Inverter

I am about to purchase and install a new inverter. My research tells me that the Magnum 2812 is the one for me. My question is should I get a large new dedicated battery for the inverter? The house bank is fine with its own charger and it seems to me that using a dedicated battery will avoid any issues with the house bank? Sure could use some advice.

Thanks

Imo, great choice on inverter (I have one). As to the bank question, it depends on your use and how much you tax your other bank. I have a 900 AH bank or T105 Trojan open lead acid batteries. If I don't use the microwave, I can usually go 2 days without drawing the bank down below 75%. Use the microwave through the inverter and it's only one day. This would be 15 minutes of cooking with the microwave.

The other issue with an inverter bank is the size or amp draw capacity. Depending on use, you can see draw rates between 100 and 200 amps typically, and over 300 amps as a maximum. So, the bank needs to be able to handle that amp draw rate for maybe 10 minutes or more with out damaging the batteries. One large bank makes more sense to me.

An inverter gives you lots of possibilities without having to fire up the generator. Making a bowl of soup is a good example. The trick is to determine when it makes more sense to run the generator than depleting the battery bank to make dinner, just because you have the capacity.

Ted

Just use one bank. In addition to distributing your loads on a larger bank, which keeps it from discharging as deeply as separate banks might, having two banks creates problems with isolation and charging underway.


David

^^^^ +1


I'll add my vote for the Magnum, also have one on a 1100AH bank. Good stuff.


Don't add another bank. It adds complexity, cost, wiring, charging, maintenance, control, fusing, and a host of other issues. Use as big a single bank as you can afford/fit.



Include a battery monitor. Best and probably the only way to know what's going on with the bank. I think you'll find that every cruiser who uses a large house bank will echo that sentiment.



Don't have tunnel vision. It's more than the inverter and the battery bank. Assess the SYSTEM to see what else may be involved, it's a significant change, and overlooking parts can create problems down the line. Is the alternator up to recharging the larger bank? How is it regulated? Where does it connect to the bank? Is the bank properly fused? Disconnect? Wiring of the bank jumpers adequate gauge? All equal length? Ground lead from inverter/charger case to system ground? Are the 120V circuits powered by the inverter all connected to the inverter's neutral? Including panel pilot lamps/LED's (ELCI/GFI issues)...Is your skill set up to the install task? If there's a doubt, call in an ABYC marine electrician to help you plan the install or review it before powering up. Well worth the investment to avoid problems you didn't anticipate.



Not to dissuade you from making what is probably the best addition to any cruising boat, but to encourage you to see the big picture and look at the SYSTEM so to avoid disappointment that comes from a short-sighted install. Enjoy!

I would agree one bank. How big is the bank?

Thanks all. I appreciate the advice. I intend to use a qualified electrician, not do it myself.

Mike Lowthian said:

Thanks all. I appreciate the advice. I intend to use a qualified electrician, not do it myself.

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By qualified, should be a marine electrician. If you have a "house" or commercial electrician who's not trained or certified as a "marine electrician" by ABYC or other accredited body, you're in for problems. Ask if they're familiar with the role of co-mingled neutrals in inverter installs and GFCI/ELCI shore power connections. If there's any hedging, you may need to look to another electrician. It can save you a whole lot of headache down the road and having to re-do work. I've been there!

Thread moved from "How To Use The Forum, Site News & Account Concerns" to "Electrical and Electronics & Navigation"

djmarchand said:

Just use one bank. In addition to distributing your loads on a larger bank, which keeps it from discharging as deeply as separate banks might, having two banks creates problems with isolation and charging underway.


David

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Huh? The inverter has it's own charger. I much prefer a dedicate bank for it if one has the room, which is completely isolated, virtually by definition, from the house bank. I strongly recommend the OP get a copy of Calder's "Boat Owners Mechanical and Electrical Manual" and read the first three chapters which cover the whole subject in easy to read detail.

I am also a Magnum fanboy, and highly recommend getting their advanced remote control, and Battery Monitor Kit, which make a really great system.

I said above "having two banks creates problems with isolation and charging underway."


Yes, if one bank is charged by the inverter and the other bank is charged by the existing shore power charger, then if you want to charge them UNDERWAY, you have to keep them isolated and connect them with an ACR or similar to be able to charge both from the propulsion engine.


David

djmarchand said:

I said above "having two banks creates problems with isolation and charging underway."


Yes, if one bank is charged by the inverter and the other bank is charged by the existing shore power charger, then if you want to charge them UNDERWAY, you have to keep them isolated and connect them with an ACR or similar to be able to charge both from the propulsion engine.


David

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Assuming one engine, of course. Or, not... or, a generator... we need more info from the OP or them having read the aforementioned book. In our specific case, despite it being on The List, I never did get around to running one of the alternators to my inverter bank, as in my case the morning and evening generator runs took care of it. But that was us. To me, one big bank potentially creates yet another single point of failure, among other logistical issues.

The concept of an Inverter bank separate from a house bank is a new one for me. Can someone explain this to me? I searched through Calder and was unable to find any reference to an Inverter Bank, separate from a house bank.

Jim

I have been installing I/C for over 20 years. The idea of a house bank and an inverter bank adds complexity to what should be a straightforward design and installation. This is doubly so with the advent of LED lighting which has reduced the non refrigeration loads on a bank to nearly nil.

One house bank with all charging sources charging it. Use a spill over (auto charge regulator or DC to DC charger) to charge the starting battery. Done and dusted.

Another Magnum user and another vote for just one house bank. I have 600 A/H but am a weekender and not a cruiser. I love the setup. And yes, the BMK and Remote are damn near necessary to know what is going on with your battery. Super slick setup!!!

Moving along. I have found an electrician I think can install my inverter. I forgot to mention there was an old existing inverter (not working) in the boat. May have been there for many years. Question raised is: is the old wiring still usable? Is there a way to test the old wiring?

Question raised is: is the old wiring still usable? Is there a way to test the old wiring?

Cannot answer those questions from here.
Ohmmeter testing is not suitable.
A megger test might be ok looking for any insulation leakage but it must be done properly or equipment damage can occur. In a case like this it is far from foolproof.
Needs to be inspected for condition of insulation and the copper conductor .
Needs to be inspected for wire type as many people used what ever they had and the acceptable types have changed over the last many years.
Needs to be inspected for the wire size, AWG, and compared to what is needed for the purpose.

Often unless you are doing it yourself it is not worth fooling around. An electrician likely will not because he will not want callbacks if the reused wire fails later from a missed flaw. He will want to know he has done the best possible especially if the installation is a PIA as many installs in a boat are.

I will reuse wire if it is suitable but if it's a question I'll buy new.

I'll say it. Get new wiring.

JDCAVE said:

The concept of an Inverter bank separate from a house bank is a new one for me. Can someone explain this to me? I searched through Calder and was unable to find any reference to an Inverter Bank, separate from a house bank.

Jim

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That is because Calder is a strong advocate of having only one bank for house and inverter use. He argues the benefits of this design at length. In my opinion, there is no good reason for a separate inverter bank.

SteveD said:

That is because Calder is a strong advocate of having only one bank for house and inverter use. He argues the benefits of this design at length. In my opinion, there is no good reason for a separate inverter bank.

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+1
I have long advocated one large bank for house and starting, plus a small isolated battery somewhere that is capable of starting the generator. Thus you get maximum use out of the batteries you have.

While I'm an advocate of one house bank, the engine(s) need to have their own dedicated battery. In an emergency, when you need to move now, the engine(s) have to start. While I haven't woken up to a dragging anchor, compounding it with no immediate propulsion could get really ugly!

Ted

I agree with Ted on separating the house and start banks. Also with thinking systematically if you intend to keep the boat.

Our Defever had two 8Ds outboard of each engine—serving as both house and engine start banks—and a single 8D to start the generator only! It was great for weight distribution and maybe a good design for the 1980s, but terrible for maintenance or—god forbid—changing out. Plus the single 8D for the genny was a total waste.

When it was time for new batteries—after I killed the 8Ds one winter—I decided to rethink, replace and upgrade everything. With the help of an ABYC consultant, we redesigned much of the system, expanding the house bank to 1250 AH, relocating it to a much more accessible location, installing a dedicated Group 31 to start all three diesels and installing a Magnum inverter/charger, Charles IsoBoost transformer and Balmar remote regulation that could be tailored to the new AGMs. I also replaced all of the heavy DC current-carrying cables, used heavy-duty heat-shrinked lugs and installed remote battery monitoring, new switches, breakers, fuses and bonding system, etc, all per current ABYC standards. Finally, I installed new AC outlets—all of which are on the inverter circuit and protected with GFCI. Before powering up, I had the consultant come aboard and inspect everything.

This was time-consuming and not cheap but I haven’t had a single hiccup with any part of the new system. On our 2,000-mile “delivery run,” we never saw less than 85 percent SOC and enjoyed not worrying about electrical issues.

Mike Lowthian said:

Moving along. I have found an electrician I think can install my inverter. I forgot to mention there was an old existing inverter (not working) in the boat. May have been there for many years. Question raised is: is the old wiring still usable? Is there a way to test the old wiring?

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Your old wiring should be fine. My boat is 35 years old, wasn't kept in the best shape, and all the wire is fine (though some of it has stiffened up a bit). Only in one run near the bilge did the insulation decay.

Wire is simple, there's the conductor, there's the insulator. The conductor is almost undoubtedly fine; you would have to be in an incredibly corrosive environment for the conductor to corrode away. If the insulation is flexible and looks fine then I'd say you're good to go.

The only thing is to make sure it's the right gauge for the amount of current you're going to push through it (https://www.westmarine.com/WestAdvisor/Marine-Wire-Size-And-Ampacity), and always put new terminals on (that's where it'll corrode).

Wire is simple, if it looks fine, it's probably fine.

Has anyone tried Outback inverter/chargers?

Westiculo said:

The only thing is to make sure it's the right gauge for the amount of current you're going to push through it

Wire is simple, if it looks fine, it's probably fine.

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Sure ... as long as the OP knows the difference between type 1, type 2, type 3 conductors and how to tell the different ratings of insulation on those conductors along with the 9 (I think) pages of ABYC standards on conductors.

Tom.B said:

Has anyone tried Outback inverter/chargers?

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We have their 2800 watt vented model and going on 12 years. It’s still supported and field serviceable. I’d buy another.

boatpoker said:

Sure ... as long as the OP knows the difference between type 1, type 2, type 3 conductors and how to tell the different ratings of insulation on those conductors along with the 9 (I think) pages of ABYC standards on conductors.

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Why are you trying to freak the guy out?
He said he found an electrician to do the install. I'm sure the guy will notice if the previous inverter was installed with thermostat wire for some crazy reason. I had to open that E-11 standard you were talking about, there's literally a handful of sentences written about the wire, stuff like
- don't use less than 16awg wire
- should have oil resistant insulation
Unfortunately, I have to hold my ground, it's honestly not that complicated.

Fully agree with Steve. We switched to a Magnum 2812 and a single 1100+ amp battery bank with 10 T-105s shortly after acquiring Sanderling 11 years ago. Keep a small battery (get rid of all the 4Ds and 8Ds and your back will thank you) on standby to start the genset if ever needed!

Do an energy audit to determine what your real 12 volt needs are while cruising. We cook with propane (so that's not a battery issue), but everything else (except lighting) is 120 volts via inverter: microwave, hot pot, hair dryer, household refrig, some device chargers (portable drill, FSR radio, hand-held VHF), vacuum cleaner, toaster, electric skillet (when we want to cook topside), small electric heater, and coffee maker (the most important of the list). Probably forgot a few things. The household refer is the big energy hog. We power our navigation computer using a brick from 12 volts straight when cruising - it's more efficient than using the 110 volts via the inverter.

We can stay at anchor for over two days without running the genset to recharge. When underway, our battery bank is recharged in about 5-6 hours via a Balmar 110 alternator. We never take the bank below 55% charge.

Maerin said:

^^^^ +1

I'll add my vote for the Magnum, also have one on a 1100AH bank. Good stuff.

Don't add another bank. It adds complexity, cost, wiring, charging, maintenance, control, fusing, and a host of other issues. Use as big a single bank as you can afford/fit.

Include a battery monitor. Best and probably the only way to know what's going on with the bank. I think you'll find that every cruiser who uses a large house bank will echo that sentiment.

Click to expand...

As you may get from other responses, the inverter to get depends on the intended use. What is mostly underestimated is the size of the bank. If you intend to use a 1000 watt microwave or a 1500 watt toaster, you not only need to consider the energy size of the battery bank but also the recommended power draw for the batteries used as well as the duration of the discharge. It is not convenient to relate energy by simply multiplying power by duration because some loads like cook top ranges draw power intermittently. Approximate consumption estimates based on experience are: about 30 amp-hours to boil a quart of water, 6 amp-hours for toast, 9 for coffee pot, about 1.4 amp-hour per microwave minute and about 2 amp-hour per minute of hair drier minute of use at full power. If LED lights are used, their consumption is practically irrelevant and the only thing left is the refrigerator, which I calculate at about 20 watts per hour (more in summer) Once all the estimates are added up, multiply by 4 and that should be the size of the bank. Yes, the bank may be smaller, but it would result in a shortened life for the batteries and a much shorter mean time between charges.


Now as to the power handling capacity of the inverter, we should consider how many of the loads may be operating simultaneously. This is another important consideration for the battery bank as well as the inverter. The tendency is to oversize the inverter for the available bank. In my case, I use a inverter with only 2000 watt power to just adequately handle a single 120 VAC but reducing the maximum possible power demand on the bank. My battery bank is separate from the starter bank and it has 6 group 24 batteries that provide 480 amp-hours. My typical usage is 120 amp-hours between charges from which you can deduct my usage of the items (half goes for the refrigerator ice maker which connects directly to the bank via DC).



IMHO the bottom line is, unless you plan to have a 12 or more batteries in the battery bank, there is no point in getting an inverter to handle much more than one single 120 VAC15 amp circuit as overspending in the inverter does not get any value for the additional money spent. In fact, there are inverters that only offer 1500 watts of power and are selling very well.


Hope this view based on experience help, Oh, one more point: never buy a charger inverter combo unless you have another separate charger available.

I concur with Westiculo.



Just make sure that both the neutral and hot are switched in or out in the Y switch that selects from the rest of the AC power sources (shore or generator) and insure that between the Y switch and the inverter the ground and the neutral are tied together. This tie allows for the return current that activates the GFCI outlets when there is a ground fault.


Then have an experienced peer review the installation before activating it.

Remember the 2812 requires DC to charge

We got a 2812 on our GB after the original inverter died. During the recent hurricane wx we got disconnected from shore power and the main bank got run down and the charger part of the 2812 will not work until you get some juice back on DC. But since in our rewire for redundancy, just fire off an engine and then shore power again works.

660 main bank.
Engine starting bank
Single battery for generator

Rollomart

“ never buy a charger inverter combo unless you have another separate charger available.”


Please explain your resoning here. We have a new to us trawler with Mastervolt inverter 2500 / 100 amp 3 stage charger. I leave comnnected all week at the dock. The amp meter shows about .015 input unless the fridge is running. At that point it just replaces what the fridge draws. 2 8D house batteries and 1 group 27 for the engine and a 2nd for the generator. Everything has functioned perfectly for the short time that we have owned boat.