Maegnus Posted February 25, 2010 Posted February 25, 2010 I just have a quick question that I could not find the answer to: If I have just put 6 fresh batteries into one of these boxes and I leave it on for around a full day--and there is nothing actually being powered except that green indicator LED--how much power has it actually chewed out of those batteries? I only ask because the model in question will be tricky to change the batteries, and I'd rather not start with them half dead. I imagine it costs almost no charge to keep that light on, and since the rest of my wiring (all lights) were on a second switch (which was off), nothing was actually in operation. Am I making sense. I gather one of the train people must know. Thanks all Quote
DLuders Posted February 26, 2010 Posted February 26, 2010 I use 6 ea. Energizer Rechargable batteries in my 9V Power Functions #8881 battery box. At full charge, they produce 2,450 mAH (milli-Amp-Hours) of power each. 6 x 2,450 mAH = 14,700 mAH. I don't know exactly how much current the little green LED on the #8881 battery box draws, but if it's anything like the second product shown on the website http://alarmcontrols.com/html/our_product....n=view&ID=4 , it could be (at the most) 8 mA (milliamps). (14,700 mAH)/8 mA = 1,837.5 Hours = 76 days. So, don't worry about it! Quote
Blakbird Posted February 26, 2010 Posted February 26, 2010 I use 6 ea. Energizer Rechargable batteries in my 9V Power Functions #8881 battery box. At full charge, they produce 2,450 mAH (milli-Amp-Hours) of power each. 6 x 2,450 mAH = 14,700 mAH. I don't know exactly how much current the little green LED on the #8881 battery box draws, but if it's anything like the second product shown on the website http://alarmcontrols.com/html/our_product....n=view&ID=4 , it could be (at the most) 8 mA (milliamps). (14,700 mAH)/8 mA = 1,837.5 Hours = 76 days. So, don't worry about it! The math doesn't quite work that way. One battery is 2,450 mAH at 1.5 Volts. 6 batteries is 2,450 mAH at 9V. You don't get more capacity by adding more batteries unless they are in parallel. When you are putting them in series (like in LEGO battery boxes) the total capacity is based on the capacity of each individual cell. Now if you are measuring power (in Watts, for instance), then you can add them together. The things I learn from my other hobby (R/C)....... Quote
DLuders Posted February 26, 2010 Posted February 26, 2010 The math doesn't quite work that way. One battery is 2,450 mAH at 1.5 Volts. 6 batteries is 2,450 mAH at 9V. You don't get more capacity by adding more batteries unless they are in parallel. When you are putting them in series (like in LEGO battery boxes) the total capacity is based on the capacity of each individual cell. Now if you are measuring power (in Watts, for instance), then you can add them together.The things I learn from my other hobby (R/C)....... Very well, the expected time for an ~8 mA green LED to drain a 6-AA-cell, 9V #8881 battery box is (2,450 mAH)/(8 mA) = 306.25 hours = 12.8 days. Please know that the Energizer Rechargable 2,450 mAH AA batteries that I'm using in these calculations may be more powerful than cheapo alkaline batteries. Anyway, don't leave your battery box "on" if you can avoid it! Quote
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