A 12volt automatic rechargeable battery with 75Ah with level indicator

[Amondesire]

Please i am asked to design and construct a A 12volt automatic rechargeable battery with 75Ah with level indicator. what Criteria im i to look out for?

and im ask to also calculate the parameters used for the design. please im stocked i really need help.

Thanks

 

[badea]

for given battery, your charger will be 13.8v, 7.5A
you can build charger by two methods:
1-switching mode power supply (hardest and complicated)
2-iron transformer (simple and less problems)

for charging stopping you can use simple comparator (ex.741) with small relay to cut off main power
for indicating voltage of battery you can use any dc voltmeter or any chip provide a logic output that shows a dc voltage on battery (ex.lm3914 drives leds) which gives you an acceptable feedback about battery voltage.

regards.

 

[Amondesire]

Thanks Man your too much...it will really help me alot....can i simulate this on multisim?

 

[badea]

Thanks Man your too much...it will really help me alot....can i simulate this on multisim?

Sorry to tell you that you can't simulate a real battery in simulation software's (batteris did'nt get low ) )
But you can simulate a comparator and lm3914, it's easy.

 

[shahbaz.ele]

can we read the LM3914 output with uC pins directly.

Is someone tried LM3914 for 12Volts battery.
Please share the circuit.

 

[srizbf]

Read the o/p at pins (10/11/...18) of lm3914 by connecting a 470 ohm resistor to 5v supply(instaed of LED).

 

[badea]

can we read the LM3914 output with uC pins directly.

Is someone tried LM3914 for 12Volts battery.
Please share the circuit.

if you have a uC in your project, so use it's internal ADC instead of LM3914.
you should build only a voltage divider (13.8v==>5v) for battery and measures it's voltage

 

[shahbaz.ele]

Thanks srizbf & badea
No actually, I want to read the status on FPGA.
just write uC for information.
so \i have to pull-up with 3.3v for FPGA pins read.

 

[badea]

Thanks srizbf & badea
No actually, I want to read the status on FPGA.
just write uC for information.
so \i have to pull-up with 3.3v for FPGA pins read.

For Accurate measurements i suggest to use ADC (like ADC0804) instead LM3914, it gives you 8Bit Resolution and just you need to convert from 5v logic to 3.3v one, you can do it by general purpose npn transistor with suitable resistors.