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View Full Version : powering SB w/ a battery pack?

Dave Owen
2005-02-03, 16:32
I wrote:
>That said, here's what I would do to answer your own question...

Follow-up: I went that far, so let's do the math, too. :)

Rule of conversion I used: 1500mAh can provide 100mA for 15 hours (if
this is wrong, let me know)

So, say you need to provide a maximum of 1000mA for 1 hour, you'll need
1000mAh at 5V. That 3300mAh pack should provide you with around 3.3
hours of listening pleasure.

Now, that assumes (1) the unit actually does need at MOST 1000mA to work
(check with SlimDevices), (2) the unit is not sharing the battery with
something else, and (3) the battery pack actually provides the rated
output (it is eBay, after all). The life might conceivably be longer,
but with wireless, I doubt that very much, and it might even be shorter.

Hope that helps.

kdf
2005-02-03, 16:42
Quoting Dave Owen <dowen (AT) sapient (DOT) com>:

> Now, that assumes (1) the unit actually does need at MOST 1000mA to work
> (check with SlimDevices), (2) the unit is not sharing the battery with
> something else, and (3) the battery pack actually provides the rated
> output

sadly, this is a very tricky thing. Many batteries will give the rated
current-time but only at a certain current draw. Depending on chemistry, the
charge curve will change for larger and smaller current draws. For example, if
you are drawing the 100mA, you may indeed get 15hours, but if you draw 1000mA,
it is entirely unlikely that you will see 1.5hours.

Again, this depends entirely on the chemistry and construction of the battery.
There are often several charts you can go by if you are directly purchasing a
battery. Being as this is a ready-made kit through ebay, you are back to try
it and see. It will work. The question is for how long, and how many cycles.

Even if this battery does hold up to high current for the full time, it is still
hard to predict what voltage will cause the squeezebox to cut out. You may
find that once teh battery goes below even as little as 4.7V that you start
having very odd things happening. The wireless card and the display are