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Old May 27, 2006, 9:02 AM   #1
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Is there such thing as a AA camera with cumulative mAh gauge? Its complicated to measure the amount left in the cell since it requires calculating the charge efficiency, self discharge coefficient, etc, but I can't see it being too expensive/difficult to include a chip that simply integrates mA usage over time and let the user see the mAh used since last reset.

My camera works great with NiMH, but the gauge is voltage based and it is completely useless. If I can just reset the counter at every battery change, I can at least predict how much "gas" I've used.

Unlike liquid fuel, you can't easily see the amount of energy left in a NiMH/NiCd battery, but if you can see how much you've used, you'll at least have a pretty good clue, much like you can get a clue from how much you can go between fills with just the odometer even if the gas gauge is broken.



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Old May 27, 2006, 5:20 PM   #2
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Hello Itsme,

I am not aware of any cameras that have that feature.

It sounds interesting and I believe there are some add on software programs that do something similar for notebook computer batteries. I have no idea if they are accurate or not.

The people at www.ztsinc.com have a nice battery tester. We are in the process of checking it out. It does seem to work, but does not seem to be as accurate as some would hope. Batteries vary and they are looking at an average response. I think it has a lot of value for general use, but when it says you have 40% remaining, I am not sure if that number is exact. I do know it will not perform as well as one that shows 100%.

I am a big fan of the Energizer 15 minute charger. It reduces cycle life when used with high capacity batteries, but the convenience of having fresh cells ready to go in less time than it takes to take a bathroom break and get a glass of water to drink is worth the reduced cycle life.

If you are going to take your batteries out to check them, throw them in the Energizer 15 minute charger and pump them back up.

Another question comes to mind... If you had a choice of two similar cameras and one of them had a battery gage indicating the mAh used, how much extra would that feature be worth to you?

Tom
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Old May 28, 2006, 9:29 AM   #3
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The best (and only) one I have seen is the Sony infolithium battery display. While it does not tell what the mAh remaining is, it does tell you how many minutes of bettery life you have left at the current level of useage.

This is Sony proprietry technology and applies only to the Sony infolithium batteries.
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Old May 28, 2006, 11:44 AM   #4
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Hello Amazingthailand,

Lithium chemistry is reasonably easy to do. While the discharge curve is reasonably flat, it still drops off in a linear fashion during the discharge. A volt meter and an understanding of the batteries performance under load will give you a pretty good idea of how much capacity is left.

We often check "resting voltage" for this information. Take the battery out and let it sit for 20 minutes, then check the voltage. This is not extremely accurate, but it gets you in the general range.

NiMh chemistry tends to hold at 1.2 volts for most of its life. This makes a simple voltage measurement to determine remaining capacity difficult. The voltage may be the same when the cell is in the 90-10% range of remaining capacity.

Tom
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Old May 28, 2006, 6:01 PM   #5
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SilverFoxCPF wrote:
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NiMh chemistry tends to hold at 1.2 volts for most of its life.* This makes a simple voltage measurement to determine remaining capacity difficult.* The voltage may be the same when the cell is in the 90-10% range of remaining capacity.
Well that certainly explains why the battery indicators on cameras that use NiMH batteries show full until they suddenly show low and then die quickly. LOL.
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Old May 28, 2006, 7:21 PM   #6
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SilverFoxCPF wrote:
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Hello Amazingthailand,

Lithium chemistry is reasonably easy to do. While the discharge curve is reasonably flat, it still drops off in a linear fashion during the discharge. A volt meter and an understanding of the batteries performance under load will give you a pretty good idea of how much capacity is left.

We often check "resting voltage" for this information. Take the battery out and let it sit for 20 minutes, then check the voltage. This is not extremely accurate, but it gets you in the general range.

NiMh chemistry tends to hold at 1.2 volts for most of its life. This makes a simple voltage measurement to determine remaining capacity difficult. The voltage may be the same when the cell is in the 90-10% range of remaining capacity.

Tom
Lithium packs usually have an IC that keeps track of energy going in and out. The newer chip actually records the cumulative energy going in and energy going out before going dead and accurately reports the status of battery.


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