Planning a simple inverter installation 06 AJ 290

W

William Miller

Member
Mar 16, 2007
327
Darnestown, Maryland
Boat Info
290 AJ
Engines
Twin Mercruiser 300 hp Bravo III
First, should the 12v connection have a fuse at the wire connection?
There are a lot of unused large wires from the factory.
If so what size fuse to protect a 1 or 2 gauge wire?

My primary wish is to power a small coffee pot 400w out back while the crew sleeps.
2nd is a very small compressor for my hookah setup. I tested 4 amp @ 120v.
Neither do I want to run the generator for these short loads.

I have tested both on the bench and neither draws much load from my 2000 watt inverter.

Two location options close to the house battery bank or disconnect switch.
1st is the transom rope locker where my shore power cord connects. I could easily plug my pigtailed adapter right into the inverter. Or any other cord. (It seems safe as long as I turn off the battery charger)
Remember this is for short term periodic use.

The second is below the cockpit sink (a smaller enclosed space) but way more difficult to run the wires and probably a few feet longer run.
Negative connection at the big bus bar for the bank.
Positive could go to the correct side of the emergency start solonoid with is fed by a 4/0 wire that comes from the main Starboard battery switch.

Or the generator switch on the port battery bank.
Or the battery terminal.

But first.... I have read several posts but have not heard anyone mention a fuse or breaker to protect the positive lead.

Thoughts on that or some ideas on a safer plan.
Thanks!
 
First, nothing with electrical is ever simple, period.

So fuses (or breakers) protect against fire, they should always be at the power source (battery).
Or where a source branches to a smaller circuit. (becomes a smaller gauge wire)
So fuse as close to battery switch as possible.
Size must be for cable and/or load expected at inverter, whichever is smaller.

2000W inverter 12VDC source, you could hit 180A current draw. (figuring 90% efficient)
Cable distance is BOTH ways positive plus negative.
At just 5 feet from the batteries (10 feet cable) you need 2AWG wire to prevent voltage drop, current capacity is 210 so that's fine. Fuse at 180A max for the inverter.
If you go to 10 feet from the batteries (20 feet cable) you need 2/0AWG cable to prevent voltage drop, current capacity is 320A so again no issue there. Fuse at 180A max for the inverter.

So you see not simple.
You likely don't really need the 2000W inverter a 1000 or 750 could work. But the motor start will be the issue. Motors can often need 4-8 times there running load for a few seconds to spin up. So right there you could peak at 150A plus for a short period.

Also if you install the inverter out of reach of the battery cut offs. There should be a DC disconnect switch at the inverter.
Also do not install in a gas engine room or area. Inverters are not ignition protected.
 
hughespat57 said:
First, nothing with electrical is ever simple, period.

So fuses (or breakers) protect against fire, they should always be at the power source (battery).
Or where a source branches to a smaller circuit. (becomes a smaller gauge wire)
So fuse as close to battery switch as possible.
Size must be for cable and/or load expected at inverter, whichever is smaller.

2000W inverter 12VDC source, you could hit 180A current draw. (figuring 90% efficient)
Cable distance is BOTH ways positive plus negative.
At just 5 feet from the batteries (10 feet cable) you need 2AWG wire to prevent voltage drop, current capacity is 210 so that's fine. Fuse at 180A max for the inverter.
If you go to 10 feet from the batteries (20 feet cable) you need 2/0AWG cable to prevent voltage drop, current capacity is 320A so again no issue there. Fuse at 180A max for the inverter.

So you see not simple.
You likely don't really need the 2000W inverter a 1000 or 750 could work. But the motor start will be the issue. Motors can often need 4-8 times there running load for a few seconds to spin up. So right there you could peak at 150A plus for a short period.

Also if you install the inverter out of reach of the battery cut offs. There should be a DC disconnect switch at the inverter.
Also do not install in a gas engine room or area. Inverters are not ignition protected.
Click to expand...
Thank you so much for the info.
I continued my search and started the project.
Here is what I have so far as of Sunday.
If you can help me refine the plan.

I have had the inverter for a few weeks.
About the only place within a reasonable distance from the batteries is cabinet under the cocpit sink/baitwell. I have to move a y valve but i have that underway.
The instructions said #2 for up to 5' but there was a sticker on it that said #1 for 3' to preserve the warrantee. (WTF)

I guessed I better get 8' red and black so I went with 2/0 and have giant ring terminals crimped on. This was after drilling a hole making sure it would reach. I don't think it's necessary, but I could probably shorten them a foot or so.

The inverter has 3x15amp recepticles. After thinking on it. I don't think I will ever use that much. But I'll have it if needed.
But I'll complete the wiring and can upgrade the inverter and tie it into the main a/c panel maybe sometime in the future.
So I'm down to choosing the fuse and maybe a switch.
The inverter directions showed direct wires to the batteries. Fuse on the positive.

I a fuse at west marine which is called a treminal fuse. Are you familiar?
I bought one at 150 amps to be safe
 
Thanks Chris..
I have the fuse but just put the holder in my cart.
So how is the top of the fuse insulated from the bottom. (So the current doesnt just go up the bolt and bypass the fuse?)
Im sure ill see when i get it!

Any thoughts on a switch?
The inverter has an internal switch (i guess relay) with a low voltage switch on the end)
Thanks!
 
No such thing as simple...took me a year to plan mine. This whole thing needs to be engineered for the load you intend to power. There are tables that will tell you what wire and component you will need to be safe.

Good quality appropriately sized and terminated (soldered and crimped so you have a mechanical and chemical connection) wires are a must. Buy the appropriate wire and lugs (they make pre soldered lugs and battery terminals). A large guage crimp tool is available on ebay/amazon for $50

You need to read understand and follow the owners manual recommendations, or adapt them to how your going to install this.

I would recommend a Class T fuse which most inverter mfg's recommend them. Blue Seas components are my go to. I had the one listed above but swapped and the class T Holder is bigger/beefier, for larger gauge wire.

Class T fuses --> https://www.bluesea.com/products/5502/Class_T_Fuse_Block_with_Insulating_Cover_-_225_to_400A

Herse how I' did it -> http://clubsearay.com/index.php?threads/inverter-install.89992/
 
Last edited:
A small simple on off battery switch will do at the inverter
The mrbf use a special mount with a brass eye lug on one end and the bolt is insulated cable terminal goes under the nut
 
You must log in or register to reply here.

Forum statistics

Threads
113,184
Messages
1,428,131
Members
61,093
Latest member
Linword
Back
Top