Charging Bow Thruster Batteries from House Batteries

[Streetcar]

I am thinking of using a DC to DC smart charger to ensure bow thruster batteries get a proper charge. Is this a reasonable solution?

Currently the bow thruster batteries (2x12V batteries in series) get charged from the 24V house batteries through a VSR. The problem is that when I arrive in a marina and have been using the thruster, the house batteries a frequently fully charged from motoring.

This means that the now depleted thruster batteries wont get a proper 'bulk' charge through the VSR when I put the house bank onto charge (as the house batteries go quickly to 'float' being fully charged).

It seems that I have two options. Install a separate battery charger for the thruster batteries, or install a DC to DC charger between the house and thruster batteries. I would prefer the second option for simplicity, but would need to keep the VSR between the house bank and the DC to DC charger to avoid the risk of drawing the house batteries down in the case of a shore power interruption.

I have not used DC to DC chargers before and am concerned about the "unintended consequences". So I am wondering whether this is good practice or not.

[smac999]

The vsr will always be charging the bow batteries if the house is charging.
Your bow battery is probably only depleting a couple percent if that.
When you araive all batteries will still be fullish. The thruster is pulling power out of both banks, and they will be pretty even.

The problem with vsrs to bow batteries. Is when you engauge the thruster you can have 100's of amps on that circuit from the house bank. Makes it hard to wire and fuse.

An echo charger works good for this instead of needing huge wire to the bow.

[espresso]

What I have done is use a 220 volt. 24 volt smart charger via my house inverter.
The total amount of energy used for the bow thrusters is low, so a small charger is fine.
This way the wiring to the batteries is thin, and the smart charger looks after the batteries properly.