I have a W4RRY battery booster and it works. It is useful to extract
the useful charge out of a lead-acid battery. I have an FT-857D, and
that gives up at about 11.5V... long before my marine battery is out of
useable charge. The battery booster fixes this... of course, if your
rig will run properly down to 10.5V, don't use it. It will probably
increase your battery drain.

Dan