Lead acid, AGM, Lithium-ion oh my.
The Tesla Powerwall is very interesting. Our generators are 240v 50Hz single-phase output and the Powerwall has a compatible option, 5kW continuous output up to 13.5kWh and inverter included as a complete charge and output pack, the Lithium-ion batteries charge from solar at 50v nominal. But at about US$7,000 each it would take four of these to provide motor-sailing speed for just under 3 hours, then a generator must be started. One of these for household use, though, would be amazing, 10 year warranty, using a decent solar array would massively decrease generator time for watermaker deployment.