They are real heavy duty premium quality, designed for daily charge / discharge cycles down to 80% discharge driving bad loads on electric vehicles with lets be honest less than ideal maintenance and enviornments and still give a minimum 5 year working life, in a domestic set up, clean enviornment, monitored properly you'll get nearer 20 years, and after 5 years you can add another bank and they won't be so mismatched as to worry.
2 quid per ampere hour is about right for top quality traction lead acids.
48vdc is a telecomms voltage, so nice trade between resistance losses etc.
Point is these are real numbers, and you work out at about ballpark 50KWh of reserve capacity, always on, always ready, always silent power for the same money as a grid tie for generation resale here in the UK.
It's a no brainer.
The batteries themselves are EPzS series, a non brainer, as the 48 vdc 1000 Ah spec is very popular with electric vehciles so they are made in some volume and you get the economies of scale.
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My mate who bought the start-o-matic asked me a few days ago about DIY building batteries, I asked this old boy about it today, he used to do it in the sixties, no fucking way it was commercially viable nowadays, he said you could buy ready made chinese batteries cheaper than you could buy the bare lead and zinc plates today, economies of scale and all that.
When he started a good quality car battery was three pounds and ten shillings, which was ten shillings more than his weekly wage....