Recharging 12V Battery w/ FIO

Hi,

I'm using the FIO w/ xBee to wirelessly turn on and off 12V LEDs and I only want to use 1 battery on my project so It'll have to be a 12V to meet LED requirements. I'd appreciate input on 4 questions:

  1. Although the input voltage is 3.5-12V for the FIO, i noticed the Input Voltage for Charge was only 3.7-7V. Does this mean I won't be able to recharge the 12V? Is there anyway to get around this?

  2. all the LEDs will require, in total, 100mA and they won't be used for more than 3-4hrs between recharges. Is there a (cheep) particular LiPo battery you would recommend I buy? something from www.dealextreme.com ?

  3. Since FIO only requires 3.3V, I assume putting in 12V means the rest is wasted as head. Would a voltage regulator or something reduce this problem?

  4. On the arduino uno, you can access the input voltage w/ VIN pin- is there no way to do this in FIO?

best,
AnAnonAnonym

I'm disappointed by the lack of information that is available for the Fio. There seem to be only a few of us working with it. What little I know has been from only a few web pages and a few days of playing with my Fio. To answer your questions:

  1. You can power the Fio with a battery that has a voltage of 3.5 to 12 volts. You can only charge LiPo batteries (apparently the charging circuit on the Fio is designed for LiPo's only) and the input voltage for that charging circuit is 3.7 to 7 volts. You can attach a standard mini-usb jack cell phone charger (5v), to the mini-usb port on the Fio, or you can solder charger wires directly to the "charge" pads on the circuit board. I bought one of these 6v solar panels that I intend to connect to my Fio: http://www.adafruit.com/index.php?main_page=product_info&cPath=44&products_id=262

  2. I've never bought a LiPo battery before, so I'm looking for a good source for them myself.

  3. The Fio has a built-in voltage regulator on the board that drops the 12v input voltage to 3.3v. Yes, you'll lose some energy as heat. But adding another regulator would do the same thing. I think you're fine using the regulator on the Fio.

  4. There are no pins to access the external battery voltage other than the 2 thru-holes labled "Batt". They tap into the traces leading from the external battery connector to the regulator on the board.

If you're dead-set on using only one battery, you'll have to find a different charger for your 12v battery. Otherwise, you could use a LiPo for the Fio power, charge it with the onboard charger, and use a separate 12v battery that has it's own charger and is triggered by the Fio to light the LED's.

Try this: 1000mAH LiPo from Grativech.us (have to ask about it, $12) and a boost regulator to get your 12V for the LEDs
Pololu Adjustable Boost Regulator 4-25V

Then a MAX1811 to control charging of the LiPo, very easy to use little part.
Ah, I see the FIO already has a charger, MAX1555, a similar part.