# How much current does a battery store?

I have always been confused when it came to how much charge does a battery charge. Let's say, a phone battery: It says 1900 mAh @3.7 v. Now i know it goes up to 4.2v, but those 1900 mAh are available in the 2.5v ( cut off voltage i think) - 4.2v area or the 1900mAh are available in the entire 0v-4.2v, meaning that some of the battery s energy remains unused, right? Let's say that i want to power a 1A led from this specific battery, it will be on for about 2 hours? Also, on car batteries there are writings like 12v, 55Ah, 550A. Does this mean that this specific battery can output 55Ah for 10 hours?

I am sorry if the question sounds dumb, but i am just trying to learn...

• You are confusing energy with power. Do a search here and there are several questions about it. Regarding you lithium batteries, the capacity is rated between two voltages, not 4.2 down to 0 but 4.2 down to about 3 V. Check the datasheet for the battery in question m, it's specified for sure. Apr 8 '17 at 20:11
• For the lead-acid battery, 55Ah would mean 1A for 55 hours. But lead acid batteries don't last so long if run flat, so it's best to assume only about half the rated capacity if you want a long life. The 550A is the maximum current that the battery can produce for just a few seconds - such as when starting a car. Apr 8 '17 at 21:07
• A battery does not store current. A battery rated in 'mAh' is storing milliampere-hours, i.e. it's storing electrical charge. Apr 8 '17 at 23:21