Charging 4.8V batteries
I want to build the Multi-Purpose Fast Charger featured in the
February & March 1998 issues of SILICON CHIP. My problem is that I want to be able
to charge 4.8V NiCd battery packs (for R/C model aircraft) of 600-1200mA.h. Have
there been any updates to the circuit to allow this? If not, what modifications
would need to be done? (B. V., Tindal, NT).
value of divider resistance for a 4.8V battery pack will be 33.3kΩ and will need to be used
instead of the dividers used for a different voltage selection. For example, you
could remove the 150kΩ and 12kΩ
paralleled resistors for the 12V NiCd position and place the 33.3kΩ value in their places. This
will change the 12V NiCd setting to 4.8V. A 47kΩ and 120kΩ resistor in parallel will be close
enough to the correct value.
13.8V regulated power supply
I have the November 1997 issue which describes the Regulated
Supply for Darkroom Lamps. It has very good regulation but I am interested in
making a 13.8V version. Can you suggest what modifications will be required? (I.
S., via email).
circuit should provide 13.8V with no modifications being necessary. Just set
trimpot VR1 for 13.8V instead of 12V. By the way, you do realise that the output
is not smooth DC but pulsed. It is OK for driving motors or lamps but not
suitable for other loads.