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I was curious as to what happens to the remaining amperage after the value needed has been dissipated from a battery. If I want 1 ampere from my battery at 4.2 volts and my battery is able to supply more than 1 ampere, what happens to the remaining 2, 3, etc amperes extra? Does it get wasted as heat or is it just that the output is just "shrinked" by a resistor or some technique to limit its flow? Is it an efficient option to limit the current?

JRE
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imran muhd
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    1 amp for how long? Amp is an instantaneous value. Batteries hold Wh or mWh, sometimes labelled as Ah or mAh as they claim the voltage is fixed. The power not used is left in the battery for next time. – Puffafish Nov 07 '23 at 16:21
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    A battery used as a voltage source would be very similar to a power supply. Please read up here and see if that clarifies any doubts: https://electronics.stackexchange.com/questions/34745/choosing-power-supply-how-to-get-the-voltage-and-current-ratings – winny Nov 07 '23 at 16:29
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    What if you don't take any current? Where does that 4 amp current flow? If you held the battery in your hand, would 4 amps be flowing through your hand? Do you understand ohm's law? – Andy aka Nov 07 '23 at 16:31

1 Answers1

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If you're asking about what happens to the extra current a battery is capable of supplying, you're thinking about it wrong. If a battery can supply 10 A and you put a load on it that draws 1 A, the other 9 A doesn't go anywhere, the current is limited by the load itself. That's like asking if your car can go 120 mph but you only drive 55 mph (I can't) where does the other 65 mph go?

There's a difference between amps (A) and amp-hours (Ah). The amount of current a battery can supply to a load instantaneously would be amps, the product of the current a battery can supply and time is amp-hours. If a battery is rated for 1 Ah and you draw 250 mA from it for 2 hours you will have used 500 mAh and the battery will have 500 mAh left.

The rate that you can draw that current is limited by the battery construction. You can't take a typical 1 Ah battery and draw 1000 A from it for 1/1000th of an hour, the internal resistance of the battery would limit the current, and it would probably overheat as you would be pretty much shorting it out. A battery will have a specification for the rate at which you can draw current to get the rated Ah out of it. For example a battery may be rated at 6 V, 10 Ah, with a maximum continous discharge current of 500 mA, so you could run it for 10 Ah / 0.5 A = 20 hours.

GodJihyo
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