devonsc said:a.) Read current load current drawn from the load, which is a 12V DC motor.
b.) Present the approximate life-time of the battery at that level with that drawn current.
c.) Present the battery level in terms of percentage.
:?: Would like to ask, how do I tap the current drawn by the load and feed it to a Current-to-Voltage Converter before applying it to the PIC microcontroller?At which point shall I tap the current point from? Advice needed.
:?: The battery level in terms of percentage, if I were to come out with a look-up table for reference before writing a programme for the PIC microcontroller, do I consider having a table with reference to the voltage or with reference to the current? Reference Figure 1.Advice needed.
For best accuracy I would suggest you plot a number of discharge curves for different loads, and implement them as a number of lookup tables in the PIC - you can measure the present load current, and battery voltage, then call the table that most closely matches the current.
devonsc said:For best accuracy I would suggest you plot a number of discharge curves for different loads, and implement them as a number of lookup tables in the PIC - you can measure the present load current, and battery voltage, then call the table that most closely matches the current.
Is this what you mean?
I should use different loads, such as:
a.) 100 ohm resistor
b.) 1 kohm resistor
c.) 10 kohm resistor
Then, using each of these loads and leave it connected to the battery for a period of time, say 5 minutes and jot down the readings for the voltage as it varies with time. From there, I plot the graph with the following axis (Figure: discharge curve)
Then, when I apply the real load, say, a motor that draws 0.6A, I will call the table that draws 0.5C (0.65A) since it is the closest? Please correct me if I'm wrong :cry:
Rather than do it manually it would be easier if you have a data logger, or multi-meters with RS232 interfaces - but manually is fine, it just takes more effort.
devonsc said:By the way, would like to ask for your opinion about the duration. Is it true that I might need to run that specific load for up to hours in order to see the changes in battery voltage level?Mind to correct me if I'm wrong?
Oznog said:Half the battery meter systems out there, developed commercially, don't work well.
The PIC's ADC state can do it if you use 2% precision resistors, use an accurate Vref, and calibrate the result versus a known voltage source.
The voltage at various states of charge is well known and easy to find on the internet, EXCEPT that it's strongly temp dependent.
devonsc said:Hi there, as mentioned earlier, I'm working on the Monitoring Portion of the battery. Currently learning up the PIC microcontroller which I will be using. I would like to ask regarding the following matters. Can anyone explain regarding the use of the following?
a.) RTCC (Real Time Clock Counter)
b.) WDT (Watch Dog Timer)
c.) Brown-out Detection
For (a) and (b), what are the differences besides the rate?
But briefly:
RTCC - an internal counter/timer, can be used from internal or external clocks.
WDT - a crude internal RC timer, of very low accuracy, if the WDT is enable it will reset the PIC as it times out. Your code should include CLRWDT instructions accordingly to prevent this. Used to reset your PIC if it gets locked in an endless loop (assuming you don't have a CLRWDT instruction in the loop).
Brown out detction - sets the voltage level that the PIC resets at, so if the power supply drops below a certain level the PIC will reset.
Used to reset your PIC if it gets locked in an endless loop (assuming you don't have a CLRWDT instruction in the loop).
devonsc said:By the way, do you mind explaining the purpose of including multiple NOP continuosly in a specific programme? I found a programme where it has multiple NOP being used continuosly in a sequence. Thanks...
devonsc said:Thanks for your explanation regarding NOP.
Would like to ask you about the using the PWM from my PIC microcontroller to control my boost DC/DC Converter. You mention before about adjusting the duty cycle of the PWM to avoid overcharge of the 12V battery. Initially, I was thinking to step-up the voltage to a level to 15V from 7.5V. Instead of stepping it up with a duty ratio of 50%, can I just step the voltage level of 7.5V to 13.5V to avoid overcharge? What are the consequences that I might face if I were to do this?
Yes, you can step it up as you like, it's up to you what value you choose. As I suggested before, you should look at the PICKit1 details, it generates 13V off a 5V USB supply, using the PIC A2D for feedback regulation.
devonsc said:Thanks for your explanation regarding NOP.
Would like to ask you about the using the PWM from my PIC microcontroller to control my boost DC/DC Converter. You mention before about adjusting the duty cycle of the PWM to avoid overcharge of the 12V battery. Initially, I was thinking to step-up the voltage to a level to 15V from 7.5V. Instead of stepping it up with a duty ratio of 50%, can I just step the voltage level of 7.5V to 13.5V to avoid overcharge? What are the consequences that I might face if I were to do this?
Thanks in advance.
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