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What rechargeable battery type has the slowest self-discharge rate ? — Parallax Forums

What rechargeable battery type has the slowest self-discharge rate ?

BeanBean Posts: 8,129
edited 2014-02-10 14:17 in General Discussion
I bought a solar powered flashlight (okay everybody laugh now and get it over with).
It had a 600mA AA ni-cad battery, I replaced that with a 2500mA ni-mh battery.

The solar panel only puts out about 40mA of charge current. So I'm worried that without constant sunlight the battery will lose alot of charge just from self-discharge.

What would be the best battery to use that has the slowest self-discharge rate.

The light uses about 180mA when it's turned on.

Bean.


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Uhhhm, that was on fire when I got here...

www.iElectronicDesigns.com

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Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2008-06-26 02:01
    Bean,
    I've seen NiMH batteries in stores that come already charged and have a low self-discharge rate. I don't remember what they're called, but that's what you want.
  • Desy2820Desy2820 Posts: 138
    edited 2008-06-26 04:02
    I think you're looking for Sanyo's "Eneloop" batteries.· I have no direct experience, but from what I've read, their capacities are slightly lower than·regular NiMH batteries.
  • RickBRickB Posts: 395
    edited 2008-06-26 05:15
    Kodak also makes a similar battery. Look for the term pre-charged. Their self discharge rate is very low.

    Rick
  • Brian CarpenterBrian Carpenter Posts: 728
    edited 2008-06-26 06:47
    how often do you have to use your flashlight in the sunlight?

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    It's Only A Stupid Question If You Have Not Googled It First!!
  • Lord SteveLord Steve Posts: 206
    edited 2008-06-26 16:09
    Brian Carpenter said...
    how often do you have to use your flashlight in the sunlight?
    Did you Google that question?
  • FranklinFranklin Posts: 4,747
    edited 2008-06-27 02:31
    No hits on Google for that exact phrase.....

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    - Stephen
  • BenoitBenoit Posts: 47
    edited 2008-06-27 04:31
    I went shopping today at Costco, and I saw the eneloop batteries that Desy2820 wrote about. The package says they keep at 80% of their charge after a year of storage.

    That might be a good candidate for your flashlight.
  • BeanBean Posts: 8,129
    edited 2008-06-27 11:12
    Benoit,
    Yeah, less than 2% per month loss. That would be pretty good.
    I'll check them out.

    Bean.

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    Uhhhm, that was on fire when I got here...

    www.iElectronicDesigns.com

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  • XNORXNOR Posts: 74
    edited 2008-07-01 18:01
    Some other brands (in addition to Sanyo Eneloop) are:

    Nexcell EnergyOn, Accupower Acculoop, Uniross Hybrio...

    www.nimhbattery.com/eneloop-hybrio-acculoop-energyon-faqs.php

    HTH
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2008-07-02 09:18
    My best guess is good old lead acid batteries. Of cource that lacks the AA form factor you seek.

    Most of today's rechargibles are designed for quick recharge and not longer term storage. This has come about by the desire to reduce the overall size and weight.

    But the lead acid batteries are sometimes referred to as 'storage cells'

    "The Art of Electronics" seems to confirm this.

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    PLEASE CONSIDER the following:

    Do you want a quickly operational black box solution or the knowledge included therein?······
    ···················· Tropically,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan
  • MikeKMikeK Posts: 118
    edited 2008-07-02 19:54
    I use Eneloop batteries in my digital camera and in Wii remotes. The self discharge rate is indeed low. It's nice to be able to charge the batteries, put them in the camera, and be able to pick up the camera a month later & still take a bunch of pictures. I don't have much experience with how they'd fare in a flashlight, though.

    For reference, I took ~800 pictures (some flash, mostly not) with a Canon A710IS camera on less than 2 full charges. I used a set of batteries for a while (maybe 400 pics), then swapped them for a fresh set, charged a week before. The 2nd set are still good. I rarely get to the point of a low-battery indication. I used to use regular NiMH, and I found I had to charge them much more often.

    Your mileage may vary...

    Mike
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2008-07-03 19:27
    I suspect specialized rechargible batteries for cameras are better than average NiMH, just because they are made for cameras.

    I have an early digital and the real heart-break is the $40USD for a lithium battery that doesn't keep a charge very long. People naturally set a camera aside and then suddenly want it to work instantly for the sudden 'photo op'. In my case, the battery is usually dead.

    I suspect there is a conspiracy by manufacturers of the AA, AAA, C, and D cells to always make NiMH more troublesome than Alkaline, After all, they really want you to keep buying their product and NOT save money.

    Still, there may be a good reason that Bean's solar recharge flashlight had only a 600ma unit. The solar cell may never put out enough to charge a higher capacity unit. Rechargible batteries have both a minimum trickle and a maximum high rate charge.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    PLEASE CONSIDER the following:

    Do you want a quickly operational black box solution or the knowledge included therein?······
    ···················· Tropically,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan
  • sam_sam_samsam_sam_sam Posts: 2,286
    edited 2010-10-04 12:31
    Now you can get AA lithium solar battery at Walmart you do not always find them
    I have use a few of these in my solar yard lights that are made with AA lithium solar battery

    I have some solar yard lights that take 3 nicad batteries and have change them to the lithium solar battery and they seem to last longer than the NiMH or the Nicads batteries
  • ercoerco Posts: 20,256
    edited 2010-10-04 13:32
    Plain old Alkalines have amazing shelf lives. I have heard of people recharging them somewhat, if they are not totally drained. Depending on how far you discharge them, or if you are keeping things for an occasional power outage, they might be a consideration.

    I was amazed to find out that the ELT (emergency locator transmitter) in my Cessna is powered by a bunch of Duracell D cells. It's inspected every year, but they spec out a 5-year battery life. Too bad the FAA just changed the ELT frequency to 406 MHz and my 121.5 MHz unit from 1980 is a boatanchor now.
  • JBWolfJBWolf Posts: 405
    edited 2014-02-10 14:17
    Sanyo eneloop low self discharge - boast they have lowest self discharge rating and will hold a single charge for 3-years of not being used.
    http://www.ebay.com/itm/151216202540

    I just ordered one... but im not concerned about self-discharge for my needs, I need highest discharge rating as im limited in case size to 10mm diameter and need highest amperage output possible.
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