Hi, i'm not able to read these datasheets:
I thought that the better way to compare batteries was based on their capacity (mAh), but i'm not able to read these value on links...To compare two batteries, capacity is the most important value or other parameters should be considered (as internal resistance)?How can i read capacity on datasheets? Thanks
Integrate the area under the discharge rate curve that most closely matches the discharge rate for the intended application.
Which battery is "better" depends on the ultimate use and the characteristics that best support that use. Some batteries are optimized for long lifetimes at very low discharge rates; they won't have particularly impressive performance when used at very high discharge rates. Some are optimized for higher current applications, but those may have shorter lifetimes at very low discharge rates.
-- Rich Webb Norfolk, VA
It's a dry cell, and they're being honest. So they have a whole bunch of charts that are "this or that vs. drain". Like the one titled "TYPICAL DELIVERED CAPACITY VS POWER DRAIN"
Figure out your power drain, look at the chart.
The _very first chart_ in this data sheet is titled "Milliamp-Hours Capacity -- Continuous discharge to 0.8 volts at 21°C", and it has four bars, for discharge rates ranging over an 8:1 ratio.
Figure out your power drain, look at the chart.
_All else being equal_ it is. But as batteries go, dry cells are really crappy. Their big advantage is that they're cheap and available.
Because???
Recharge cycles before wear-out. Temperature range. Weight. Energy/ weight. Energy/volume. Internal resistance. Internal resistance vs. temperature. Voltage regulation. Potential to burst into flame. Storage/self-discharge characteristics. Moisture resistance. Orientation (car batteries don't like working upside down). Sealed vs. unsealed. Toxicity, inside and out. Expense.
The list goes on.
Engage eyes and brain _simultaneously_.
-- www.wescottdesign.com
Thanks for your reply..but i don't understand... for example: if i consider first link-"Typical service hours vs power drain" and i'm in these conditions
Another question: i really don't understand first link-"milliamp-hours capacity"...what does it means?At 25mA discharge, battery capacity is
120mAh; at 100mA battery capacity is 900mAh?Battery capacity is current discharge dependent?Why? thansk
Ampere-hour or milliamp-hour means the *product* of the current a battery can provide multiplied by the time it can supply that current. It's a measure of the usable amount of electrical charge stored in a battery. It's determined by the battery's particular chemistry, structure, size, heat dissipation ability, and so on.
If a given battery has a stated capacity of one amp-hour, you can theoretically* draw one amp from it for one hour, or one-half amp for two hours, one milliamp for a thousand hours, etc.
Knowing that should help you make sense of ratings.
*Practically speaking you can't draw that current until the battery is completely drained since it will tail off toward the end per the curves.Mark L. Fergerson
For that particular application, yes.
I think you mean that at 25mA discharge the battery capacity is 1200mAh.
Battery voltage is current dependent: the battery acts like a resistor in series with a voltage source. As the battery discharges, the open- circuit voltage stays pretty much constant, but the apparent resistance increases. At high discharge rates that apparent resistance makes for an earlier drop below useful values -- then the battery isn't useful any more, and you toss it (or recharge, if it's a secondary cell).
Dry cells are particularly prone to this effect -- hence the various listings. You can, in fact, take a 'dead' dry cell out of a flashlight and slap it into a clock and have it deliver perhaps half of a normal lifetime -- because the clock has such a lower current draw.
-- www.wescottdesign.com
r.com/PDFs/E92.pdf
Primary cells should be drained down to the point where your system stops working. That is how you get the most capacity out of the battery.
Thus you have to pick the discharge voltage where your system will cease to function, then compare the service hours at your typical current and that particular voltage.
I've seen devices that will suck a AA cell down to half a volt. If you have a buck/boost, you can really get all the capacity of a primary cell.
The proper title should be "What is the best power cell", because they are not "batteries", and that'best' depends on application, expected life span, environ factors, etc., etc..
Most cameras or other small devices use NimH 'poly' cells these days.
It also has to do with mass production costs, so the best place to see the best power cells is still going to be at one Univerity or another, not out in production so much. They eventually merge closer, but not presently.
That one is going into 'the book. ;-)
Did you ever make a log amp? What about what I gave you?
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