# Charging Lithium Ion Battery with 3.3V

#1

I am trying to use a piezoelectric element to charge a li-ion battery. Basically my set-up so far is the following:

My piezoelectric element is connected to a LTC3588-1 module (1568-1038-ND‎) which outputs a 3.3V. I am trying to charge a single cell li-ion battery that requires 4.2V for charging. I am missing a component that takes the 3.3V output and converts in into a 4.2V for battery charging. Note the li-ion battery capacity will be pretty small, between 50 and 150 mah.

I searched all over and I cannot find components that work.

Ps. I am in my last year of mechanical engineering, I am not too familiar with electrical engineering.

Thank you

#2

Charging a Lithium battery can be a bit of a challenge to start. Do you know your Voltage and Current ratings on your piezoelectric element?

I am not sure you will be able to get a solution that will put out a straight 4.2V. I know Adafruit has a board that will charge 4.2V, however it takes an input of 3.75-6V so you would need to boost your voltage out of the piezo element. 1528-1833-ND

You might be able to use just the chip which is MCP73831T-2ATI/OTCT-ND , however again you will need to boost voltage and make sure you have enough current out of you element to support the charging as there will be loses.

-Robert

#3

Hi Robert,

Thank you for your response. I cannot use a usb power. Basically, my issue comes after converting the piezoelectric element.

The piezo generates between 2-10V which is fed through the LTC3588 module which converts the AC generated voltage to 3.3V DC.

So I’d need a component that takes the 3.3V to be converted to a 4.2V DC.

-Nick

#4

I understand that you do not have a usb. That board also has inputs to take a voltage ranging from 3.75 to 6VDC. The biggest question is what is the current being put out of your generator and will it support the charging needs of the battery.

#5

I couldn’t find the output current of the piezoelectric. However, the output current of the LTC3588 module is 100mA.

#6

That is true, however it can only supply out what it is given in. Have you tested you application to see what you actual output current is?

You maybe able to take your output of 3.3V into a Boost chip like TPS61222DCKR and output could go to a chip like XC6805A2D14R-G.

In a perfect world with a constant output on your LTC3588 you may be able to get a 40mA charge on the battery, however I would have to dig in a bit more to see what the energy use will be on these chips and you would have to know that you are going to get a constant output on your piezo to even be able to calculate specifications.

You may also want to check the charge requirements on the battery you are using to know what you need to properly charge.