Mad Dog,
I was hoping one of the younger guys would step up to the plate cause I
don't think deeply about this stuff any more and I hate writing long
posts, but here goes.
Using a 6 volt battery can be done quite simply with a double pole
double throw switch. When in charge mode the 6v negative is connected
to the 12v negative and the 6v positive is connected to the 12v positive
thru a dropping resistor of suitable size. When in the 18v supply mode
the 6v negative is switched to the 12v positive and the 6v positive is
switched to the 18v output. Monitor the 6v on charge and switch to 18v
output when the 6v is charged. One of the 6v Kiddy car batteries at
WalMart would probably be enough.
The source of the interference, according to Tony, is the inverter.
This has nothing to due with the alternator.
A full wave bridge rectifier has four diodes.
AC ripple is the primary frequency of the alternating current source
used for conversion of AC to DC. Virtually all power supplies have some
of it no matter how much filtering is done and most appliances and
components will handle it unless it is at ridiculous levels which
usually means something in the power supply failed. The "dirty DC" as
you call it, has little or no thru put in an inverter. It is quite
isolated by the circuitry and the toroidal transformer used in most
modern inverters.
For about the last 75 years condensers have been components of
refrigeration equipment. In electronics, condenser and capacitor are
now the same thing. Only the auto industry still calls them condensers
(supprise, supprise).
Capacitors do not store AC. A capacitor does not block AC, it blocks DC
and passes AC.
The current flow thru the battery is irrelevant. Equal current flows
thru the negative (ground) and the positive.
A properly designed filter would dramatically reduce your need for such
large oil filled capacitors. A DC filter is comprised of capacitance
(C), reactance (R) and inductance (L). You get some filtering at low
loads with large C only because the circuit has some residual R and L,
but not much. The C component could be cut down considerably by adding
R and L but this requires some specific knowledge of electronics design
to achieve.
I believe you are confusing ripple with switching transients that come
from solid state junctions such as the transistors used in inverters and
the diodes in the alternator. These are much higher in frequency than
the 60 hertz of the AC line or the 15 to 20 thousand hertz of most
inverters (alternators are in between I believe) and will propagate as
radio waves. These frequencies could be coming into Tony's ssb by air
as easily as on the supply line. The cures, short of buying another
(probably more expensive) inverter could be to make sure the inverter
case has a good ground path ( in the engineering lab, we used braid
instead of wire, something to do with the way rf propogates on wire),
shield the inverter with another grounded enclosure and add small
capacitors (.001, .0001 mmf) between the output to ground hopefully
shunting to ground the offending interference.
Regards, Ron
