Inverter on a boat

Poseidon

New Member
Oct 19, 2006
11
Pleasant Hill, Iowa
Has anyone installed an inverter on their boat? I have heard one could be installed to run things such as your microwave, coffee maker, or TV granted only one at a time. If anyone has, can you point me in the direction of where to even buy such a large inverter?

Thanks in advance for any input.

Jeffrey
 
XANTREX

Xantrex is a popular brand, I'll best our host could help you out:

http://www.byownerelectronics.com

The biggest issue about inverters, is that you need a lot of battery capacity to do anything useful. A microwave will run down your average car size battery in an hour. A coffee pot will probably will be worse. A TV is more practical.

The math:
Microwave = 700 watts = 12 volts times 58 Amps (assuming a perfect inverter)

Group 27 battery is about 100 amps/hours = 102 minutes

But there are no perfect inverters, so the currect draw will be higher, plus you really don't want to and probably can't drain a battery that fast or all the way down. It will cause a ton of problems.
 
I have an inverter on my boat, but it was there when I bought the boat. It will easily run the things you mention, probably all at once. It is a Xantrex (Heart Interface), although an older model than what is on the market right now. It is a 2.5 KW unit. I do run the MW and a coffee maker. I doubt that I have run them at the same time, but I think the unit would do it OK. I know it will start and run the roof mounted air conditioner in my fifth wheel. I tried it out of curiosity.

http://www.xantrex.com/web/id/7/learn.asp

You do need some significant battery power to run this, however. In my case I have GC3 golf cart batteries, 4 of them, in addition to the two normal group 27 engine start batteries. The 4 GC3 batteries give me about 400 amp hours of capacity. For the golf cart batteries, you should try and not go below half charge, so that is 200 useful amp-hours. So that would run the microwave over 3 hours between charges.

Figure about 60+ lbs per battery, you are adding 250 lbs to the boat. This may or may not be significant to you. If you put information about your boat in your signature, it helps people give better answers.

The cheaper units output what is called 'modified sine wave'. I think that is a very charitable description. It is more like a square wave. Most things will work fine on it, but some things really need a sine wave, and won't work. For example, AC powered tools with a variable speed control work by turning on or off switching transistors at controlled points in the sine wave to control power flow. Without a sine wave, they can't work.

A better unit, such as the ProSine 2.5KW units, output a true sine wave. This unit also has a built in transfer switch, so it gets wired into your boat wiring. It also has a built in charger to charge the 'house batteries'.

http://www.xantrex.com/web/id/42/p/1/pt/10/product.asp

A note of caution. Installation is not easy for this type of setup. Also, if you install a large battery bank, it may be more than your alternator can handle. If you use 200 amp-hrs out of the battery bank, then your alternator needs to put back 200 amp-hrs (plus losses). Considering the alternator has other loads also to handle, it might mean it is putting out full current for hours on end putting the charge back. This may fry something due to max load for too long.

All that said, I really like mine except that it won't run my Porter-Cable variable speed polisher. Mine is a modified sine wave.

This thread belongs in the electrical section.
 
Inverter cost

Wow, it looks like to get a good inverter it would run around 2K or better then you need to get the battery bank for it. That gets the cost right up there to where I might as well purchase a gen, huh.

Thank you for all your very insightful input. I love that I found this forum. It will server my needs for many years to come.

Jeffrey
:smt038
 
Poseidon, not sure what size boat you have, and didn't see it in the virtual marina, but if you have the room go for the genset! Far superior in performance, etc. as compared to what you would get out of an inverter. I however don't really have the room for a genset, so I'm about to install an inverter. I purchased the xantrex Pro 1800. http://www.xantrex.com/web/id/198/p/1/pt/7/product.asp

It has a nice detachable face you can mount elsewhere to keep on eye on things and can be mounted just about anywhere, horizontal or vertical (everywhere but the bilge and on further than 7 feet from the bats.) I'm also going to have 3 bats total, 1 for starting, and 2 for playing, but I only have a 25' boat and don't have a/c so I should be ok.

Good luck!
 
Re: Inverter cost

Poseidon said:
Wow, it looks like to get a good inverter it would run around 2K or better.....
:smt038

I think a good inverter can be had for much less than $2000. Even at full price, west marine there are 1800 watt modified sine wave inverters for less than $400. Add a few hundred for batteries and your well under the $5000 to $10,000 a marine generator will cost. A Honda general purpose generator will be in the same ballpark as an inverter but there are safety issues to consider.
 
Hello Poseidon,

When you go for an inverter, take care of the place where you want mount it…
This because they need cooling, and sometimes get hot.

Peter
 
The two posts above are correct in that you can get by with a less expensive inverter, especially if you choose not to go with a true sine wave inverter. The inverter that slack250 linked to would work. It has a built in transfer switch, so it can be wired to provide AC power to some items on your boat while you are not connected to shore power. This wiring can be done in your AC breaker panel, and switchover is automatic.

I thought there was a breakpoint for choosing between an inverter and a generator. If you needed to run an air conditioner, then you needed a generator. If you didn't need to run an AC, then you needed an inverter. NoWakey has pointed out in a following post that this is not true, he runs an AC on an inverter successfully. A 6500 BTU AC might draw about 75 amps when operating. If you have a 200 amp-hr house battery, then you could run the AC for over an hour before you discharge to 50% capacity. If you are running the AC while under way, then the alternator helps offset the current drain, giving longer run time.

If you don't plan to run an AC, then I think a generator is a bad choice. You need to load up a generator for it to run properly. If you don't, it won't break in properly, the rings won't seat, you will get oil by the rings, and you will foul the plugs. Plus to me it doesn't make sense to fire up a generator just because you want to make a cup of tea in the MW. With an inverter the AC is always there when you need it. And you don't need to worry about 'quiet time' when others would object to the EG.

The things I state above about an inverter assumes you buy one with a built in transfer switch. The one slack250 linked to does have that. I just grabbed a 2005 West Marine catalog, and I see an MS2000 Sine wave inverter/charger listed for $1600. I think the 4 golf cart batteries I bought were about $65 each, so if you allow $300 for that, you are still less than $2000.

When talking about in 'inverter', you can be talking about several things:

1. A device the converts DC to AC and has an outlet on it that you can plug an AC cord into (only an inverter). The device may produce a modified sine wave output or a true sine waver output.

2. A device that is an inverter, as above, plus a built in transfer switch. This device provides power from an external source when available, but generates AC and makes it available when external power is not available. The transfer switch chooses between shore power and inverter power. Its contacts need to be rated for the maximum load that can be placed on its output.

A device of this type will need to decide when shore power is available. While this may seem obvious, consider if you would say shore power is acceptable when a) the freq is 50 Hz, b) the incoming voltage is 85 V AC, c) the incoming voltage is 135 V AC, d) the shore power was gone, by now it has come back at 60 Hz, 115 VAC, and has been present for 1/2 second.

3. A device that is an inverter, and transfer switch, and a charger. Hopefully the charger would be a good three stage charger. And it may be aware of what its shore power input current limit is. So if it has a high AC load and also needs a lot of amps to charge a battery, it will control the current into the battery while the AC load is present so as not to trip its input circuit breaker.
 
Poseidon,

I'll throw my two-bits worth in on this one.....
We have a Xantrex Pro 1800 and have been very happy with it. More than enough moxy to keep the wifes hair dryer running, coffee pot, etc. Also we have a 6500 BTU A/C onboard and it has enough grunt to start-up and run the A/C for about 40 minutes on the house battery. That is very nice on a hot summer night to be able to crank up the A/C while you are motoring back in to the marina for the night and have a nice cool cabin by the time you get back and plug in.
Just one word of caution on the Xantrex. The relay for the AC transfer switch is rated at 25 amps. I did'nt, but you should knock your main AC breaker down to a 25 amp unit so the inverter relay is not the weak link in the chain. FYI

Things go better with boating,

Jim

:thumbsup:
 
I was just telling my wife last night about all the informataion I have at my disposal on this site. Thank you to the hosters and forum care takers. This is truely a great place for Sea Ray owners.

Back to the subject at hand. Okay it sound better with the 1800 plus batteries that can be bought for under 2K. Does this unit plug right into the existing wiring? I have a TON of space in my engine compartment of the 310 so I don't think cooling will be an issue. The main reason for the power away from shore is to run a TV for my daughter or run the microwave to heat her something or possible run the coffee pot in the morning. If it is hot enough I would probably be at the marina to run the air.

Sounds like I need to request a WestMarine catelogue.

:thumbsup:
 
Poseidon,

Here is where things get a little dicey with an inverter install. Most inverters that I know of are not approved for installation in an explosive environment. This is also the case with the Xantrex 1800. There is just too much arcy sparky stuff going on to be exposed to gasoline fumes and gasses from charging batteries. (hydrogen)
Therefore you need to find a place that is outside of the engine compartment, is within 5 feet of your house batteries, is weatherproof, and has decent ventilation. Oh, and also is in a fairly close proximity to your main AC run from the stern to your main AC panel so you don't have to pull, and try to hide a bunch of cabling to enable the use of the AC transfer switch in the Xantrex. It can end up being quite a hat-trick to find such a place on a sport cruiser.
I would wait for some other 310 owners to pick up on this thread and see if they have any pearls for you on where to locate the unit.
We installed ours on the inside of the engine compartment firewall, port side, inside the aft berth. I fabbed a cover to go over it for cosmetics.
FYI, I purchased our unit from DonRowe.com @ $349.00, including shipping.

Best regards,

Jim


:thumbsup:
 
NoWakey said:
Poseidon,

Also we have a 6500 BTU A/C onboard and it has enough grunt to start-up and run the A/C for about 40 minutes on the house battery. That is very nice on a hot summer night to be able to crank up the A/C while you are motoring back in to the marina for the night and have a nice cool cabin by the time you get back and plug in.

:thumbsup:

I think NoWakey has kindly pointed out that I was wrong in stating that you should have a gen set if you want to run an AC. I have read this in past posts, but had not gone through the numbers. I plan to do that. Plus I think I will go back and modify my post.

Here is a link to a 6500 BTU unit for reference.

http://www.mmair.com/marine_division/air_conditioning/6_500_btu_cabin_air_conditioner

It states this unit draws 6.4 amps plus 1 amp for the seawater pump. So that is 7.5 amps total of AC load (assuming the seawater pump is AC) That would present a current load of about 10 times that on the DC side, so that is 75 amps. So if you had a 200 amp-hr house battery, you could run the AC for over an hour before you discharged the house battery to 50%. If that run time is adequate, then that is all you need.

Plus in NoWakey's case, he is motoring back to the marina while cooling the cabin. So he has the advantage of the alternator providing some of the current, maybe a third to a half, which might will add that much to the run time possible. In addition, I assume he can plug in to shore power when he gets there, so the batteries can get recharged fairly quickly and be ready for the next day.

This thread belongs in the electrical section.
 
Dave M.,

Correct-A-Mundo on everything you said.....

I'll tell you Dave, you are going to be my go-to-guy on battery info!
Are you in the business? You put up some great info on the subject. Keep it coming!

Have a great weekend, wish I was going to be boating!!

Take care,

Jim

:thumbsup:
 
Jim,

Thanks for the kind words. I am not in the business, I am retired. But in my former life I had to deal with 48v battery plants quite a bit. Most were in the 400 to 1200 amp-hr range. I don't have nearly as much experience with the smaller batteries like we are talking about.

Dave
 
NoWakey said:
Poseidon,

Here is where things get a little dicey with an inverter install... Oh, and also is in a fairly close proximity to your main AC run from the stern to your main AC panel so you don't have to pull, and try to hide a bunch of cabling to enable the use of the AC transfer switch in the Xantrex.

Poseidon,

I don't agree with NoWakey on this one. I think you should not interrupt the main cable from you shore power connection to the AC panel. I think you should leave that intact so that all sensing and protection circuitry built into the panel and cabling remains always as designed.

I think the inverter should be fed from its own circuit breaker in the AC panel.

Dave
 
Dave M.,

You have brought up a good point worthy of additional discussion.
Please find below a link the the install manual for the Xantrex 1800.

http://www.xantrex.com/web/id/198/p/docs/pt/7/product.asp

This really boils down to a different strokes for different folks issue, and if you want the Xantrex to operate as designed.
I will offer a couple of semi brief points.

If the Xantrex inverter does not interrupt the AC main feed the auto-transfer switch will not function as designed and therefore why pay for having it.
Any AC back-feed to the inverter will blow it up. If it not installed per spec you will need to install an isolation switch to protect the AC OUT of the inverter. You can't automate the task with a relay because of latency issues. So, bottom line is you will have to remember to open the isolation switch every time you connect to shore power or you will blow the inverter. Just speaking for myself, this is not something I want to leave up to memory after a couple of cocktails.

As for wiring, I just installed a junction box in the boat AC main feed to facilitate the the patch. At any time that a future owner of the boat would want to remove the inverter all he has to do is uncouple the inverter and reconnect AC main feeds. I would also recommend using SOO cable to run the inverter patch. This is a considerably better cable product than what Sea Ray uses.

Just as post commentary I will have to say that if the Xantrex unit is installed per spec, it is an absolute delight. The transfer from inverter to shore power, and vise-versa is completely seamless. Everything that was running is still running, and in my case, no-brain was required!

O.K., there we go. I will look forward to hearing your thoughts.

Best regards,

Jim


:thumbsup:
 
Jim,

I am on board about the auto transfer function and how it works. Mine works the same. However, the inverter should be powered from a breaker in the AC breaker panel. What you are recommending is not in accordance with the installation instructions on the Xantrex link you posted. Specifically, page 3-15 of the manual tells how to connect AC input power to the inverter. Step 1 is to install the required circuit breaker in the AC outlet panel supplying the unit. Then you wire from that breaker to the input of the inverter.

Then on page 3-18 it explains to connect the output to a circuit breaker in the AC load panel.

Mine is connected to more than one breaker in the AC load panel. The inverter output terminals, and nothing else, supply each breaker that is powered through the inverter. Breakers for items not powered by the inverter have the original wiring back to the panel main disconnect breaker. Thus there is no possibility of backfeed into the inverter output, and operation is automatic as you describe. Also, items that are too much load for the inverter are not connected to its output, so it can never try and power them.

Implicit in all this is that you need to rewire your AC breaker panel. My previous post was intentionally vague, as I was trying to avoid recommending that anyone rewire their own breaker panel. This needs to be done by qualified person.

That's my view on the whole thing!

Dave
 
Dave,

10-4, now the picture is clear...
See I did not want to do the inverter sub-panel routine. I have the remote face plate for the Xantrex mounted right on the AC panel in the boat so I can monitor load and battery status.
I can't argue with your logic of taking all brain work out of it. In knowing that the Pro 1800 will just shut down and present an error code if it is overloaded I elected not to split it off.
Well there you have it. At least 3 or 4 ways to skin the cat.
Take care Dave, hope the day is finding you well.

Reagrds,

Jim

:thumbsup:
 
Jim,

I think we understand each other now! :thumbsup: I still don't think that on a 310 you should put the inverter in line before the AC panel, but that is personal choice. The way I propose is quite a bit more work.

Have we lost Poseidon here? He started this all off. I think he would be well server with an inverter setup, judging from all the previous discussion. I also saw a comment that Skolbe had a 3KW inverter, 4 golf cart batteries, and powered his AC with it.

Sounds like Poseidon would also be well served with 4 golf cart batteries and have room for them. In my boat, only two of the golf cart batteries are within the required distance of the inverter, the other two are on the other side of the boat. And it works just fine that way.
 
Wow, I actually started this thread back on SRO getting ready to install this inverter myself, now I'm throughly confused. Luckily, I found a electrician that advised if I can/will do the rough in and mount the inverter, etc. He'll button it up for me! Thank goodness!! :wink:

Can one of you guys quickly outline what I should in preparation? I'm going to mount the inverter in a custom box and to be installed somewhere in the aft cabin on my 250.

Regards and thank you.

Jim
 

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