The proliferation of "wall cubes" or "wall-warts" to recharge various battery
powered portable devices along with the proliferation of computers
and displays created a significant harmonic powerline problem in business buildings. As a result the drive (requirement) has been for the manufacturers of such devices to use "switch-mode" off-line supplies which produce very low harmonics on the line. The result is higher efficiency.
What this means to you is that they draw minimal power. The "catch" is that when operating a power inverter
one must monitor
the battery current
to determine if it is sufficiently low for your continuous energy budget
. If you are motoring along with the inverter
on and an alternator
is keeping ahead of the inverter drain then you don't care.
Some inverters have a "on" mode which, when there is no ac load, draws only "idle" current
. If a small load like a "wall cube" is connected that only draws a few watts it will pull the inverter out of the "no-load" mode which, in at least one case, carries an overhead current draw of 5 to 7 Amps even though the "wall-wart" might add only 0.1 Amp battery draw. Obviously in this case one might wait until heavier loads are operated (like an LCD TV and sound system) before plugging in the "wall-wart".
For convenience use a power strip to plug
in all your rechargeables and use the strip's on/off switch to switch them off when you don't want the drain. Make sure that the power strip is either encased in metal or has the U/L 1459 revB (if I correctly recall
the number). It is a designation that means if a power transient sufficiently high so as to destroy the internal transient protection devices an internal fuse will open rather than causing a fire. Boats and homes have had fires from such instances with devices not having such internal protection.