You make an excellent point that no battery is safe. Anytime you store
up that much power in a small package there is going to be risk when
things go wrong. AGM's certainly can explode if abused.

However, explosions are only part of it. The free liquid acid,
corrosive fumes, and explosive vapors of wet cells are all minimized
with AGM's. If something does go wrong and one blows up, the acid
impregnated mat in the AGM should be less dangerous and easier to
clean up than the liquid.

This is analogous to the gas / diesel propulsion question. If you need
the very best performance and power to weight ration, you have to go
with gas and learn to keep large amounts of explosive fume producing
liquid on board. With care, understanding, and proper equipment, gas
can be made acceptably safe. Diesel is not perfectly safe but it is
much safer and has other advantages such as more moisture tolerant
ignition.

Despite the blanket statement I started this thread with, there are
certainly operational situations in which I might choose wet cells. I
wouldn't expect them in normal yachting situations though.

Speaking of internal shorts, the AGM, with everything held in place
with the glass mat should be far less likely to short than the wet
cell where chunks can fall off the plates and there is only liquid to
keep them from moving around.

--

Roger Long