I thought that something had fallen from a great height and smacked on the deck.
Couldn't see anything. Still dark. Alison shot up to see what had happened. As we wondered, Alison noticed shredded bits in the cockpit. A cockpit stereo speaker had exploded and the deck shower compartment lid was down.
We looked at each other 'The battery box'.
Once it got light I carefully opened the battery locker.
One of the batteries had exploded shearing the top off it and spraying acid all over.
What a mess.
Unhooking the shore power lead and switching everything off we surveyed the damage.
The blast had taken out the affore mentioned speaker and blown the shower cover down.
A quick Google showed that this isn't unheard of and water and bicarbonate of soda was called for.
We went to the marina office to tell them and see if they could dispose of a partial battery. Yes, but leave it outside.
On carefully removing the damaged batt. With protective gloves and upmost care. We put it in a battery box we had spare and trollied it to the office.
The onboard shore power trip had activated, so after a thorough clean up I insulated the hanging terminals and tried the electrics. Everything worked. Thank God.
Now a warning to others in a similar situation.
We had heard a whistling sound for a few days before, when the batteries were on charge. I had Googled it and 'Nothing to worry about' was my conclusion. 'I was wrong!!'
The battery in question had been inspected by myself a few weeks earlier. Topped up with distilled water, terminals cleaned and the the green ok indicator was showing.
It was our oldest battery and seems the noise was the acid bubbling under charge. It could of boiled too dry, 'been overcharged. ( it was the first in line in a bank of three ) or just become defective due to age. Don't know which.
With a replacement battery fitted I carefully checked the wiring. Also swapped the largest battery over to the electronics side and put the new one on the engine, as it has a Green indicator for quick checking.
Found the battery charger, under the settee in the saloon. Sterling Marine Power, battery charger/power pack. Looked online for an installation guide to check that it had been installed correctly. Couldn't find the right model. All seem newer than mine.
I am going to give the company a call or email tomorrow and check a few things out.
Also, after my activities in the battery compartment, Alison noticed holes appearing in my jeans. Going to clean the locker again with more bicarb.
Down below, our bedroom woodwork was showing damp patches. The water I had put in to dilute the acid hadn't found its way to the bilges but sat behind the hanging locker. How annoying.
Lots of screws and panels were removed and any water soaked up with paper towel.
Water has got in there before by the looks of it. Will be checking that out.