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12vdc BATTERY LEVEL MONITOR

Mike Barnacastle
Prodigy 10 points
Other Parts Discussed in Thread: TL331, TLV3401, TLV431, TL431

Hello all:

Does TI offer a simple battery voltage level indicator for a sealed lead acid battery, 12VDC?

We use an off the shelf UB1280 8AH battery in our 'to go kit' sat radio cases, and my source that we obtained a simple battery  monitor / level board from has "gone away"

Basically, I need to know when the battery gets down to 11.0VDC,  a low battery level LED can either light up,  solid or blink. Just a simple visually indicator for the operator to know that battery level has reached a critical low level.

 

Thanks for any advise or recomendations that you might have.

 

Mike B

MJ Sales, inc.

www.mcom1.com

  • 0
    TI__Guru**** 150910 points

    It sounds like you want a comparator circuit that monitors the battery voltage and drives an LED.  For the comparator, the TL331 is the most cost effective solution.  For lower operating current (to prolong your battery life), I recommend the TLV3401.  Either of these comparators run off of 12V and have open-collector outputs.  The comparator output would then drive a FET to turn on or off your LED.

    A voltage reference is also needed for this solution.  I suggest the TLV431.

  • 0 in reply to Chris Glaser
    Prodigy 10 points

    I like TLV431. How can I do the circuit to monitor the battery voltage?  When the battery gain to the require voltage, the led turn on or off.

    Luis

  • 0 in reply to Luis Andreu
    TI__Guru**** 150910 points

    You could use the TLV431, as the TL431 is used in figure 26 of its datasheet: http://focus.ti.com/lit/ds/symlink/tl431.pdf 

    What I was referring to in my first post was simply using a voltage reference (TLV431) and a comparator to directly drive an LED.  The TLV431 would be used with any comparator.  The comparator output would drive the LED through a resistor, pulled up to some voltage.  The battery would power the TLV431 through a resistor to generate a voltage reference.  If you wanted the LED on when the battery was low, then the TLV431 would be connected to the inverting input of the comparator, while the battery voltage would be connected to the positive input through a voltage divider.  Thus, when the battery is charged enough, the positive input is greater than the inverting input and the comparator output goes high impedance.  Thus, no current flows through the LED.

    If you wanted the LED to be on when the battery was charged enough, you would switch which input the TLV431 and the battery were connected to.  Then, when the battery voltage is high enough the inverting input would be higher and the comparator output would go low.  The comparator would then sink current through the LED, turning it on.