5 ms·

Hypothetically, for the lithium batteries, what if you made a big stainless steel vacuum wall insulated enclosure? Or just a metal box with r-60 value of foam a

Hypothetically, for the lithium batteries, what if you made a big stainless steel vacuum wall insulated enclosure? Or just a metal box with r-60 value of foam around it? The amount of heat needing to be generated can then be calculated based on the average temp over a longer period of time, and those batteries I don't imagine have to be "warm" exactly.

diamondlovesyou 5y ago
What about summer? Those batteries also need to stay cool...
- londons_explore 5y ago
  A $2 circulation pump and an outdoor radiator... It's good practice to snake a water pipe around every lithium cell anyway in big packs, because otherwise one bad cell can self-heat to the point of catching fire, even while other nearby cells are cold. The flowing water means the bad cell can't get to the point of fire.
- theshrike79 5y ago
  You can just dig a big hole for them, the earth stays cool enough when you go a meter or two down. Unless you live in the desert, having the batteries too hot isn't as big of an issue as freezing them.
- Solar2 5y ago
  They do not need to stay that cool at all. When used for solar, the C rate for charging usually never exceeds .2C for overpaneled systems. And usually never goes beyond .5C for discharge. So the heat generated is very small. Now when I am pushing 30-100C rates with a lithium polymer, cooling is an issue. this is why nissan leaf cells were recalled. The battery size was too small for the application, and they overheated which caused significant degradation rates. This is not an issue for solar. Just keep them at room temperature and they are fine.
lazide 5y ago
Lithium batteries don’t need to be warm for discharge (generally and with an asterisk), it’s charging. Discharge while freezing causes slower chemical reactions (aka lower discharge current), but that is rarely a huge problem compared to the charging problem. Any charging around or below freezing causes pretty quick destruction of the cells as the chemistry switches to a more favorable destructive one way electroplating process instead of the desirable (and reversible) ion exchange process. A common engineering solution to this has started to be temperature dependent shunts that route charging energy to heating pads around the battery until the battery temp gets above a certain safe point. It adds complexity, cost, and adds several undesirable failure mode however, and Lithium battery cost is already a major factor in these systems, so if you’re in a situation where you can’t reliably temperature control your batteries (cold climate, non-conditioned battery space), lead acid is still a very viable and often desirable chemistry instead. Round trip efficiency isn’t great with them, and you have to way over provision to get good cell lifespan, but it works.

diamondlovesyou 5y ago

What about summer? Those batteries also need to stay cool...

londons_explore 5y ago
A $2 circulation pump and an outdoor radiator... It's good practice to snake a water pipe around every lithium cell anyway in big packs, because otherwise one bad cell can self-heat to the point of catching fire, even while other nearby cells are cold. The flowing water means the bad cell can't get to the point of fire.
theshrike79 5y ago
You can just dig a big hole for them, the earth stays cool enough when you go a meter or two down. Unless you live in the desert, having the batteries too hot isn't as big of an issue as freezing them.
Solar2 5y ago
They do not need to stay that cool at all. When used for solar, the C rate for charging usually never exceeds .2C for overpaneled systems. And usually never goes beyond .5C for discharge. So the heat generated is very small. Now when I am pushing 30-100C rates with a lithium polymer, cooling is an issue. this is why nissan leaf cells were recalled. The battery size was too small for the application, and they overheated which caused significant degradation rates. This is not an issue for solar. Just keep them at room temperature and they are fine.

lazide 5y ago

Lithium batteries don’t need to be warm for discharge (generally and with an asterisk), it’s charging. Discharge while freezing causes slower chemical reactions (aka lower discharge current), but that is rarely a huge problem compared to the charging problem. Any charging around or below freezing causes pretty quick destruction of the cells as the chemistry switches to a more favorable destructive one way electroplating process instead of the desirable (and reversible) ion exchange process. A common engineering solution to this has started to be temperature dependent shunts that route charging energy to heating pads around the battery until the battery temp gets above a certain safe point. It adds complexity, cost, and adds several undesirable failure mode however, and Lithium battery cost is already a major factor in these systems, so if you’re in a situation where you can’t reliably temperature control your batteries (cold climate, non-conditioned battery space), lead acid is still a very viable and often desirable chemistry instead. Round trip efficiency isn’t great with them, and you have to way over provision to get good cell lifespan, but it works.