mAh explained

[littlepigboy5]

Can somebody explain why voltage doesn't affect mAh?  If i have a phone, rated at whatever mAh and a battery back rated at let's say 10000 mAh, why does the amount of recharge cycles not depend on voltage at all?  why can this battery bank supply 10000 milliamps of current at 1 volt and 10000 milliamps of current at 5v without it changing how long it lasts?  (or maybe i have that wrong and somebody can explain what actually happens)

[Djole123]

mAh is a measure of how much energy a battery can store iirc.

 

Imagine this: You have a swimming pool.

The amount of liquid it can store is mAh, and the pump that fills that pool is your current.

[littlepigboy5]

Just now, Djole123 said:

mAh is a measure of how much energy a battery can store iirc.

 

Imagine this: You have a swimming pool.

The amount of liquid it can store is mAh, and the pump that fills that pool is your current.

I understand it at that level, i'm trying to really be able to understand, not in terms of a metaphor but how it actually works.  I know that amps are not dependant on volts just as volts are not dependant on amps, but if mah is the measure of amps a battery can supply in 1 hour, why does changing the voltage not change how quickly the battery depletes?

[Djole123]

1 minute ago, littlepigboy5 said:

I understand it at that level, i'm trying to really be able to understand, not in terms of a metaphor but how it actually works.  I know that amps are not dependant on volts just as volts are not dependant on amps, but if mah is the measure of amps a battery can supply in 1 hour, why does changing the voltage not change how quickly the battery depletes?

Great question. Will have to think about it.

[littlepigboy5]

Just now, Djole123 said:

Great question. Will have to think about it.

thanks

[Djole123]

12 minutes ago, littlepigboy5 said:

thanks

Ok. Let's go to that pool analogy from above.

You need to empty the swimming pool, and you have one tube which can supply, let's say, 1000mAh. You can have as many taps coming from that tube as you can (taps=amount of volts), but the tube will always operate at the same 1000mAh rate.

Correct me if I'm wrong.

[tomaatvk]

3 minutes ago, littlepigboy5 said:

I understand it at that level, i'm trying to really be able to understand, not in terms of a metaphor but how it actually works.  I know that amps are not dependant on volts just as volts are not dependant on amps, but if mah is the measure of amps a battery can supply in 1 hour, why does changing the voltage not change how quickly the battery depletes?

I'm not 100% sure I'm correct but I think it works in the following way:

If you discharge a battery by using it the electrons in the negative part of the battery flow though the circuit to the positive part of the battery. If you charge it they are forced back.

 

The current flowing through something (expressed in A/ampere) is just the ammount of electrons moving through something/second (6,241 506·10¹⁸ electrons/second=1A).

Lets say that in a fully charged battery there are 6,241 506·10¹⁸ electrons on the negative side that can move to the positive side in the form of current.

If you connect that battery to a circuit that draws 1A, all the 6,241 506·10¹⁸ electrons will be used after 1 second so you have 1As (ampere second).

If you connect that battery to a circuit that draws 0,1A, all the 6,241 506·10¹⁸ electrons will last 10 seconds. You will supply 0,1A for 10seconds so 0,1*10=1As (the same as above).

 

The same works with mAh although mAh indicates how many milliampere can be supplied for how many hours.

If you have a 3000mAh battery you can supply 3000mA for 1 hour (3000*1=3000mAh) or 1000mAh for 3 hours (1000*3=3000mAh) because that is how many electrons it stores and the lower the current is the longer it takes for them to all flow to the positive part of the battery.

 

(I know that electrons aren't really stored in the batteries but they are being freed through chemical reactions, however, I chose not to make it that complicated and in this explanation it has the same effect.)

[littlepigboy5]

2 minutes ago, Djole123 said:

Ok. Let's go to that pool analogy from above.

You need to empty the swimming pool, and you have one tube which can supply, let's say, 1000mAh. You can have as many taps coming from that tube as you can (taps=amount of volts), but the tube will always operate at the same 1000mAh rate.

Correct me if I'm wrong.

That's correct, and I understand it more thanks

 

2 minutes ago, tomaatvk said:

I'm not 100% sure I'm correct but I think it works in the following way:

If you discharge a battery by using it the electrons in the negative part of the battery flow though the circuit to the positive part of the battery. If you charge it they are forced back.

 

The current flowing through something (expressed in A/ampere) is just the ammount of electrons moving through something/second (6,241 506·10¹⁸ electrons/second=1A).

Lets say that in a fully charged battery there are 6,241 506·10¹⁸ electrons on the negative side that can move to the positive side in the form of current.

If you connect that battery to a circuit that draws 1A, all the 6,241 506·10¹⁸ electrons will be used after 1 second so you have 1As (ampere second).

If you connect that battery to a circuit that draws 0,1A, all the 6,241 506·10¹⁸ electrons will last 10 seconds. You will supply 0,1A for 10seconds so 0,1*10=1As (the same as above).

 

The same works with mAh although mAh indicates how many milliampere can be supplied for how many hours.

If you have a 3000mAh battery you can supply 3000mA for 1 hour (3000*1=3000mAh) or 1000mAh for 3 hours (1000*3=3000mAh) because that is how many electrons it stores and the lower the current is the longer it takes for them to all flow to the positive part of the battery.

 

(I know that electrons aren't really stored in the batteries but they are being freed through chemical reactions, however, I chose not to make it that complicated and in this explanation it has the same effect.)

This was very helpful, now I can visualize it, thanks

[ElZamo92]

I understand it quite well, but I find it hard to explain:

According to Ohm's law Current = Voltage / Resistance. Current is the amount of electric flow, voltage is the electric pressure that pushes current through a circuit, and resistance is a force that resists the flow of the current. The rate of discharge of a battery depends on the amount of the current it delivers to a circuit. Taking a glance at Ohm's law reveals that current is inversely proportional to resistance, so the higher the resistance, the lower the current will be, if voltage is constant. 

To make i simple. imagine the same pool mentioned by Djole123, but this time it is full, and you want to take a shower with the water in the pool. To achieve that you apply pressure to the water with a pump so it travels through a pipe and reaches your shower head. The stronger the pressure the pump applies (voltage) the more water (current) will come out of the tube (resistance), but if the tube is really thin (higher resistance), even with tons of pressure (voltage) only a small amount of water (current) will come out of the shower. 

[ChrisCross]

voltage*current=energy

 

current = how much is flowing (speed) 

voltage = how big is the pressure (pool analogy)