Hello Everyone,

I am designing a project that will be powered by a 3.6V rechargeable coin-cell battery. The purpose of the project is to help me understand how to design low-power circuits. I know that bulk capacitors (like 10uF tantalum) can help mitigate noise and temporarily store a charge if the battery is connected, but I'm not too sure on what else I can do to have a steady supply with a varying load. Perhaps I can use a diode to help? Here is an overview of my project:

The board uses a low-power MSP430 MCU, temperature sensor, XBee module, battery management IC, and a couple of LEDs for debugging. Most of the time, everything is in a low-power state. The current temperature and battery life will be transmitted every 5 minutes to an XBee I have connected to a PC. The XBee module has the highest power consumption of about 35-40mA during RX/TX.​

Does anyone have any advise about using a battery to power a circuit board without the use of any regulators? I would appreciate any feedback you have to offer!

Anson

 

Lots of battery operated electronics do not include voltage regulators since they can only consume power; you just need to ensure that the circuits to be powered can operate over the expected voltage range (which is largely dependent on the choice of battery) but you don't say what that range is. Have you built this device? Is there a problem operating it from the 3.6V cell?

 

Will the battery management IC have low-voltage cut-off? That might be more important than a regulator. Remember that Li batteries can have voltage as high as 4.2V and as low as 3.4V (3.0V) or so at cut-off.

John

 

Thank you for the replies! For this project, I expect the board operate with a voltage as low as 2.4V. This is the minimum voltage required to power on the battery management IC. Everything else can operate at lower voltages. The only device that doesn't have a 5V or higher maximum power rating is the temperature sensor, which allows up to 4V to power it.

I haven't built the device yet. I've been working on the design in Eagle, but I'm trying to make it "perfect" before I order the board. As I have never designed a circuit board without the use of a regulator, I'm not sure what to expect from just using a battery. I know that batteries can have a higher/lower voltage rating than what their label indicates (Just as jpanhalt said) but that's about all I know what to expect.

 

The battery you plan to use has a nominal voltage of 3.6V, a higher voltage when it is fully charged, and a lower voltage when it is discharged. You need to determine if and how your circuit will function at any given voltage and whether the battery you've selected will give you an acceptable operating time.