0
\$\begingroup\$

I am trying to build a portable RGB LED display that runs off a Lithium Ion battery. After a few days of research, I understand the importance of using a dedicated IC to handle charging the battery, but I am having trouble with the over discharge aspect.

If I want to monitor the voltage of the battery, I can use the ADC on the micro-controller, or better yet, find a charging IC that incorporates an over discharge feature like the DW01-P.

But if I disconnect the main load (the RGB LED) when the battery voltage gets too low, won't the IC or micro-controller still need power from the battery to run (i.e to keep the LED disconnected)? And wouldn't that cause the battery to further discharge and damage it?

\$\endgroup\$
0
\$\begingroup\$

Some such circuits DO keep slowly discharging the 'protecte' cell.

It is possible to design circuits which "self disable" so that they draw no current once they have performed their function. [I designed portable solar lights which did this. The circuit was re-enabled by a feed from the (solar) charging circuit.

Current discharge can be extremely low if desired while still retaining a testing function. eg at say 1 uA drain you lose 1 mAh every 1000 hours or about 40 days.
Custom monitoring ICs could be implemented with drains of well under 1 uA.

You could use eg a zener diode in the monitoring circuit so that when the voltage falls below about Vzener (essentially) no current is drawn. As zeners are of low precision this could be used to disable the higher precision monitor.

| improve this answer | |
\$\endgroup\$
  • \$\begingroup\$ That makes sense. Discharging a few microamps would take a very long time to damage the battery. As for the zener diode, would that be placed in series with one of the power rails heading to the load? I.e if the reverse voltage is not exceeded on the rail the zener acts as an open circuit? \$\endgroup\$ – Sal M Oct 30 '19 at 12:55

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.