    Default Re: D-cell Alkaline VS AA nimh

    Quote Originally Posted by lightseeker2009 View Post
    I'm sure. The D-cell have a much higher mah rating than AA nimh cells.

    But now that this was established. How will the use of the AA's affect the life of my spotlights led's since they were originally designed to work with alkalines? The Nimh's makes the light output very close to twice as bright, I kid you not!
    have you tried to figure out the current used by both alkalines and nimh in the light? If it is twice as bright you could be using over twice the current.
    Fenix Split rings 1400+ sent, SWIVELS now available also!
    Psalm 112:4 Light shines in the darkness for the godly. They are generous, compassionate, and righteous.

  11. #11
    Flashaholic* 45/70's Avatar
    Join Date
    Oct 2005
    Location
    Rural Ohio
    Posts
    2,800

    Default Re: D-cell Alkaline VS AA nimh

    Quote Originally Posted by lightseeker2009 View Post
    I'm sure. The D-cell have a much higher mah rating than AA nimh cells.
    The mAh rating of a cell really has nothing to do with how much power the cell can deliver, although it can help. Don't confuse power with power over time (energy), ie. Watts with Watt hours. They are two different things. So, while what you say is probably true, it really has nothing to do with how brightly a cell can drive an LED. For example, the AA NiMh cell may drive the LED much brighter, but for only 10 Minutes. On the other hand the D cell may not drive the LED nearly as bright, but for two hours. These are just figures "pulled from a hat", but this is an example of power vs. power over time. In this example the AA cell has more available power, but less power over time (more Watts, but less Watt hours).

    How will the use of the AA's affect the life of my spotlights led's since they were originally designed to work with alkalines?
    Just as in the example above, the AA NiMh cells will no doubt not run the light nearly as long as the alkaline D cells. There is a tradeoff when a cell is able to deliver current at a higher rate. Add to this the fact that an AA cell is only approximately one fourth the size of a D cell, and you have your answer, more or less.

    Dave

  12. #12

    Default Re: D-cell Alkaline VS AA nimh

    The average D-cell alkaline battery has about 300 milli-ohms of internal resistance, shorted out this equates to a 5 amp short circuit discharge rate. I know for a fact my good AA nimhs can pump out close to 20 amps maximum discharge on a dead short, this equates to about 60 milli-ohms internal resistance. So it's no wonder why D-cell alkalines don't perform as well as even a smaller AA nimh. In fact the D-cell battery really has no more current capacity than a AA, just simply more capacity. It's their construction that gives it that limitation, the anode is simply a brass pin so that tiny surface area which is pretty much the same size, maybe a little longer in the D-cell would ultimately be what restricts maximum current. Nimh on the other hand uses a coiled up sheet with much more surface area so even a AA would be able to have more surface area, and hence discharge capability, than a D-cell alkaline.

  13. #13
    Flashaholic* 45/70's Avatar
    Join Date
    Oct 2005
    Location
    Rural Ohio
    Posts
    2,800

    Default Re: D-cell Alkaline VS AA nimh

    Quote Originally Posted by lightseeker2009 View Post
    How will the use of the AA's affect the life of my spotlights led's since they were originally designed to work with alkalines?
    My apologies, lightseeker. After rereading your question, I see that I somehow totally missed it! My answer related to the difference in predicted runtime between AA NiMh cells and alkaline D cells.

    As for how the higher drive current applied to the LEDs will affect their lifespan, it depends entirely on how much current they are actually being driven at. Without a measurement of this value, it is hard to predict how they will be affected. It is true that higher drive currents shorten LED longevity, but if the current is still within the LED's specification, the effect may be minimal.

    Dave
    Last edited by 45/70; 09-01-2011 at 10:10 PM. Reason: sp

  14. #14

    Default Re: D-cell Alkaline VS AA nimh

    Quote Originally Posted by 45/70 View Post
    My apologies, lightseeker. After rereading your question, I see that I somehow totally missed it! My answer related to the difference in predicted runtime between AA NiMh cells and alkaline D cells.

    As for how the higher drive current applied to the LEDs will affect their lifespan, it depends entirely on how much current they are actually being driven at. Without a measurement of this value, it is hard to predict how they will be affected. It is true that higher drive currents shorten LED longevity, but if the current is still within the LED's specification, the effect may be minimal.

    Dave
    I just wanted to correct you but you caught it before me lol.
    Well I've figured each LED is being driven at around 0.32 amps. I've looked at the light on the Osram webite and apparently they are driven at 350 ma at 6V, according to the documentation. So I believe I'm well within safe specs but it does not hurt to make sure. With freshly charged AA's it draws 0.96 amps in total for the 3 led's.

    @Lynx. I never tested the power consumption with the Alkalines and now that the light was stripped I wont be able too, unless I can get another double D-cell holder.

  15. #15
    Flashaholic*
    Join Date
    Nov 2006
    Location
    Wisconsin
    Posts
    643

    Default Re: D-cell Alkaline VS AA nimh

    Quote Originally Posted by qwertyydude View Post
    The average D-cell alkaline battery has about 300 milli-ohms of internal resistance, shorted out this equates to a 5 amp short circuit discharge rate. I know for a fact my good AA nimhs can pump out close to 20 amps maximum discharge on a dead short, this equates to about 60 milli-ohms internal resistance. So it's no wonder why D-cell alkalines don't perform as well as even a smaller AA nimh. In fact the D-cell battery really has no more current capacity than a AA, just simply more capacity. It's their construction that gives it that limitation, the anode is simply a brass pin so that tiny surface area which is pretty much the same size, maybe a little longer in the D-cell would ultimately be what restricts maximum current. Nimh on the other hand uses a coiled up sheet with much more surface area so even a AA would be able to have more surface area, and hence discharge capability, than a D-cell alkaline.
    Alkaline D cells can put out 20 amps into a dead short without too much trouble. Current will quickly drop, however. This is about twice as much current in to a dead short as a typical alkaline AA cell. Granted, mostly what larger alkaline cells give you is more capacity, but the current collector (brass nail) isn't what's limiting the current capacity of the cells. Inter-facial area between the anode and cathode is a major contributor to rate capability of alkaline cells. D cells simply have a much larger inter-facial area than AA cells.

  16. #16

    Default Re: D-cell Alkaline VS AA nimh

    I just finished testing a brand new Energizer D-cell, 1.603 volts. Dead shorted it on my multimeter. I got 7 amps. To compare I also tested a brand new AA Kirkland Alkaline 1.610 volts and it actually did better 8.5 amps.

    I still stand by my previous observation. D-cell alkaline pretty much has the same discharge capability as AA alkaline.

  17. #17

    Default Re: D-cell Alkaline VS AA nimh

    What is the reading when this is being done to say an Eneloop?

  18. #18
    Flashaholic*
    Join Date
    Nov 2006
    Location
    Wisconsin
    Posts
    643

    Default Re: D-cell Alkaline VS AA nimh

    Quote Originally Posted by qwertyydude View Post
    I just finished testing a brand new Energizer D-cell, 1.603 volts. Dead shorted it on my multimeter. I got 7 amps. To compare I also tested a brand new AA Kirkland Alkaline 1.610 volts and it actually did better 8.5 amps.

    I still stand by my previous observation. D-cell alkaline pretty much has the same discharge capability as AA alkaline.
    Your multimeter has more resistance than a true dead short. We test cells at 10 milliohm resistance when measuring flash amps. I have stacks of data showing D cells putting out 20 to 25 flash amps, while AA cells typically fall between 8 and 12 amps into the same load.

  19. #19
    Flashaholic
    Join Date
    Aug 2011
    Location
    Czech Republic
    Posts
    266

    Default Re: D-cell Alkaline VS AA nimh

    I tested GP ReCyko AA with clamp, non contact A-metter and thick copper wire and they easily delivered 45Amps. Alkaline AA can deliver max 10A. Will test D cell alkaline as soon as I get home but i think there will be not so big difference due the alkaline design- negative pole is brass rod dipped in powdered zinc paste-and the contact area between zinc (which acts in chemical reaction) and this rod (which is just current collector) in AA is very similar to D.

  20. #20
    Flashaholic*
    Join Date
    Nov 2006
    Location
    Wisconsin
    Posts
    643

    Default Re: D-cell Alkaline VS AA nimh

    Quote Originally Posted by czAtlantis View Post
    I tested GP ReCyko AA with clamp, non contact A-metter and thick copper wire and they easily delivered 45Amps. Alkaline AA can deliver max 10A. Will test D cell alkaline as soon as I get home but i think there will be not so big difference due the alkaline design- negative pole is brass rod dipped in powdered zinc paste-and the contact area between zinc (which acts in chemical reaction) and this rod (which is just current collector) in AA is very similar to D.
    The contact area between the zinc paste and the brass current collector is not the limiting factor. It's the surface area between the zinc paste and the cathode.

  21. #21

    Default Re: D-cell Alkaline VS AA nimh

    Quote Originally Posted by MorePower View Post
    Your multimeter has more resistance than a true dead short. We test cells at 10 milliohm resistance when measuring flash amps. I have stacks of data showing D cells putting out 20 to 25 flash amps, while AA cells typically fall between 8 and 12 amps into the same load.
    Even if it did have more resistance than a dead short, that still doesn't explain why the AA would basically outperform the D battery in an equal resistance test. Same multimeter, essentially the same state of charge, the .007v difference shouldn't lower the D cell current by 3 amps if the D-cell truly had lower internal resistance. And I do use very low resistance short length 16 gauge wires on my multimeter, it's about as close to a dead short as you're really going to get and considering the high resistance of the batteries it's a gives a good representation of the discharge capability of alkalines. Nimh not at all because AA can go up to 20 amps, D-cell forget it, it can smoke 16 gauge wire on a dead short. I know my high performance 5300 mah sub-c RC cells can put out 75 amps peak on a dead short.
    Last edited by qwertyydude; 09-04-2011 at 01:22 AM.

  22. #22
    Flashaholic*
    Join Date
    Nov 2006
    Location
    Wisconsin
    Posts
    643

    Default Re: D-cell Alkaline VS AA nimh

    Quote Originally Posted by qwertyydude View Post
    Even if it did have more resistance than a dead short, that still doesn't explain why the AA would basically outperform the D battery in an equal resistance test. Same multimeter, essentially the same state of charge, the .007v difference shouldn't lower the D cell current by 3 amps if the D-cell truly had lower internal resistance. And I do use very low resistance short length 16 gauge wires on my multimeter, it's about as close to a dead short as you're really going to get and considering the high resistance of the batteries it's a gives a good representation of the discharge capability of alkalines. Nimh not at all because AA can go up to 20 amps, D-cell forget it, it can smoke 16 gauge wire on a dead short. I know my high performance 5300 mah sub-c RC cells can put out 75 amps peak on a dead short.
    No, as close to a dead short you're going to get is the method we use, day in and day out. 10 milliohms read at 20 milliseconds. I'm not saying NiMH cells can't output higher current than alkaline cells; they certainly are more than capable of doing so. What I am saying is that you are wrong in your comparison of the discharge capability of alkaline AA and D cells.

    Since no one ever wins an argument on the internet, I'm going to stop now.

  23. #23

    Default Re: D-cell Alkaline VS AA nimh

    Quote Originally Posted by MorePower View Post
    No, as close to a dead short you're going to get is the method we use, day in and day out. 10 milliohms read at 20 milliseconds. I'm not saying NiMH cells can't output higher current than alkaline cells; they certainly are more than capable of doing so. What I am saying is that you are wrong in your comparison of the discharge capability of alkaline AA and D cells.

    Since no one ever wins an argument on the internet, I'm going to stop now.
    Wise words

    We've gone a bit off the path here. Thanks for all the responces. I got the answer I was looking for, part of it anyway.
    Regarding the AA VS D-Cell Alkalines dilema. It should be easy to prove which cell can provide the most current for a specific task, without the need for any of us to have to battle it out over the web

    I just feel that too short out a cell only means so much. If it can provide 7 Amps why can't it sufficiently power a less than 1 Amp led? It struggles to do so. I'm glad I gutted the spotlight and will never buy alkalines again, exept in an emergency of course. I don't see the point if you can use rechargebles. Its far cheaper in the long run and you charge them again when you've used just 20%. With alkalines you will go on a trip with 80% full batteries under the same circumstances.

    I've done my last test in this regard. I've measured the voltages under load.
    With the alkalines I got 2.85V unloaded for the two. The moment the flashlight is turned on the reading drops to only 0.68V! But as can be seen the batteries are not fresh anymore, and no, I won't be buying some anytime soon
    With the Nimh's, and they are over 3 year old 2000mah Energizers, I bought them before I knew about Eneloops The unloaded voltage was 2.68V for two, the loaded voltage was 2.41V. ( Sorry, its a mistake, it was 2.21V )
    Not bad hey?
    Last edited by lightseeker2009; 09-04-2011 at 10:58 AM.

  24. #24

    Default Re: D-cell Alkaline VS AA nimh

    Testing batteries using a dead short gets you nowhere because it doesn't tell you what voltage you can expect at what current levels which is key to battery choice. Knowing internal resistance does tell you which batteries can supply large currents with minimal voltage depression and alkalines are not them. For currents under an amp alkaline D cells do well enough with currents 500ma and under yielding long runtimes that make them worth using if it were not for the risk of leakage.
    The biggest issue today is more and more lights and electronics are gobbling up more power which is problematic for both alkaline D cells and AAs of any type as both have capacity issues when it comes to high power usage runtime. Many people are opting for AA to D adapters (2AA versions becoming more popular) so they do not have to pay for the alkaline D cells issues with larger current loads.
    I think the biggest question is at what current level does an alkaline D cell have identical runtime to 1 or 2 eneloop AAs (that have been sitting off the charger for a week or two). If we knew this we could know when it would make sense to use adapters and forget using alkaline D cells altogether.
    Fenix Split rings 1400+ sent, SWIVELS now available also!
    Psalm 112:4 Light shines in the darkness for the godly. They are generous, compassionate, and righteous.

  25. #25
    Flashaholic* 45/70's Avatar
    Join Date
    Oct 2005
    Location
    Rural Ohio
    Posts
    2,800

    Default Re: D-cell Alkaline VS AA nimh

    Quote Originally Posted by Lynx_Arc View Post
    I think the biggest question is at what current level does an alkaline D cell have identical runtime to 1 or 2 eneloop AAs (that have been sitting off the charger for a week or two). If we knew this we could know when it would make sense to use adapters and forget using alkaline D cells altogether.
    In my years and years of experience (well OK, not that many, only about 30) with both alkaline cells, and NiCd/NiMh cells, my general conclusion has been that the break even point as to which chemistry is preferable, is ~500mA for D cells, and ~300mA for AA cells. This does not take into consideration cost, ease of use, having to make a special trip to the store to get replacement cells and so on, only a head to head comparison as to which chemistry will work for the longest from fully charged, to empty.

    Dave

  26. #26
    Flashaholic* 45/70's Avatar
    Join Date
    Oct 2005
    Location
    Rural Ohio
    Posts
    2,800

    Default Re: D-cell Alkaline VS AA nimh

    dbl post
    Last edited by 45/70; 09-04-2011 at 03:28 PM. Reason: Double post due to crash

  27. #27
    Flashaholic* Battery Guy's Avatar
    Join Date
    Apr 2010
    Location
    Portland, Oregon
    Posts
    807

    Default Re: D-cell Alkaline VS AA nimh

    Greetings Everyone,

    I thought that the following discharge curves might be useful for this discussion:



    This plot shows 1 A discharge curves for a standard Eneloop and new Energizer and Duracell D cells. I think that what these curves show is that unless you have brand new, out of the package, alkaline D cells, a fully charged Eneloop (and any other good quality NiMH AA) is going to have a higher voltage compared to the alkaline D. And even with a brand new alkaline D, there is still a significant length of time where the NiMH has a higher voltage (at least until the NiMH is depleted, of course).

    btw: please don't make the conclusion that the Duracell is better than the Energizer. I have found that D alkaline cells are highly variable in their performance at discharge currents of 0.5 A and higher. As has been pointed out already, a 1 A discharge is really at the upper limit of what these cells are designed to perform at.

    Cheers,
    BG
    Friends don't let friends use alkaline batteries.

  28. #28
    *Flashaholic* Mr Happy's Avatar
    Join Date
    Nov 2007
    Location
    Southern California
    Posts
    5,390

    Default Re: D-cell Alkaline VS AA nimh

    Quote Originally Posted by Battery Guy View Post
    I thought that the following discharge curves might be useful for this discussion...
    That's an interesting graph. Now if you stretched the black curve across to the right by a scale factor of 5x I imagine that would be a fair approximation of a 10,000 mAh D size NiMH cell. And that would be a stunning indication of what D size NiMH cells are capable of...
    Tiefer, tiefer, irgendwo in der Tiefe gibt es ein Licht

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •