A quote from a Slashdot story on a new fast charge/discharge lithium battery:
…in any high current circuit, the power wasted in the circuit as heat can be very high. It’s current squared times resistance. With batteries that have a high internal resistance, that power heats the battery and is also power that’s wasted. With a high current delivery capability, these would have very low internal resistance and under heavy loads, the batteries would run cooler and would be able to deliver more power to the actual load instead of throwing it away as heat.
Just to illustrate battery self heating - if you ever get stranded in extreme cold because your battery doesn’t have the power available to turn the engine over, just turn on the headlights for a while. It’s a medium load but will heat the battery from the inside due to internal resistance and make the battery better able to start the car. This really works.
My dad also has a story of a his school teacher in Alaska keeping a Coleman stove underneath their Volkswagen Bug and rushing out to tend to it between periods