On Sun, 14 Sep 2008 13:17:58 -0400, Gerald Atkin
wrote:

So my
question is are these units prone to failure?

In a word, yes. They are very nice when working properly but glitchy
and unreliable in my experience.

All you really need is a decent digital voltmeter. Under light to
moderate load the batteries need to be recharged when they drop below
11.8 volts. That's about 60% of full charge. Anything lower will
begin to damage the batteries.