2021 R27 - House Batteries

[Brian 27 OB]

The four 110ah batteries in the port lazarette appear to be setup with 1 dedicated to the thruster that is charged by the 20amp 110volt charger when connected to shore power, as well as the outboard feed to the start battery when the ACR closes, a closed ACR would tie the solar feed to this as well. The other 3 batteries are wired to the 3000 watt inverter & house loads and are easy to identify the shore charging feed, the solar feed and the outboard dedicated aux charging leads, although the posts they connect to with the 3 batteries in parallel don’t make sense, typically you pull from opposite ends not from one end and the middle, but that can be fixed easily.

Questions:
Is the thruster battery the same UB121100 as the other 3? It’s so far back I can’t see it and don’t want to move 3 batteries to get to it...yet
Why are the ground jumper cables on the 3 house battery negative posts different gauge wire between the batteries in parallel? Was this by design or an error?

Somewhat unrelated to this battery thread, what size/model AC Unit is in the boat? 16000btu? The manuals in my owners bag show 4 sizes. It seems to be drawing 12amps running.

By the way, love this boat! My wife says it’s our Airstream on the water.

 

[JeffRad54]

The Thruster Battery 'should' be measured by CCA, not Ah. In other words, it should be like the Engine Battery
(not the House Batteries) as it is used similarly for high current discharge of short duration.

Jeff Radwill,
Margaux - R29 OB

 

[JeffRad54]

Out of curiosity, because you are the second person I know with the 2021 R27 sans genny, do you plan on anchoring out much?
With 3 110Ah house batteries, you have 165 Ah available before you hit the 50% discharge mark.
I don't know what BTU A/C you have, but 12 amps over 12 hours = 144 Ah. (or 12 over 8 hours = 96.. )Add refrigerator(s), Anchor light, lights, TV, microwave use, grill use, device charging, chart plotter if you use the anchor position warning, water heater, etc. You see where I'm going with this?

LED lights are a minimal Ah expense, as is the microwave, even though it is a 1050 watt item, it's typically only used for a few minutes. The grill is a high draw item at 1300 W, and may be used for 20 minutes or so (7 or 8 minutes warm-up, plus cook time for thin steaks or burgers, etc.), but that adds up to 390 Ah (1300 x .3). The water heater is 750 W and takes roughly 30 minutes to heat water, after which you can shut it off and have 5 gallons or so of hot water. 375 Ah.

FWIW, I suggest you make a spreadsheet of your planned electrical usage if you do indeed plan on overnights at anchor.
You may find yourself setting a 4:30 AM alarm to start the engine! 🙂

Let me know what you find, please. My friends will be very interested.

Thanks,
Jeff Radwill
Margaux - R27 OB (2019, with genny)

 

[Brian 27 OB]

Jeff - You’re math is a little messy. But I’m picking up what you’re putting down.

So the 4th battery is in fact the same as the 3 house batteries. I reached my camera up there today. I would have though it was the exact type as the cranking battery since they connect thru an ACR and the thruster is a brief heavy load. I plan to require the 3 house batteries anyway so I will add it to the others, I hardly use the thruster. So that will increase my bank to 440 and I know people will say keep DOD to 50%, but I would go 80% with these batteries since they are only 200 bucks a piece and I want to replace with Lithium in the spring anyway.

No gen set wasn’t my call. The boat was ordered by and delivered to the dealer without one and my wife wanted the boat now. I was going to have a NextGen and a diesel tank installed but we ended up deciding the 8.5’ beam would require a SeaKeeper to help keep us comfortable. So the space where the generator would go is full.

The SeaKeeper pulls 40amp @ 12v to start up (20 minutes) and then 12-18 running. So your calculations where even lighter than you knew. And the Air conditioner 12 amps was at 115v. Would only last a two hours on the inverter without the outboard running. And even then, you only get 6 or 7 hours before the batteries are flat with the engine running.

We have always had a generator. Our last boat was a Regal and the gen set was the first thing on when we got in the boat and didn’t shut off until we were back on shore power. But, I’m looking forward to try and go without. We do typically stay at marinas with the occasional haul out and trip to a lake with no power where we anchor out. It’s September right now so it’s easy. We are on the Potomac in Virginia, the weather doesn’t require AC. We will need heat soon. But our slip has 30amp power so we can heat up the boat before we venture out.

We will see. Maybe it works for us and maybe it doesn’t. It will be an adventure nonetheless.

 

[JeffRad54]

Jeff - You’re math is a little messy. But I’m picking up what you’re putting down.

So the 4th battery is in fact the same as the 3 house batteries. I reached my camera up there today. I would have though it was the exact type as the cranking battery since they connect thru an ACR and the thruster is a brief heavy load. I plan to require the 3 house batteries anyway so I will add it to the others, I hardly use the thruster. So that will increase my bank to 440 and I know people will say keep DOD to 50%, but I would go 80% with these batteries since they are only 200 bucks a piece and I want to replace with Lithium in the spring anyway.

No gen set wasn’t my call. The boat was ordered by and delivered to the dealer without one and my wife wanted the boat now. I was going to have a NextGen and a diesel tank installed but we ended up deciding the 8.5’ beam would require a SeaKeeper to help keep us comfortable. So the space where the generator would go is full.

The SeaKeeper pulls 40amp @ 12v to start up (20 minutes) and then 12-18 running. So your calculations where even lighter than you knew. And the Air conditioner 12 amps was at 115v. Would only last a two hours on the inverter without the outboard running. And even then, you only get 6 or 7 hours before the batteries are flat with the engine running.

We have always had a generator. Our last boat was a Regal and the gen set was the first thing on when we got in the boat and didn’t shut off until we were back on shore power. But, I’m looking forward to try and go without. We do typically stay at marinas with the occasional haul out and trip to a lake with no power where we anchor out. It’s September right now so it’s easy. We are on the Potomac in Virginia, the weather doesn’t require AC. We will need heat soon. But our slip has 30amp power so we can heat up the boat before we venture out.

We will see. Maybe it works for us and maybe it doesn’t. It will be an adventure nonetheless.

"... You math is a little messy." That's very kind of you to put it that way. I admit, my electrical knowledge is lacking, even though I have an electronics background. I never really dealt with power distribution and am learning quite a bit from my mistakes.

I'm surprised the 4th battery is the same. Yes, the Thruster is rarely needed. On my 2019 the Thruster battery is also the generator starter, so I assumed...

FM discontinued the genny with your model. Apparently something to do with Webasto emissions, or so I've heard.

Enjoy your new R27!

 

[JeffRad54]

Driving on the highway today, my mind wandered over to my original reply. I suddendly realized what a bone head mistake I made with the math. Chalk it up to an embarassing public brain fart. Watts x Hours do NOT = Ah!
I'm glad you got my train of thought, even though it was derailed. 😳