I bought a data acquistion system for my experiment to record battery voltage readings. The problem so far is that the charging output voltage curves I have are distorted. Can any one tell me how the battery charging curve should be looked like in real world? Is it be very smooth curve keep increasing all the time to MAX voltage or it varies when you look at it in a small scale? And how to set the sampling rate if I doing voltage and temperature recording? 100Hz? or can be much less?
I suspect the true battery voltage curve will be very smooth, but if you are monitoring it while it is being charged, then it really depends on the charging circuit. Chargers have no need to put out smooth DC, so you may be getting anything from half-wave rectified mains frequency to some sort of PWM. If this is a real issue, you might consider some sort of switching circuit to remove the charger during the reading.
For any sort of acquisition system, the sample rate needs to be twice the highest signal frequency. For true battery voltage (disconnected from charger) the frequency is 0 (DC) so you can sample as slow as you like. If you will be switching out the charger to take a reading, just decide how often you need to know the voltage... I'd guess that 1 Hz would be fast enough, and once per minute might not even be a problem when charging at any sort of reasonable rate.
But if you are trying to read the voltage waveform with the charger running, then you may need a fairly high sample rate if you expect to follow pulse edges.
Best regards,
Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis
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