Is this possible with Arduino??

Hello everyone XD , i have a project in mind with a couple of challenges... here i go

I have a nextel that im using as a GPS locator in my car, now the battery on the phone dies out a little too fast (about 1 day life span) and this is my plan...

Splice 2 wires into the phone battery, plug it into the Arduino board so that the Arduino could read the phones battery voltage (5.0v=full charge, 2.0 or less=low battery) and id like to the Arduino to automatically (with transistors) to charge and stop charging my phone...

now for a car, anything over .02amps will drain the car battery in about 1 weeks time so id need the Arduino to operate under .02 while charging and operating the Arduino Chip...

Would this be possible or would u like me to explain this further ?
Thank you very much in advance ; )

20mA will drain a car battery?
20mA * 7 days * 24 hrs/day = 3360mAH. Isn't that about the capacity of 2 AA batteries?

What kind of battery is it? Using an arduino is total overkill, I think all you really need is something like a max1811 (for a LiPO battery) or its equivalent for a NiMH or whatever the battery is.
Don't the NEXTEL phones have car power adapters that do this for you already?

Use a cigarette lighter adapter to charge the cell phone.

Electrons is electrons and there's no free lunch. If it takes a certain number of electrons to charge your battery there's nothing the arduino can do to reduce that number.

Thanks for replys n advice guys ; )

i understand that the arduino cant and wont control how much mA output is givin up by the main batter but id like limit...

what i mean is that since the nextel phone is a pretty old phone, it wont limit how much charge is going into the phone, if i was to keep the charger on the phone 24/7 (1) i will keep sucking current from my main battery and eventually drain out my main battery and (2) it will detonate the cell phone battery as a member from my car forum said that it happened since the nextel wont auto shut off the main charge.

Now with the arduino, i could use it as a "smart" switch, by detecting the charge of the battery in the phone (voltage reader) i would program the arduino to set out commands on rather to activate a transistor to charge or to turn off the charge to the cell battery but im just wondering if the combination of running the arduino and the cell phone charger at the same will drain my main batter out of juice

did i explain it a little better now ?? lol im not too good at this, please bare with me guys :grin:

Take the battery out of the cell phone and run it through a cigarette lighter charger.

DCContrarian:
Take the battery out of the cell phone and run it through a cigarette lighter charger.

how will it transmit the GPS signal when the car is off ?

DCContrarian:
Take the battery out of the cell phone and run it through a cigarette lighter charger.

Most mobile handsets will not operate when powered only by the charger. They need to be able to draw upwards of 1,500mA and they are designed to suck this kind of instantaneous current from the battery, not the charger.

The O/P seems to be describing a scheme to charge the mobile's batteries behind the scenes, without using the mobile handset's charging circuit. This is also a bit dodgy as the charging of LiPoly cells is something that takes some finesse that the mobile's circuits are designed for. Just feeding charge current willy-nilly into the cells is likely to result in a costly automobile fire.

It is possible to power a handset through its battery terminals, without an actual battery. This usually requires a bit of extra circuitry to fool the handset into believing that a battery is present, plus a good stout regulator (1.5A or better) and a good big filter capacitor.

The MAX1811 is designed to charge LiPO batteries, and stop charging when they are full.
Ok, just checked, it wants to run from 6V, so you'd need a stepdown regulator as well.

The MAX1898 is good for 12V sources (14V max), and needs few external components.
http://www.maxim-ic.com/datasheet/index.mvp/id/3250

You don't need to waste a whole arduino on this.

CrossRoads:
The MAX1811 is designed to charge LiPO batteries, and stop charging when they are full.
Ok, just checked, it wants to run from 6V, so you'd need a stepdown regulator as well.

The MAX1898 is good for 12V sources (14V max), and needs few external components.
http://www.maxim-ic.com/datasheet/index.mvp/id/3250

You don't need to waste a whole arduino on this.

That is exactly it!! lol wow u guys are amazing ; ) i'll read up on this as i have to head to school now, but thank u so much for the input

It is a surface mount part, you may need to get an adapter board, like something from these guys
http://www.schmartboard.com/index.asp?page=products_so
Can solder the part down, get some holes for a couple of caps, whatever, and for securing your power in/power out wires.