May 4th, 2006

How not to charge nokia 6230

There are few different chargers for 6230; and I probably have the wrong one:

ACP-7X 3.7V 355mA (and pretty old)

(there are few others that should work:)
ACP-8X 5.3V 500mA (Travel Charger that came with 6310i)
ACP-8X 5.8V 450mA (Travel Charger that came with 3310)
ACP-12X 5.7V 800mA (Fast Travel Charger that came with 7250i)

... but I'd prefer Nokia to charge from usb, like my Zauruses already do (handy cable came with dlink wireless router, IIRC :-), and my Ericsson cell phones do (had to make cable, but it was easy -- two pieces of wire + two connectors).

After some pondering of numbers above... it looks to me like Nokia behaves like 10Ohm resistor in most cases. I kind of remembered that Nokia would prefer current source (not voltage source), and figured out that 2Ohm resistor in paralel is probably okay to simulate that...

Well, it is not :-(.

I tried connecting USB with old nokia (3310, IIRC)... and it seemed to work in all cases (but I did not check that too thoroughly, and did see some "Not charging" messages after a while when it pretended to be charging but probably was not); directly connected, connected through 2Ohm resistor, connected through 3Ohm resistor. Unfortunately, 6230 just displayed "not charging" message, and was done with it :-(.

I tried taking ACP-7X charger (that obviously works with 3310, and works badly with 6230), and yes it still worked with 3310 and 6230, and it even worked when it was connected through 2Ohm (more precisely 2.2Ohm) resistor.

I also tried with el-cheapo power brick (that is not properly regulated, so gives ~10V when unloaded, as does original nokia charger).

I wonder what is going on, what magic is needed so that 6230 actually gets some energy from USB?