Battery Charger Demand Controller

[superheat6k]

With my boatyard introducing charges for electricity and because I don't need to continually cook the batteries I have come up with this idea for an automatic Battery Charger Demand Controller.

I am thinking of two primary control setpoints:

1 Falling Voltage to turn on - for now I have set this to 12.4 volts on the service / domestic battery bank.

I wil have to fine tune the Buck controller so the desired trigger is matched to the Turn On / Off level of the Sontay IO-RM1 module (~ 10 vdc)

2 Period to remain on for after the trigger voltage level is restored - for now I am thinking ~ 3 hours.

The battery charger is a Sterling 4 stage conected to two battery banks: Service & Port engine bank 2 x 110AH; Stbd engine & Windlass bank 1 x 110 AH.

Does any one know if 3 hours is OK for this charger to run through its normal cycle, or should I allow it to cycle longer, or indeed for less time. I expect the background demand to be very minimal, just a few LEDs on the distribution panel, unless a bilge pump kicks in.

I am also thinking of hooking up a run time counter to see how much it runs for over extended periods.

Thoughts please on this idea.

Diagram attached.

 

[Rappey]

Surely the amount of power a modern mains powered smart charger uses is very minimal, especially in maintain mode so why not just leave it plugged in.
Option 2 could be solar and wind ?

 

[superheat6k]

I suppose one reason is that I can see I am going to be very bored and with full access to a well equipped workshop within the bounds of my own home, I have the IO modules at the factory, and EBAY remains open.

 

[PaulRainbow]

If you are not onboard and there is no appreciable loads on the batteries, the Sterling charger will spend most of its time in standby, it won't cook the batteries.

I have an auto mains charger setup, but for a different reason. I get most of my power from solar panels. During the Summer i rarely need to run the engine or use the mains charger. In Spring/Autumn, there isn't enough Sunshine for my needs though. I have a Victron battery monitor with low voltage alarm and a built in relay that can be configured to close at a particular voltage. I've connected the relay to a 240v relay, with a 12v coil, fitted into the consumer unit. So, on those days when the Sun doesn't shine enough, the relay closes and the mains charger comes on. But, in my case, i don't want to fully charge the batteries, i want the solar panels to do that the next day, but i don't want to overly discharge the batteries. I find that leaving the charger on for one hour puts enough power into the batteries to prevent too much discharge, until the next day.