> The loss of capacity to heat is significant - often 10-30% capacity but that figure depends. But it isn't a loss of capacity (although there is also a loss o

> The loss of capacity to heat is significant - often 10-30% capacity but that figure depends. But it isn't a loss of capacity (although there is also a loss of capacity due to cold, in any chemistry). The capacity is the same, it just takes more energy to put the same amount of energy in. If you are putting energy in, you usually have an oversupply, and heating the battery is not an issue. > If ambient is - 5 C, a delta of +5 C doesn’t change my core point. I used the phrase "above ambient" specifically because the battery does not need to be warm unless you need to charge it quickly. If it's above 0 Celsius, it can charge. The warmer you make it the faster you can charge it. If the wasted energy is an issue you can charge slower. > most industrial inverters operate at nearly 90% efficiency. An inverter is significantly simpler than a battery charger. FePO4 charging can start as low as 2.5 volts and go past 3.6 volts. Making a converter with a 50% swing in voltage is not particularly easy. This higher-end charger picked at random[1] drops to <75% efficiency at the end of charge. [1]: https://www.analog.com/media/en/technical-documentation/data-sheets/36508284fd.pdf https://www.analog.com/media/en/technical-documentation/data...