Using a dedicated AC or car USB charger

I wanted to report the results of measurements I made with a breadboarded charging circuit - in case this might be relevant to others who may be having problems.

But first, a quick reminder.  When connected to an AC or car charger, the Clip behaves normally, meaning that the screen goes dark after 15 seconds, and you can play songs, etc.,  just as if it wasn’t plugged it.   However, the Clip does actually have to be turned ON to charge.  So, you need to turn Auto Power and Sleep OFF when charging.  Otherwise, the Clip will shut down at the end of the Auto Power or Sleep period, and charging will stop.

Anyway, in  March, 2007, a new USB standard was issued for charging through a USB port.  The standard says that a “dedicated charger”, which is just a non-intelligent power source provided through a USB socket, should have its Data lines shorted together.  The Data lines are the two middle pins of the socket.  A connecting device, upon detecting that these two pins are shorted together, will know it need not try to negotiate a formal connection, and can just proceed to draw current.  Older chargers, and possibly newer proprietary USB chargers for other devices, may not have the Data lines shorted.

My 1 GB Clip with .20A firmware, turned ON but with audio playback paused and the screen allowed to go dark, and with the Data pins of the charger shorted together, draws 154 ma.  from a 5VDC supply.  After charging has completed, current drops to 62 ma.  It looks like the net charging current is therefore 92 ma.

With the Data lines in any other configuration - either unconnected, or tied high or low through a number of different resistor values - the total current is only 114 ma.  Since the new standard requires the downstream device to negotiate permission to draw more than 100 ma., perhaps the Clip refuses to draw more than that from what *might* be a normal USB port.

In any case, it appears the net charging current drops from 92 ma. to 52 ma. if the Data lines are not shorted, which would roughly double the time required to charge the batteries.  But even a non-compliant charger would still charge the Clip overnight.  So if someone gets no significant charging at all through a USB charger, it may well be because Auto Power or Sleep is turning charging off after 10 minutes, or whatever the setting is.

Hope this is helpful.

Peabody, thanks for the report and the results of your testing.

I’d like to make a comment based on my own experience. I regularly use a dedicated AC wall adapter to charge my 2GB Clip. I have the Auto-Power setting at 5 minutes and do not change this when I charge the Clip. I have never experienced the Clip turning off when it is connected to the AC wall adapter. At any time, I can click on the center button and the display will come on, whether the Clip is still charging or it is finished charging. You may be thinking that I must have the Clip in Play mode, but I don’t. There are many times I will play my Clip with it connected to the AC wall adapter, but when I charge it (which I usually do overnight), it is always turned on and kept in Pause mode. Once I disconnect the Clip from the AC wall adapter, if I don’t use it or turn it OFF right away, it will auto-power OFF in 5 minutes, as expected.

I’ve never used the SLEEP mode. If someone has their Clip’s SLEEP mode activated when it is connected to an AC wall adapter, perhaps that is what is causing the Clip to power down and not finish charging completely.

Well, BigJohn, I guess that’s what makes life interesting.  I specifically tested this, and it turned itself off  in the middle of charging at 10 minutes, which was how I had Auto Power set.  Now that’s with a charger I know is compliant with the new standard.  I didn’t test that in a non-compliant configuration, which might make a difference.

The only other thing I can think of is that my Clip wasn’t actually paused - it had played the last song and had stopped on its own (display showed it paused, but it was really just idle).  Maybe that makes a difference.  I don’t know.

Or, you know, maybe I just imagined it.  :slight_smile:

I guess the bottom line is if you can’t get a charger to work, you might try turning off Auto Power and see if that helps.

I just bought a kit from iConcepts with a wall charger, a car charger, and a USB 2.0 to Mini USB. It’s supposed to work for a multitude of devices including GPS, Motorola phones, Blackberry, and MP3 players. The small end of the Mini USB retractable cable does not fit the Clip port (It looked like it would but it doesn’t).  Is it OK to connect the white USB cable that came with the Clip and use this cable for charging from a wall charger? Are the data wires supposed to be shorted together in the charger or in the USB cable? Or, to put it another way, where is the “non-intelligent” part (cheap joke can be made here, but it would be way too easy.)? Sorry if I missed the answer somewhere else, just searched and couldn’t find it.

I use the USB cable that came with the Clip with the AC charger I built.  It’s just a standard cable so far as I know.  So it should work with any charger that has a standard USB port socket like the ones on your computer.

The data lines should be shorted inside the charger.  That’s so any device plugged into it, with any cable, will know the device is non-intelligent.

If your charger is fairly new, it should be compliant with the new standard.

Please do not use any charger made for iPods. They will overcharge and damage the Sansa.

I do not know what the iConcepts package contains. I recommend using only chargers that say “Made for Sansa”

Actually, that does not seem to be what SanDisk itself says–SanDisk indicates that a routine USB charger is fine (not just "made for Sansa"s). 

Unless a charger is putting out more than 5V, it’s hard to see how it would overcharge.  The charging is controlled entirely by the Clip - it draws the current it needs, and quits drawing current when it determines its battery is charged.  I doubt a genuine Sansa charger differs in any material way from a generic charger.

Well I suppose in theory chargers could differ somewhat in the quality of the voltage regulation - ripple and such - but it’s hard to see that making much difference in battery charging.

I do not know why it makes a difference. However, I have sceen a burnt spot on a display that was plugged into an iPod charger