Batteries gain weight?

[Gary Warner]

Since electrons have weight, how much weight does my 2000ma LIPoly cell change from a full charge to empty?

[Andy W]

You don't remove electrons, or replace them with a charger.
What electrons there are inside a battery are simply pushed around by chemical process.
..a

[barney]

You don't remove electrons, or replace them with a charger.
What electrons there are inside a battery are simply pushed around by chemical process.
..a

This is true as far as I am aware, but if the electro -light or acid that carries the electrons from one dissimilar metal to another, changes specific gravity (density) depending on the state of charge ,and the volume remains the same then a weight differential must exist between a fully charged battery and a fully discharged battery ?
Barney

[Gary Warner]

This is true as far as I am aware, but if the electro -light or acid that carries the electrons from one dissimilar metal to another, changes specific gravity (density) depending on the state of charge ,and the volume remains the same then a weight differential must exist between a fully charged battery and a fully discharged battery ?
Barney

That's what I was thinking. Maybe the weight change is not due to the collection of electrons, but something has to change weight, like in lead acid electrolyte changing specific gravity.

I think I see the two ideas coming together. Though the weight of acid might grow with a charge, the electrons that are gained in the electrolyte are lost from one of the other metal components of the battery. It's separation of the two that allows for a greater electron collection in the electrolyte and provides for the voltage force felt at the terminals.

Andy, is this correct?

[Andy W]

I'm no chemist, but that's close to my understanding.
It's more like winding a spring in a clock - potential energy stored in the spring doesn't make it gain mass. Moving the right molecules or atomic components around doesn't make the whole change weight, although perhaps at a molecular level, different parts of a battery are changing slightly.
..a

[vintage1]

This is true as far as I am aware, but if the electro -light or acid that carries the electrons from one dissimilar metal to another, changes specific gravity (density) depending on the state of charge ,and the volume remains the same then a weight differential must exist between a fully charged battery and a fully discharged battery ?
Barney

The battery is sealed. Teh same number of atoms exist wiuthin it. It doesn't chage weight.

Whether a hydrogen ion is attached to an oxygen, to form water, or whether they bioth exist as gases, does not change weight.

At least not measurably. I guess E=mc^2 means the higher energy states of the atoms result in the odd microgram weight increase per ton of battery, but even in a few lbs of uranium in a nuclear device, 99.9999% weight still exists in the atomic nuclei and particles flung off.

Not very much actual weight loss constitutes the odd megaton explosion. A few grammes I guess.

Hmm. 3s LIPO pack at 10v and about 1000mA/h is about 3600 Joules.

Thats E, now C^2 is about 10^17 meters per sec squared, or 10^19 cm/s Squared, so m is 3600/10^-19 or 3.6 x 10^ 16, or 0.00036 picograms, which should be the difference in weignt between a fully charged and fully discharged 3s LIPO pack.

Give or take a few noughts. Not sure about the various constants.

[Berdie]

Referring to the lead acid battery example the acid in the battery does actually gain mass but not from electrons. In the lead acid battery there are commonly two electrodes, lead (Pb) and lead peroxide (PbO2). When the battery discharges the lead electrode consumes itself (much like iron rusting) and makes lead sulphate (PbSO4). This frees two electrons that travel to the lead peroxide electrode to convert it to lead sulphate as well.

The side product of this reaction is water which diultes the sulphuric acid electrode, it is also the case that lead sulphate is soluble in water which causes the specific gravity of the water to change. Overall the mass of the battery doesn't change, the mass is simply transferred around from one part to another. Charging the battery simply moves the mass back to where it came from while discharging.

[TMorita]

Since electrons have weight, how much weight does my 2000ma LIPoly cell change from a full charge to empty?

Bad model.

Think of it two jugs connected by a tube, and one is at a higher altitude than the other, and there's water in the system.

When you charge the battery, you pump all the water from the lower jug to the upper jug.

When you discharge the battery, the water flows from the top jug to the bottom jug.

Toshi

[Marion]

What !! Haven't you noticed your electric powered models change trim as the battery runs down ?? I think vintage1 is on to something. Think maybe Einstine was wrong about E=MC^2 ?? :D