Battery Management System

KlausST said:

Hi,

3.6V means single LiIon cell, so why do you choose a 14 cell controller IC?

Klaus

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Chantelle said:

I am using a Max17852 BMS IC to manage three Li-ion cells in series. I have some idea of what to do from reading the pin descriptions, but the datasheet is massive and I am struggling to find the information I need. How does the BMS know what voltage/current to regulate the battery charge/discharge? I presume it is via some sort of communication, as indicated in the following typical application diagram:

View attachment 170792
Can someone please explain what the upper and lower uart interfaces means? These controllers its talking about... do I need them? To be clear, I know what UART is. But I have only ever used the single line type of UART.

There is another diagram given:

View attachment 170793
This is using SPI communication, which I am not familiar with. So I don't think this is an option for me.

I simply want the BMS to allow the batteries to charge up to 3.6V with a constant 3A current which we will be providing. And ideally ensure nothing blows up, or overheats.

Any help is much appreciated!

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navbp said:

Hi,
MAX17852 is new for me. I just glanced through the datasheet.
MAX17852 is a 14 cell Data acquisition IC and I feel that this is not suitable for your application.

Li ion cells max voltage - 4.2V, Min voltage - 2V (depends on Chemistry)

And min. VDCIN of MAX17852 is 9V. As you will be using 3x Li Ion cells to power on the MAX17852, MAX17852 will get switched off when voltage per cell is <3V.

If you want to limit your min. voltage per cell to >3V, you can still use this.
But you will not be fully utilizing the cell capacity and MAX17852 is an over-designed chip.

MC33772 or any other battery controller IC meant for 3 to 6 cells suits better for your application.

MC33772B | 6-Channel Li-ion Battery Cell Controller IC

NXP's MC33772 is a Li-Ion Battery Cell Controller IC designed for automotive and industrial applications such as 14 V Li-ion batteries, HEV, EV , ESS, UPS systems

www.nxp.com

Can someone please explain what the upper and lower uart interfaces means?
You neednt worry about Upper UART and Lower UART communication, as you will be using only 3 cells.
This is daisy chain communication.

When there are more number of cells to be managed, multiple data acquisition ICs has to be used. All the cells will be connected in series, and multiple ICs has to be connected to those cells. Daisy chain communication will be used to communicate between the ICs .

Attached is a block diagram representation of the circuit.

How does the BMS know what voltage/current to regulate the battery charge/discharge?
Data acquisition IC is a slave device. The microcontroller is the brain of the BMS. Microcontroller gets the measured voltage / current values and you can code the controller when to stop charging / discharging and when to limit the output current or disconnect the cells from the load.

These threshold values depends on the type of the Li Ion cells being used.

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