while was doing search on goolge I came across this project which look like what was looking for , the rate and amp.
http://www.hobbielektronika.hu/kapcsolasok/12v20a-es_tirisztoros_automata_olom-savas_akkumulatortolto.html
but I have problem finding the IC UAA145 . so if any one has idea about equivalent to it or another IC function the same .
http://www.hobbielektronika.hu/kapcsolasok/12v20a-es_tirisztoros_automata_olom-savas_akkumulatortolto.html
but I have problem finding the IC UAA145 . so if any one has idea about equivalent to it or another IC function the same .