Is there a reason why this does not happen on mobile phone or tablet, what do they use ?

The message: "your battery needs charging" then the device will automatically shutoff when battery voltage is at a critical level if you don't put it on the charger.
Seriously though I'm wondering if you could use that battery monitoring app to do some type of switching.
Another way is to use a comparator (either digital or analog) circuit monitoring the battery then switching a mosfet to power the device ON or OFF.
A single cell Lipo battery is normally charged to 4.2 volts. At that voltage the circuit would power the device ON and shut the device OFF at lets say 3 volts if required.

 

When the voltage on a charging Lithium battery reaches 4.2V it is still charging at about 75% of a full charge, The charging IC senses a full charge when the charging current drops to about 1/20th its aH rating which will not happen if something turns on and uses the charging current.

 

When the voltage on a charging Lithium battery reaches 4.2V it is still charging at about 75% of a full charge

That depends on the current during charging. A slow charge at below .18C the battery is fully charged at 4.2 volts for all practical purposes.

 

It seems when the battery voltage drops below 2.5V, the charge current becomes 10mA, but part of this is getting consumed by my circuit. I think one of the microcontrollers is powering up and consuming the power.

Therefore I aim to place a load switch between charger+battery and the rest of the circuit. This way they enable on load switch can be all ways pulled up, but if the battery does very low user can toggle that pin to low.

 

You need to prevent the battery from dropping below 3 volts to stay out of that 10ma conditioner phase. Wouldn't you want that to be automatic just like in a phone or laptop?

 

You need to prevent the battery from dropping below 3 volts to stay out of that 10ma conditioner phase. Wouldn't you want that to be automatic just like in a phone or laptop?

Yes I would would prefer that . At the moment, I am using an ADC on a microcontroller and GSM module that once the battery drops below 5% it goes into sleep mode for 20mins, and then recheck the battery level. If level was to increase to 10%, then the restarts the system beings.

But for any given reason if user chooses not to charge the device again, then in process in theory will drain the battery out as its doing a small check every 20mins. There is been an incident, where a device was not placed back power for several months.

What I am thinking ,maybe this ADC process can be modified to, that if battery voltage drops below 5%, it could preform a check for few hours, but if after few hours there is NO increase to 10% then we can just force the device into deep sleep, till the user presses RST or POWER ON. This way with deep sleep there is no power consumption

 

To do it right, you need to use a Coulomb counter IC. Voltage is not necessarily a good indicator of SoC, and since you can't count on the user to charge the battery, as some point the battery needs to turn off (through its protection circuit, possibly) until it is charged forcing the user to do so and protecting the battery.

 

Is this the same as a Li-ion gauge? Can you suggest a part?

 

Maxim has a very good reputation in this area.

https://datasheets.maximintegrated.com/en/ds/MAX17330.pdf

 

So this seems to be a charge, protection and gauge in one package.

The only issue is that our li-ion charges have already been purchased, and we would like to still use them if we can solve this issue with MOSFET?