Hard to blame the batteries when the installation was not really done to acceptable safety standards for battery installations.
Any battery that has a liquid electrolyte, that could spill or leak, needs to have acid-proof surfaces / containment. This means no screws or penetrations through the acid proof container that could be eaten by battery acid and then get to areas that can be damaged by the acid.
NOTE: When installing flooded batteries on a sailing vessel, consideration should be given so that the orientation of the battery minimizes the uncovering of battery plates while heeling.
10.7.1 Battery mounting materials and surfaces shall
withstand electrolyte attack.
10.7.2 Provision shall be made to contain incidental leakage and spillage of electrolyte.
Consideration should be given to:
1. the type of battery installed (e.g. liquid electrolyte or immobilized electrolyte).
2. the boat in which the battery is installed (e.g. angles of heel for sailboats
, and accelerations for powerboats)."
With regard to "NOTE" above your batteries appear installed in an incorrect orientation for a sailboat. Installation & Orientation of Flooded Batteries on Boats
The T105's have offset filler caps when healed and oriented incorrectly the lower cap can leak. This is why we strongly encourage correct orientation and the use of a product such as Water Miser Caps...
If you do install an acid proof containment system care must be given to drilling any holes in an area where electrolyte could wind up..
"10.7.3 Fasteners for the attachment of battery boxes or trays shall be isolated from areas intended to collect spilled electrolyte."
The batteries do not appear to have had any sort of restraining system. Below goes into detail on how strong this hold down system should be for each battery. With large cruising banks, this normally involves though bolting of mounting systems not just small screws and plastic strap holders. If using straps they should be made of a polypropylene type material as opposed to nylon. Nylon is prone to acid attack.
"10.7.4 Each installed battery shall not move more than one inch (25mm) in any direction when a pulling force of 90 pounds (41kg) or twice the battery weight, whichever is less, is applied through the center of gravity of the battery as follows:
10.7.4.1 vertically for a duration of one minute, and
10.7.4.2 horizontally and parallel to the boat's centerline, for a duration of one minute fore and one minute aft, and
10.7.4.3 horizontally and perpendicular to the boat's centerline for a duration of one minute to starboard and one minute to port."
If that compartment holds nothing but batteries you may get by without terminal covers/protection but it is still a good idea.
"10.7.7 To prevent accidental contact of the ungrounded battery connection to ground, each battery shall be protected so that metallic objects cannot come into contact with the ungrounded battery terminal and uninsulated cell straps. This may be accomplished by means such as:
10.7.7.1 covering the ungrounded battery terminal with a boot or non-conductive shield, or
10.7.7.2 installing the battery in a covered battery box, or
10.7.7.3 installing the battery in a compartment specially designed only for the battery
Once the box is constructed it needs to be vented.
"10.7.9 A vent system or other means shall be provided to permit the discharge from the boat of hydrogen gas released by the battery.
10.7.10 Battery boxes, whose cover forms a pocket over the battery, shall be vented at the uppermost portion of the cover.
NOTE to 10.7.9 and 10.7.10: These requirements also apply to installations of all batteries whether they employ removable vent caps, non-removable caps, are “sealed” or “maintenance free” batteries, or have pressure regulated valve vent systems with immobilized electrolyte (gel and AGM batteries).
NOTE: When batteries have both a stud and post arrangement, protection should preclude contact with any part of the terminal."
While you don't have wing nuts this is just a good reminder. Sadly the current Trojan studs are too short to have any locking washer. We only order ours with the longer studs. One area that always needs caution is laying intra bank wiring across one another. A positive cable should not touch or directly cross over a negative cable or connection. If these points chafe and short this is before the required bank fusing. You have a negative cable laying across the positive that could very easily be rectified..
"10.8.3 Battery cables and other conductors size 6 AWG (13.3 mm˛) and larger shall not be connected to the battery with wing nuts.
10.8.4 Multiple conductors connected to a battery shall be installed with the highest ampacity conductor terminal closest to the battery, followed by successively smaller ampacity conductor terminals.
10.8.4.1 A maximum of four conductor terminals shall be permitted to be installed on a single battery stud.
10.8.5 Flat washers, if used, shall only be installed immediately under the split lock washer and nut of the attachment stud."
Over current protection.. When they refer to "source of power" below this is the battery bank. Ungrounded simply means "positive". "Along the conductor" means 7" of wire not 7" as the Crow flies.
"220.127.116.11.1 Overcurrent Protection Device Location - Ungrounded conductors shall be provided with overcurrent protection within a distance of seven inches (178 mm) of the point at which the conductor is connected to the source of power measured along the conductor (see FIGURE 14)."
Below is basically telling you that a bank of your size, over 500Ah's, should be protected by a Class T fuse.
"Main Battery Overcurrent Protection
18.104.22.168.1 Overcurrent protection devices when installed as a main battery overcurrent protection device shall meet the requirements of E-22.214.171.124 or E-126.96.36.199.
188.8.131.52.2 For batteries or battery banks with a rating of 2200 CCA or 500 amp hours or less, battery overcurrent protection shall have a minimum ampere interrupting capacity (AIC) rating according to TABLE 4A.
184.108.40.206.3 For batteries or battery banks with a CCA rating greater than 2200 CCA, or 500 amp hours, battery overcurrent protection shall have a minimum ampere interrupting capacity (AIC) rating at least as great as the battery manufacturer’s short circuit rating or be rated at a minimum of 20kA at 125 VDC or higher."
When redesigning the battery box be sure to leave a bit of airspace around each battery. Does not need to be much, but tight together retains more heat.
I did not see any temp sensors on those batteries. Temp compensation for charging is critical especially if cruising in areas where the batteries will routinely be above 80F.