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Please help with my plan for electrical upgrades for my sailboat

prskier17

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I posted this in the marine section, but this one seems much more active so I hope it's okay that I'm posting in both places.
My sailboat currently has 2x 100Ah Renogy 12v lithium batteries that I've been charging from shore power. These were setup by the previous owner to provide house power as well as starting for a 9.9HP outboard. I'm going to add solar and an inverter, as well as a DC-DC MPPT charge controller that will allow me to add a separate AGM starting battery. The components I've purchased include 2x 100W 12v Renogy solar panels, Renogy 30A DC-DC MPPT Solar Charge Controller, and a 1000W Renogy Inverter. Below is my first draft at a wiring diagram, and I'd appreciate any feedback. Some questions I have include:

  1. Should I use positive and negative busbars? My diagram currently assumes multiple ring terminals stacked on lugs. For a 12v system, is this better or are busbars preferred?
  2. I currently have a 1, 2, 1+2, Off battery selector switch. Is there any advantage in placing the 1,2,1+2, Off Battery selector between the positive terminals of the batteries so that I can isolate one battery as well disconnect both? Should I replace that switch with a on/off battery disconnect so that the batteries can be disconnected?
  3. Expanding on question 2, should I have a circuit breaker at the batteries or is the 100A fuse appropriate?
 

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1 use buss bars.
2 being able to disconnect the batteries with an isolation switch is a useful safety feature.
3 over current protection is required as close as practical to the battery positive so no excessive length of cable is unprotected.
Advise a separate fuse in the inverter feed cable in adition to the fuse feed to the DC panel.

Comments.
Starter battery negative needs connection to system negative.
Can your outboard generator supply the power needed for the DC to DC converter?
Need to ensure shore power is integrated correctly, example, shore power charging of starter battery may need DCtoDC converter disabled, ( or you allow all batteries to be charged from shore charger connection to starter battery).

Mike
 
@mikefitz - thanks! I mistyped when I said shore power. What I have is a simple Victron 15A AC-DC charger that I have been using with an extension cord to charge the Renogy batteries while at the dock. I don't have a shore power connection on this boat and do not want to add one (I do not intend to have AC shore power sharing receptacles with the new inverter). I'll update the schematic to reflect this.
 
With regard to the busbar, I like this approach as it is very organized. Should I be concerned with increased resistance, or will it be equivalent to having multiple terminal rings on various studs?
 
Here's an updated schematic with busbars. It's a bit sloppy but I'll clean it up once I'm converging on the best solution. Based on this, my positive busbar has 5 connections and my negative busbar has 7 connections. I still have to confirm fuse values, but are there any flaws with this layout? I like the busbar that have integrated fuses, but I think I'd still need additional fuses close the the DC-DC MPPT Charger, close to the positive battery terminal, close the the AC/DC charger... is that accurate?

Schematic v.2.png
 
Fuses are positioned at/near the source with the high current capability, usually this is the battery (positive buss bar). Example Renogy 40 amp fuses at the starter battery and at positive buss bar, AC charger 20 amp fuse at buss bar.
Buss bar, 200A rated, 3/8 stud, 2 cable terminations max per stud.
Most DC panels are rated at 100 amps total distributed current, a rough calculation on the current taken by your DC loads should identify a suitable fuse value, say 50 amps?
Master fuse at battery may be too low if inverter and DC loads exceed 100A.
Check the current rating of the 4awg you are using.
I am still not convinced the 9.9 outboard can deliver over 30 amps, have you checked the specification?
I have, the specification suggests 2 amps at 1000 rpm, 12 amps at 3000 rpm.

Mike
 
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Fuses are positioned at/near the source with the high current capability, usually this is the battery (positive buss bar). Example Renogy 40 amp fuses at the starter battery and at positive buss bar, AC charger 20 amp fuse at buss bar.
Buss bar, 200A rated, 3/8 stud, 2 cable terminations max per stud.
Most DC panels are rated at 100 amps total distributed current, a rough calculation on the current taken by your DC loads should identify a suitable fuse value, say 50 amps?
Master fuse at battery may be too low if inverter and DC loads exceed 100A.
Check the current rating of the 4awg you are using.
I am still not convinced the 9.9 outboard can deliver over 30 amps, have you checked the specification?
I have, the specification suggests 2 amps at 1000 rpm, 12 amps at 3000 rpm.

Mike
Thanks Mike, the 9.9HP outboard can only deliver 12amps. The Renogy DC-DC MPPT controller will charge the starter battery from solar once the house batteries are full.
 
The Renogy DC to DC / MPPT primary design action is to take power from the starter battery once its voltage exceeds a voltage threshold and charge the house battery. Thus once the outboard starts charging the Renogy will attempt to pull 30 amps, exactly how the system will respond is uncertain but the outcome may not be good news.
The secondary feature of trickle charging, at a few amps, the starter battery from excess solar, may function as you hope but given the problems some have with Renogy equipment this function may not operate well. There have been reports of house batteries being completly discharged.

My advice would be to install a quality MPPT that would alow series connection of the panels and find an alternative trickle charger for starter battery maintenence . I carry out marine Installations and now only use Victron products, the failure rate is high among alternatives.

Mike
 
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The Renogy DC to DC / MPPT primary design action is to take power from the starter battery once its voltage exceeds a voltage threshold and charge the house battery. Thus once the outboard starts charging the Renogy will attempt to pull 30 amps, exactly how the system will respond is uncertain but the outcome may not be good news.
The secondary feature of trickle charging, at a few amps, the starter battery from excess solar, may function as you hope but given the problems some have with Renogy equipment this function may not operate well. There have been reports of house batteries being completly discharged.

My advice would be to install a quality MPPT that would alow series connection of the panels and find an alternative trickle charger for starter battery maintenence . I carry out marine Installations and now only use Victron products, the failure rate is high among alternatives.

Mike
Thanks Mike (and apologies for the duplicate thread in the marine section - I will end the use of that one). Prior to this pending install, the outboard was directly connected to the two lithium 100Ah batteries (in parallel) as setup by the previous owner. As a sailboat, the engine is frequently unused for a long period of time while the batteries are depleted by other electronics on the sailboat. I haven't had issues in this scenario running the outboard for 1+ hours at a time, numerous times, while the batteries where at low state of charge. In this scenario, wouldn't the charge rate and it's effect on the outboard be similar to what I am planning to do with the DC-DC charger? I have a friend with this exact setup (I just confirmed today) that has been running without issue including motoring at least 60 hours so far. If an issue is encountered, I could disconnect the AGM battery from the DC-DC charger and rely on the outboard to keep it charged and utilize the MPPT function to use only solar for charging the lithium.

I am a fan of Victron, and have so far had good experiences with the Renogy products I've used. I appreciate the system-wide energy monitoring option that I will have through their hub and upcoming Core monitor. That being said, none of that matters if it doesn't actually work.

Here is my latest wiring diagram.
 

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