Capt Odyssea

Ok, I have smelled the smell! Three Exide starting batteries in parallel, single screw diesel, last night came back to the boat and phew!

Of the three batteries, center one had moisture under the box cover, not acid, tasted like straight water. also much hotter than the other two.
charger is shut down, no loads on, letting things settle.
Any danger of runaway batt temp? Nothing is shorted.
The smell has dissipated, I'm aware of the boom factor,

I will disconnect that batt, and check all batt voltages separately.
Batteries are 2/3years old, supplied as new with new boat.

Need some input!

Thanks all

GTBecker

Sounds like a bad battery that's either mechanically faulty, sulphated to the point of shorting, or was allowed to boil down. Are the three batteries the same age or is the hot battery older than the others? Paralleled batteries should be similar age. Exide dates them with a white sticker.

Seems a no-brainer to remove the hot battery and check it out thoroughly. I wouldn't be surprised to find exposed plates and swollen case ends; if that's so, replace it or - ideally - all three.

Exide Nautilus Dual-Purpose batteries, in my experience, use much more water than Johnson Controls deep cycles on the same charger over the same period. Keep a keen eye on them.

Capt Odyssea

Got a load tester today, digital so should show if one of the three in the bank is different ie internal resistance, voltage, charge level and CCA rating.

In hindsight, I prob asked for it by keeping the house charger on, then doing a 4 hour run across the stream.
Usually I would bridge house and starting on a run like that.

If one reads diff I'll pull it, and replace all three in a while, and disconnect the charging line to the starting batteries for awhile so I can still float the house batts from gen/shore