[Shop-talk] Which diodes for a battery charger?

[Randall]

Think of the output of the transformer as a sine wave.  It goes smoothly
from peak to peak, but spends very little time at each peak.  Diodes only
conduct when the anode is more positive than the cathode.  So in a battery
charger, the diodes only conduct (to produce output) when the voltage is
near the peak, higher than the battery voltage.  The rest of the time, you
are reading battery voltage.  Without the battery, the average voltage is
much lower.

-- Randall