/diy/ - Do It Yourself

>>1605727
Take a look at discharge curves.

After 0.9V the battery is basically spent.

Enter some data points and approximate a function.
Even a linear one isn't that inaccurate:
https://www.wolframalpha.com/input/?i=linear+fit+%7B0,+1.6%7D,+%7B0.2,+1.3%7D,+%7B0.4,+1.2%7D,+%7B0.6,+1.125%7D,+%7B0.8,+1.075%7D,+%7B1,+1.025%7D,+%7B1.1,1%7D,+%7B1.2,+0.9%7D

The more you increase the polynomial degree the better it gets:
https://www.wolframalpha.com/input/?i=cubic+fit+%7B0,+1.6%7D,+%7B0.2,+1.3%7D,+%7B0.4,+1.2%7D,+%7B0.6,+1.125%7D,+%7B0.8,+1.075%7D,+%7B1,+1.025%7D,+%7B1.1,1%7D,+%7B1.2,+0.9%7D

https://www.wolframalpha.com/input/?i=quintic+fit+%7B0,+1.6%7D,+%7B0.2,+1.3%7D,+%7B0.4,+1.2%7D,+%7B0.6,+1.125%7D,+%7B0.8,+1.075%7D,+%7B1,+1.025%7D,+%7B1.1,1%7D,+%7B1.2,+0.9%7D