Now I have switched over to the Tesla Powerwall system I have my SolaX 3700E X-Hybrid inverter with 2 Pylon lithium batteries up for sale on eBay.
Opening bids from £500 and buy it now at £1,500. No reserve though so could go nice and cheap. Same system new is around &3,300 although mine includes a twin gam cooling rack to hold the batteries.
Batteries are 2.4kW each and the inverter can work with or without solar (charge the batteries with cheap electric at night for use during the day)
Suitable for a standard 16 panel solar installation, circa 4kw