Does a fully charged battery weigh more than a depleted one?

CraigC
CraigC Registered Users Posts: 16
Maybe this thread can be posted under Stupid Questions but.... does a fully charged battery weigh more than a depleted one?

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Does a fully charged battery weigh more than a depleted one?

    Saving water loss, no.
    The material mass is all still there, it's just a difference of whether the sulphor is clinging to the plates (discharged) or still in the electrolyte (charged).
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Does a fully charged battery weigh more than a depleted one?

    In theory, yes... E=MC2.

    In practice, no--The amount of mass increase due to the increased energy is practically zero.

    I think I read that in an article a while ago trying to answer exactly that question.

    Of course, there are batteries (such as Zinc-Air) which exchange mass outside of the battery box. Those would have significant weight differences.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    Re: Does a fully charged battery weigh more than a depleted one?

    Less.

    First, as 'Coot said, there will be loss of water during charging.

    Second, the volume of the electrolyte increases, so it'll be more buoyacy in the air. When put on scales, it'll weight less.

    So, charge your batteries before moving :D
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Does a fully charged battery weigh more than a depleted one?

    I was talking about sealed (VRLA/AGM/GEL/NiCAD/NMHi) batteries. Obviously, any battery that "boils" off moisture and gases, is going to weigh less.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Does a fully charged battery weigh more than a depleted one?
    NorthGuy wrote: »
    Less.
    ....
    Second, the volume of the electrolyte increases, so it'll be more buoyacy in the air. When put on scales, it'll weight less.
    Nice thinking!
    As the volume of the electrolyte increases, it displaces air from the inside of the battery case (for FLA only), so the effective volume of the electrolyte inside the battery will increase even though the outside dimensions of the battery do not change.
    And as the material of which the battery is constructed changes from internal heating, the same thing will happen, just not by as great a percentage. And you have to be careful not to let it cool off before you move it. The electrolyte volume change, on the other hand, is chemical. But does the volume of the plate decrease by the same amount? That is a tough one....
    An AGM or GEL will only get lighter from the thermal expansion of the battery case.

    And I am glad that nobody tried to bring up the mass of all of the electrons that have been forced into the battery (but also out the other side!)
    SMA SB 3000, old BP panels.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Does a fully charged battery weigh more than a depleted one?

    Why don't you boys run some tests with your bathroom scales and tell us how much difference you see between charged and discharged? :p
  • bmet
    bmet Solar Expert Posts: 630 ✭✭
    Re: Does a fully charged battery weigh more than a depleted one?
    inetdog wrote: »
    And I am glad that nobody tried to bring up the mass of all of the electrons that have been forced into the battery (but also out the other side!)


    But I submit that as the battery chemistry is altered during discharge, the distribution of electrons will throw the batttery off balance, switch polarity, and go "out of phase", with an infinite number of varying batteries across multiple universes, all connected via curved energy from the 'vacuum of space-time. :p
  • northerner
    northerner Solar Expert Posts: 492 ✭✭✭✭✭✭
    Re: Does a fully charged battery weigh more than a depleted one?

    If you capture all the hydrogen gas into a large balloon and tie that to the batteries, I would think that the batteries would gradually become lighter. If the balloon is big enough, eventually the batteries would be floating.:p
  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    Re: Does a fully charged battery weigh more than a depleted one?
    northerner wrote: »
    ... eventually the batteries would be floating.:p

    When it's sunny, mine are floating every day :D
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Does a fully charged battery weigh more than a depleted one?

    after out gassing one is supposed to replace the lost water.

    when the volume of an agm or gel battery expands this does not change its weight.

    the question matters not anyway as my aching back still says they're just as heavy.:p
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Does a fully charged battery weigh more than a depleted one?
    bmet wrote: »
    But I submit that as the battery chemistry is altered during discharge, the distribution of electrons will throw the batttery off balance, switch polarity, and go "out of phase", with an infinite number of varying batteries across multiple universes, all connected via curved energy from the 'vacuum of space-time. :p
    Now you are reminding me of a Tom Swift book I read as a kid. Tom has built a space station, and rather then continually ferry more oxygen up from the surface he puts oxygen atoms into a cyclotron (all good space stations have them, you know) and accelerates them to near light speed to increase their mass. Thereby providing as much oxygen as he can use.
    SMA SB 3000, old BP panels.
  • bmet
    bmet Solar Expert Posts: 630 ✭✭
    Re: Does a fully charged battery weigh more than a depleted one?
    inetdog wrote: »
    Now you are reminding me of a Tom Swift book I read as a kid. Tom has built a space station, and rather then continually ferry more oxygen up from the surface he puts oxygen atoms into a cyclotron (all good space stations have them, you know) and accelerates them to near light speed to increase their mass. Thereby providing as much oxygen as he can use.

    Sort of a reverse-Fantastic Voyage thingy....