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if this led was connected to one of your switched battery boxes with 2 AA batteries how long would you estimate this unit would flash for.
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Qif this led was connected to one of your switched battery boxes with 2 AA batteries how long woul......
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Asked by Anonymous on November 28, 2011 12:00 am
Answered by the admin If you use two AA batteries then when they are brand new there will be 3.2V across them both. This quickly drops to 3V hence the 1.5V per cell value. The problem is that for the rest of the batteries life the voltage slowly drops from 1.5V down to 1V. So if you want to get the most out of the two batteries then you will only have 2V across both of them at the end of their life. Since the flashing LED is only rated down to 3V you will only be using a fraction of the batteries capacity. With this in mind I?m going to do the sums for 3x AA batteries as 100% of the batteries capacity will be used. A good alkaline battery has a capacity of 1500mA/h, which means that if you draw 1500mA out of the battery it will last 1 hour. The current taken by the LED will vary depending on battery voltage, but let's as
sume the worst case of a current of 20mA. So the battery capacity is 1500mA/h divided by the current (20mA) so it will last for 75 hours. A cheaper zinc carbon battery will probably be half this amount. This is based on using 3 AA batteries.
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