Battery Voltage for Resistor Calculations

[Scarecrow]

When you do your resistor equations do you use the typical battery voltage (3.7v/7.4v) or do you pull the voltage off of a fully charged battery? I know to pull the voltage off of the led with a bench power supply to be precise but wouldn't it throw your numbers off if your battery was fully charged to over 3.7v/7.4v? Just wondering. Thanks.

[Cire Yeldarb]

I always just use typical battery voltage

Not quite an expert however, so peak voltage could very well be the better way... but I usually see other people use typical voltage as well.

[Taki117]

It is better to go off of rated voltage as "Fully charged" Voltage isn't going to last very long and is only ever so slightly higher anyway.

[Scarecrow]

Thank you guys. I did some reading and found out why we use those numbers. I just didn't want to drive the dice too hard.

[Bark]

Generally, we also usually round-up when purchasing the resistors in stock here, rarely getting the EXACT resistor the calculations indicate. Perhaps I'm foolishly being indifferent, but I ASSUME the extra padding of numbers by the round-ups are good enough to cover any slight "over-voltage" of a fully charged battery.

[Forgetful Jedi Knight]

Bark essentially has it right, we use "averages" and "median" values for a reason, there is a bit of "play" factored into any values that are used. Between using the "average" values, and "rounding up" on the resistor values (due to what is mass produced), variances in various elements are "accounted" for.