How to Wire DC-to-DC Charger

[Tom_F]

My electrical woes continue, but I think I am on the right path to finally getting these resolved. Lots of the PO's questionable wiring has been removed, components have been replaced or reconfigured, battery switches have been/are being added, etc. My questions here are around charging, especially for the auxiliary battery in the bow for the thruster.

My boat is generally on a mooring during the season. I am adding 3 200-watt solar panels, each connected to a disconnect/circuit breaker (not shown on the diagram as I forgot to include them) and then each connected to a Victron SmartSolar 100/20 MPPT Controller. Those will be connected to a charging bus which is connected to the house bank. I am also adding a Sterling ProAlt C to improve charging from the alternator, which will be connected directly to each battery bank. My old inverter/charger died and I replaced it with a Xantrex Freedom Xc Pro Marine 3000w Inverter/Charger.

Question 1: Is there a benefit in connecting the inverter charger to the same positive bus as the solar panels rather than directly to the house bank?

I have a single, simple On-Off battery switch to combine or separate the house and start banks even though both are currently separately charged by both the inverter/charger and the alternator. I am replacing the on-off switch with a pair of remote battery switches and a Blue Sea ACR to connect the house and start batts. As part of that add I will eliminate any other direct connections between the 2 banks. There is a separate disconnect switch for each of the house bank, the start batt and the negative circuit which I will live with for now.

There is a battery for the bow thruster in the bow which only powers the bow thruster and is only charged by a stand-alone shore-power AC battery charger (useless since I'm on a mooring). The windlass power comes directly from the alternator and it only operates when the engine is running. There is a washdown pump for the anchor and the power comes from the house bank and bypasses the main panel (the on-off switch/breaker was hidden in a cubby under the v-berth that took me a long time to find). I want all of the bow thruster, windlass and washdown pump to now be powered from the thruster battery, and I want the thruster battery to be charged by other means than shore power. For those reasons, I am adding the Sterling Pro-Alt C and the expansion module that lets me charge 3 banks. I also want to add a DC-to-DC charger to charge the bow battery from the house bank.

Question 2: Where do I connect the DC-to-DC charger? To the battery switch between the house and start banks? That does not seem right to me. Directly to the house battery? To the unswitched DC distribution bus?

Question 3: Assuming I connect this to the house batt or the DC distribution bus, do I need a second remote battery switch before the bow battery? If so, best to locate it near the charging source or the battery?

Question 4: Right now, the windlass has a breaker which is used as a switch to keep it powered off when it is not being used. This is in the aft cabin along with the 3 main disconnects because that's where the dealer put it. I do not want to relocate that. Do I need another switch to disconnect the DC power from the bow battery? Is there a remote switch suitable for that purpose so I can locate both switches together without having to run another pair of heavy gauge wires?

I realize the best option here is to call a marine electrician, but that is not an option. The marina where the boat is on the hard for the winter has no electrician as he retired and the independent electrician I called was a disaster - I'm still waiting for an estimate from an appointment in June. I have no choice but to DIY this.

[Pete7]

Can't see the point of the bow thruster shore power charger. Remove it and keep as a spare. You are unlikely to ever have to use the windlass and not have the engine running. So just use the Sterling expansion box to charge the bow battery when the engine is running.

If you use the engine regularly, then you won't need the DC>DC charger so another saving.

The output from the inverter charger can't use that switch, ideally you need a RCD or better still RCBO called something like GFCI in the US.

[Tom_F]

Pete, when you say "that switch" do you mean the one I used as a disconnect for the inverter? If so, the picture is just a picture of a Blue Sea switch. The one I used meets Xantrex's recommendations, but I don't remember which one I actually used. If that's not the switch you are referring to would you mind clarifying as I'm not following what you mean?

My thought on the DC-to-DC charger was to get some of the benefits of the solar panels for that battery. Am I overthinking things? It wouldn't be the first time.

Thanks.

Tom

[Pete7]

Tom, sure its the one in the top photo I am referring to.

Yes I think you are over thinking things, I prefer the "KISS" approach (keep it simple), says me having installed LFP rather than an oil lamp So question the need for the DC>DC if the boat is used regularly and batteries charged by the alternator.

We have recently been through this exercise and chose to mount a DIN rail RCBO (GFGI in USA) inside a small consumer unit close to the inverter. It means that if a fault occurs the RCBO will trip in 30 milli seconds. It also acts as a switch if needed, though we tend to use the inverter remote on/off switch. The photo is mid "work in progress" but you get the idea. It was actually quite cheap to do, £40.

Pete

[MerMike]

As Pete says, KISS. Use the Sterling to charge the bow thruster, as long as all batteries are the same chemistry. If they were different (i.e. one bank was LFP) then a DC-DC charger with its own charging profile would be useful.

[flee27]

Definitely not trying to be negative.

I agree with the others. This design using too many pcs. of equipment to are not needed.

I know it might not be the point of your diagram but remember implement proper fusing in your system.

I don't understand the ACR, as the Sterling Pro provides a separate output for the house bank and the start battery already.

IMO the remote battery switches are great but you seem to be over using them (if cost is any concern).

Good luck

Foster

[Tom_F]

Pete, Mike and Foster,

Thanks for the great advice. Some of the complexity is based on recommendations the electrician who showed up to look but never actually provided an estimate made, but now I'm wondering if he was just trying to sell me stuff I do not really need. The batts are all the same chemistry so I think I will skip the DC-to-DC charger for now but add it later if I'm not running the engine enough to keep that bow battery charged. We generally use the engine for just a few minutes to depart and arrive at our mooring so I am a little concerned. The PO only stayed at marinas, so there are some changes I have made to accommodate the different way we use the boat.

Pete, thanks for the suggestion on the GFCI breaker rather than a simple switch. I also use the remote panel to switch the inverter, but I installed the switch as a service disconnect as suggested by the installation manual.

Foster, I did not take anything you said as a negative so don't worry about that. I do like the remote battery switches, despite the expense, because the switches are in tough to get to locations so having the ability to flip them off from the nav station is really a plus. Also, everything is fused as appropriate but it's a good reminder.
Tom