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I have a personal anecdote that is maybe related? I store some spare car/boat batteries in my garage, and you would think that batteries, in their plastic/insu

I have a personal anecdote that is maybe related? I store some spare car/boat batteries in my garage, and you would think that batteries, in their plastic/insulated containers, should be fairly inert or impervious to odd discharge effects. However, over years, I have noticed that if batteries are left on the bare floor of a garage, they will discharge over time. Something to do with gradual leakage via the plastic contacting ground (and maybe plus humidity) -- there is some conduction going on! So instead, you have to store them on well-insulating platforms, say styrofoam or acrylic, and they will hold their charge far longer. But this is on the timescale of months -- I wonder how that relates to the timescale these researchers are investigating (and for often used batteries, I would imagine it matters less). These little parasitic losses that are rarely studied...

slug 4y ago
Another hypothesis: I think that the batteries on the floor will be colder, so are prone to lose charge / fail faster (internal discharge through plates). Being colder (due to being on the floor) could also bring water vapor condensation on the battery surface, so that could be a path of external discharge (between the battery terminals).
- mmmwww 4y ago
  That’s what I would have thought as well.
- Maursault 4y ago
  > I think that the batteries on the floor will be colder, so are prone to lose charge / fail faster (internal discharge through plates). Cold is good, as long as the air is very dry. It will reduce self-discharge. > Being colder (due to being on the floor) could also bring water vapor condensation on the battery surface, so that could be a path of external discharge (between the battery terminals). Bingo. Warmer air holds more water, and as the temperature drops, because cooler air can't hold as much water, it will condensate out and form droplets. Water and moisture are bad for cells, even humidity is bad. A garage is usually not climate controlled. Some awesome folks do climate control their garage, most don't though. Whatever the %RH outside is, the garage will follow. Most US states have a surprisingly high average %RH.
  - totetsu 4y ago
    whats the physical process by which water condensation discharges batteries?
    - doubleg72 4y ago
      Yeah I'm not sure how such low voltage can overcome the lack of any ions in the condensation in which this could occur.
      - dtgriscom 4y ago
        There's likely contaminants on the surface of the battery which, when water is added, become conductive.
        refurb 4y ago
        if youve ever rubbed pH paper on an auto battery youll realize there is a lot of residual sulfuric acid on the outside of the case. That mixed with water is pretty conductive.
      - Maursault 4y ago
        Yeah humidity increases the conductivity of air by reducing the breakdown voltage of air, not by conducting electricity, because it doesn't conduct electricty, because it's an insulator.
    - Maursault 4y ago
      I think of it this way: when it's dry, static electricity can build up, and that's why there are static shocks, when that built up electricity is released. But when it's humid, there's never any static electricity or static shocks because electricity can't build up; it is just constantly absorbed by water vapor. Water is technically an insulator, which is why distilled water is a poor conductor and salty water is a good conductor. But water vapor, even though free of contaminants, increases the conductivity of the air by reducing the air's breakdown voltage,[1] helping to ionizing the air to form plasma. Condensation helps absorb static charges by keeping surfaces moist, increasing surface conductivity. Condensation also damages batteries by oxidizing the contacts, which are steel. Water can even condense under the cathode contact, which is vented, and get into and dilute the electrolyte, leading to capacity loss and possibly shorting the cell by causing the formation of dendrites. [1] https://en.wikipedia.org/wiki/Breakdown_voltage https://en.wikipedia.org/wiki/Breakdown_voltage
chrismeller 4y ago
In my first job we had several UPSes for racks of equipment that had been augmented with marine batteries for longer life and all the batteries were on slats of wood to keep them off the floor. I asked and got the same answer you did - they will last longer - but I’ve never understood why.
Maursault 4y ago
Either your batteries were old[1], or you're overlooking something else that might have caused increased self-discharge, such as high humidity. Some will say it was a myth, but it was true at one time. What is a myth is that storing cylindrical cells in your freezer will slow self-discharge, and while it is proven cold storage will reduce self-discharge, the problem with a consumer freezer or refrigerator is that they are humid, so any gains the cold would provide are more than defeated by the humidity, which not only will increase self-discharge, it can damage and short a cell. The humidity in a consumer-grade freezer drastically increases to 80%-95%RH twice a day and slowly drops over several hours. The best place to store cells is in a cool, dry location. And cells are cheap and readily available, and storing cells for years in a freezer, even if it worked, would be wasting a ton of energy just to save a tiny amount of energy, which, again, wouldn't happen anyway. [1] https://www.mcgill.ca/oss/article/general-science-you-asked/concrete-truth-about-batteries-stored-concrete https://www.mcgill.ca/oss/article/general-science-you-asked/...
- amelius 4y ago
  Sounds like you could store them in the freezer, but e.g. in a vacuum sealed bag.
  - Maursault 4y ago
    As long as it is vacuum sealed from moisture, with all the air evacuated, and not just a ZipLoc bag out of which you "pressed all the air." Otherwise, the air inside the bag is the same air as where it was sealed, maybe the 50%RH of the air in a climate controlled home and kitchen, and temperature changes will cause the vapor in the air to precipitate out into moisture, and back to vapor, and this repeats every time the temperature fluctuates, which usually is twice a day as part of a freezer's frost cycle. But then you are still using far more energy, and money, to save a minuscule amount lost from self-discharge. Li-ion cells have low self-discharge and only lose about 15% capacity per year. LSD NiMH cells like Eneloop lose about 30% capacity after 5 years. Alkaline cells, surprisingly, lose only 2-3% per year in self-discharge. LiFeS2 cells, like Energizer Ultimate Lithium, have an extremely low self-discharge rate, well under 1% per year, and have more than a 10 year shelf life, though they'll probably hold charge for at least 20 years of dry storage. I wonder what it would amount to in mAh to lower the temperature of cells to below freezing and maintain that temperature for a year. You'd probably lose in a contest with someone panning gold out of a bottle of Goldschläger.
throwawaylinux 4y ago
I've heard this, I have a friend whose father was in the auto industry all his life, owned a body shop so they would constantly have a bunch of cars in various stages of disassembly in their shop. He was adamant about not leaving batteries on the concrete floor. There might be something to it.

slug 4y ago

Another hypothesis: I think that the batteries on the floor will be colder, so are prone to lose charge / fail faster (internal discharge through plates). Being colder (due to being on the floor) could also bring water vapor condensation on the battery surface, so that could be a path of external discharge (between the battery terminals).

mmmwww 4y ago
That’s what I would have thought as well.
Maursault 4y ago
> I think that the batteries on the floor will be colder, so are prone to lose charge / fail faster (internal discharge through plates). Cold is good, as long as the air is very dry. It will reduce self-discharge. > Being colder (due to being on the floor) could also bring water vapor condensation on the battery surface, so that could be a path of external discharge (between the battery terminals). Bingo. Warmer air holds more water, and as the temperature drops, because cooler air can't hold as much water, it will condensate out and form droplets. Water and moisture are bad for cells, even humidity is bad. A garage is usually not climate controlled. Some awesome folks do climate control their garage, most don't though. Whatever the %RH outside is, the garage will follow. Most US states have a surprisingly high average %RH.
- totetsu 4y ago
  whats the physical process by which water condensation discharges batteries?
  - doubleg72 4y ago
    Yeah I'm not sure how such low voltage can overcome the lack of any ions in the condensation in which this could occur.
    - dtgriscom 4y ago
      There's likely contaminants on the surface of the battery which, when water is added, become conductive.
      - refurb 4y ago
        if youve ever rubbed pH paper on an auto battery youll realize there is a lot of residual sulfuric acid on the outside of the case. That mixed with water is pretty conductive.
    - Maursault 4y ago
      Yeah humidity increases the conductivity of air by reducing the breakdown voltage of air, not by conducting electricity, because it doesn't conduct electricty, because it's an insulator.
  - Maursault 4y ago
    I think of it this way: when it's dry, static electricity can build up, and that's why there are static shocks, when that built up electricity is released. But when it's humid, there's never any static electricity or static shocks because electricity can't build up; it is just constantly absorbed by water vapor. Water is technically an insulator, which is why distilled water is a poor conductor and salty water is a good conductor. But water vapor, even though free of contaminants, increases the conductivity of the air by reducing the air's breakdown voltage,[1] helping to ionizing the air to form plasma. Condensation helps absorb static charges by keeping surfaces moist, increasing surface conductivity. Condensation also damages batteries by oxidizing the contacts, which are steel. Water can even condense under the cathode contact, which is vented, and get into and dilute the electrolyte, leading to capacity loss and possibly shorting the cell by causing the formation of dendrites. [1] https://en.wikipedia.org/wiki/Breakdown_voltage https://en.wikipedia.org/wiki/Breakdown_voltage

chrismeller 4y ago

In my first job we had several UPSes for racks of equipment that had been augmented with marine batteries for longer life and all the batteries were on slats of wood to keep them off the floor. I asked and got the same answer you did - they will last longer - but I’ve never understood why.

Maursault 4y ago

Either your batteries were old[1], or you're overlooking something else that might have caused increased self-discharge, such as high humidity. Some will say it was a myth, but it was true at one time. What is a myth is that storing cylindrical cells in your freezer will slow self-discharge, and while it is proven cold storage will reduce self-discharge, the problem with a consumer freezer or refrigerator is that they are humid, so any gains the cold would provide are more than defeated by the humidity, which not only will increase self-discharge, it can damage and short a cell. The humidity in a consumer-grade freezer drastically increases to 80%-95%RH twice a day and slowly drops over several hours. The best place to store cells is in a cool, dry location. And cells are cheap and readily available, and storing cells for years in a freezer, even if it worked, would be wasting a ton of energy just to save a tiny amount of energy, which, again, wouldn't happen anyway. [1] https://www.mcgill.ca/oss/article/general-science-you-asked/concrete-truth-about-batteries-stored-concrete https://www.mcgill.ca/oss/article/general-science-you-asked/...

amelius 4y ago
Sounds like you could store them in the freezer, but e.g. in a vacuum sealed bag.
- Maursault 4y ago
  As long as it is vacuum sealed from moisture, with all the air evacuated, and not just a ZipLoc bag out of which you "pressed all the air." Otherwise, the air inside the bag is the same air as where it was sealed, maybe the 50%RH of the air in a climate controlled home and kitchen, and temperature changes will cause the vapor in the air to precipitate out into moisture, and back to vapor, and this repeats every time the temperature fluctuates, which usually is twice a day as part of a freezer's frost cycle. But then you are still using far more energy, and money, to save a minuscule amount lost from self-discharge. Li-ion cells have low self-discharge and only lose about 15% capacity per year. LSD NiMH cells like Eneloop lose about 30% capacity after 5 years. Alkaline cells, surprisingly, lose only 2-3% per year in self-discharge. LiFeS2 cells, like Energizer Ultimate Lithium, have an extremely low self-discharge rate, well under 1% per year, and have more than a 10 year shelf life, though they'll probably hold charge for at least 20 years of dry storage. I wonder what it would amount to in mAh to lower the temperature of cells to below freezing and maintain that temperature for a year. You'd probably lose in a contest with someone panning gold out of a bottle of Goldschläger.

throwawaylinux 4y ago

I've heard this, I have a friend whose father was in the auto industry all his life, owned a body shop so they would constantly have a bunch of cars in various stages of disassembly in their shop. He was adamant about not leaving batteries on the concrete floor. There might be something to it.