The dry solid polymer battery has found a niche market as backup power in warm climates. The battery is kept at the operating temperature with built-in heating elements that is fed by the utility grid during normal operation. On a power outage, the battery would need to provide its own power to maintain the temperature. Although said to be long lasting, price is an obstacle.
I guess that about the -40, they are talking about the LiFePo4...While -20Â°C (-4Â°F) is threshold at which the nickel-metal-hydride, sealed lead-acid and lithium-ion battery cease to function, the nickel-cadmium can go down to -40Â°C (-40Â°F). At that frigid temperature, the nickel-cadmium is limited to a discharge rate of 0.2C (5 hour rate). There are new types of Li?ion batteries that are said to operate down to -40Â°C.
Now we have answers!Lithium-ion works within the discharge temperature limits of -20Â°C to 60Â°C (-4Â°F to 140Â°F). The performance is temperature based, meaning that the rate capability at or below -20Â°C is reduced due to the increased impedance of the electrolyte. Discharging at low temperatures does not harm the battery. Lithium-ion may be used down to -30Â°C (-22Â°F) with acceptable results. Larger packs will be necessary to compensate for the reduced capacity at these temperatures.
YES ! Thanks for information.Doctorbass wrote: ...
Now we have answers!
So the use of heating element IS usefull
Lithium- ion offers good charging performance at cold and hot temperatures. The acceptable charge range is 0Â° to 45Â°C (32Â°F to 113Â°F). It is recommended, however, to reduce the charge rate to less than 1C at temperatures of 5Â°C to 0Â°C (41Â°F to 32Â°F).
It is important to know that consumer grade lithium-ion batteries cannot be charged below 0Â°C (32Â°F). Although the packs appear to be charging normally at freezing temperatures, the cell impedance goes up and the acceptance of the ions on the anode is drastically reduced.
What is most troubling is the plating of metallic lithium that occurs on the anode. The higher the charge rate, the more pronounced the plating will be. A prolonged charge at cold temperatures will eventually compromise the safety of the pack. The plating is permanent and no amount of cycling can reverse this effect. Unknown to the user, such a battery will become more vulnerable to failure if subjected to impact, crush or high rate charging. Venting with flame could be the result.
Quality chargers reduce the charge current at cold temperatures and avert a charge altogether below 0Â°C (32Â°F). When charging a cold battery, allow the pack to warm up before putting it into the charger. Discharging a lithium-ion battery at cold temperature does not cause any harm. The lower performance will only be noticeable while the pack is dwelling in the cold state.
If I read the study correctly, the repetitive cycling was all done at 50 deg C at 3C. Only the temperature during "characterization", which occurs only every 300 cycles, varies. The only thing I can conclude is that if I drove to work for a year ( or 300 days) at 50 deg G (don't know how I would manage that) and then one day it was suddenly -10 deg C, I would expect the capacity to increase, although the average voltage would decrease. Then, after driving around at 50 deg C for another year, and it was suddenly -10 deg C, I'd see a big change in the capacity over when it was new or after the first year.The study is recent and had funding from gererous motors . Its a prismatic high capacity cell . 600 1C cycles at temps of -10C to +50C . The elevated temps are as important to battery heating as the low temp facts . Equally important to the facts within this study is the reference , another 39 papers . ( there appears to be a misprint of 6000 cycles in one reference , I think #20 or #22...maybe not...find that paper )