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Thread: Rechargeable batteries - help needed

  1. #1
    Sleep is overrated Thundergod's Avatar
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    Rechargeable batteries - help needed

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    The other night I got caught when both spare sets (4AAs) of batteries for my camera gave up the ghost immediately I turned the camera on.

    The annoying thing was Id checked them in the morning with a multimeter and they were showing the correct voltage (1.2v).

    What Im thinking then is they (or some of them) have had it and arent packing any punch (amperage?).

    I found one this morning out of a set of 4 that wasnt holding its voltage reading after a few minutes off the charger.

    Replacing just this one allowed the camera to fire up OK.

    However with the other set I found one that shows enough volts but when put in the camera with 3 other good batteries I get the problem again.

    I obviously now cant trust just the voltage readout.

    Is there a way I can check with the multimeter that they either have or have not got any strength left in them?

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    Re: Rechargeable batteries - help needed

    Free standing voltage is a good way of checking - the higher the better. Otherwise, load test them by connecting them to a light bulb and measure how much the voltage drops.

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    Senior Membear Bean_Bear's Avatar
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    Re: Rechargeable batteries - help needed

    There is a quick dirty way to check that the capacities are similar, especialy if you have the CS DMM. Put each battery on a load (some type of resistor, probably about 10 ohms, and run a roast profile on the battery with DMM set to dc volts. you will probably have to set the roast monitor to a low value (5 instead of 300C). Use one of the batterys that you think is good as a template and run each battery as another "roast".

    May have to play with settings, you could use a torch globe as a load also. You will see very quickly which batteries are OK.

    BeanBay

    PS. area under the curve will be aprox = capacity. Dont discharge NiCads or NiMH much below 0.8 to 0.9 volts.

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    Re: Rechargeable batteries - help needed

    Vested interest here I sell NiMhs and have been using and abusing them and NiCads for years in model planes before going to lithiums.

    Not mentioned but I gather you are using NiMhs of 2000-2500 mAh Capacity?

    1st not all batteries are created equal. More "rated capacity" DOES NOT mean a better battery, quite the reverse depending on application.

    NiMhs while they dont suffer from the memory issues of the older NiCads they do suffer when not used for a while and capacity will drop for the first few cycles of non use. NiMhs lose up to 30% capacity per week after coming off charge.

    Packing some punch as TG mentions above, generally the higher capacity AAs (2500 mAh) achieve this by cutting down on internal conductors to carry the current and maintain higher terminal voltages when in use (you dont get something for nothing). So personally I avoid like the plague anythng much over 2000 mAh as they wont deliver the same punch. There is within the Range of NiMh battery technologies smaller batteries that will deliver much more punch than any AAs on the market albeit it at lower capacity so size of battery is no guide to punchability either ;)

    Quote Originally Posted by 5A78747476747E7978170 link=1293326997/1#1 date=1293327465
    Free standing voltage is a good way of checking
    This will only tell you if it is not dead flat, you really need to measure the voltage under load to test them. This will also give you an idea of if they are good or bad quality cells. A simple load tester can be made using a resistor between the probes of the multimeter then placed across the terminals. If you get a 4.7 ohm resistor it will load the battery to approximately 250mAh, make sure it is a 1 or 2W rated resistor to handle the power without getting to hot and burning your pinkies, leave on test for a good 5-10 seconds). The 10 ohm mentioned above will give you about a 100mAh discharge which I reckon is a bit low for camera type use. Do this and you have a simple load tester :) EDIT: Forgot decent batteries should hold 1.05-1.1 v+ with this load.

    Charging is the bit that kills off NiMhs more often than not the wall chargers are a simple and dirty way to charge batteries but used within the instructions are just OK (that is unless they auto shut off DONT leave batteries in them) Peak detection chargers or auto shut off chargers are a much better option but that comes at a price.

    As to brands have a serious look at the Sanyo Enerloop range, 2000 mAh decent ability for punch, very low self discharge rate (less than 5% per week) if not in regular use. Available at the importer Master Instruments (Sydney and Melbourne) or Dick Smith and other electronic stores generally.

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    Re: Rechargeable batteries - help needed

    Quote Originally Posted by 4F6D616163616B6C6D020 link=1293326997/1#1 date=1293327465
    Free standing voltage is a good way of checking - the higher the better. *Otherwise, load test them by connecting them to a light bulb and measure how much the voltage drops.
    What is free standing voltage?
    These are rated 1.2v and thats what they read when charged.

    What rating bulb do you suggest?
    Quote Originally Posted by 4067636C5D40676370020 link=1293326997/2#2 date=1293327605
    if you have the CS DMM
    I dont have.

    Im looking for any possible tests with a generic multimeter.

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    Re: Rechargeable batteries - help needed

    Quote Originally Posted by 4344404F474D58484F46210 link=1293326997/3#3 date=1293332077
    Not mentioned but I gather you are using NiMhs of 2000-2500 mAh Capacity?
    Yes.
    2650mAh and 2400mAh.

    Quote Originally Posted by 4344404F474D58484F46210 link=1293326997/3#3 date=1293332077
    A simple load tester can be made using a resistor between the probes of the multimeter then placed across the terminals. If you get a 4.7 ohm resistor it will load the battery to approximately 250mAh, make sure it is a 1 or 2W rated resistor to handle the power without getting to hot and burning your pinkies, leave on test for a good 5-10 seconds). The 10 ohm mentioned above will give you about a 100mAh discharge which I reckon is a bit low for camera type use. Do this and you have a simple load tester Smiley EDIT: Forgot decent batteries should hold 1.05-1.1 v+ with this load.
    Thanks for that.
    Ill dig out my resistors (from a previous hobby) and see if I can find a 4.7ohm.




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    Re: Rechargeable batteries - help needed

    Quote Originally Posted by 467A677C767760757D76120 link=1293326997/4#4 date=1293337331
    What is free standing voltage
    Generally just the unloaded voltage. Straight off the charger typical would be 1.35-1.4V the 1.2V is a nominal figure.

    2650 mAh is a bit like perpetual motion never going to happen, last time I did a discharge cycle on some stickered like this I got 2100mAh at a 100mA discharge rate (around 20 hour to flatten) you get closer to the sticker the lower the discharge with these :D

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    Re: Rechargeable batteries - help needed

    Quote Originally Posted by 6C504D565C5D4A5F575C380 link=1293326997/5#5 date=1293337671
    2650mAh and 2400mAh.
    ...dont mix em in the same device.

    Typically in most devices they are in series and they will try and charge the lowest value battery, flattening the higher amperage ones first and/or over heating the lowest value one.


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    Re: Rechargeable batteries - help needed

    Quote Originally Posted by 49666C71080 link=1293326997/7#7 date=1293343192
    Quote Originally Posted by 6C504D565C5D4A5F575C380 link=1293326997/5#5 date=1293337671
    2650mAh and 2400mAh.
    ...dont mix em in the same device.

    Typically in most devices they are in series and they will try and charge the lowest value battery, flattening the higher amperage ones first and/or over heating the lowest value one.
    Sage advice.

    Dont worry, I only did it briefly for the first time today (for a few seconds) when trying to find suspect batteries.

    Normally I only use them in matching sets and have done it that way for years.


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    Re: Rechargeable batteries - help needed

    A little more reading on the topic of batteries here http://batteryuniversity.com/learn/a...ased_batteries a lot of it is way OTT but interesting for some of the geeky amongst us *::)

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    Re: Rechargeable batteries - help needed

    The best batteries depend on hoe you use them.

    If you want to have the item sitting idle for an extended period you need a battery that hods its charge a long time eneloops are very good for this and hold their charge well over 6 months. The newer ones they claim for 3 years

    Some rechargeable batteries self discharge within a week

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    Re: Rechargeable batteries - help needed

    The best batteries are the Sanyo eneloop or Varta Ready2Use. Both are long shelf life NiMH. They are lower in capacity than typical hi capacity 2500mAh + batteries however I find they last longer in my GPS than the higher rated batteries. Also look for batteries that are made in Japan as they tend to be better quality.

    You will also need a good a charger and the best in my opinion is the Maha MH-C9000 battery charger / analyzer. It will charge / discharge the batteries and tell you on the display what the capacity is for each cell. I have used this charger for over a year now and have weeded out a stack of under-rated batteries I have collected over the years. It monitors cell temp too so it will not overcharge or cause damage to your batteries.

    Dex

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    Re: Rechargeable batteries - help needed

    Thanks everyone.
    Im looking at getting some eneloops next week.

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    Re: Rechargeable batteries - help needed

    eneloops are available from dick smith

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    Re: Rechargeable batteries - help needed

    Hi , Try " Powerex " Ebay or Google for both chargers that work and batteries . Read some tests / reviews on camera sites as they make batteries work hard . I have been using their stuff for about two years .Thanks Rick

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    Re: Rechargeable batteries - help needed

    Quote Originally Posted by 667D777F707B637A617A707166140 link=1293326997/14#14 date=1295176587
    Hi , Try " Powerex " Ebay or Google for both chargers that work and batteries . Read some tests / reviews on camera sites as they make batteries work hard . I have been using their stuff for about two years .Thanks Rick
    I seem to have had a different experience with Powerex than you. I got a Powerex charger quite a while ago. I havent had any problems with the charger, but the 2500 Powerex batteries that came with it were next to useless. They didnt last long at all, and soon wouldnt hold a charge for more than 1 -2 days any more so I stopped using them. The Sony batteries that came with my camera (2100 ones *I think) have worked heaps better, but Ive been using Eneloops for a while now and I think theyre great. I love it that the Eneloops dont self-discharge anywhere near as much as other batteries. With previous batteries I was getting really sick of having to charge the batteries up every time I wanted to use my camera. With the Eneloops I can put the camera away for weeks between uses and the battery maintains its charge.

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    Re: Rechargeable batteries - help needed

    Hi Bill , That is interesting re Powerex not lasting . Dont know if it makes a difference but the ones I have are 2700 . My daughters camera just gets thrown in a drawer for extended periods and the Eneloops you mention might be what I need for that so Ill give them a try . Thanks Rick

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    Re: Rechargeable batteries - help needed

    The higher capacity of some of the AAs comes at a price. Part of this is higher internal resistance and also quicker self discharge. Also as I mentioned above some of the capacities claimed are bull stuff.



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