jsatan Posted February 23, 2008 Posted February 23, 2008 Hi guys, Its been a while and my brain has gne soft, (blows the dust off the chess set). Right, I've got a LED it is a 2.5V at 11mA I've got a battery at 1.5V 1800mA How long would the battery last if the led worked at this low voltage. worked it out and I got some silly number, something like 43 sec's. Can someone show me the way this would be worked out so I know for the future. My cals were: (1.5 * 1.8)/(2.5 * 0.011) That says my led would only last 108s, my maths has gone!!! Jon.
swansont Posted February 24, 2008 Posted February 24, 2008 Batteries are rated in mAh, i.e. milliamps * hours
YT2095 Posted February 24, 2008 Posted February 24, 2008 I work it out to 98.18 hours as an Ideal, however without having the LED specs of current by voltage curve, it`s impossible to be 100% accurate.
jsatan Posted February 24, 2008 Author Posted February 24, 2008 Batteries are rated in mAh, i.e. milliamps * hours oops, thats why My cal are off by a long way. Thanks guys! PS can you show me how this was worked out as I can the numbers close to YT's but I'm out by a factor of 10. (EG 981.81 HR)
YT2095 Posted February 24, 2008 Posted February 24, 2008 the batt is capable of 2.7Watts for 1 hour the LED draws 0.0275Watts so 2.7 / 0.0275 = 98.18 at least that`s how I worked it out
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