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Thread: How long do NiMH batteries hold their charge?

  1. #21
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    Default Re: How long do NiMH batteries hold their charge?

    Quote Originally Posted by deckard View Post
    one thing I want to ask...

    is keeping batteries in the fridge good for the batteries?

    I heard from people, cold temperature will extend the life of the batteries...
    It is actually very true. Especially for primary cells ( those cells that cannot be recharge ). When not in use, it is best store the dry cells in fridge where the temperature is low. The self-discharge rate will be at its lowest.

    However, you should wrap the cells in a plastic bag or something to prevent moisture.

    Putting rechargeable cells into a fridge will not be making so much a significant difference , because the self-discharge rate for re-chargeables is already quite high ( about 25% / month ). Either you use or not use the cells, the capacity will actually drain away quite rapidly.

  2. #22
    Senior Member Canew's Avatar
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    Default Re: How long do NiMH batteries hold their charge?

    Quote Originally Posted by lkkang View Post
    I design / customise battery pack for a living...

    Normally, we will take a 25%/month self-discharge rate as a norm. meaning that if you fully charge a re-chargeable battery cell . in 4 months time, the remaining capacity will go to ZERO.
    What about Eneloops, Bro? What is their discharge rate like?

  3. #23
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    Default Re: How long do NiMH batteries hold their charge?

    Quote Originally Posted by Canew View Post
    What about Eneloops, Bro? What is their discharge rate like?
    I am sorry, I cannot answer that question as I have not thoughoutly tested the repeatability of the Eneloops.

    These cells are actually targetting at slow discharge rate devices like remote control for your TV and hi-fi systems. Therefore, I would personally expect that the self-discharge rate to be very low. In other words, once you fully charge the cells, you may use the cells for quite some time ( say 1/2 year or so )....

  4. #24
    Senior Member Canew's Avatar
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    Default Re: How long do NiMH batteries hold their charge?

    Thanks, lkkang.

  5. #25

    Default Re: How long do NiMH batteries hold their charge?

    One other question:

    Is the mAh rating on the batteries reliable in deciding how long the batteries can last before it needs to be recharged again? Or is it brand dependent?

    Although the eneloop battery is only 2000mAh, compared with some others at 2500mAh and 2700mAh, I find it could last a long time. Very strong. And I think it doesn't self-discharge as fast as even the popular Powerex brand rated higher than 2000mAh.

    So even if a battery is rated highly, but it self-discharges fairly quickly, it's useless right? Unless you charge it b4 use, you'll not going to get a lot out of its remaining power?
    Last edited by kiwi2; 17th July 2007 at 11:51 AM.

  6. #26
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    Default Re: How long do NiMH batteries hold their charge?

    Also depends on usage I guess

  7. #27
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    Default Re: How long do NiMH batteries hold their charge?

    Quote Originally Posted by kiwi2 View Post
    One other question:

    Is the mAh rating on the batteries reliable in deciding how long the batteries can last before it needs to be recharged again? Or is it brand dependent?

    Although the eneloop battery is only 2000mAh, compared with some others at 2500mAh and 2700mAh, I find it could last a long time. Very strong. And I think it doesn't self-discharge as fast as even the popular Powerex brand rated higher than 2000mAh.

    So even if a battery is rated highly, but it self-discharges fairly quickly, it's useless right? Unless you charge it b4 use, you'll not going to get a lot out of its remaining power?
    ha ha.. you have asked a very interesting question...

    You should rightfully only compare apple to apple, Sanyo is the world leader in re-chargeable cell business, it is not a fair comparison to Powerex ( China cells ). You should not compare Japan cells with China cells... If you compare Panasonic or Sony cells with Sanyo cells, you will find that the mAh is quite telle with the label.

    I should say that there are lots of manufacturers out there that claims the capacity ( mAh ) not telle with the actual cell performance ( especially china made cells ). Just because other manufacturers raises the mAh values, they simply do the same to the product labels ( I cannot mention names ) so that their parts can "move".

    However, if you seriously go into technical detail testing of the cells against the specification and launch a complaint. Then the manufacturer will get back to you saying that the values indicated on the product label only correspond to say first 3 charge or is subjected to many environment conditions.... you never able to beat them.

    My personal opinion is ... go for brand , don't go for capacity as indicated on the label.

  8. #28
    Senior Member Canew's Avatar
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    Default Re: How long do NiMH batteries hold their charge?

    Quote Originally Posted by lkkang View Post
    ha ha.. you have asked a very interesting question...

    You should rightfully only compare apple to apple, Sanyo is the world leader in re-chargeable cell business, it is not a fair comparison to Powerex ( China cells ). You should not compare Japan cells with China cells... If you compare Panasonic or Sony cells with Sanyo cells, you will find that the mAh is quite telle with the label.

    I should say that there are lots of manufacturers out there that claims the capacity ( mAh ) not telle with the actual cell performance ( especially china made cells ). Just because other manufacturers raises the mAh values, they simply do the same to the product labels ( I cannot mention names ) so that their parts can "move".

    However, if you seriously go into technical detail testing of the cells against the specification and launch a complaint. Then the manufacturer will get back to you saying that the values indicated on the product label only correspond to say first 3 charge or is subjected to many environment conditions.... you never able to beat them.

    My personal opinion is ... go for brand , don't go for capacity as indicated on the label.
    PRO advice!

  9. #29

    Default Re: How long do NiMH batteries hold their charge?

    Lkkang - so what battery charger would you recommend?

  10. #30
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    Default Re: How long do NiMH batteries hold their charge?

    Quote Originally Posted by dnaxe View Post
    Lkkang - so what battery charger would you recommend?
    Errr... you guys are driving me to the corner already... I must be very careful with my words now.

    I should say that get the charger that comes along with the re-chargeable cells will be the safest choice. Personally I will prefer slower charge ( something in a range of say 6hours and above ). Those charger that indicated temperature cut-off or temperature sensing is a GOOD choice.

  11. #31

    Default Re: How long do NiMH batteries hold their charge?

    Quote Originally Posted by Canew View Post
    PRO advice!
    Some manufacturer rates the capacity as "Up to xxxx mAh".

  12. #32

    Default Re: How long do NiMH batteries hold their charge?

    Quote Originally Posted by dnaxe View Post
    I'm using Sanyo 2500mAhs - but I'm not sure if they're faulty... I doubt mine in late sept 2006, which seems to be well after the faulty sanyo battery batches.
    What about before? Did they discharge this quickly? Maybe you should consider a slower charger like lkkang suggested.

  13. #33

    Default Re: How long do NiMH batteries hold their charge?

    Quote Originally Posted by lkkang View Post
    Errr... you guys are driving me to the corner already... I must be very careful with my words now.

    I should say that get the charger that comes along with the re-chargeable cells will be the safest choice. Personally I will prefer slower charge ( something in a range of say 6hours and above ). Those charger that indicated temperature cut-off or temperature sensing is a GOOD choice.
    Okay - is it possible to charge it TOO slowly?

    I guess i'll get a set or eneloops with their standard charger, and see if that works out.

    edit: Thanks so much lkkang!!
    Last edited by dnaxe; 17th July 2007 at 02:48 PM.

  14. #34

    Default Re: How long do NiMH batteries hold their charge?

    Quote Originally Posted by lsisaxon View Post
    What about before? Did they discharge this quickly? Maybe you should consider a slower charger like lkkang suggested.
    I'll try a slower charger.

    I'm quite sure they didn't discharge that quickly initially - because my first charged set did 400-500 pictures (i use them in a K100D) over a week.

    It might also be due to how I stored them - in discharged instead of charged state.

    Generally I just charge before I use the camera, and the battery lasts the day fine.

    I only noticed the 3 day period because I recently went on a 3 day trip, and by the 3rd day both freshly charged sets had depleted to the extent that they were unable to power the camera... (and I had taken no more than 30 shots in total).

  15. #35
    Senior Member zac08's Avatar
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    Default Re: How long do NiMH batteries hold their charge?

    Quote Originally Posted by dnaxe View Post
    I'll try a slower charger.

    I'm quite sure they didn't discharge that quickly initially - because my first charged set did 400-500 pictures (i use them in a K100D) over a week.

    It might also be due to how I stored them - in discharged instead of charged state.

    Generally I just charge before I use the camera, and the battery lasts the day fine.

    I only noticed the 3 day period because I recently went on a 3 day trip, and by the 3rd day both freshly charged sets had depleted to the extent that they were unable to power the camera... (and I had taken no more than 30 shots in total).
    Ah.... another killing point... storing batteries in their discharged state will do harm to them... Much easier to leak also...
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  16. #36

    Default Re: How long do NiMH batteries hold their charge?

    Quote Originally Posted by zac08 View Post
    Ah.... another killing point... storing batteries in their discharged state will do harm to them... Much easier to leak also...
    bleah.

    Wish i'd know earlier.

    oh well. they were $12 for a set of 4, so it's not all that bad.

  17. #37
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    Default Re: How long do NiMH batteries hold their charge?

    Quote Originally Posted by dnaxe View Post
    Okay - is it possible to charge it TOO slowly?

    I guess i'll get a set or eneloops with their standard charger, and see if that works out.

    edit: Thanks so much lkkang!!
    hi dnaxe, I have not heard the term TOO slowly in my life...this is the first time. Nevertheless, there is a term call "over-charge". Meaning that should the cells are already full, and the charge is still forced into the cell. Over charging is definately not healthy to the cells, because the cells will start to heat up very quickly. The pressure inside the cell will also increase and hence the recharge life cycle will reduce.

    After hearing so much advices from so many people... I hope you have not loose your confidence level in using re-chargeable cells. The consumer re-chargeable cells are actually quite raggered in a sense that...

    1. if you drain the cells completely.. only if you leave them idle for about say 2 ~ 3month, the cells will start to degrade... else, once you recharge them, they should return to normal again.

    2. If you once a while overcharge the cells, nothing drastic will happen also.

  18. #38
    Senior Member Canew's Avatar
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    Default Re: How long do NiMH batteries hold their charge?

    Quote Originally Posted by lsisaxon View Post
    Some manufacturer rates the capacity as "Up to xxxx mAh".
    Ahhh. Noted, Bro. Thanks.

  19. #39
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    Default Re: How long do NiMH batteries hold their charge?

    my gp batt charges every week because i use it very frequently
    D800 | D700|16mm f2.8D|35 f1.4G|50 f1.8G|60mm F2.8D|85mm f1.4G|16-35 f4G|70-200 f2.8 VR2| SB900

  20. #40

    Default Re: How long do NiMH batteries hold their charge?

    Quote Originally Posted by lkkang View Post
    ha ha.. you have asked a very interesting question...

    You should rightfully only compare apple to apple, Sanyo is the world leader in re-chargeable cell business, it is not a fair comparison to Powerex ( China cells ). You should not compare Japan cells with China cells... If you compare Panasonic or Sony cells with Sanyo cells, you will find that the mAh is quite telle with the label.
    Oh ha.. I didn't know I was comparing apples with oranges.

    Actually, I'm only using Powerex as an eg. I'm comparing eneloop with most other brands, even by Sanyo itself. (I have 2500mAh Sanyo.) Cos I was thinking so what if the rating is a high 2700mAh but the discharge rate is faster than a lower 2000mAh eneloop?

    For eg, if I use the batteries over a period of 1-2 weeks, the 2700mAh batteries cannot sustain their power long enough. Somewhere along the way, the eneloop would ironically "catch up" and have more charge stored in it bcos it self-discharges slower. By the end of the second week, the 2700 batteries are as good as flat but the eneloop still lives on. So eventually, I need to do more frequent charging on the 2700!

    Maybe for those who use them very frequently on a daily basis may fully utilize the higher rated batteries before they could even self-discharge on their own. Am I right here?

    For me, I don't use my camera every day and it's frustrating having to charge first every time I wish to spontaneously just take it out to shoot.

    Pls correct me if I'm wrong, but I think the self-discharging phenomenon is a curse or big disadvantage in rechargeable batteries!

    Oh.. I haven't heard that storing batteries in a discharged state is no good. So if I don't use them for some time, and since they will self-discharge, I should still take them out just to charge them? Then let them self-discharge on their own, and repeat....?

    (Btw, for Powerex, it's very confusing. I didn't know the cells were from China. The batteries say Made in Japan, the simple manual has an address in the US, which I thought originated from there, and the box says the charger is made in Taiwan!! Phew... )

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