What battery can I use?

Discussion in 'The Projects Forum' started by Enio Freitas, Nov 6, 2007.

  1. Enio Freitas

    Thread Starter New Member

    Oct 7, 2007
    7
    0
    Hi,

    I have a doubt, i'm doing a project, in this project I have a PIC16f877A, this pic needs of 250mA of current. In this project I want to put a battery for to supply the pic. Can I use the CR2032, I would use 2 batterys of 3 Volts in series giving me 6 Volts using the LM7805 for to have 5V for the PIC? This battery can be reloaded? If not this, which battery can I use?
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    3 volt batteries? If they are like lithium coin cells, they do not have the current capability for the 250 ma load. The 7805 regulator needs more voltage to operate, in any case. It needs about 2 more volts in than it puts out.

    Assuming you wish to have the PIC operate for some length of time, using a larger capacity and voltage battery makes sense. 12 volt 7 amp-hour batteries are easy to find and most are reasonably priced. You will need to heat sink the 7805, but such a battery will run the PIC for hours, and may be recharged with a lighter adapter in a car.
     
  3. Enio Freitas

    Thread Starter New Member

    Oct 7, 2007
    7
    0
    The batteries of 12V 7A are very big, I would like to have a little battery for to put in a module. I'm doing a module with pic for to be reloaded by the reverse lamp of the car.
    Do you know a little battery for to supply the pic in this module. Can I use that 9V battery for this?
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    A 9 volt battery is only rated for a 15 ma draw. The usable lifetime would be in seconds. If the PIC needs to be active continuously, you may need to make a connection to the car's battery. The alternative is to get some NICAD batteries to sum to above 7 volts, but arranging a charger for them would be a challenge.
     
  5. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    You can get AA sized Lithium Thionyl Chloride batteries (3.6V, 2Ah, 1A continuous current) - two of them in series would serve you. Will they also be too large?
     
  6. Enio Freitas

    Thread Starter New Member

    Oct 7, 2007
    7
    0
    This AA sized Lithium battery will give me 1A continuos current, I did'nt understand if my pic will work time a lot with this load. Do you know how many load has that 9Volts Battery?
     
  7. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    The Ah rating of a battery is "amp-hours." This is the number of hours the battery will last at a given current draw. For example, the AA sized Lithium Thionyl Chloride batteries are rated at 2Ah. If your pic draws 250 milliAmps, the batteries will last about eight hours.

    The 1A rating I cited is the maximum amperage those batteries can safely source. Actual current draw from a battery depends on the load. If your pic requires a quarter Amp, then it will draw a quarter Amp regardless of what the battery can safely supply. (This is why the CR2032 would be a bad choice - it can only source 2 milliAmps continuous current safely.)
     
  8. Enio Freitas

    Thread Starter New Member

    Oct 7, 2007
    7
    0
    What is your opinion about the use for the 9 Volts battery for this aplication, I am limited because of the size of the module.
    The size of the module that I have is this in the picture in attachment, what do you think that I shall use?
    Thanks for attention.
     
  9. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    What 9V battery? There are many 9V batteries to choose from. If you can find one that will safely source the current you need for the time you want, then it will work. If not, It wont.

    I wish you good luck in your online battery searching. Let us know what you find!
     
Loading...