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Old Jan 23, 2007, 8:52 AM   #1
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Wanted to get some feedback from you out there. i am a professional photogrpaher and have been using rechargable betteries but now they come out with a 15 minute charger. From what the people at best buy have told me that you only charge the betteries for 15 minutes and you have to remove them after 15 minutes or else it destroys the batteries.

My question to all of you is that I know they have higher rated batteries 2500 mah even as high as 2650. Now when looking for a charger do you have to get a charger for the higher rated batteries or as long as the you charge all the same ratting battery together it does not matter. I purchased the Durcell 15 min but have not used it yet. Wanted to get feedback from you and see if there might be something better out there.

Howard


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Old Jan 23, 2007, 11:56 AM   #2
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Assuming you're talking about NiMH batteries here, I'm sorry to be the bearer of bad news but that 15minute charger more than likely junk. NiMH is a more complex beast to charge than the old NiCad batteries and requires some fairly well engineered circuitry to accurately detect the maximum charge point. Failing to detect this point tends to lead to two possible outcomes a overcharged and very warm battery or a battery that is cut off before reaching its maximum charge potential. Keep in mind heat rapidly destroys NiMH cells lowering both their capacity and potential lifespan in charge/discharge cycles and you can probably guess why the Best Buy guys say pull those batteries out on 15mins... then comes another problem, as those batteries start losing their capacity the full charge point will take less time to reach and then spend a longer time being overcharged and heated. All in all you end up with a recipie for dead batteries no matter how you look at it.

The big problem is we as consumers want the highest capacity batteries, charged in the shortest time possible at the lowest possible price and someone will always step forward to better the competition and take our hard earned money. With batteries and other thing which consumers understand poorly it's like taking candy from a baby.

So what's my suggestion...
Get some good quality cells, enough to last you between charges. Then divide them into sets (of the number of cells your camera takes) label all batteries of each set with a distinct marking to distinguish them from other sets. This way each battery of a set has been exposed to the same conditions and should be at similar state of deterioration to others within the set over its operational lifespan.

Get a good quality "smart" (microprocessor controlled) charger specified for NiMH cells, make sure it's one that monitors/charges each cell individually as some will cut power to two or more cells once one cell reaches max capacity. NiMH don't like trickle charge as such and require relatively high currents to accept charge, most high end chargers will have a "maintenance mode" (often called trickle charge though it's not exactly that) generally it's a relatively high current pulsed at intervals and depending on the rate of discharge of your cells can still have some capacity to do damage, so it's best to not leave cells in the charger for more than a couple days. Variable charge rates is also a nice feature, but generally NiMH are happy with anything that'll fill a ~2500mAH cell in a 2 to 4 hour time window and accurately detect the cutoff point.


I won't recommend any charger models in particular, although I will say Maha in general have a good reputation and it would be worth asking here for long term user experiences with different models.

Hope that is of some help.
Kari.
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Old Jan 23, 2007, 1:03 PM   #3
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I have an Energizer 15minute charger with 2500mAh batteries that works just great. My charger shuts down when ever the batteries are fully charged. I've been using it for over a year now with no problems at all.
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Old Jan 23, 2007, 1:41 PM   #4
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first off i think you so much for such a detailed response. Very helpful. Just a couple questions for you. The Duracell charger is a NiMH charging system. This other system that you spoke about is not a 15 minute charging system. i would have to charge the batteries for anything from 2-4 hours. From what I have found there is no 15 minute system out there that is as good. I just want to have batteries charged just in case. The system that you mentioned charges the batteries individually which I understand. Jusat want to ge the best system for the money but I also need the speed and turnover. Is there another charging system that you might recommend that might be faster.


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Old Jan 23, 2007, 1:47 PM   #5
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I was told that you have to remove the batteries at 15 minutes. The system will not shut off automatically. That might be something new with the energizer system.

Howard


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Old Jan 23, 2007, 4:09 PM   #6
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Hello Howard,

The people at Best Buy do not know the product they are selling...

Fast charging is a great convenience and it works great. However, there is a trade off.

High capacity cells (2500 mAh and higher) suffer from a reduced cycle life as a result of 15 minute charging. You can expect around 125 cycles when using a 3 hour charger and only about 100 cycles with the 15 minute charger.

If you drop down to 2000 - 2200 mAh cells, you can expect over 150 cycles from either charger.

The Duracell 15 minute charger seems to have better air flow thantheEnergizer 15 minute charger. The cells seem to stay a little bit cooler, but don't come off the charger at quite as full a charge. At the end of the fast charge, both chargers go into a trickle charge that brings the cells up to a full charge. The trickle charge lasts for 24 hours, then the charger shuts off.

It is safe to leave cells on the charger. It is probably safer on these 15 minute chargers than other chargers because they shut off after 24 hours. It is not good to leave cells trickle charging for extended periods of time.

Tom
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Old Jan 23, 2007, 4:24 PM   #7
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Hello Kari,

I completely disagree with you...

The 15 minute chargers are the most sophisticated chargers around. There are more checks and safeties in those chargers than any other charger costing 2X to 3X as much.

Keep in mind that the faster you charge, the more pronounced the end of charge signal is. The more pronounced the end of charge signal is, the less likely you are to miss the termination and overcharge the cell.

Cells do get warm on the 15 minute chargers, but not hot. Heat is always an issue, but these chargers have thermal protection.

The 15 minute chargers charge each cell independently. If one cell finishes first, it is not overcharged for the rest of the charge time. The fastest charge I have experienced was charging some 1200 mAh cells. The charge finished in 4 minutes. The cell temperature was 125 F.

There is a price to pay for the convenience of fast charging. You will not get the cycle life from your cells. I am seeing that you loose around 25 cycles. Some people think this is a small price to pay for having cells ready to go over a cup of coffee.

Tom
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Old Jan 23, 2007, 4:59 PM   #8
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But is it is worth paying $35.00 for the 15 minute compared to the charger that charges the batteries individually for $ 60.00 and last longer. As a photographer I need to be reasured that the patteries will perfom when I am working. i iwll alwasy have an extra batteries on hand.

in terms of the charger shutting off after each of the batteries are I am not sure of. I think they might shut off after the the pair is charged. The unit that was recommended charges the batteries individually.

So the question is are we splitting hairs here. Not sure what to do.

Also to make this more complicated I hear that there are these other batteries that are designed specifically to be recharged and they are not the NiMH but can not think of the name of the batteries. I know they are much more exspensive though than the NiMH batteries.

Howard


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Old Jan 23, 2007, 5:55 PM   #9
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Hello Howard,

The 15 minute chargers charge each cell individually.

The 15 minute chargers charge the Eneloop cells without problems.

The $60 charger must be the Maha C9000. It is more of an analyzer that also charges. You probably could make good use of both of these chargers. When you are in a hurry, charge on the 15 minute charger. If you notice something strange going on with your cells, analyze them on the C9000.

Early testing is showing that it is possible to see higher cell temperatures while charging at 2 amps on the C9000 than you see on the 15 minute chargers. If you get the C9000 and are charging 4 cells at a time, I would recommend limiting the charge rate to 1.5 amps.

Tom
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Old Jan 23, 2007, 6:00 PM   #10
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i would only want one charger and the question that I trying to figure out is what charger to get. I heard that the mura only takes an hour to charge four batteries instead of the 2-4 hours on other chargers. Any advice woudl be much appreciated.

Howard


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