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Is my assumption correct that the main limiting factor of maximum discharge current of a Li-ion battery is that the cell heats up too much due to its internal resistance/the current flowing through the cell? Does cooling the cell (for example in a Tesla battery pack) increase the max current that the cell can provide without overheating? Or is it merely to increase the longevity of the cells/their lifespan by keeping them relatively cool even under high loads and is it never permitted to discharge the cells with more amps than what they are rated for regardless of how well they are cooled?

I was wondering if 18650 Li-ion cells can be temporarily discharged at a higher discharge current than their max rated discharge current? (provided the battery is adequately cooled/temperature stays below 50 degrees celcius)

For example take the following cell: Sanyo NCR18650BL (3350mAh, 7A discharge current) Could you discharge this cell at for example 10Amp for duration of 1 minute? (provided cell is properly cooled)? How much impact on the discharge efficiency will this discharging of 10Amp have approximately? (since more energy will be converted to heat efficiency should be lower) Provided the cell is properly cooled (meaning no part of the cell reaches too high a temperature during the discharge)... is there a limit to the max discharge rate the cell can handle? Is this directly linked to the amount of "surface area of active cell materials" (as mentioned on battery-university's website; https://batteryuniversity.com/learn/article/discharge_characteristics_li?

Thank you!

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Does cooling the cell (for example in a Tesla battery pack) increase the max current that the cell can provide without overheating

Yes. But it's a fallacy that you can do much with that: the energy used for cooling has to come from the battery. So, this only works as long as the cooling efficiency is higher than the heat losses.

I was wondering if 18650 Li-ion cells can be temporarily discharged at a higher discharge current than their max rated discharge current? (provided the battery is adequately cooled/temperature stays below 50 degrees celcius)

"rated" means "rated". So, if you want to be safe: no.

Practically, operating a LiIon battery warm is desirable: while it increases ohmic losses, it greatly increases charge carrier mobility, which is where most of the internal resistance comes from. So, you need some temperature to even draw a high current. But. 50 °C might be totally sufficient for that. If you can keep it at that temperature internally without freezing the outer half of it, you might just be fine. Don't forget that "can be operated heat-damage-free" doesn't mean "damage-free": you might still have electrode migration, gassing, … at high curents.

Also, nothing says the battery will let you draw any current higher than rated: There might simply be physical limits, and in a logically designed cell, these wouldn't be extremely far beyond thermal limits – no use to make a cell that is capable of more current than its thermal design allows for. Better use the space / weight / cost you saved for more capacity / lighter battery / cheaper battery.

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