Apple Video Ipod – Battery Life analysis HDD vs. CF
As promised I have been spending sleepless nights measuring and testing the battery life to bring you the ultimate and most comprehensive battery analysis for apples Video Ipod (5g & 5.5G) players ever!
My original intention was to just compare the run-time of the hard drive based iPod i.e. standard off the shelf video iPod with my compact flash based solution, but being slightly of the rails when it comes to things like this I really pushed the boat out and made some electrical Current measurements as well.
First thing I needed to invent was a method of breaking out the battery supply, so I could insert my Current meter. The easiest solution I felt would be to make something which was similar to the battery fitting which I could then use to power up the iPod from my bench power supply.
So after some cutting and soldering I produced my own custom flexible PCB stick to fit in to the battery connector on iPod. I set my bench power supply to 3.7V the nominal voltage as supplied by the internal battery. In-line with the supply I attached my Current meter, which would show me current drawn from the power supply.
Playtime measuring was going to be a little more interesting as I was not about to stand around my iPod for 15 plus hours waiting for it to die while holding a stop watch. So after some racking of the brains, I came up with the simplest and most novel method you will ever witness.
I will record the audio output from the iPod using my computer and sound recorder software, till the player switches off from the low battery. I will then analyse the wave file to find when the music stopped to determine how long the playtime was. I said it was simple
Obviously I will record at the smallest bit length and sampling frequency as I don’t want to end up with a 20Gb wav file.
To demonstrate my utter boredom, I even soldered in 47Ohm resistors to the output lead to mimic earphones!! (before the geeks amongst you starting commenting most earphones have lower DC resistance – around 30Ohms, but they are inductive loads, so resistance does change with frequency - being on the safe side I settled on 47Ohms, plus I had the resistor lying here!)
To improve accuracy of the data, I have devised this charging and measuring cycle.
- Charge battery till full
- Play Music till it switches off
- Charge for 6hours and start test
This will bring the battery up-to a known starting level, before the above is repeated while recording the output. This will be repeated twice and the average of the time will be used. I will also do these tests playing HQ Video files rather than MP3′s.
Once the timings have been noted the Hard drive will be removed and the Compact Flash adaptor and 8Gb card will be installed, and all the above testing will be repeated.
To maintain consistency, the 8gb CF card and HDD are loaded up with exactly the same MP3 and Video files, even the order of play will be the same – so don’t accuse me of not being meticulous.
Move on the next page to see the results.
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