Does V or I remain constant in a discharging battery?

In summary, as a battery discharges, the voltage will generally stay the same until it reaches a point where it can no longer supply the required current for the load. At this point, the voltage will begin to decrease. The discharge characteristic of a battery varies depending on its type, capacity, age, and temperature. Alkaline batteries, for example, will lose about 15% of their voltage after using 50% of their capacity. In order to maintain a constant amount of work over the course of its discharge, a battery would require some form of regulation circuit to provide a lower voltage than its raw voltage output.
In a discharging battery, do current and voltage decrease over time? if so how does the battery accomplish the same amount of work over the course of its discharge with a lesser voltage or current?

In a discharging battery, do current and voltage decrease over time? if so how does the battery accomplish the same amount of work over the course of its discharge with a lesser voltage or current?
Voltage stays more or less the same until the point where the battery is no longer able to supply the current required by the load, at which time the voltage starts to decrease.

I suspect you can find full expositions about all that using Google.

In a discharging battery, do current and voltage decrease over time? if so how does the battery accomplish the same amount of work over the course of its discharge with a lesser voltage or current?

Note that at higher output currents, the internal battery resistance is more of a factor. You can find discharge curves like the one below by looking at the battery's datasheet...

http://www.steveduncan.net/assets/images/mfg_curves.jpg

The discharge characteristic of batteries varies according to the type of battery, its capacity (Amp-hr rating) , the age of the battery. temperature. The graph in @berkeman post looks like one for a Lead Acid car storage battery. Their voltage typically drops to 90% of initial voltage at full discharge. In fact the terminal voltage is used as a measure of the state of charge of the battery. Mercury and silver batteries will maintain the same voltage until they reach their capacity. The voltage of alkaline batteries loose drop about 15% after using 50 % of their capacity.and about 35% at full discharge. And the normal dry cell Zn-C battery voltage drops 50% at 80% discharge.

So the energy delivered with time drops with discharge for many batteries.

berkeman
Just to make it clear, the actual current from the battery depends on the circuit it is connected to more than the battery characteristics.

In a discharging battery, do current and voltage decrease over time? if so how does the battery accomplish the same amount of work over the course of its discharge with a lesser voltage or current?

Constant power load circuits are possible, but unusual. In most cases, the battery will not supply constant power during discharge.

On second thought, I use a nearly constant power load every day. It is a 12v refrigeration system. The lower the voltage, the longer the compressor runs each cycle. Averaged over a day, the power is nearly constant.

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In a discharging battery, do current and voltage decrease over time? if so how does the battery accomplish the same amount of work over the course of its discharge with a lesser voltage or current?
It helps to get things the right way round in this sort of problem. Assuming the load is the same value all the time (a constant resistance), it will be the Volts that determine the Current that will flow (cause and effect) and Power delivered will be V2/Rload.
As a battery discharges, the (unloaded) Volts will drop towards the end and the internal resistance could also be effected. If it increases, the terminal volts of the battery under load can fall faster than the unloaded volts would. So a battery cannot be expected to deliver ("accomplish") the same amount of power over its discharge period without some help. If you want to achieve this, you need to have some sort of regulation circuit which will supply a lower voltage than the raw volts from the battery (as per a normal voltage regulator).

1. Does the voltage (V) remain constant in a discharging battery?

No, the voltage in a discharging battery decreases as the battery's energy is being used up. This is due to the decrease in the chemical potential energy of the battery's components.

2. Does the current (I) remain constant in a discharging battery?

No, the current in a discharging battery also decreases as the battery's voltage drops. This is because the resistance of the battery's components remain the same, but the voltage is decreasing, resulting in a lower current.

3. Why does the voltage decrease in a discharging battery?

The voltage decreases in a discharging battery because the chemical reactions that produce the battery's energy are not able to sustain a constant voltage as the battery's energy is being used up. This results in a decrease in the battery's voltage over time.

4. How does the internal resistance of a battery affect the voltage and current during discharge?

The internal resistance of a battery can cause the voltage to drop more quickly during discharge, as it creates a larger voltage drop across the battery's components. However, it also limits the maximum current that can be drawn from the battery, resulting in a decrease in current.

5. Is the voltage or current more important in determining the battery's state of charge?

The voltage of a battery is typically more important in determining its state of charge, as it is a direct measure of the battery's energy level. However, the current can also provide valuable information, as a sudden decrease in current can indicate a low battery or other issues. Both voltage and current should be monitored for accurate determination of a battery's state of charge.

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