Capstone Project Virtual Battery Help

[capstonestudent]

Hi guys

I am a 4th year electrical engineering student at an accredited university in Canada

My capstone project is called the virtual battery and the proof of concept is vehicle to grid technology.

We are trying to control a small lithium ion battery (12.8V dc) using a PLC.

Our school has supplied us with a working siemens PLC the main module is
CPU 1214C DC/DC/DC
6ES7 214-1AG31-0XB0

In order for our project to work it is vital that we know the charge of the battery and the power consumed from the battery

My question is what is the best way to finding the charge on the battery and the power consumed by the battery.

Note we need to be able to log the charge and the power consumed as much as possible and our remaining budget is ~300$

Many Thanks

 

[Ken Roach]

what is the best way to finding the charge on the battery and the power consumed by the battery.

In short, you need to learn what kind of technologies are used in Battery Management Systems to monitor voltage and current and predict state of charge.

The first thing you'll need is an accurate shunt and a millivolt input module, or another kind of DC current measurement device.

And you'll need a signal conditioner to get your main voltages down to the usual 0-10V DC analog input range.

 

[AustralIan]

You might have to sweet talk your local wago rep to get under 300, but try their 750 series and hook it up to your S7-1200

750-475 will do 1A DC current measurement. They have a 5A version as well.
You should be able to find a 0...30VDC input card also. Then you just need either a modbus TCP coupler or a Profinet coupler.

Bodging a system together with some resistors and op amps and the like is more for the embedded systems industry than the PLC industry where you try to use off the shelf products as much as possible. Some times it works out a nicer solution just to pop a resistor or a diode in somewhere, especially when you are trying to keep to a particular brand, and their 'solution' costs half your yearly salary.