Time to add an inverter

[PJHoffnet]

We’ve checked off everything on our Prepare to Cruise checklist (hand over head systems, underways/landings, anchoring, mooring balls, locks, long day cruises, meal prep, and tender ops) with the exception of overnighting on the hook. Because I use a CPAP, and because I want a ready ‘clean’ source of AC power while underway (without the need to fire up the generator), I want to install an pure sine wave inverter (2KW-2.5KW). Stove/Convection-Microwave and AC would be generator loads, but I want all the ‘hotel’ services (network, laptop, printer, tablet/phone chargers, handheld radio chargers) to have ready power.

Here is the current DC power set up on our 1999 Maxum 4100 SCA as shown in the boat’s owner’s manual supplement. All batteries are Deka 8A8D 1450CCA 245AH@20hr AGM2.



Here is the inverter wiring, also from the supplement. I’ll take this as the manufacturer's desired wiring for when an inverter is added. The inverter battery I’d add will be identical to the other three.



We have a ProMariner brand ProTech 1240i Plus charger wired in the two bank configuration as shown in the charger’s owner’s manual and installation guide with the ‘spare’ third bank being jumpered to the second bank lug.





While I haven’t been able to completely hand over hand the DC output from the charger (the wires disappear into areas I can’t easily access) to verify the configuration, I’m assuming one bank goes to the single port engine/generator battery and one goes to the starboard engine battery and the house battery which are wired in series as shown in the DC wiring diagram.

Right now, unless I hear from folks who have a better way to do it, I’m planning on going with the supplement’s wiring. The one thing that doesn’t seem to make sense to me is why the inverter battery seems to be on the stbd engine/house side of things with its positive wire on the same lug on the battery isolator and the negative wire going to the house battery. Seems, at least to me, to be better to spread the love out and hook on the port engine/generator side. I’m only guessing here, but could it just be the simple fact the wiring would be shorter going that way then to add a foot or so to the positive side to reach the other side of the isolator and maybe two more feet to get the negative over to the port/gen battery? I’m assuming the battery isolator balances out the loads no matter what.

[smac999]

don't add an "inverter" battery. make the house bank bigger. the inverter should be on the house bank. I can't tell from that pic. it looks like they have simply added another battery in parrell. in that case it is not an inverter battery.... it is a bigger house bank.

you should also try to seperate the house and engine, if they are the same. the diagram is kinda weird. not sure why they would name 3 and 7 as 2 different batteries if they are joined together. it's just one bank of house / engine.

[ranger58sb]

First pic, looks like house (7) and starboard engine battery (3) are connected together. Looks like port engine (6) is separate

Second pic, looks like house battery (2) and inverter battery are connected. Looks like starboard engine battery (4) is shown without connections (presumably wires would lead off to the right, on that pic).

If I have that right, I can't quite reconcile the two pics...

It wouldn't be unsurprising in that style of boat to have engine start batteries also servicing house loads. That design often raises great angst here and on other sites with more "traditional" electrical schema... but it actually works well enough given the designer's/builder's likely assumptions about how a boat like that would be used. And it could easily mean that your current batteries are simply dual-purpose start/house banks, one made up of two 8Ds, and one being a single 8D.

So... that might mean Maxum does a complete rewire in the inverter instance: 3 in the first pic becomes 4 in the second, 7 in the first pic becomes 2 in the second, 6 in the fist pic is connected to 4 in the second (3 in the first, another battery is added ahead of the port engine (just as 6 is ahead of the starboard engine in the second pic), and that new battery is connected to 7 in the first pic.

IOW, 6 and 3 in the first pic become the starboard bank, and 7 and the new battery become the port bank.

Uhhh.... if I said all that the way I meant it. Or even if I did, could be all wrong.

BUT IF SO... then it would seem like you'd end up with two banks of two each 8Ds, one bank for each engine and each bank would service about half of the house. Not all that bad.

Gas or diesel, BTW? If gas, that will influence inverter location (i.e., probably not in engine room).

-Chris

[PJHoffnet]

Originally Posted by ranger42c

Gas or diesel, BTW? If gas, that will influence inverter location (i.e., probably not in engine room).
-Chris

Still digesting your whole reply, thank you and you also SMAC999.

To answer the question - Diesel, twin Cummins 6BTA 5.9 M2s. 330HP each. The inverter, as show in the supplement, goes in what's called the utility room - a space forward of the engine room. The white 'square' just aft of the inverter in the diagram is the water heater.

Fig 1 battery 7 (house) = Fig 2 battery 2; Fig 1 battery 3 (stbd engine) = Fig 2 battery 4 (I'm not sure why it's not 'wired' in Fig 2).

I'm also wondering why, after adding an inverter & additional house battery (battery 3 in Fig 2) they just didn't go to a three bank system with bank one being stbd engine, bank two being port engine/generator and bank three being house. That three bank configuration would work great with my current charger.

[ranger58sb]

Originally Posted by PJHoffnet

To answer the question - Diesel, twin Cummins 6BTA 5.9 M2s. 330HP each. The inverter, as show in the supplement, goes in what's called the utility room - a space forward of the engine room. The white 'square' just aft of the inverter in the diagram is the water heater.

Should be good to go, then.

Originally Posted by PJHoffnet

Fig 1 battery 7 (house) = Fig 2 battery 2; Fig 1 battery 3 (stbd engine) = Fig 2 battery 4 (I'm not sure why it's not 'wired' in Fig 2).

That tracks with what I think I was trying to say.

Originally Posted by PJHoffnet

I'm also wondering why, after adding an inverter & additional house battery (battery 3 in Fig 2) they just didn't go to a three bank system with bank one being stbd engine, bank two being port engine/generator and bank three being house. That three bank configuration would work great with my current charger.

Dunno, but the starter/house dual-purpose configuration is quite common. You might also find that one bank runs bridge electrics, while the other bank runs bridge electronics.

It's also not uncommon to install a separate genset start battery, and make that use the third pole on your 3-bank charger. Size differences can be an issue, but that approach also adds another layer of redundancy. (I'm guessing you'll have a momentary parallel switch on at your helm, too, usually sort of a quick fix if you've drawn down one or the other main bank a bit too far.) OTOH, a genset with it's own alternator can usually keep that battery charged easily enough, anyway... so I wouldn't say it's critical to put that battery on the charger, too.

It would also not be unheard of to have bow a thruster and it's own dedicated battery bank located near the thruster; another possible use for the 3rd charger pole.

Digressing: if you have a little extra room to play with near the obvious battery installation locations, you could maybe increase your capacity using 12V Group 31s or 6V GC2s. And that could make each individual dead lift slightly easier. Might not be worth the effort, though...

-Chris

[CharlieJ]

Wired IAW the boatbuilder's 1991 design does not take advantage of the advances in inverter/charger that have taken place over the last twenty years. As wired, the inverter (only) is managed as a separate source of AC power. The newer designs provide mains or genset input to the inv/chgr which than either passes through the AC using some of the incoming power to charge the batteries or the inv/chgr will automatically switch to inverting when the mains or genset power is removed.

I typically install an inv/chgr as discussed above and then recommend the addition of a battery charger as a backup should the inv/chgr fail.

Comments on battery capacity: Inverters require a lot of DC power to operate. Assuming perfect performance, it will take 10 amps of 12VDC power to produce 1 amp of 120VAC power. So the 1200W required to brew a pot of coffee will require 10AAC and the battery bank will have to provide 100ADC to the inverter. Assume the brew cycle on the coffee pot
is 6 minutes (0.1 hour) than that pot of coffee will "cost" you: 100A x 0.1hr = 10Ahr.

As lead acid batteries should only be discharged to about 50% to maximize longevity, a standard, flooded lead acid (FLA) Group 8D battery has a capacity, C, of 220Ahrs of which 110Ahr are available. That pot of coffee cost you about 10% of the capacity of the 8D battery.

It gets worse. The C rating of a battery is generally based on the 20 hour discharge rate which is found by applying a constant load to a battery until it is depleted. For an 8D with C = 220Ahr; the 20 hour rate is 220Ahr/20hr = 11A. If the load is held to 11A, the 8D will produce 220Ahr over 20hr. Here is the gotcha: if a load > 20hr rate is applied, the battery will produce significantly fewer Ahrs; i.e., the battery shrinks.

Since the coffee brew took 110A, the battery's size is significantly reduced but, more importantly, the voltage sag caused by that DC load may cause the inverter to shut down on low input voltage.

So the take away's are:
> in 1999, inverters were added to pleasure boats to handle incidental, minor AC loads
> one or two 8D batteries will not be sufficient to handle any real AC loads
> if you are going to live off your house bank you absolutely must have a battery monitor such as the BMV 700 series or the Balmar SG200.
> your dependance on the CRAP demands a well thought out, robust battery system providing sufficient DC power to the inverter or inverter/charger to operate your AC loads through the night.

BTW: I install a lot of inverter/chargers every year.

[captstu]

I've sailed with a CPAP for 20+ years and can share some advice specific to the need to provide power for that device.

My current boat, a Ranger 25 (small tug) has a ProMariner 2500 inverter installed - it easily runs my smaller air conditioner underway and meets all my at-anchor needs without running either the generator or the engine during short peak loads such as post-shower Admiral hair drying or late evening microwave tea. At these times, I use the ProMariner auto-sense mode to turn on the inverter in response to a demand for power.

Clearly, it will run my CPAP if necessary - but not in auto-sense mode since the CPAP demand is so low. When I run the ProMariner continuously to supply the CPAP, the inverter overhead is far larger than the actual demand from the CPAP - and results in a noticeable depletion of the modest house bank overnight.

I have a dedicated very small (60 watt) inverter dedicated to the CPAP. The CPAP operates comfortably on that inverter, wiring requirements are minimal, and there is no measurable reduction of the house bank voltage overnight. It is an inexpensive and uncomplicated way to provide the reliable power I need for my breathing condition.

For several years I used a CPAP that was 12 volt powered directly but two things happened - the current device provides better support for my condition's medical needs and the total overall power drain thru the inverter/110 volt CPAP is lower.

CPAPs are not like microwaves - they MUST run and MUST be reliable. With my present setup, I can fall back from the small dedicated inverter to the house ProMariner if necessary.

[Privilege]

Just another minor consideration for you... most phones and tablets use DC power to charge, usually 5v. 1amp for the phones 2.1amp for iPads. They come with 110v AC adapters that take them down to 5v DC. By charging them with an inverter, you are taking 12v from the battery, converting it to 110 AC, feeding the AC plug which then converts it back to DC.

If power saving is a consideration, buy the cheap chargers from eBay which have the USB charging port built in. You can then charge them without having to turn the inverter on.

[MJH]

Originally Posted by Privilege

Just another minor consideration for you... most phones and tablets use DC power to charge, usually 5v. 1amp for the phones 2.1amp for iPads. They come with 110v AC adapters that take them down to 5v DC. By charging them with an inverter, you are taking 12v from the battery, converting it to 110 AC, feeding the AC plug which then converts it back to DC.

If power saving is a consideration, buy the cheap chargers from eBay which have the USB charging port built in. You can then charge them without having to turn the inverter on.

Attachment 183115

FWIW I also use a medical CPAP. I called the CPAP machine manufacturer and for $15-20 got a 12V DC inverter cigarette plug-in cord to run the machine...works fine.

~ ~ _/) ~ ~ MJH

[dkenny64]

seems I'm not the only one wondering why such a large inverter..
when the large loads will be run from the generator..unless from time to time you want to run them from battery..ok..go with a 2kw sine inverter..
if all you want to run off the inverter is phones/laptops/tablets..light loads.

what about a 500-800 sine inverter? 2nd most of the mentioned light loads don't need s sine wave. modified is fine...
someone else mentioned tablets/phones - charge from USB..get a 12V USB hub forget using the inverter to charge them.. I got a 4 port model with 2amps/port at Walmart for under $20.


what size alternator does each engine have? that size engine should be running a serpentine belt. so you could get 200-400amps from each engine.. enough DC to run the inverter directly without drawing from batteries..you'll need large DC cables 2/0 or 4/0..


-dkenny64

[a64pilot]

I didn’t go through all of this, my only comment will be about the CPAP.
Don’t run it through an inverter, get one that is native 12 VDC.
Our Phillips Resperonics system 1’s are. You unplug the power “Brick” and plug in a plug that goes directly into a 12 VDC cigarette lighter outlet.
http://www.gocpap.com/philips-system...ics-for-24-50/
No inverter required and no inverter to break, and no inverter inefficiencies to deal with.
For example my 2800W inverter draws 20W just being on and powering nothing, and that is a pretty good one, some are worse.

Then learn to do without the humidifier, you really don’t need one on a boat unless maybe winter when your heating the boat, and the humidifier draws way more power than the CPAP does.

If you don’t have a second CPAP, buy one if your going cruising, it’s too important a piece of kit not to have a spare, and they cost way less online than your Insurence company paid for one I can assure you. You will need a copy of the prescription though.

[PJHoffnet]

Originally Posted by captstu

I've sailed with a CPAP for 20+ years and can share some advice specific to the need to provide power for that device.
...
I have a dedicated very small (60 watt) inverter dedicated to the CPAP. The CPAP operates comfortably on that inverter, wiring requirements are minimal, and there is no measurable reduction of the house bank voltage overnight. It is an inexpensive and uncomplicated way to provide the reliable power I need for my breathing condition.

Great solution, one I'll certainly look into. I've seen the smaller direct to DC wired types, having one in the aft cabin would probably do the trick. There's already a 'aux' DC line that goes back there that PO had to run a car radio/cd player that we've never used. I'll check the panel breaker and wire size and see if it will do the trick for a small inverter. I can always replace both if necessary.

Originally Posted by Privilege

Just another minor consideration for you...
Attachment 183115

Have the cig lighter version of those, use them all the time. I don't see why I can't put in a few permanent ones in the 'work' areas.

Originally Posted by MJH

FWIW I also use a medical CPAP. I called the CPAP machine manufacturer and for $15-20 got a 12V DC inverter cigarette plug-in cord to run the machine...works fine.

~ ~ _/) ~ ~ MJH

My only concern about going that way is running a cig plug 'extension' the ten or so feet between the nearest installed cig plug ... or putting the manufactures into the installed cig plug and then running the AC extension cord those ten feet.

Originally Posted by a64pilot

I didn’t go through all of this, my only comment will be about the CPAP.
Don’t run it through an inverter, get one that is native 12 VDC.
...
Then learn to do without the humidifier, you really don’t need one on a boat unless maybe winter when your heating the boat, and the humidifier draws way more power than the CPAP does.

If you don’t have a second CPAP, buy one if your going cruising, it’s too important a piece of kit not to have a spare ...

The direct DC, from a cig plug was certainly one of my first options for the CPAP. I have a RESMED, and I can't find the DC-12 Converter (per the Escape II's manual) anywhere on line. Heck, the machine simply says 12V 2.5A ... shouldn't be that hard huh?

I have the humidifier, but don't ever turn on the 'heater' ... just having air blowing across the 'pan' works fine for me, so no issue there.

I have a back up CPAP on the boat - that way if we're ever working on the boat in the slip and it gets late we'll just sleep over and I don't need to worry about not having a CPAP.

... BK BK ...

The one thing missing from everyone's recommendations and in my 'matrix' of costs v. benefits of doing the big installed unit vice several smaller direct wired inverters/cig plug ones is the ease and convenience of always being able to turn on the TV, DVD, network equipment, stereo, and all the other AC powered 'non-cooking/non-AC-heater hotel loads' without having to 'dig' their cords out from behind them and change them from their 'normal' Shore power locations (some are really buried) and plugging them into a stand alone inverter when under way and then having to move them back when hooked back into shore power (yes, I understand I could just leave them plugged into the inverters. Since the cost of doing the permanent installation, including another battery, are in the boat upgrade budget for this year, I still think I'll go for the full monty.

[dkenny64]

Originally Posted by PJHoffnet

Great solution, one I'll certainly look into. I've seen the smaller direct to DC wired types, having one in the aft cabin would probably do the trick. There's already a 'aux' DC line that goes back there that PO had to run a car radio/cd player that we've never used. I'll check the panel breaker and wire size and see if it will do the trick for a small inverter. I can always replace both if necessary.



Have the cig lighter version of those, use them all the time. I don't see why I can't put in a few permanent ones in the 'work' areas.



My only concern about going that way is running a cig plug 'extension' the ten or so feet between the nearest installed cig plug ... or putting the manufactures into the installed cig plug and then running the AC extension cord those ten feet.



The direct DC, from a cig plug was certainly one of my first options for the CPAP. I have a RESMED, and I can't find the DC-12 Converter (per the Escape II's manual) anywhere on line. Heck, the machine simply says 12V 2.5A ... shouldn't be that hard huh?

I have the humidifier, but don't ever turn on the 'heater' ... just having air blowing across the 'pan' works fine for me, so no issue there.

I have a back up CPAP on the boat - that way if we're ever working on the boat in the slip and it gets late we'll just sleep over and I don't need to worry about not having a CPAP.

... BK BK ...

The one thing missing from everyone's recommendations and in my 'matrix' of costs v. benefits of doing the big installed unit vice several smaller direct wired inverters/cig plug ones is the ease and convenience of always being able to turn on the TV, DVD, network equipment, stereo, and all the other AC powered 'non-cooking/non-AC-heater hotel loads' without having to 'dig' their cords out from behind them and change them from their 'normal' Shore power locations (some are really buried) and plugging them into a stand alone inverter when under way and then having to move them back when hooked back into shore power (yes, I understand I could just leave them plugged into the inverters. Since the cost of doing the permanent installation, including another battery, are in the boat upgrade budget for this year, I still think I'll go for the full monty.

could that be done with just changing the main transfer switch?


good question.
-dkenny64

[ranger58sb]

Originally Posted by CharlieJ

> one or two 8D batteries will not be sufficient to handle any real AC loads

PJ, I mentioned earlier the potential to increase bank capacity. Six 6V GC2s (~660 Ah) will usually fit in the same space as two 8Ds (~490 Ah). Or there are taller 6V versions which could increase capacity even more if you have clearance.

Lifeline makes all those in AGM, if that's a continuing requirement.

-Chris

[captstu]

I never did anything like a cost benefit analysis on the small inverter. $20, originally bought as a backup for my boat’s main inverter. Quickly found small used MUCH less power (nearly no bank drop) compared with Promariner.

Small is not wired in, just plugged CPAP in directly. No complexity, nearly no cost. What’s to analyze?