Originally Posted by APWTryfan
I am hoping for meaningful responses that can help me understand what happened and hopefully help others too.
I am truly sorry for the unfortunate turn of events
and am grateful that you posted here with detail so that others can learn.
I have seen equipment
fires involving a shorted battery connection like that and they are, just as you describe, very fast and very frightening.
Like several commenters upthread, I believe that there was a short circuit in or very, very near to the shore charger. It is possible that careful examination and disassembly of the charger may provide more detail, for example, you may find that a piece of hardware
came loose and fell onto current-carrying components. Or you may find evidence that the wire terminals came into contact with each other where they connect to the charger. Either way, I think it is unlikely that any other components on the boat played any sort of role in the sequence of events
I would not expect to find other damage to your electrical system
, beyond those wires and cables
obviously damaged by their proximity to the wires that burned.
Looking at your wiring diagram, it appears to me that there is insufficient circuit protection overall. A number of approaches for remediation is posisble. ABYC standards would have varying requirements depending on the length of some of the cable runs and whether they are in conduit.
In general, however, there should be some sort of overcurrent protection in these places:
1) In the + connection to the start battery, as close to the battery as possible, so that current to both the ACR and the OFF-1-2-BOTH switch goes through the overcurrent protection.
2) In the + connection from the house bank to the OFF-1-2-BOTH switch, as close to the battery as possible.
3) In the + connection from the house bank to the ACR, unless the cable can be relocated to share the overcurrent connection for the OFF-1-2-BOTH switch.
4) In the + connection from the house bank to the solar controller
5) In each of the two + connections from the OFF-1-2-BOTH switch to the battery charger. If your replacement charger only has one battery connection, then you can remove the extra cable and won't need overcurrent protection for it.
6) While not required, I would consider overcurrent protection between the OFF-1-2-BOTH switch and the panel, especially if the run is long or is made of lighter gauge wire.
These will be expensive changes and take time. You may want to survey
your overall electrical system
as there are some practices which, while not necessarily unsafe, may not be the best recommended practices.