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Charge and Sync with a USB-only-Dockingstation


Caution: I won‘t take any responsibility for any damge!

If you own some Palm devices, you might be fimilar with this picture:

Okay, your chargers and dockingstaitons are not such a mess, but you will probably have a few chargers and dockingstations. Since, Palm devices from Palm were the most popular Palms, I guess, that this is one of the most common dockingstaitons:

The dock was available with a usb- or serial-cable. This one shown, is a dockingstation with a USB-cable and a dedicated charger.

At the time, when Palms with the Palm Universal Connector got released, e.g. the Tungsten T, T2, T3, C, W, Zire 71, m500, m505, m515, i705, m125 or m130, (also the Garmin iQue 3600, 3200 used this connector), USB 2.0 was the standard USB-Connector. And since USB 2.0 is limit to 500mA, a dedicated charger with more current was needed to charge the devices properly.

The charger, which came with this dockingstation is a original charger from Palm and outputs 1A at 5v, 5W in total:

Currently USB 3.0 or even USB 3.1 is the "new USB 2.0" and a lot of computers have USB 3.0 ports. But how much current can provide USB 3.0? A look in the Wikipedia article about USB 3.0 tells us: 900mA. Not exactly 1A, but I would guess, that Palm calculated some head room in their chargers. So maybe it is possible to get rid of the charger and charge the device the the usb-cable only.

So I opened the dockingstation and cut the wires from the charging port.

The thin red (+) and black (-) cables are the ones from the usb-port, in this case: "U3" and "U4":

So I soldered the cables, which were attached to the charging port to "U3" and "U4". A bit of heat shrink tubing should prevent shorts, ince it is a bit tight there after all:

After putting everything back together, here was the test. This is a unmodified dockingstation, only the USB-Connector is connected to a USB-Charger. It does not charge:

But with the modified docking, the Tungsten C is charging:

Success, so far. And on a USB 3.0 port, it draws nearly 750mA. Which is more than the allowed 500mA for the USB 2.0 port, but less than the 900mA, which USB 3.0 can provide.

Since the Tungsten C has interanlly two batteries, a Palm m515, with only one battery, draws even less current: Only around 470mA. Which could theoretically handle also USB 2.0, but practically, you don't want to work so close to the limit.

And since it is still USB, a Hotsync is of course also possible:

So, with this modification, you could theoretically get rid of all your chargers for Palm devices with the Palm Universal Connector. ;-)