Originally Posted by Pete O Static
I will be looking at a battery
replacement for my boat in about 24 months and seriously considering Lithium.
24 months from now, you will probably have the option of being either a conservative adopter of LiFePO4
or an early adopter of Lithium-Silicon. 2016 will probably be the first year of commercial
availability for Lithium-Silicon batteries, though they've been used for years in experimental applications, like electric
aircraft, satellites, etc. While Lithium-Silicon batteries will offer a lot of advantages, one disadvantage is that the voltage-discharge curve is steep (1.5V to 2.7V per cell), so a DC-DC converter must be placed between the battery
and the load bus to provide a stable voltage over the charge/discharge cycle (unless all your loads will accept 12V to 24V, which is unlikely).
For a marine
house bank of Lithium-Silicon cells, I would put eight (or maybe nine) in series, then use one DC-DC converter to step down to 12V for the load bus and another DC-DC converter either to step up from nominal 12V charging
systems or to step down from nominal 24V charging
systems to whatever is the optimal charging voltage (probably somewhere between 21V and 22V) for eight Lithium-Silicon cells.