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Old 05-11-2008, 12:25 PM   #1
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inverter while running......

My boat has a 3000 Watt inverter but has very little AC requirements.(eg) TV, U-Line Icemaker, microwave, two lamps, coffee maker and a small AC refrigerator. My question is this: <u>When running, can I leave the inverter on to service the frig and icemaker and will the alternator keep up with whatever battery juice I'm expending. </u>(I'm not sure what the alternator's output is and I don't have a generator on board.) Not being electrically competent,
I seem to be anal over protecting my battery supply. (3 AGMs) One dedicated to engine start and two for the house. I'm thinking about adding a cruise generator but am not convinced that I really need it! My goal, while cruising, is to "keep the beer cold, have ice for the cocktails and make an occasional cup of coffee." I don't want to haul ice for the cooler every time I go out.
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Old 05-11-2008, 01:02 PM   #2
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RE: inverter while running......

I don't see why not as long as the AC and DC loads don't exceed your alternator output. We use our inverter (Heart Freedom 25) occasionally when running to power the microwave, vacuum cleaner, or battery charger (phone, camera, laptop, portable VHF radio batteries). Whether or not the alternator(s) can keep up with the combined draw of the inverter and the boat's DC requirements will be dependent on the output of your alternator(s) so you need to find out what that output rating is. If you have ammeters in your system you should be able to tell if the alternator(s) are keeping up or not. If they're up to their maximum amperage then perhaps not. If they're not producing their maximum amperage than they're probably keeping up with everything.

Our boat has stock Motorola alternators (about 45 amps each) and its as-built battery system (two 8Ds plus a 4D for the generator). So we have a pretty minimal electrical system by today's standards. When we're running we put the battery switch on "All" which combines the output of both alternators. The inverter runs off the port battery only, so combining the alternator outputs means both alternators will pick up the load if we use the microwave (or the anchor windlass which draws a lot of DC current). Leaving the switch on "2" (the port battery we normally use as "house") means each alternator will only charge the battery on its side of the boat. So the port alternator will have to pick up the entire DC and AC load while the starboard (start) battery just goes along for the ride.

But before you can accurately answer your question you need to find out what your alternator output rating is. You can't determine your ability to keep up with your electrical load without knowing this figure.

-- Edited by Marin at 14:04, 2008-05-11
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Old 05-11-2008, 01:34 PM   #3
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RE: inverter while running......

We always run our 3000 watt inverter while under way. We turn off the breakers for the water heater, house plugs, washer/dryer etc. We mainly want to run the refer and ice maker. Occassionally will also run the microwave for lunch during long runs. If the grand kids are aboard they sometimes use the TV/home theater system. We have never had a problem.

We have 5 8D batteries. 4 are together through 3 battery switches. While under power they are all hooked together to the inverter and are charged by the 75 amp alternators on each engine. We change the battery switch setting depending on our power requiremens, wether under power, or running one of the generators, etc.
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Old 05-11-2008, 05:39 PM   #4
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RE: inverter while running......

Thanks guys......I must bite the bullet and lower myself into the ER to check* the alternator. (I have one hell uv a bad back)
*
I was at the boat today and did what Jim advised. While in the slip, I turned off the shore power,* turned on the inverter, turned off the hot water tank, charger, etc. and just had the refrigerator and the ice maker on. The amp gage showed 2 amps with both appliances running. (Seems low to me) As Marin stated, I have to ascertain the alternator output. I'm supposing it's stated on the nameplate or model plate on the unit.

Thanks again,
Walt
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Old 05-11-2008, 10:09 PM   #5
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RE: inverter while running......

Even without knowing your alt output I'm sure you will not have a problem with that load. As for cruise gens or running a genset underway that would only really apply if you were going to run your Air Conditioning. I run our single 70 amp alt* feeding 2 4ds and 4 6v golf cart batteries which then feed through a modified sine wave 2500 watt inverter . The golf carts are run as a bank and each of the 4ds are on seperate banks. The house load is switchable between one of the 4ds and or the golf carts and the genset and engine starter are hooked to the remaining 4d. This has been no problem even with the original internal (not smart) regulator. We are always running two fridges, microwave or cuisinart griddle often as well as coffee pot all morning. We switch off the breaker for the water heater as the water is heated by the engine but in cool/cold weather we are also running a fan forced boat heater that runs off the engine heat.

-- Edited by Daddyo at 23:19, 2008-05-11
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Old 05-12-2008, 04:09 AM   #6
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RE: inverter while running......

Happily most fridges and ice makers cycle , so you should be fine underway , even if the alt is tiny.

However if the batt system is used to run the inverter all night you may never get fully recharged.

If you go to marinas , simply watch the shore power charger , after you plug the power hose in.
If its only charging a bit , your'e doing fine underway.

If it charges like crazy for 5-10 hours , you need a larger , perhaps smarter alt.

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Old 05-18-2008, 05:58 PM   #7
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RE: inverter while running......

I just happened to be looking at the Link 10 this weekend as various things turned on and off with the inverter supplying them.

In general, since the inverter efficiency is amazingly good, assume your 12V current will be about 10x the current that your 110V appliance takes. Or if you know the wattage, it'll be about 10% of the wattage.

The fridge is no problem for the engine alternator. It pulls about 100 watts when running - less than ten amps into the inverter. I leave the inverter running and turn the fridge to "way cold" when the engines are running. The soft drinks start to get a little slushy, but it keeps the fridge for having to run at all for a couple of hours after turning the engines off and turning the fridge back to "normal"

Coffee pot is about 600 watts - 60 amps of 12 V - but for just a minute or two. Microwave is even more of a load - over 100 amps. But it's usually for a minute or two.

I run the noisemaker for an hour or so in the morning when anchored - again, with the fridge turned to way cold, and with the water heater turned on so that I make a tank of water. The hour seems to get the water tank hot, the batts pretty well topped off, and the fridge cold enough not to have to run for a couple of hours.
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Old 05-20-2008, 06:18 AM   #8
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RE: inverter while running......

Quote:
SeaHorse II wrote:

Thanks guys......I must bite the bullet and lower myself into the ER to check* the alternator. (I have one hell uv a bad back)
*
I was at the boat today and did what Jim advised. While in the slip, I turned off the shore power,* turned on the inverter, turned off the hot water tank, charger, etc. and just had the refrigerator and the ice maker on. The amp gage showed 2 amps with both appliances running. (Seems low to me) As Marin stated, I have to ascertain the alternator output. I'm supposing it's stated on the nameplate or model plate on the unit.

Thanks again,
Walt
Walt, like someone said, these things cycle.* You probably caught the fridge while it was idle and also the icemaker.* The big draw for the icemaker and the reason you never see 12V icemakers is the cutting cycle...not the actual cooling of the unit which is relatively low draw.* The icemaker uses red hot heating elements(like a hair dryer or toaster oven...never see them in 12V either)*to cut the ice into cubes...

So your 2 amp reading was most likely the power needed to run the inverter while everythig else was idle....just my guess.
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Old 05-20-2008, 08:15 AM   #9
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RE: inverter while running......

Thanks John....I hadn't thought of the cutting process and the heat. I have an electrician coming over in two hours and we'll check that out (amps) too!
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Old 05-20-2008, 02:48 PM   #10
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RE: inverter while running......

Today, I had an ABCY certified electrician and boat builder on my boat . He went through my entire electrical system and ascertained that I have a 105 amp engine driven alternator, 3x 280 amp AGMs (2 for the house and one dedicated to the engine with a parallel switch), a 3k watt inverter and a smart battery charger which can charge and hold up to three separate battery banks simultaneously. Since I don't have my hot water tank or batt charger on when I'm running (inverting), I should have <u>absolutely no problems with draining the house batteries</u> when using the refrigerator, ice maker, microwave and coffemaker. He also said that I was "paranoid"when using the inverter and to try and relax a little and enjoy some 110V power while underway and on the hook. He charged me $80 for the visit and advice and I was elated to pay it. His only recommendation was that I might want to consider a 150 amp charger and another for more capacity.

I am going to follow his advice, to the tee, and make sure that my towing membership is paid up.

Walt
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Old 05-20-2008, 02:50 PM   #11
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RE: inverter while running......

I'm typing 8-d and getting smiley faces! ????????
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Old 05-21-2008, 04:17 AM   #12
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RE: inverter while running......

"and make sure that my towing membership is paid up."

The only way you can get bit is to leave the combiner (parallel switch )on when drawing down the system.

Since the parallel switch is YOURS to forget , the simplest way of having NOT to need to remember is to use a different setup.

If your start switch has no ACC position , change it out for a good Cole Hersey that does.

Then hit the local RV store for a cont duty combiner solenoid , under $20.

Install it powered by the ACC switch position and when the engine is operating , the start is being charged.When you stop the engine the solenoid opens and your all set to camp out.

Your 3 batt charger will take care of recharging at the slip.

Folks with a cheap charger simply turn the :ignition" key to ACC every few weeks to put the start batt in the house charger.

Seamless and cheap, a real WWFFD

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