18F452 project need run/charge from 12 gel cel

Thread Starter

ve3sjk

Joined Jul 27, 2010
1
I have a project designed using a PIC18F452 the needs 5 volts @ 500ma and 12 volts @ 500 Ma. I would like to desing a circuit where the unit can be plugged in to charge a gel cel 12 volt battery and then run off that battery untill discharged at which time the unit will notify the user to recharge battery.
What is the simplest circuit to use to charge a 12 Gel Cel battery and monitor the voltage hopefully implementing the exisiting PIC18F in the project.
I already have a 1 sec precision timing loop in my software and available Comparator/Anaogue inputs. So i believe i can use an Analogue input in my loop to monitor the battery voltage for low shutdown. I am having trouble finding or designing a suitable simple circuit for the charging.
I need to unit to operate for at least 10 hours on battery. It's not necessary for the unit to run off the mains power at the same time the user will charge it then use it until discharged and then recharge.
Any help would be appreciated
Thnks
 
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