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Old Oct 4, 2005, 7:04 PM   #1
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I'm planning to order a Digital Camera by the end of the week.¬* Either the Canon a520, a610 or a620, though I'm leaning on the a620.¬* I want to get some rechargeable¬*NiMHs to go with it, but I have absolutely no idea which are good, and which are more powerful, and the best deal.¬* I've checked Steve's page on¬*NiMH batteries, but I'm completely oblivious to it all.¬* ¬*I'm really not that technical a person.¬* Can anyone help me out and make some recommendations?Thanks.¬*
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Old Oct 5, 2005, 9:03 AM   #2
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Hello Spooie,

The way to understand batteries is to know a few things about them. This involves learning some technical terms and studying some graphs. Sorry, but that's just the way it is. If you have a few moments, continue on. If you don't, purchase whatever is available in your area and take your chances...

Size is important. In your camera I believe you are looking for AA batteries.

Voltage is important. NiMh cells are rated at their mid point voltage of 1.2 volts. They start off at 1.45 volts off the charger, and your camera shuts off at around 1.0 volts. While different chemistries can provide different voltages, all NiMh cells will be similar in voltage.

Capacity is important and influences how many pictures you can take before having to recharge. The usable capacity changes with load, environmental conditions (temperature), quality of manufacturer, and engineering design. The standard testing that the battery manufacturers use to rate their batteries for capacity is done at very low current drains and allows them to advertise optimistic (and sometimes very optimistic) capacities.

Voltage retention is important because if the camera drops below a certain point, it will shut off. A very good way to compare voltage retention is by checking Watt Hours.

The load is also important. This is given in amps or milliamp. A good basis for comparison for camera use is 1.0 amps. Battery tests are often run at a constant load. Your camera operates differently, but you can usually get a good idea of a batteries performance from how it behaves under a constant load. This could be considered a worst case scenario.

Most battery graphs do not give you all of this information, so you have to dig a bit. The other problem is that a lot of graphs are done at a constant drain on the battery. This is not exactly how you will be using them in your camera, but gives a close enough idea to pick a brand that will work.

Those are the basics, now lets get down to the details.

A graph of a battery test has an X axis that usually measures voltage, and a Y axis that measures capacity or time. There should also be some indication of what current draw the graph represents.

What you are looking for is a battery that maintains voltage under load and lasts a long time. Look at the X axis value and realize that when comparing different brands, higher voltage is better. Look at the Y axis and the same applies.

If you don't have a graph, remember that higher numbers are generally better.

Here is some testing I am currently involved in...


The first graph is just an overall comparison at 1 amp draw. This should be close to what your camera runs at. The individual graphs give you both a picture of the performance of the battery at different loads, and numerical data to compare the different brands.

Remember to check for AA size in the title. There are other sizes included that will not fit your camera.


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Old Oct 5, 2005, 5:24 PM   #3
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Thanks.¬* ¬*I think I have a better understanding of it all now.¬*
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