[aprssig] RE: Charge Controllers

[VE3TK]

Many solar "charge controllers" use a FET to switch the NEGATIVE side on or
off.  Since your radio equipment is negative ground, depending on how your
station is wired, you may end up bypassing the FET, thus making your charge
controller ineffective (Astron always feeding the battery).  

Some solar controllers will also have another FET to short the solar panel
to ground while the charge path to the battery is disconnected.  This would
not be desirable in with your Astron.  

Most charge controllers also have a blocking diode on their solar input.
This will add 0.6V drop which would force you to set your Aston voltage
higher.  

As one lister pointed out, the solar controller is useful only where the
power supply voltage is much higher.  The Motorola MTR2000 with its ~14.8V
power supply comes to mind.  This voltage would damage the battery

Simple Solution:  Adjust your Astron to 13.8V or as recommended by the
battery manufacturer.  Connect your battery with a DIODE and RESISTOR in
parallel.  The diode will be biased to prevent a direct path TO the battery.
Charge must flow through the low value resistor to limit worst case charge
current.  In a discharge scenario, the resistor will be bypassed with the
diode.  Full load current will flow with only the 0.6V drop.  

Regards,

Tony K
VE3TK