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Power inverters again ??

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Old 02-05-2003, 02:20 PM
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Default Power inverters again ??

I want to know who is running big inverters and how they work . I am thinking about 3000-4000 watt with battery charger built in . Does anyone run these ones . I want to run AC ,TV, and whatever else I need all day or all night without being plugged to shore power or runnning the engine . Sounds like it will work with this big of one and charger. I see it looks like "sine" wave is the way to go . WHat do you all think ? What brand do I get ? I looked at Xantrex. They do cost some money but I hate generators ! Some one help ........ Thanks Joe

PS. This is for My motor home not the boat ..........
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Old 02-06-2003, 11:35 PM
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Do you have the formulas for sizing the battery banks?

You better have some 20-ply tires on it to haul all that lead!

Charles Marine, Xantrex, Statpower - all good brands.

A 3000 watt load at 13 volts is 250 amps, then you figure the efficiency at 95% and you get 263 amps.

"all day" would be what, 10 hours?

That's 2,630 Amp-hrs.
One group 31 battery is 90 Amp-hrs.

You'd need 30 group 31 batteries...

Are you SURE you hate generators?

They make sound boxes for RV generators, and better mufflers, too.


for the record, I kinda LIKE generators...
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Old 02-07-2003, 01:29 AM
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you have to get you total continous load in watts below 800
to even make it 7 hours on 4 battery system and you still need your starting battery kept fresh

a 5000 btu ac unit would cycle on and off all night possibly
saving you some total amp hours
then include a frig 12v 3-4 amps cycling on and off
couple night lights too
you would be waking up with close to dead batteries
that would need many hours of engine on time to recharge



the generator is still your best bet
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Old 02-08-2003, 11:08 AM
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Thanks for your input guys ! I am just wondering about these inverters with built in battery chargers ! They have them up to around 140 amp multilevel and maintaining charging levels !!

NOone seams to know anything about the charging on them . It seams to me that if the inverters charger will do 140 amps if needed , that should do as good or BETTER then the motor runnig with a 90 amp alternater .......... WHat do you think ?

It sounds too good to be true ! Sounds like FREE ,QUIET , and unlimited power to go !! I guess I'll have to call the companies and ask them . I just like to hear from you guys that will tell the truth of your experiences rather then the guy trying to sell me the inverter ! THanks agian , JOE

PS. If not , I guess I'll be the first QUAD AXEL motor home to carry the batteries !!
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Old 02-08-2003, 11:47 PM
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What are you asking?
Are you asking if the built-in chargers are better than your alternators? The answer is YES, but for a reason different than you expect...

Your engine alternator feeds thru a "regular" single setvoltage regulator. It will feed full current (at whatever rpm it is running at) until it sees a line voltage (at the regulator) of 13.8 volts. Once it sees 13.8 volts, it will taper drop the field voltage to the alternator - keeping the line voltage at 13.8 until the required field voltage drops to zero (no output).

Generally, the alternator's rated output will occur at 3000 rpm (alternator rpm) or so. You will usually see max alternator output up to around 13.4 to 13.6 line volts.

The regulators on the charging side of the high-quality inverters is usually an electronic three-stage regulator. This provides full-current charging in the bulk phase to 14.2 volts. It holds this voltage until the charge rate drops to zero during the absorption phase. Then it stops charging altogether until the voltage drops below 13.6, where it will "float" the batteries so as to avoid electrolyte loss due to overcharge.

THIS is why the charger in an inverter is "better", not because of the higher amperage (although that is not a drawback in a multi battery system).

Now keep in mind that lead-acid (conventional) batteries have a max recommended charge rate, above which they tend to overheat (and you'll be adding water often). Gel batteries can be terminally damaged by charging too fast or to a too-high voltage. AGM batteried will accept a charge as fast as you can throw it in...

I like to charge regularly-sized lead-acid batteries at a rate no higher than 30 amps per battery (this is only my preference and is based on nothing inparticular other than my own sense of what seems to work for me). This means that a 4-battery bank shoudl be charged at a rate no higher than 120-amps (and a ten-battery bank at 300 amps).

Another twist, is that you can replace your emgine's regulator with a three-stage electronic one for a hundred bucks or so and then your alternator will provide the same quality of charging as your inverter...

So I guess you can run off the inverter, then crank the genset and charge with the charger on the inverter. Is that what you're asking?

I hope this answered something for you.
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Old 02-09-2003, 06:44 AM
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Inverters are nice when it comes to running the refrigerator, microwave, blender, tv/dvd (quiet during the movie or race), or hair dryer. It is not practical to run the air conditioner because of the constant high load during operation not to mention the start up load. Factor in the added weight of the battery bank required to run the ac and you will be looking for a barge to keep in tow! Cool the boat down with the ac using the genset and then run some nice, quiet 120 volt portable fans with the inverter. Be sure to add increased ventilation to the battery compartment and run the blower during recharging. Batteries produce explosive gases when recharging.
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Old 02-09-2003, 07:30 AM
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Boot, I may be misunderstanding you but the chargers on the inverters only work when plugged into shore power or running a generator. And high amperage doesn't necesarily charge faster. The battery will only take as much current as it can according to the voltage difference between its surface charge and the charging source. Voltage determines the speed of charging, along with battery state and condition. Its better for the batteries to be charged slowly than fast.
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Old 02-09-2003, 09:45 PM
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Boy ,thats a lot of information to take in all at once !!

Thanks !! WHat I realy want to know is what will it take if anything to only have an inverter with no other power source and run all my stuff . So you guys think I will have to have the generator for the AC ? There is no way around it ??? Dosen't the inverter POWER the charger itself ? THats the way they make it sound . Thank you all ! JOE
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Old 02-09-2003, 10:33 PM
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There is no such thing as perpetual motion. For example: you cannot plug a extension cord into itself and create power. Power has to come from somewhere to power the inverter charger. It is built in to provide some space saving convenience and less wiring. Forget about the a/c on the inverter and start with a good genset if you dont already have one. Westerbeke has always been a good brand to own and they have a good parts and service network should anything arise. Kohler and Onan also make marine units.
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Old 02-09-2003, 11:30 PM
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Joe, the charger section of any inverter only works when you are plugged in to shore power or if you have a generator and it's running. You will not be able to run an AC off an inverter for any significant period of time. A dual system with a genset and an inverter is the best way to go, if you choose only one,better get used to a genset.
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