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  1. #1
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    AA rechargable question

    I've got some Duracell 2000mA and Energizer 2500 mA. Will the 2500 make my light brighter on a fresh charge or just last longer?

  2. #2
    Senior Member mechBgon's Avatar
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    For all intents and purposes, they'd just last longer. With many lights, they will start to dim as the cell begins to run out of power, so there'd be a segment of the runtime where you'd have brighter light from the higher-capacity cells. But if you hit that point, the higher-capacity cells will be close behind.

    Example:


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    It's important to note that some of the higher end and higher mAh batteries will really push the envelop of voltage. For example I've found Energizer Ultimate Lithium AA's typically run about 1.9 volts. Indeed most AA batteries measure way over the 1.2 volts they're typically suppose to put out. What's more if you've read up on NiZn AA's (the latest greatest rechargeable technology for high demand devices like digital cameras) you'll note that people regularly report that these push the voltage envelope for a typical AA. Some have even reported damage to their devices.

    That said most lights and most electronic devices are now regulated so they are not affected by the increased voltage. This goes from digital cameras to the latest headlamps and flashlights. Occasionally though you'll find a light or device that's not regulated. For example I have a favorite touring headlamp that puts out about 136 lumen. I've noticed when I put energizer ultimate in it gets much brighter. In extremely rare cases because these rare and often cheap unregulated lights loose efficiency as they get brighter they will actually drain batteries quicker. This is however, as mentioned, a very rare scenario.

    Needless to say I think you're plenty safe enough assuming that a 2500mAh battery will last longer then a 2000mAh... and not make the light any brighter... unless you have one of those rare cheap lights with no regulating circuitry.

    == LED lights for touring ==

    @mechBgon, nice gif, good way to measure longevity, I think I might be able to set up my camera to take videos like this without wasting too much memory if I can set it to a low enough fps. BTW, do you hang out on Candlepower Forums?

    I'm curious if you or anyone here has any experience with the Fennix HP10, River Rock 6V Headlamp, or the my most recent acquisition for touring, a 176 lumen headlamp that runs on 3AA from a company called "LED Lenser" that I picked up at Lowes for $50. While I have absolutely fallen in love with it I have yet to thoroughly longevity test it and still have some concerns about it's weather / waterproof-ness / durability (since I do a lot of winter and wet weather riding) but so far I'm hugely pleased with it's brightness, longevity, lite weight and it's incredible features which include a beam intensity focus and dimmer slider.

    It's amazing how bright, efficient and cheap LED's are getting... and how fast their making it into mass consumer lights. I bought my 136 lumen River Rock headlamp two years ago at Target for $25. It puts out 136 lumen for 5 hours on 4AA and rideable light for 8-10 hours. That kicks the snot out of most specialty lights that are many times the price.

    == why cheap mass market lamps rule ==

    I use these cheap mass market headlamps because the innovation in LED brightness and efficiency is happening so quick. They are extremely bright, efficient and effective. Most importantly I can't deal with rechargeable proprietary batteries used by specialty makers when I'm touring. I do a ton of night riding. Indeed I do a lot of winter riding and a lot of winter touring when daylight is short.

    These mass consumable (and usually cheap) lights are usually not that high a quality, but they're cheap enough I can and often do mod them for my specific purposes. Examples include waterproofing with silicon sealer, creating external battery packs and creating mounts for handlebars, forks or helmets.


    == externalizing battery packs on headlamps ==

    One other extremely important tip I have is to externalize the battery pack on lights for winter riding.

    By simply running a couple wires out of a headlamp (I prefer to use RCA cables / connectors and $1.97 4AA enclosures from radioshack) I can move the battery pack into my clothing so my headlamps are completely unaffected by the cold. It's usually very simple to connect wires into the built in battery port on a headlamp, the trick is resealing the headlamp so it continues to be waterproof / water resistant.


    == secondary recharging power packs ==

    On a related side note I've been reading up on resisters. Apparently it's become extremely popular for people to make external secondary battery packs for the iPods, mp3 players, iPhones, Android pones and other smartphones which are well known for being ridiculously power hungry.

    The key is that everything is standardizing around USB for charging and syncing. This is a great thing since one can theoretically make a secondary battery pack that will power multiple devices. The key element to these simple battery packs is a resistor. For example Radioshack sells a 5-volt resistor for $1.47. This resistor with theoretically knock anything up to 35 volts down to 5-volts which is the USB standard for power. Therefore it's theoretically possible to create a little black box or battery pack that you can connect anyting from a 4AA battery pack, to a 9-volt or a 6-volt to and get clean consistent power to your light, camera, mp3 player or smartphone. Been meaning to build one, but haven't had the time yet. I guess I've been to busy reading / writing on special topics on forums and mailing lists passive aggressively.



    == candlepower forums website, an excellent resource ==

    One last tip I've found the Candlepower Forums to be an excellent research tool. Indeed I've found a tremendous amount of research and discussion on the Fennix lights and the LED Lenser headlamp I got from Lowes. It's a good place to find out what's hot and why. The variants of what people are looking at from expensive setups to cheap mass consumables is pretty impressive, but what makes it really cook is the amount of people who really know there stuff and thoroughly test their lights. For me it is to lights what the backpackinglight forums are to ultralight gear.
    Last edited by mmeiser; 10-06-10 at 08:35 AM. Reason: mispellring

  4. #4
    Because I thought I could ks1g's Avatar
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    Quote Originally Posted by mmeiser View Post
    == secondary recharging power packs ==

    On a related side note I've been reading up on resisters. Apparently it's become extremely popular for people to make external secondary battery packs for the iPods, mp3 players, iPhones, Android pones and other smartphones which are well known for being ridiculously power hungry.

    The key is that everything is standardizing around USB for charging and syncing. This is a great thing since one can theoretically make a secondary battery pack that will power multiple devices. The key element to these simple battery packs is a resistor. For example Radioshack sells a 5-volt resistor for $1.47. This resistor with theoretically knock anything up to 35 volts down to 5-volts which is the USB standard for power. Therefore it's theoretically possible to create a little black box or battery pack that you can connect anyting from a 4AA battery pack, to a 9-volt or a 6-volt to and get clean consistent power to your light, camera, mp3 player or smartphone. Been meaning to build one, but haven't had the time yet. I guess I've been to busy reading / writing on special topics on forums and mailing lists passive aggressively.
    I think you mean regulator, not resistor. You can use a network of resistors to get a desired voltage, but a regulator is a much better way to go. For example: http://www.radioshack.com/product/in...howFullReviews

    Even better, some nice folks have done all the design, PCB fabrication, kitting, illustrated instructions, and packaging ideas for you. Do a search for "Mintyboost" or as posted recently on a local email list by a local hardware hacking group:

    The Mintyboost, created by Limor Fried of Adafruit in Brooklyn, is a rechargeable booster pack for USB powered devices. Now, rather than running out of juice on the airplane or bus, you can bring your own power. This is for version 3 of the device which works on all kinds of gadgets including GPS units, iPhones, iPods, & Android phones.

    Links: http://www.ladyada.net/make/mintyboost/compat3.html
    http://www.adafruit.com/index.php?ma...products_id=14

    The recommended packaging is intended for AA batteries for recharging a phone or MP3 player, but there's no reason you couldn't use the kit with larger

  5. #5
    Senior Member Richard Cranium's Avatar
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    Will the 2500 make my light brighter on a fresh charge or just last longer?
    Right, the terminal voltage determines the brightness -assuming the battery is charged. So increasing the capacity by 500 mA has no effect on brightness.

    However as others have mentioned, different battery types deliver different voltages -even if they are the same cell size. Whether are not your light will dim as the voltage drops has to do with the particular circuitry of your light.

  6. #6
    Bike addict, dreamer AdamDZ's Avatar
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    That mA number denotes capacity, that is how long the battery will last. The voltage and the power output is the same so will be the light brightness, it 'll just run a bit longer.

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    Depending on the light, you may find that rechargeable cells with an equivalent capacity actually perform better in your light, especially fairly modern LED flashlights, many of which are starting to be designed around rechargeable cells for their better current delivery characteristics.

    Sanyo Eneloop rechargeables (or Duracell 2000mAh "Pre-charged" rechargeable cells -- these are made by Sanyo with a Duracell wrapper on them) as compared to a run of the mill 2000mAh drug store alkaline cells will in my lights put out a bright, constant, light for more than 2 hours while the alkaline starts to dim dramatically after 30 minutes.

    In fact it is safe to say that any good quality NiMH rechargeable cell will outperform standard disposable alkaline cells of equal capacity, and in many cases will outperform those with much greater labelled capacity.

    Same capacity. Different delivery.

  8. #8
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    Quote Originally Posted by ks1g View Post
    I think you mean regulator, not resistor. You can use a network of resistors to get a desired voltage, but a regulator is a much better way to go. For example: http://www.radioshack.com/product/in...howFullReviews
    Did I say resistor... lol. Yes I meant regulator. Obviously I know my sh*t, thanks for correcting me.

    Quote Originally Posted by ks1g View Post
    Even better, some nice folks have done all the design, PCB fabrication, kitting, illustrated instructions, and packaging ideas for you.

    [...]

    The recommended packaging is intended for AA batteries for recharging a phone or MP3 player, but there's no reason you couldn't use the kit with larger
    Exactly. I've been studying their design. I'm not sure if I need all the complexity though. I think I just need the single 5v regulator inline between any battery or battery pack over 5v and my smart phone. I'm no electrical engineer though and am going to have to read up more and obviously test it before I plug it into my $400+ phone. I guess I could otherwise buy their $5 board, that would work too. Obviously though I am going to want to run it on more then two AA. Smartphones, particularly when using GPS waste way more juice.
    Last edited by mmeiser; 10-06-10 at 01:28 PM.

  9. #9
    Seņior Member ItsJustMe's Avatar
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    Quote Originally Posted by mmeiser View Post
    For example Radioshack sells a 5-volt [regulator] for $1.47. This resistor with theoretically knock anything up to 35 volts down to 5-volts which is the USB standard for power. Therefore it's theoretically possible to create a little black box or battery pack that you can connect anyting from a 4AA battery pack, to a 9-volt or a 6-volt to and get clean consistent power to your light, camera, mp3 player or smartphone. Been meaning to build one, but haven't had the time yet. I guess I've been to busy reading / writing on special topics on forums and mailing lists passive aggressively.
    That's a linear regulator. You don't want to use a linear regulator unless you don't care about carrying a big chunk of battery around.

    Linear regulators DO act like an intelligent resistor. If you have a 9 volt battery and you're regulating down to 5 volts, a linear regulator does it by turning 9/5, or nearly half, of the output of the battery into heat, and delivering the rest to the device.

    It's OK for quick-and-dirty but what you really want to do is to use a switching power regulator. They're certainly more complex than a linear regulator, but not horribly so. You can easily get 80% efficiencies with switchers, and probably higher. Google "simple switcher" - the manufacturer has a web page that will calculate all the parts you need.
    Work: the 8 hours that separates bike rides.

  10. #10
    Senior Member dougmc's Avatar
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    Quote Originally Posted by mmeiser View Post
    It's important to note that some of the higher end and higher mAh batteries will really push the envelop of voltage. For example I've found Energizer Ultimate Lithium AA's typically run about 1.9 volts.
    Really, that high? I'm skeptical. Some googling shows no evidence of this, and really, if this were the case, people would be blaming them for all sorts of failures of electronic devices -- and some of it would even be justified.

    (Though I don't buy these "lithium" AA batteries -- too expensive, not rechargeable -- so I guess I'll never know.)
    Indeed most AA batteries measure way over the 1.2 volts they're typically suppose to put out. What's more if you've read up on NiZn AA's (the latest greatest rechargeable technology for high demand devices like digital cameras) you'll note that people regularly report that these push the voltage envelope for a typical AA. Some have even reported damage to their devices.
    NiZn AA's are still pretty rare. And yes, if they have a nominal rating of 1.6 volts and a discharge curve similar to NiCd/NiMH -- then they probably start at 1.88 volts or so. Most items are likely to be OK with this, but it certainly could damage some items, and I'll bet those packages have warnings to that effect. Are you sure you're not thinking of NiZn batteries when you think of the 1.9 volts?

    NiMH and NiCd batteries have a "nominal" rating of 1.2 volts -- but they start at about 1.41 volts fully charged. This is well known. Alkaline batteries have a "nominal" rating of 1.5 volts -- but that's when fully charged, it's all down hill from there. So their voltages are pretty close to each other, closer than people give them credit for.

    One thing that's worth mentioning (and possibly useful to the original poster) is that the only way you can make a battery of a given size and chemistry have more capacity nowadays is to replace other bits with more electrolyte -- smaller electrodes, thinner case, etc. So a 2500 mAh cell is likely to have a higher internal resistance than a 2000 mAh -- so the 2000 mAh cell may actually make your light a bit brighter than the 2500 maH cell. The difference is likely tiny with lights, but it can matter with other things. Ultimately, the way you get over 2000 mAh for AA NiMH cells is to skimp on other stuff -- so the higher capacity cells are not always better.

    Personally, I'm really fond of the low self discharge rate NiMH cells nowadays -- Eneloops, Rayovac 4.0, etc. Well worth the extra money (and really, lately it's not even much extra money.)
    The key is that everything is standardizing around USB for charging and syncing. This is a great thing since one can theoretically make a secondary battery pack that will power multiple devices. The key element to these simple battery packs is a resistor. For example Radioshack sells a 5-volt resistor for $1.47.
    As somebody else pointed out, you have described is a linear regulator, not a resistor. And as they also pointed out, they're inefficient -- a switching DC-DC power supply is more efficient, though depending on the application it may not matter. (Heat is often a big problem with linear regulators, as all that excess voltage is turned into heat.)
    Last edited by dougmc; 10-06-10 at 03:49 PM.

  11. #11
    Senior Member mechBgon's Avatar
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    Quote Originally Posted by mmeiser View Post
    @mechBgon, nice gif, good way to measure longevity, I think I might be able to set up my camera to take videos like this without wasting too much memory if I can set it to a low enough fps. BTW, do you hang out on Candlepower Forums?
    I used to, but was driven off by trolls. For that GIF, I just shot the photos manually and then used a GIF program to make the GIF.

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