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Old Aug 18, 2007, 3:41 PM   #1
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I had ordered 2 CRV3 rechargeable batteries for my Kodak Z612, and they sent 4! So my question is....I know if you leave a battery dead for too long, it will kill it, and I have heard if you charge a battery completely and dont use it, that will kill it as well. Sooooo should I charge these extra batteries, or since they are from the factory, not charge them at all and just wait 6 months down the road and swap them out for the ones I am using now?

Thx for any input offered.
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Old Aug 18, 2007, 11:29 PM   #2
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The CRV3 rechargables are most likely li-ion batteries. You can charge them all if you wish. No problem. Once you charge them they will remain charged for months just sitting unused. If they are going to remain sitting unused for maybe half a year, give them a brief "topping off" to make sure they are fully charged before using them. And no matter what kind of battery you use, always remember to take a spare along with you. Some times the battery indicator will tell you the battery is low and then you only get maybe 10-15 pictures more. Go easy on use of the lcd and you can get a lot more pictures.

Some of what you said in your post refers to NiMH batteries. Li-ion batteries are much more user-friendly.

I have a Z712, by the way and have used rechargable CRV3 batteries with no problem.
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Old Aug 20, 2007, 3:39 PM   #3
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Hello Tsmartin,

If the cells in your pack are Li-Ion, then the best storage is to store them half charged in a zip loc bag, in the refrigerator. Half charged is around 3.8 volts per cell.

Tom
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Old Aug 22, 2007, 8:50 PM   #4
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Really depends on your usage pattern. I shoot 200-300 photos a month with my Z612 and have two KLIC8000s. When I shoot down to replacement I put in my spare which I charged when I removed it from the camera. That basically gives me assured power whenever I start shooting with enough power to do at least 300-350 shots at an event.

A different model might be more appropriate for someone shooting 10-12 photos a month. I think those that are shooting a 1000 a month are using something close to my model.
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Old Aug 26, 2007, 11:40 AM   #5
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SilverFoxCPF wrote:
Quote:
...Half charged is around 3.8 volts per cell....
Brilliant! I knew about the half charged bit, but I've been wondering all along how to tell when I'd got it.

If you have other gems like this, as I'm sure you have, we'd all be delighted to hear them. So far as I've seen, that particular snippet isn't even in 'Battery University' unless I've always missed it, or it's been added recently.

If you have an on-line source you can recommend for the voltage vs state of charge curves for the various current systems, under typical digicam use, it would be of enormous value to any photographer who can use a DVM. Please have you any published work yourself you can share?

I'd also love to know what's inside a KLIC-8000 or rechargeable CR-V3 Li-ion's case, e.g., built-in protection circuits. I assume from the fact you say 3.8V per cell that there are two individual cells in parallel to give the funny 2xAA shape, or is it a shaped case around a single cell? I'm too poor and mean to take one to bits. My late father, an electrical engineering lecturer, would have done so, and performed many dangerous charging experiments but fortunately he never owned any Li or Li-ion batteries. He was bad enough with his Zn-air hearing aid batteries.

I'd be happy to hunt for answers myself if you could give us some clues where to start looking. I've hunted here and there but never found anything much that's useful apart from Battery University.

I should mention that I'm a retired electrochemist from an electricity industry research centre, and am expected to know all about it, but the technology left me behind a long time ago. I'm an enthusiast for every wind farm and every town having its own gas-holder sized tanks of aqueous electrolytes working through rechargeable redox flow cells, and have several ideas on how to do it better, but when at work I could never raise funding for them. There was a large pilot plant using iron & chromium salts run by an electricity generating company at Didcot power station in S.England, but it stopped for unspecified reasons.

Thanks again for the tip, Alan T
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Old Aug 26, 2007, 2:23 PM   #6
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Hello Alan,

Assumptions are often risky, but I am going to take a chance here and given your background I will assume that in addition to knowing your way around a volt meter, you can also figure out how to use a calculator... :-)

We have been playing with a formula that approximates the state of charge of a Li-Ion cell based on its open circuit resting voltage. To measure the voltage for this formula, remove the cell and let it sit on the table for around 10 minutes, or longer. Then measure the voltage.

SOC% = 100(0.1966 + SqrRoot(0.0387-1.4523(3.7835-Vcell)))

At 3.7835 volts, your cell is at around 39%. Below this voltage, the data varies by brand, so this ended up being the cut off for the formula. You are on your own at lower voltages, however 3.7 volts is roughly 20%, and 3.5 volts is empty.

If you have a battery made up of several cells you will have to use a multiplier to get to the single cell voltage.

Have fun...

Tom
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Old Aug 26, 2007, 3:10 PM   #7
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Thanks very much, Tom, that's excellent!

Alan
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