Battery Status Indicators in Devices

[FrontlineWarrior]

In devices like portable cd players, there is usually an indicator of how much battery is left. Like 4 bars for a new battery, 3 bars, then 2, then 1, then none when the battery is all gone, etc.

What do these bars represent? I have two theories, and maybe someone can confirm either one or come up with another explanation.

Theory 1: The indicator shows how much RELATIVE charge is in the battery. So it somehow knows how much charge this PARTICULAR battery has WHEN IT IS FULL, and divides that from the charge that it currently reads. So for example, if a 1800 mah battery has 900 mah's left, then the indicator would show 2 out of 4 bars.

Theory 2: The indicator shows how much TOTAL charge is in the battery. The bars represent a certain amount of charge, but it is made so that it more or less is configured for an average battery. So for example, every bar on the indicator always represents 200 mah of charge. Given two batteries, of 800 mah and 1600 mah, and supposing that the former is full, and the latter is half full, in both situations the indicator will display 4 bars.

Which one of these is true? I ask because I'm going to start using rechargeables, and they have different storage capacities, and I would like to know how to interpret how much juice is left in them while using a portable device.

Thanks

 

[Zugzwang152]

best bet is to replace as soon as it hits 1 bar.

 

[brtspears2]

I believe they work on how much acutal voltage is still being produced by the batteries. More volts = more bars.

 

[Scootin159]

My guess is they read the incoming voltage & take an educated guess off of that.

mAh is milli-amps * hours, it's not something that can be read easily. Also as far as I know these devices don't keep track of when you change the battery to know how many mah it has, or do they know the charge when it is put in there.