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Old 08-21-2010, 03:49 PM   #21
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I swear I need to get you guys to spec out my power needs for the boat. It would be a lot easier than doing all the math myself, LOL!
Ditto on the golf cart batteries, though--easier option than a gen.
Having said that, one of the justifications I'm trying out for buying the Honda generator for the boat is that it could be used for other stuff, like on the RV and around the house if we had a power outage or hurricane.
Are you talking about the popular 2kW Honda EU2000i? For around $1K, it's hard to beat. It's too small to run an AC, but using 2 of them along with a parallel cable kit (yes, I had never heard of paralleling generators before, but these Honda generators have sophisticated electronics inside), people have run RV AC with them. Maybe you can splurge to get an Onan marine generator with a starter. A diesel one?

Seriously, despite the 4kW generator in my RV, I thought of getting a small 1kW Honda generator. The Onan is still too loud, and I am thinking of boondocking where it is cool and I do not need AC. The small Honda would recharge the batteries with much less noise.

I willl find out what I want or need after this coming trip.
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Old 08-21-2010, 04:06 PM   #22
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I am "on the road" (Des Moines) so I don't have acces to much research but...

The Inverter in our Roadtrek controls the charging of the two 6v Golf Batteries. The batteries are charged either by the engine alternator or the generator. We have never needed the generator to charge the batteries but I have been told that if the batteries are depleted the Generator is the recoomended source of recharging.

In any event, if you could wire the Invertor into the vehicle's charging system (the Alternator), then that would solve your problem of unexpectedly draining the batteries. (That is my guess, anyway.)
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Old 08-21-2010, 04:24 PM   #23
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The Inverter in our Roadtrek controls the charging of the two 6v Golf Batteries. The batteries are charged either by the engine alternator or the generator. We have never needed the generator to charge the batteries but I have been told that if the batteries are depleted the Generator is the recoomended source of recharging.

In any event, if you could wire the Invertor into the vehicle's charging system (the Alternator), then that would solve your problem of unexpectedly draining the batteries. (That is my guess, anyway.)
When my RV engine is running, its alternator automatically charges the house batteries. The house batteries will then supply the inverter, which provides me with 115VAC. This AC power will run the refrigerator while I am on the road, instead of the propane. I intend to shut down the propane at the tank unless I am stopped.

When the RV engine is off, a battery separator relay disconnects the engine battery and the house batteries. The house batteries can be run down, but the engine battery is isolated and will not leave me stranded.

Now, the onboard genset starter runs off the house batteries. But if the house batteries get drained, how does one start the genset? There are two ways. One is to start the RV engine, which then charges up the house batteries as described above. But of course it is wasteful to run a big 7.4L engine for this. So, there is an emergency switch to allow cranking the genset starter using the RV engine battery. Then, once the genset is running, its AC will supply the charger to recharge the house batteries.

Much of the wiring and switching above is stock. It may not differ that much between different RVs.

But, my RV did not come with an inverter. By trying to incorporate the inverter (which is of course independent from the stock converter/charger), I have to trace out the wiring of this RV, and reverse-engineer its design. I can now redesign how I want the different subsystems to function.

It's been fun.
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Old 08-21-2010, 05:29 PM   #24
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I got a bit carried away with my RV stuff. Back on the OP problem... I think the OP's question has been answered by many people here. Yes, modern TV power usage is low enough that what he wants to do is feasible.

A single 12V battery may be all he needs, although not of the common car battery type, which will surely leave him disappointed. A marine, or deep-cycle battery, or an AGM battery is called for here. If money is no object, yeah, go for two 6V golf-cart batteries, then there should be enough power for audio amplifiers or what have you. But as some have pointed out, you may exceed the capacity of the inverter.

I would just lay the battery on the ground, and the inverter a few feet from it. I just looked and saw that true sine-wave inverters are so cheap now, particularly the ones in the 200-300 Watt range. Some inverters come with cords ended with alligator clips to clamp onto the battery post. You really need nothing else. If you happen to still run out of power, a battery jumper cable set will let you recharge this battery from the car alternator in an emergency, with its engine idling of course.

At home, a low-cost battery tender will keep the battery freshly charged, ready to go. Of course, you do not need a fancy 3-stage charger like what's in RVs. In that application where the battery is charged off a big generator running, you want to pump a lot of juice into the battery to minimize the genset running time. You have no such constraint here when charging at home and using the battery only once in a big while.
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Old 08-21-2010, 08:02 PM   #25
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Thanks for all the responses. I will definetly look into the golf cart batteries. After looking at the prices, I will probably get a pure sine converter just to be safe and to have on hand if I need one in the future.

Is there any downside to getting say a 400 watt inverter if I will only be powering the tv or will that use too much juice?
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Old 08-21-2010, 08:09 PM   #26
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Is there any downside to getting say a 400 watt inverter if I will only be powering the tv or will that use too much juice?
Other than the higher price for a larger capacity inverter, no downside. The watt rating defines the maximum sustained load the inverter can supply - a 400 watt inverter won't use any more energy (battery drawdown) than a smaller inverter when powering your TV.
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Old 08-22-2010, 08:06 AM   #27
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Are you talking about the popular 2kW Honda EU2000i? For around $1K, it's hard to beat. It's too small to run an AC, but using 2 of them along with a parallel cable kit (yes, I had never heard of paralleling generators before, but these Honda generators have sophisticated electronics inside), people have run RV AC with them. Maybe you can splurge to get an Onan marine generator with a starter. A diesel one?

Seriously, despite the 4kW generator in my RV, I thought of getting a small 1kW Honda generator. The Onan is still too loud, and I am thinking of boondocking where it is cool and I do not need AC. The small Honda would recharge the batteries with much less noise.

I willl find out what I want or need after this coming trip.
That's the Honda I'm talking about. Heard great things about them.
We have an old Onan in our RV that is LOUD but does the job when needed. The boat didn't have one and an installed one is a big hairy job and pricey. Diesel would be convenient, no doubt. But we carry gasoline for the outboard anyway.

I'd love to be able to power the AC in both the RV and the boat as you've described, because the Onan won't handle it on the RV and one Honda2000 wouldn't cut it running the boat AC (17k btu). Parallel is a great idea, but dang that's a lot of money in generators. Would be nice, though, and transferable between the boat and RV.
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Old 08-22-2010, 09:35 AM   #28
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Strictly speaking, a larger inverter, when idling, tends to draw a bit more current compared to a smaller one. But it is still just a fraction of the current when it is loaded. For example, I measured 0.8A when my 2kW inverter was idling. That's 0.8A x 12V = 9.6Watts. That's just a fraction of the power it draws when loaded. When I turn on the microwave, the current jumps to a scary 160A, and I could almost hear the batteries groaning.

For comparison, a car running-light bulb draws 0.5A, and a car brake-light bulb draws 2.5A.


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That's the Honda I'm talking about. Heard great things about them.
We have an old Onan in our RV that is LOUD but does the job when needed. The boat didn't have one and an installed one is a big hairy job and pricey. Diesel would be convenient, no doubt. But we carry gasoline for the outboard anyway.

I'd love to be able to power the AC in both the RV and the boat as you've described, because the Onan won't handle it on the RV and one Honda2000 wouldn't cut it running the boat AC (17k btu). Parallel is a great idea, but dang that's a lot of money in generators. Would be nice, though, and transferable between the boat and RV.
I don't have one, but it would be what I buy if I need one. So many users out there can't be wrong.

And the price of 2 grands for 2 of them, plus a bit for the parallel kit, is not really bad, considering that you can use them for so many things. They are certainly less expensive than a new 4kW Onan that costs more than $3K. There are inconveniences compared to a permanent installation, but the portability makes up for it.

And how 'bout a wind generator for your boat? I saw some for around $400 or $500.
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Old 08-22-2010, 09:51 AM   #29
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Strictly speaking, a larger inverter, when idling, tends to draw a bit more current compared to a smaller one. But it is still just a fraction of the current when it is loaded. For example, I measured 0.8A when my 2kW inverter was idling.
You're the expert here, but is there really any meaningful difference in the idling load drawn by a 400w inverter vs. a 200w? Enough to forgo the advantage of a little added capacity for the OP's planned application?
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And how 'bout a wind generator for your boat? I saw some for around $400 or $500.
Beans are much cheaper...
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Old 08-22-2010, 11:47 AM   #30
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You're the expert here, but is there really any meaningful difference in the idling load drawn by a 400w inverter vs. a 200w? Enough to forgo the advantage of a little added capacity for the OP's planned application?
No, I was not contradicting at all what you and others said: Better have some extra capacity, since a slightly larger inverter does not cost that much more, and the power consumption overhead is higher, but not that big a deal.

In fact, I was pointing out that even my fairly large inverter does not have that much of a punitive overhead: 0.8A idling vs. 0.5A for a little running-light bulb.

Now, I have seen boondockers counting every amp that they use. That's like extreme LBYM'ers who count to the pennies, but I'd rather not.
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Old 08-22-2010, 04:18 PM   #31
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This subject was pretty well exhausted with lots of good stuff. Earlier there was a question of marine v car and deepcycle batteries.

A discussion by a wordsmith better than me is referenced for those who want to know about the marine v car battery:
The difference between car and boat batteries - The Globe and Mail
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Old 08-22-2010, 04:23 PM   #32
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This thread is priceless.
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Old 08-22-2010, 04:24 PM   #33
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This thread is priceless.
Nice to see you got a charge out of it...
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Old 08-22-2010, 07:14 PM   #34
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A discussion by a wordsmith better than me is referenced for those who want to know about the marine v car battery:
The difference between car and boat batteries - The Globe and Mail
The following link will provide further satisfaction to those with the inquiring mind about different types of lead acid batteries: Deep Cycle Battery FAQ
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