I wire a Lilypad USB on 4.2-4.5 V (3AAA) to the pins + and -.
I am planning to connect an ADXL345 Accelerometer to the same power source.
Internet confuses me: both devices have 3.3 V operating voltage, but 5V is stated as input voltage.
I am not looking for precision, but just to detect movements sufficiently to command 3 LEDs (3axis) - as an costume art project (10 degrees precision is more than enough).
So I want the keep things simple. Smoke excluded, however. 
Can a obtain acceptable sensitivity (see above) and reliability by connecting both accelerometer and Lilypad USB to the same 3xAAA source?
Thank you!
i found ADXL345 statements: "5V tolerant", "regulated 3.3 V", "2.5- 3.6V", "3.3V, 5V" "working voltage 3-5 V" and variations.
According to DS (Analog Device), the maximum voltage is 3.9V.
My understanding: ADXL345 can work fed anywhere in the range 2.5- 5V, but the output values differs with the supplied voltage. Most preferable 3.3 V.
What I cant figure out is whether I can power it at 4.5V without blowing it up.
Component U2 on that circuit board is a 3.3V voltage regulator. Whatever voltage you put in will come out as 3.3V.
The Lilypad has a similar chip. (Coincidentally labelled as U2.)
It is important to know how these chips work if battery life is important to you. They are both "linear regulators" which means excess voltage input results in wasted heat. 3 batteries in series is almost perfect. If you added a 4th battery in series then it would work just fine but almost all the extra power is wasted - battery life will be almost identical to 3 batteries. It also will not work well with a 1S lithium battery, even though that type of battery is labelled as 3.7V
@MorganS
Thank you!
I am hooking the ADXL to Lilypad USB (USB powered) on I2C - to code LEDon/LED off according to sensor moves (or position?). Lets see