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Old Jul 11, 2003, 8:50 PM   #11
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[quote="voxmagna"]Following the previous posting and analagy to car batteries, the main reason for upping the ampere hours, is not just more power to run the lights etc. When you think about it, most of the time, this load is met by the generator.

It's all to do with 'Cranking Current'. Generally the higher the ampere hour capacity of a lead acid battery, the higher the cranking current. So a V8 or diesel car will have much the same electric power load. But try starting your V8 or diesel in sub zero temperatures (cold thick oil) and you need BIG cranking current. However battery makers have got clever. They now use the same plate area, but get them closer together. The battery continuous capacity and size is about the same - but it can deliver more cranking current. The problem is, to much continuous cranking can burnout the battery sooner.

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:shock: Where do you guys come from? :shock:
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Old Jul 26, 2003, 8:14 AM   #12
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Another silly american who don't know what Uk means and where is europe
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Old Jul 26, 2003, 8:30 AM   #13
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Laserjock is an expert in this field (power) though (better listen to his mAh)!
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Old Jul 27, 2003, 3:52 PM   #14
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Quote:
Originally Posted by voxmagna
Following the previous posting and analagy to car batteries, the main reason for upping the ampere hours, is not just more power to run the lights etc. When you think about it, most of the time, this load is met by the generator.

It's all to do with 'Cranking Current'. Generally the higher the ampere hour capacity of a lead acid battery, the higher the cranking current. So a V8 or diesel car will have much the same electric power load. But try starting your V8 or diesel in sub zero temperatures (cold thick oil) and you need BIG cranking current. However battery makers have got clever. They now use the same plate area, but get them closer together. The battery continuous capacity and size is about the same - but it can deliver more cranking current.
For example tractors have nice batteries:
180 Ah capasity and I don't remember what exact term was but battery have label with sign "1300 A".
(BTW start motor is 2,7 kW so it takes around 220A continuous current)
But even then it's not enough if temperature goes under -10 celsius. (half year ago it was around -30 for almost one month)

Back to topic and one correction:
Mechanical/manual zoom (like in Minolta's 7-serie) doesn't need any power!
It's those "button-zooms" and "fly-by-wire" (Sony 717) zooms which need power.

Multimeters which have test function for AA-cells use 150mA current when measuring voltage. (and that's "little" less than what digicams take)
Alkalines are good for that kind of currents, not for currents of one ampere-class.
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