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Does anyone know whether or not a car charger for a cell phone contain circuitry to regulate it's input?<p>If not, is the voltage then regulated by the car voltage regulator? Or when the cell phone is charged, does the demand for current go away?<p>Much appreciated.<p>tony
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It's hard to tell - The characteristics of the charging circuits vary with quality of chargers and change from manufacturer to manufacturer - Also the requirements change according to whether the phone batteries are Ni Cad Li Mh etc. Forget regulation of automobile circuits - they are mostly crude and vary from 12 to 16 volts according to what's going on.
A practical way to check what is going on with your phone battery is to run the battery down and then put it on charge, in the car preferably and then monitor the charging current from initial charge rate to full charge. Note the current when the battery is fully charged and then monitor the operation to see if the battery temperature rises significantly - that will tell you whether or not the batteryu is being overcharged. If it is then you should remember to only leave it charging for a specific time and then disconnect it.

I believe that most car chargers do have some sort of regulating circuit given that most phones want far less than 12V to charge. Overcurrent protection is an issue also. Not so much on a good battery but you wouldnt want to burn up anything because the battery is shorted. <p>The last charger I bought had a little tag bragging about a new 3 terminal device inside to regulate charging. Looked a lot like a transistor and I suspect it works like a LM337 or 7805 or similar.<p>Incidently, most new phones also will have some circuitry to regulate charging as well. In my new LG phone, I can get into the service menu and see the temperature and battery voltage directly

Tony,
If I understand correctly, you need to know if a car charger for a phone has regulation. Most likely not. Cell phone car adapters are just a plug, usually with a fuse that connects into the 12V power outler / cigarette lighter, to a special connecter that fits the phone. If the cell phone charges off of a usb cable, and the car adapter is a 12V plug with a usb connector, then the power is regulated to 5VDC. Otherwise, I would assume the phone does the regulation. <p>-Mike

I had one that got driven over, obviously broken.<p>Upon inspection there was some chips (unidentifyable) bus also a small toroidal inductor.<p>I could be wrong, but 2+2= switching regulator.<p>Denny