Is it a matter of how strong the current is coming out of the battery? Is less power in the battery meaning “free space” in the battery and that’s what is measured?
In: Technology
Depends on the amount of fucks the manufacturer gives. Some just measure voltage, since a fully charged battery will have a specific voltage and will gradually decrease to another well known “empty” value. The scale is not linear though, while this works okay on old batteries, li-ion chemistry has the middle half of its capacity at almost the same voltage. Going by voltage also brings current into the equation, a battery actively supplying more current at the moment will experience a sag in the voltage.
The proper way is a coulomb counter/fuel gauge chip. It does what it says on the tin, measures the total amount of energy going in and out of the battery by performing continuous current measurements. The input to output energy ratio will be something around 90% for lithium ion, and not subject to nearly as many annoying inaccuracies as voltage measurement.
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