stoatwblr wrote:...I'm interested from the POV of replacing the (ancient) 12V FLA in my 2012 imiev with a LiFePO4...
Nowadays, I think that is a great idea! In the last couple of years there has been an explosion of "12v" LiFePO4 batteries on the market with integral BMS', and the prices continue getting better as the competition heats up. Here in the US, RV'ers, especially, have glommed onto them, appreciating the deeper cycling abilities compared to lead. I have heard glowing reports about, for example, a company called Battle Born and its superb BMS and the excellent matched cells that it uses, although they are rather pricey. (Disclosure: I have no financial interest in this company)
The key is a BMS that can handle a steady-state 14.4vdc (20°C) that the i-MiEV produces when driving and one that will NOT cut out open circuit if it's not happy at the high end. At the voltage low end we don't need to worry unless the dc-dc fails.
Does anyone know what the temperature profile is of the i-MiEV dc-dc, as I would be concerned that at very low temperatures the resulting voltage might be too high for a BMS?
If you can find a nice small battery with the appropriate terminal configuration, go for it! - and do let us know how things turn out.
Slightly off-topic -
I've recently been experimenting with paralleling '12v' LiFePO4 with Gel cells and am in the middle of daily testing using my solar trailer as an energy source and feeding an inverter to run my home refrigerators during daylight hours (long story as to why I would want to do that...). Monitoring the current in both directions for both the Gels and LiFePO4 to see how well they share. So far, so good - the Headway LiFePO4 cells stay wonderfully balanced using a Heltec capacitive balancer, I've limited the Aussie Plasmatronics solar regulator upper voltage to a conservative 13.50vdc (I may go up to 13.60v if all goes well), and the 12.20vdc low voltage shutoff has not happened, yet...