Patent ID: 7564222

Claim:
A method of fast-charging a secondary battery comprising: a) converting AC supply voltage U AC into DC voltage U DC the value of which equals approximately twice the nominal voltage of a secondary battery to be charged, b) converting of the DC voltage U DC into a pulsating voltage U P with a pulse length T 1 and a pause length T 2 , having current pulses with peaks between 30 and 40 times capacity of the secondary battery to be charged, c) transmitting the pulsating voltage U P to the secondary battery to be charged, wherein the pause length T 2 between the pulses of the pulsating voltage U P depends on the voltage in the battery to be charged, and d) at least one measuring of the charge of the secondary battery, comprising: i. generating in a first generator a pulse in charging the secondary battery of a length T 3 between measurements of a length T 4 apart, ii. transmitting said pause T 3 to a second generator. iii. generating an actual measuring pulse of the length T 5 in the second generator, iv. stopping fast-charging the secondary battery for the time T 3 , v. transmitting said pulse from the second generator to a digital switch which is thereby short circuited for a duration of T 5 , and vi. measuring an open terminal voltage of the secondary battery within pause T 3 and within the measuring pulse T 5 .