R1-R4 battery drain?

by DEADBEEF on Mon Feb 27, 2012 12:23 pm

Support,

looking at the v3 minty boost schematic and R1-R4 (which I assume are sense resistors used by some devices to detect a charger), in the build instructions you advise leaving the batteries in when not used but it appears to me that the sense resistors have a constant current drain of almost 1mA which gives a 5mW constant drain on the batteries.  carrying this a bit further to 2x3400mAh AA cells (being generous here with the largest capacity I could find) (3400mAh*3V=10200mWh) says that every ((10200/5)/24) or 85 days the resistors alone will drain the best batteries one can find.  should the R1-R4 be optional?  what is the effect of leaving them out?

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Re: R1-R4 battery drain?

by adafruit on Mon Feb 27, 2012 1:08 pm

R1-R4 are required for use with Apple Iphone devices. If you are not using an Apple device, you can try to leave them out, if it works, then you don't need them!
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Re: R1-R4 battery drain?

by evilgeniusha on Mon Apr 09, 2012 9:25 pm

Can anyone confirm that it works with these parts taken out? I don't have any apple devices to charge and I would love to increase efficiency if I can but i don't want to remove them from an already assembled kit just to find out I have to put them back for it to function.
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Re: R1-R4 battery drain?

by adafruit_support_bill on Tue Apr 10, 2012 4:46 am

Nobody can answer the question unless you tell them what you are trying to charge. Most smart-phones need the resistors to set a voltage on D1 & D2 to control the charge rate. Some phones work better with D1 and D2 bridged. In that case you can eliminate one pair of resistors for slightly more efficiency.
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Re: R1-R4 battery drain?

by evilgeniusha on Tue Apr 10, 2012 10:08 am

Ooh I see, I thought the charger in general might stop functioning without those resistors.
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