Another stupid inverter question

[Jaxfishgyd]

At the moment, I have removed the 4 old 8D's and have 6 group 24 batteries in the two front boxes. Am happy with how they are doing for starting the motors and running the 12v lights.(They are now 3 months old and we have done 6 trips, one being 5 days long).
That leaves the rear 2 boxes empty and I want to install an inverter but just to run the refrig (6.5 amp when running) and maybe the icemaker (hey, we need ice here most of the year for our drinks).
Know golf cart batteries are great but that would mean mixing different types of batteries for the charger to work with.
Seems to me, I just need to put in 6 more group 24's, already have battery switches in for the port and starboard front and back banks so can isolate the boxes. I can also run cable across the engine room to both rear boxes (what guage wire should I use) with still a 3rd battery switch so I can then have the option of combining any combination of the 4 battery boxes.
I can even use 3 boxes for the inverter and 12v lights and isolate the 4 box for starting power. (think I'm getting a headache now)
Reality is that I only need to use the inverter 6hrs, to from time to time, 12 hrs a day. In the summertime we will use the genset as A/C is our friend!!
For the genset I have a group 31 battery dedicated just to it.
My thought is to go ahead and buy a big inverter even though I don't have any plans on adding any major items to it but we all know how things change on a boat.
So what am I leaving out or have forgotten????

[spartonboat1]

There are some good, long threads on this in prior posts.

Cable size I think should be #6 I think, basically welding cable and about as heavy as it gets. Ensure batt switches are very heavy duty. Use marine grade!

Inverter should match the genset capacity, so as to not overload genny.

Call the techs on phone at Heart/Xantrax/Trace or whoever owns the brand of inverter you are considering. Heart was very helpful.

ENSURE IS INSTALLED CORRECTLY. Mistakes happen and I lived with a major fire hazard for a year, caught by accident, due to improper installation in two areas. Installed by ABYC tech...go figure, but they let him go, so maybe not only issue.

[Nonchalant1]

Big wires will be required, like 0 to 0000 sizes to the inverter depending on how far away it is. Remember, 6.5 amps at 110V is 60 amps at 12V, and 6.5 amps is average, so the surge at startup will be MUCH more, although you don't have to size your wires for the startup surge. Now figure another 6 amps for the icemaker and whatever else you may add in the future, plus the inverter draws more amps than it puts out. Dealing with 12V systems to run anything serious requires really big wires.

You can google amps, volts, wire size to get some calculators for OHM's Law. For DC current, the big deal is how long the wire is and how many amps you want to run through it, or you start getting larger than acceptble voltage drops. I think 2% drop is max ABYC standards. Therefore, the closer you can put your inverter to it's battery bank, the better off you'll be, since 110V AC current doesn't need big wires at all.

Doug Shuman

[SKYCHENEY]

This is one good reason to keep everything DC at 32volts--wire size. I bought a 32v inverter and I know we have rehashed this in several other threads in the past, but I still think if you have a 32v system, it is best to keep it. It seems we all have a differing opinion on this, but I just felt compelled to put in my 2 cents as it relates to wire size -- sorry, I couldn't help myself.

[Pascal]

since you mention group 24 batteries and 12v lights, i take it your boat is all 12v not 32??

if you get an inverter/charger combo (Xantrex freedoms are pretty cheap) then you can keep this system separate from everything else and not have any problems using different batteries since the combo will recharge that bank.

for the freedom 30, i used 4/0 battery cables which is ok up to 6'. smaller models require smaller cable, instal manual has a chart... ex 1/0 is ok for a 1000W inverter at 6'... when choosing an inverter, don't go too small, you never know who will want to use the microwave or coffee maker while the fridge is running :-) , i don't think i'd go below 2000W for a fridge and ice maker, price difference is minimal.

[Jaxfishgyd]

Yes I'm only 12v.
I keep putting Scott's Plus fertilizer and water all over the boat but it refuses to grow to 53'.
To run cable from one battery box across to the other will take about 20' of cable.
I can place the inverter less than 5' from either battery box and from there it will take less than 15' to the to the galley and 15' to the icemaker.
Our genset is 9 kw.

[Nonchalant1]

Just put the inverter as close as you can to it's battery bank. Don't worry about the distance from the inverter to the 110V fridge or other consumers because 110V AC travels fine over regular wires. It's DC current, and particularly 12V DC, that requires the big wires.

When you're getting your big wire, also get the right type connectors, crimped on correctly. BoatUS, diesel truck repair stops, forklift battery shops and other places have special large crimpers for the wire ends and wire they sell.

Doug

[SKYCHENEY]

You can also use a special anvil made for crimping those wire ends. If you are buying the tool just for this job, the anvil is cheaper than the big crimp pliers.

[DickB]

Two thoughts. My Heart 2.5kw is about 6-7 years old at this point. I think it's getting tired, and no longer enjoys the warm engine room. It overheats and cycles on and off. I'm about ready to install Jim's fan to air out the engine room. If I had to do it over, I'd install the inverter out of the engine room. It may require larger and longer cable, but that's cheap by comparison the the whole sys cost.

Second, you might check with WestMarine. Out here (Seattle), they loan some tools.

Dick

[Nonchalant1]

BoatUS here has the big bench-mounted crimpers just for the customers to use free. In fact, they won't do any crimping for you for liability reasons, but they will show you how to use them.