Adding Blinking LED to Low Battery Circuit

I'm thinking of designing a PCB based on this low battery indicator circuit:

It hooks up to your battery of choice and has a green and red LED, and uses a trimmer pot to adjust at what voltage want the red LED to turn on and the green off. I want to add a function where the red LED will start blinking when the battery life is extra low, or right about to die. If I can't make the existing red LED blink, i'm open to adding a third LED (a blinking one), and possibly having to add another pot to specify its voltage. If I were using a 7.4v battery pack, this would make the new setup: Green - 6.5v-8.4v; Red - 6.3v-6.4v; Blinking Red - 6.2v. The first two settings can be set with the existing potentiometer, I just need to add the third setting. Thanks!

• you want to drain the battery faster once it starts to run low? Dec 30, 2017 at 19:47
• Who is this blinking Red for? and when is it not useful? Perhaps a better solution is needed such as battery cutoff. Dec 30, 2017 at 20:08
• The battery will cut off at 6.1-6.2v by use of the protection circuitry. If someone is using a device running on batteries, then the blinking red will let them know they have that much time to finish what they were doing on the device. So green means they are fine, red means get to a stopping point, and blinking red means the device is about to die. Perhaps I don't understand the question? Dec 30, 2017 at 20:22
• The whole thing can be done for about $10\:\mu\textrm{W}$ overhead. Of course, the LED power would swamp this. Even with $2\:\textrm{mA}$ high efficiency LEDs, that is $4\:\textrm{mW}$, or 400 times as much. So I guess there's no real point in looking for a low power circuit. Since you want blinking, I'd probably start with a voltage to frequency converter concept and enable the blinking directly when the frequency is slower than some limit. If faster, use an added circuit that overrides the blinking. If still faster, override that (shutting it off) while now driving the green.
– jonk
Dec 30, 2017 at 21:28
• Of course, a single, very cheap MCU could do all of this with an ADC and some I/O. On the order of $\mu\textrm{W}$ of overhead power (added to the LED power), using sleep modes which still keep the I/O active but only periodically wake up to do an ADC measurement and adjust things. But that entrains a toolset, programming skills, etc.
– jonk
Dec 30, 2017 at 21:33