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Old 09-17-2020, 04:28 PM   #1
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Inverter Install

I have a 3000 watt inverter and have a question regarding the install. Obviously I need to disable the converter or the inverter will freak out trying to run 110v items while converting back to 12v for the battery. My control panel has a switchable fuse for the converter. Can I just turn this fuse off and disable the converter so it will not receive power from the inverter? Will my 12v items still work without the converter on? (ie: still receive power from the batteries?) I also have a solar panel on the roof that is wired separately to the batteries so this shouldn't matter.
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Old 09-17-2020, 04:46 PM   #2
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Oh and my intentions are just plugging in to the inverter like it is shore power.
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Old 09-17-2020, 05:28 PM   #3
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Plugging the inverter just to the shore is the easy method.

But, you need to flip the breaker on the converter. Otherwise it is a battery discharge loop. Simple.

I assume you know to install big wires and a 300 amp breaker or fuse on the wire. Wire should be as short as possible. As big as possible. 4/0. That is 0000.
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Old 09-17-2020, 05:39 PM   #4
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Originally Posted by tomkatb View Post
Plugging the inverter just to the shore is the easy method.

But, you need to flip the breaker on the converter. Otherwise it is a battery discharge loop. Simple.

I assume you know to install big wires and a 300 amp breaker or fuse on the wire. Wire should be as short as possible. As big as possible. 4/0. That is 0000.

Yes I found a wire chart, luckily I am only 4' away from the batteries so 00 is what I have. I also got the 300amp breaker but not sure what the point of it is, as I don't see 300 amps ever traveling from the battery to the inverter. maybe I am wrong? My question is whether the Converter breaker will do the trick. I am assuming it is to disable the converter. I guess I can easily check to see if I still have 12v in the trailer after i flip the switch. Thanks!!!
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Old 09-17-2020, 06:14 PM   #5
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Do the math.

The inverter output of 3,000 watts. P=IV use 4000 Watts because most inverters will go over for short periods. Divide by 12.5. Or 320 amps dc. Prevents the wire from the battery to the inverter from burning. Assumes you have enough batteries. Like four or more.

Converter is not involved here. Should be turned off. Has nothing to do here. Wire from the battery goes direct to the fuse panel. Typically the inverter output is in the same location. Two wires from the panel to the converter.
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Old 09-17-2020, 06:27 PM   #6
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Yes, you will have 12v with the converter breaker off. Until your batteries are dead anyway......
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Old 09-17-2020, 08:17 PM   #7
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Quote:
Originally Posted by tomkatb View Post
Plugging the inverter just to the shore is the easy method.

But, you need to flip the breaker on the converter. Otherwise it is a battery discharge loop. Simple.

I assume you know to install big wires and a 300 amp breaker or fuse on the wire. Wire should be as short as possible. As big as possible. 4/0. That is 0000.
No argument that large wires are required however the actual size is determined by distance from batteries.

Here's a calculator that makes for easy wire size selection based on Amperage and Distance.

https://www.wirebarn.com/Wire-Calculator-_ep_41.html


To keep wire size down consider mounting the Inverter as close as practical to the batteries. This reduced the need for HUGE wires. For example, if you can keep the "round trip distance" (total of positive and negative wires) to less than 10 feet you can run 300 amps through 2/0 (00) wire.

If you still want to use smaller wire (often less expensive) you can pair wires for both oisitive and negative conductors. For example, a pair of #2 wires can be more flexible if you have to make tight bends than a singe 2/0 wire.

Many large inverters are built with input lugs that allow for connection to each side with a single bolt.

With a large inverter like described I certainly would mount it as close as I could to my batteries leaving just enough room for air circulation as specified in the manufacturer's installation directions. Running large copper wires any distance gets expensive real quick.

In closing, I used Welding Cable for my inverter installation and battery wiring. Very flexible and not terribly expensive as copper wire goes.
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Old 09-18-2020, 09:58 AM   #8
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I am only 3' from the batteries if that. So I purchased single "0" cable, 5'.

I have 2 batteries and a solar panel to recharge them. I only will be using the 3000watt/6000watt surge pure sine converter for laptop charging and tv/dvd watching. The inverter output is only 25 amps, and the input is 300amp dc. Now that I see this, I understand the reason for the breaker on the DC line. Before it didn't make sense how it can draw 300amp and put out 25 amps.
Thanks for all the advice, I will be installing this next week.
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Old 09-18-2020, 11:18 AM   #9
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Goodness.
I'd go to Walmart and buy a couple 100w inverters. One for TV, one for laptop.

The inverter, just being on, will draw as much as your loads.
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Old 09-18-2020, 12:37 PM   #10
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Goodness.
I'd go to Walmart and buy a couple 100w inverters. One for TV, one for laptop.

The inverter, just being on, will draw as much as your loads.
I agree!
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Old 09-18-2020, 12:40 PM   #11
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I have a 75w (with no fan) inverter just for my TV. That way the TV is effectively a 12v model and the inverter can stay off almost all the time. Don't care if I'm plugged in or not, it just works.
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Old 09-18-2020, 12:41 PM   #12
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I have a 75w (with no fan) inverter just for my TV. That way the TV is effectively a 12v model and the inverter can stay off almost all the time. Don't care if I'm plugged in or not, it just works.
300 watt inverter for CPAP here. Digital display on inverter shows the CPAP actually draws 60 watts at 110 volts. Laptop charging would be very similar.
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Old 09-18-2020, 02:57 PM   #13
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Remember the 10 to one relation between ac and dc amps. 10 ac equals 100 dc. Your converter draws 5 amps ac and puts out roughly 50 amps dc.

When possible always run the cpap on dc. Because every conversion is a 10-20% loss in amps. So plugging in the converter looses 20% to convert to 110.

The cpap then converts again to 12 volts and looses 20% again.

Most of the cpap units can purchase a dc cord. Saves a bunch of amps.
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