Thermal Runaway - or as they say in England, that was a near-run thing.

Something made me get up this morning at 3am.  Don't know what it was but something.  I wandered around the saloon wondering what I could smell.  Checked the engine bay.  Nope, not diesel.  Checked the garage.  Place was h-o-t hot.  All the toolboxes.  The wood cover over the batteries red hot.  Ripped everything out as fast as I could.  Starboard side battery was fizzing and hissing like all get-out.  Too hot to touch.  Off with shorepower instantly.  Off with the wind generator just to be sure.  Woke the Admiral in case things deteriorated.  Removed all three fire extinguishers from their holders and put them next to the sink.  Opened both lazarettes to let in cool air.

Dialled up the Catalina 42 Technical Discussion Group and keyed in boiling batteries.  There was my answer in one succinct short paragraph - Thermal Runaway.  A battery cell dies and the charger tries to charge it.  The battery heats up and the charger tries harder to charge the battery again.  This is self-defeating and the heat build up is amazing (the battery was still hot 5 hours later).  If I hadn't woken up, chances are big explosion and/or fire.  Not a good wakeup.


Postscript.  Nicos the Sparky came.  Checked the house bank.  Both gone to battery heaven.  Good news - he had 2 x 180ah lead acids in stock in Iraklion, delivered here in the hour-and-a-bit, 210 euros each.  Nicos is a strong boy and though I helped he basically shoved them in.  These things are huge.

Then he extracted the bow thruster, took that away and cleaned a lot of salt out of it and now it too runs.  Which was what he was coming here for in the first place.

Boat is safe, lessons learned as usual.