Re: [EVGRAY] charging a coil like a cap

Body

Yes, indeed, Ole. 
 That would be perfect for charging large  batteries. The circuit I have, works perfectly good for up to  9V small batteries and does it's magic on watch batteries.
 Yesterday, I recharged 2 watch batteries that had been in a closet inside the watches for over 10 years! 
 They were completely dead.
 Both watches are now up and running and batteries were measuring way over  1.6V after removing them from charger, which were charging for a period of  2+ hours. 
 I really want to do the higher voltage circuit. Time is my main obstacle now (work) 
 

 Thanks!
 

---In [email protected], <onielsen@...> wrote :

 Hi Karl,

"The 73 volts is measured open circuit  across the coil from collector to top of coil. Not from top of coil to base of transistor."
Then from 0V (emitter) to collector is the voltage across the coil (73V) plus the voltage across the voltage supply (5V) minus the voltage across the rectifying diode.

If the peak voltage is a smooth half sine wave (bottom up parable) the transistor doesn't go into avalanche mode. Then it's the parasitic capacitance of the coil that limits the peak voltage.

If a higher flyback voltage is wanted a high voltage transistor like the ones used to drive the flyback transformer in old CRT screens could be used. Some of these have breakdown voltages above 1kV like the BU208 http://www.alltronics.com/mas_assets/acrobat/BU208A.pdf or BU508 http://pdf.datasheetcatalog.com/datasheets/savantic/787.pdf. The flyback voltage were further stepped up by using a high tension secondary winding on the flyback transformer and then feeding a voltage tripler http://www.interfacebus.com/Glossary-of-Terms-Voltage-Quadrupler.html to reach the extremely high tension for accelerating the electron beam. When using a step up winding this down transforms the current at the same ratio as the voltage step up ratio. The peak current of the flyback pulse is the current reached when breaking the input cycle assuming no secondary winding is used.

Regards
Ole