How to Direct Wire Inverter

[jesseannie]

I have a 400 watt continuous 800 watt peak Cobra inverter. It has 2' long clamp on style connectors for attaching directly to the battery.
I would like to direct wire the unit and install it inside the trailer about 12' from the pair of TT batteries or alternately wired to the electrical panel that is located under the bed. (easy access)
I will only be using the invertor to charge my phone, camera and to power two laptops. I am not going to try to operate any appliances.
In my last trailer I had a unit that I was able to wire to the main electrical panel in the trailer. This unit did not come with any option to do that.
Any help would be appreciated.
PS Yes I did do a search and so many of the questions had to do with larger units and solar power.
jesse

[jesseannie]

smkettner wrote:
Depending on use just pop in a 20 amp fuse in an empty slot in the stack of fuses and connect with #10 wire.

Now that sounds like a great solution. What I am going to be using the inverter for is very low power draw and this seems like it would work for me.

Thanks
jesse

[time2roll]

Depending on use just pop in a 20 amp fuse in an empty slot in the stack of fuses and connect with #10 wire.

[pianotuna]

Hi RJ

Doubling up makes #10 about the same as #7.

[RJsfishin]

I'm running a 400 watt Cobra all of 15 ft from the batts, It runs everything in the entertainment center. 10 ga seemed a little small, so I doubled up on the 10 ga, (whatever that's equiv to) and it works fantastically, w/ minimal voltage drop.
Sounds like you'd want to connect it to the battery lugs in the 12v distribution panel.

[mena661]

tenbear wrote:

I agree, use a fuse. However, for your planned use I would use a much smaller fuse than 80 amps. The actual size fuse would depend on the current carrying capacity of the wire you use.

Inverter manufacturers don't normally recommend fuses at the peak rating anyways cause the inverter doesn't run at that very long and the typical ANL fuse can handle the short surges.

[tenbear]

wa8yxm wrote:
I DO recommend using a fuse, 800 watt peak think 80-90 amps, or less if you can find the manual and it specifies one.

I agree, use a fuse. However, for your planned use I would use a much smaller fuse than 80 amps. The actual size fuse would depend on the current carrying capacity of the wire you use.

[MrWizard]

Moved from technology corner

[wa8yxm]

On inverters of that size there are often terminals where the wires attach, You can get Starter Cable from your local Auto Dept/store and use them to make the connection.

IF not.. Well you can cut off the clamps and put on lugs.

I DO recommend using a fuse, 800 watt peak think 80-90 amps, or less if you can find the manual and it specifies one.

[jesseannie]

Thanks for the replies.
I will have to look some more at my options on where to mount, to get the best performance.

[tenbear]

What counts is the voltage drop in the wire between the battery and the inverter. That is determined by the resistance of the wire. Assuming that you have 12' of wire between the battery and the inverter and wire is used for both positive and negative, that is 24' of wire. With #10 wire at the full rated current of your inverter, 40A, you would have a 0.96v voltage drop so if your battery voltage was 12.1v (50% charge), you would have about 11.1v at the inverter, pretty marginal. #10 wire is only rated for 30A anyway.

With the phones and computers you are planning to charge, you could be using about 200 watts so you would have about half that voltage drop or 11.6v at the inverter.

As a rule of thumb, a decrease of 3 in the wire size cuts the resistance in half and therefore the voltage drop in half. However there is no such thing as #7 wire so you would have to use #6.

Sorry if I an getting too technical. Just trying to explain the tradeoffs.

Edit: Your power distribution panel is a long way from the battery. I don't know what the wiring is between the battery and the panel but you would have to take that into consideration if putting the inverter there and taking the 12v from the panel.

[time2roll]

I wired my 300w inverter behind the main breaker/fuse panel. Connected the 12v to the existing 12v feed to the battery. Used two transfer switches to connect to the two 120v branch circuits that feed the outlets. I would use the small Xantrex Prowatt transfer switch if installing today.

If you are just charging small items or running a tv/dvd you will be pulling about 1 to 8 amps maybe 20 max so the wire is not a huge deal. Virtually no surge issues at this level.

[jesseannie]

OP again. I think I am getting the picture. Put the inverter as close to the 12 volt power as possible and run 120v further if needed.
So my next question is: the TT electrical panel is under the bed at the opposite end as the batteries is there a way to wire it in there.
At that location is there 12 volt power from the battery that I could tap into. The batteries are on the tongue of the trailer outside so that is pretty inconvenient.
The inverter is self contained it has an off/on rocker switch and two 120v plug-ins.
jesse

[pianotuna]

Hi,

12 feet is a long run for DC power. I'd suggest keeping the unit within 2 or 3 feet of the battery bank.

The 120 AC side doesn't suffer from voltage drop nearly as much.

[Golden_HVAC]

You can cut off the ends of the wires going into the inverter and install a plug. Then run some #10 wire from the battery to a 30 amp fuse, then to a electrical plug. THen you can plug in the inverter anytime you want to. Check here for a sample 30 amp plug, I would suggest a locking type, so nobody ever plugs it into a 120 or 240 amp plug in a home. http://www.homedepot.com/s/30%2520amp%2520plug?NCNI-5

Then you can plug in the TV or charger when you want to. For that, I would suggest a power strip, and then plug in each thing to that. You can use a 15' extension cord to run the high voltage much less money than running the #10 wire to separate the inverter from the battery. In other words, it is better to use shorter 12 volt wires that is very large diameter (due to having 10 times higher amperage at 1/10 the voltage) and a longer 120 volt extension cord then to run longer 12 volt wires then plug in the charger directly to the inverter located near say the coffee table.