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Re: [IP] Power to the people

>Date: Tue, 11 Jan 2000 20:36:06 -0800 (PST)
>From: Michael Robinton <email @ redacted>
>Subject: Re: [IP] Power to the people
>On Tue, 11 Jan 2000, gianna marzilli wrote:
>> I took the batteries out and changed their position and then put
>> them back in again. To my delight when I looked on the pump, there was no 
>>   Ian -- it also does this when you put the batteries back in without 
>> changing the position at all! At least, it did when I tried it, which makes 
>The problem you are seeing is probably modest oxidation of the surface of 
>the battery. Take them out, rub the top and bottom with a clean piece of 
>copy paper -- the abrasiveness of the paper is just enough to clean off 
>the battery surfaces. 

What you're seeing may also be a result of how the pump detects a "low
battery" condition. The power delivery curve for batteries isn't smooth
enough that you could take an instantaneous reading and say that at some 
point there is enough power to run the pump and at some other point the 
batteries are "low". Rather, you would take a "filtered" value that 
samples the strength of the battery over a period of time. When the 
filtered value falls below a particular "threshold", the batteries 
are declared to be "low". 

If you remove the batteries the pump will have to start monitoring the
power flow all over again. In other words, it goes back to square one.
As soon as the minimum amount of time to get a filtered value passes, 
the batteries would again be declared "low".

The real danger in all this is that you aren't getting any more power
out of the battery, you're just taking advantage of a quirk in the
pump's algorithm. Kind of like not listening to your doctor when he
says something you don't want to hear.

Most likely it's a combination of better contact between the batteries,
as Michael suggest, and the algorithm used to detect low batteries.

In any case, the best course of action is changing the batteries in
a timely enough fashion to keep the pump working. Being frugal is one
thing. Being so cheap that you threaten your own life is another.

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