Computed Battery formula needed

I would like a computed formula to calculate percentage of remaining battery life. Lithium batteries are not linear so their discharge rate is not a simple formula. I don't seem to be smart enough to use examples to make this work, or any computed formula for that matter. On phones and higher end devices their is a circuit with intelligence that does this more accurately.

Any ideas or help would be greatly appreciated.

Pseudo:
If battery >=4.20 then 100% else >=4.03 then 75% else >=3.86 ...etc
With a popup(alert) on the the web interface for equal to and below 3.67

4.20v = 100%
4.03v = 76%
3.86v = 52%
3.83v = 42%
3.79v = 30%
3.70v = 11%
3.6?v = 0%

Hello Friend.
It depends a lot on external factors but maybe this web can help you understand
http://bateriasdelitio.net/?p=80

Not pretty, and not even sure if totally functional yet. But here is my solution to Battery percentage Levels. Five separate computed Attributes. Are there any suggestions for a better way.

75-100Percent

Battery Level

if (battery <=4.50 && battery >=4.00) { 100; } else {null;}```

50Percent

Battery Level

if (battery <=3.99 && battery >=3.83) { 50; } else {null;}```

25Percent

Battery Level

if (battery <=3.79 && battery >=3.73) { 25; } else {null;}```

10Percent

Battery Level

if (battery <=3.72 && battery >=3.67) { 10; } else {null;}```

solow

Alarm

if (battery <=4.50 && battery >=3.65) { null; }  else {'Help';}```

Previous post does not work. But it turn's out you can use nested if-else statements. Will let you know if it works as expected.

This does work:

Description: batteryPercentage

Attribute: BatteryLevel

if (battery <=4.60 && battery >=4.03) { 100; } else
if (battery <=4.03 && battery >=3.86) { 76; } else
if (battery <=3.86 && battery >=3.83) { 52; } else
if (battery <=3.83 && battery >=3.79) { 42; } else
if (battery <=3.79 && battery >=3.70) { 30; } else
if (battery <=3.70 && battery >=3.6) { 10; } else {null;}

Type: Number

I use this to send alarm:

Description: LowBattery

Attribute: Alarm

if (battery <=4.50 && battery >=3.65) { null; } else {'Help your killing me';}

Type: String

nice thank you, it seems to work sometimes i will try with my ruptela trace5

Hello, this command worked for me

battery ? battery <= 3.6 ? 0 : battery >= 4.2 ? 100 :math:round(((battery - 3.6) / (4.2 - 3.6)) * 100) : null