Car charger?

[#1]

Hello all!

Newbie here.

I have discovered the annoying fact that my XperiaArcS wont charge properly in my car. If I run Waze, a navigation/trafic info/community program, and have the charger connected the battery will drain almost as fast as without the charger it seems. So, my conclusion, the charger delivers less current than Waze consumes with GPS, internet and the phones screen. I have used three different lighter plugs: one unmarked, one 5V 1A and one 5V 2,1A but it is all the same. Tried to charge the phone with my wall plug charger, rated 850mA, while running Waze and even after as little as 20 minutes the battery had gone from 51% to 64% even though Waze was running with screen on and everything.

I have read on the net, don't know if its true though, that the iPhone has a function that senses if a dedicated wall socket charger or an ordinary USB connection is used and adjusts its power consumtion accordingly to not load the USB from your computer for more than the 500mA that they are rated at. Is this the same with XperiaArcS and, if so, how do I do to get it to charge fully while in the car?

Are there specially lighter plugs that work? (My childrens iPads seems to charge correctly with the 2,1A plug. The iPad wont charge with my Ipad Nanos 1A charger.)

Are there specially USB charge cables for Xperia wich permits full charge?

The problem I have, practically, is that I can only run the navigation for a limited time even if the charger is connected. NO GOOD, that is. Never had that problem with my Nokia 5230 which, on the other hand, had a dedicated charge connector and didnt use the USB for this.

Any comments, advices....?

[#2]

Update:

A genuine SonyEricsson car charger, AN-300, can cope with charging my phones battery while Waze is running. So, this will be my solution to the actual problem.

I sent a mail to SonyEricsson support asking why just the SonyEricsson chargers are able to charge with full current. Waiting for reply. I don’t expect a reply with any description about coding and such though.

Tried my self to hook up a DVM to a slaughtered USB cable to measure charging current but reached only 270mA even with the SonyEricsson wall plug charger. Seems like the charger has pins 3 & 4 shorted, like Nokia above, but there might be more to it than that.

I might ad that I’ve been working with electronics for a living for 30 years. Don’t mess with things like Litium batteries if you’re inexperienced. You might ruin your phone but even worse things might happen.