Saving data at a specific time that is determined by an event.

[JoeR_87]

Hey all,

I am setting up a battery characterization test in which I use a power supply and an electronic load to charge and discharge a battery. I am trying to get the program to continuously calculate the state of charge (SOC) of the battery. The program starts at time t=0 in charging mode, at some unknown time t=x the current into the battery drops below a set limit and the battery starts to dicharge. In order to calculate the SOC of the battery during discharge I need to know it's SOC just before the system switched from charging to discharging.

So my question is this:

Is there some technique I could use that would save the SOC data just before the system switched and the time at which the the switching event happened, so I can use that information during the discharge cycle for my SOC calculations?

Thanks,
Joe

[code-lux]

Hi Joe

What exactly is the step where you are stuck? I guess you start charging and calculate the SOC and put the results in an array. Once the current is < than the limmit you save the array with "Write To Spreadsheet File VI".

Regards

[RTSLVU]

Having done similar tests I would say the three basic states of charge would be:

1. Bulk: A constant current charge mode that ends when the battery voltage reaches the Equalize charge voltage
2. Equalize: A constant voltage charge mode at the battery's rated charge voltage that ends when charge current drops below 500mA
3. Float: A constant voltage charge mode at the battery's rated float voltage.

Now a battery is not fully charged when the Float stage starts but is usually 90-95% full capacity.

To do it properly you need to keep track of the amp hours discharged and you should recharge to at least 100% better %110 or more.

If you are using a state machine it should be simple to pass SOC values from the charge to discharge state using a shift register.