It would not be a difficult thing to ensure that the windlass/bow thruster Chargers are run from the inverter. Another option would be to run a smaller set of wires from the engine room to the forward batteries to charge them from the DC side of the house. You could get by with a smaller set up charging wires, then would be needed for supplying power to thrusters/windlass.
Gordon
The reason windasses are run off ER batteries is so they are charged/powered by an engine alternator. The engine(s) always run when a windlass is being use, and a windlass can draw a lot of current. Personally, I wouldn't want to fire up the generator every time as a safety measure or depend on whatever charge was left from the last shore hook-up.
It would not be a difficult thing to ensure that the windlass/bow thruster Chargers are run from the inverter. ...........
Taking 12 volts DC from one battery and converting it to 120 volts AC with an inverter to operate a charger to convert it back to 12 volts DC to charge another battery would seem a bit inefficient.
I can't believe for that size boat, the required windlass would only require 8/3.
My 2/0 is barely adequate for the 15 foot run and 1200 watt motor according to the installation manual.
Thus why people start thinking remote battery and ways to charge it, even if inefficient.
There are several companies that make sealed battery chargers to avoid corrosion issues. Coat all exposed connectors with CorrosionX. Here is my 24 volt thruster with seal batteries and sealed charger. Would work just as easily with a windlass. My charger runs happily off the modified sine wave inverter, so charging isn't dependent on shore power or generator.
View attachment 55638
Ted
Your surveyor and insurance company may take exception with a battery charger mounted over a battery (and a non-ignition protected one at that) and an AC outlet mounted over a battery and the lack of fuse protection.
All contrary to ABYC but your choice. I am familiar with the arguments about AGM's not gassing but I have several photos of burst AGM's in my files and if they burst they do release hydrogen right into that charger and AC outlet.
There is also the lack of a means to trap spilled electrolyte (it does spill if the case bursts), lack of positive terminal protection and lack of means of securement.
PS. my windlass/thruster run from two group 31's at the bow and are charged via #6AWG cables from an echo charger in my engine compartment. There are many ways to do it and all are a compromise.
........... Both positive and negative leads off charger are all fused (yellow holders by battery terminal)...........
Fuse the positive only.
Hydrogen is the lightest know element and will go straight up which is why there are restrictions on what electrical equipment can be mounted above a battery.
As to AGM's bursting, over charging from a faulty or cheap charger or improperly set charger or internal fault in the battery itself.
There is a reason ABYC holds AGM, GEL and conventional wet cells to the same standard as evidenced by the AGM shown in the photo below.