Thread: 12V Charger
View Single Post
Old 6th Dec 2014, 1:08 am   #6
BGmidsUK's Avatar
Join Date: Oct 2007
Location: Leicester, UK.
Posts: 809
Default Re: 12V Charger

When I worked for a transformer and charger manufacturer (J M Clarke) from around 1995 to 2004 all of our chargers for lead-acid batteries (except the tiny ones) were thyristor-based, including the later software-controlled units with PIC 16C711(?) ICs. I know there was at least one other company making similar products as we had some sort of trading arrangement with them.

The "fun" occurred when the assemblers would sometimes accidentally(?) transpose the driver transistors with the thyristors (same package), resulting in a very loud bang and flying shrapnel when I plugged it in to calibrate/test it. Safety glasses would have been advisable, including for the visitors who happened to be walking past on one occasion.

I'll open up my modern 4/8 amp unit as this thread has sparked my interest to see what lurks inside. I'll be surprised if the design is significantly different from those I worked on as it does bear quite a resemblance to a Clarke charger.

My old Halfords unit is simply a transformer with thermal switch and a bridge rectifier screwed to a (partially melted) plastic post! I should measure the output with various meters to see what readings this gives off- and on-load.

BGmidsUK is offline