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I recently acquired a 2000 Watt Inverter with a 4000 Watt Peak from a friend who did not like they way it worked in his RV. How would I safely wire it into my car? If it helps I drive a 2005 Nissan Sentra SE-R Spec V. I have a single battery under the hood.

So far my plan was to mount the inverter in the trunk and run 4 gauge cables from the battery to it. For convince I was planning on wiring a switch in the dashboard with a 200 amp relay (https://www.amazon.com/dp/B01I9CI3VS). Would this be a safe option to shut it off when I am not using it? I do plan on putting a 200 amp fuse close to the battery.

In the front of the car I was looking at running an extension cable and cutting the ends and splitting the power to a few of these (https://www.amazon.com/dp/B0031C11DY). Is this the best way to do this or is there something better I can do?

Also my car is around 14 feet in length so I am imagining I will be using around that much in wire. Will 4 gauge be safe enough or will I need to use 2 gauge? I am somewhat new to this and do not want to set my car on fire.

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    \$\begingroup\$ About the socket, don't use one which has an earth contact, because your circuit doesn't have an earth. You should never plug in devices which need earth — so it's best to prevent it mechanically. \$\endgroup\$
    – Janka
    Nov 6, 2016 at 16:26
  • \$\begingroup\$ From what I understand my inverter has an earth connection. \$\endgroup\$
    – Austin
    Nov 6, 2016 at 16:35
  • \$\begingroup\$ How come? You car doesn't have an earth connection. If you want earthing, you had to have a steel lance and sledgehammer with you and literally drive it into earth. And hope this is sufficient as you sure wouldn't test it for earth's electrical resistance at the place. \$\endgroup\$
    – Janka
    Nov 6, 2016 at 16:39
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    \$\begingroup\$ You do not have an earth but you can gain much of the safety and function of an earthed system if you install a residual current circuit interrupter (earth leakage circuit breaker) before your loads. However in effect you are operating on a floating/isolated supply as far as mother earth is concerned and only have to protect yourself from grounding to the car chassis when touching a live conductor. \$\endgroup\$
    – KalleMP
    Nov 6, 2016 at 20:58
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    \$\begingroup\$ Have you considered what a 200Amp draw from a starter battery is going to do to the battery if applied for more than a few seconds. \$\endgroup\$
    – RoyC
    Jan 10, 2017 at 11:02

3 Answers 3

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You are best served with short thick input cabling.

You may also find that having just one battery will cause you to rethink your friends kind gift when you run your battery flat in 20 minutes. Perhaps less than an hour with the engine at cruising revs. If you decide to add a second battery you can mount it close tot he inverter solving your cabling concerns a lot easier. Make sure you arrange a suitable charging system to isolate the starter battery if the engine is not running.

The peak current may be around 350A, that is welding currents and will need welding cables.

If you only plan to use it occasionally, you could add carry handles and then fit nice traction battery power connectors (the sort used in electric forklift trucks) and lug the unit to the battery when needed.

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The 200 A relay appears to be fine to use for a shut-off. You should consider wiring it to shut off the inverter whenever the engine is not running. Your battery will discharge very quickly if you use it to power the inverter with anything close to rated load. If you significantly discharge your battery very often, it will fail before long. Consider a second small inverter for things you must run with the engine not running. Even the alternator will not be capable of running the inverter at rated load. You should consider fusing the alternator at the current rating of the alternator or less. You need to consider what is required from the alternator to operate the normal load it has when the engine is running.

You need to determine what ambient temperature the inverter is rated for. Look to see if the inverter power rating is for operation in normal outside air temperature or the temperature under the hood or in the trunk.

There are different types of wire insulation with different temperature ratings. Wire with a higher temperature rating can safely carry a higher current for a given size. However you must adjust for the temperature of the areas where the wire is located. You should be able to find tables to help with that.

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According to wikipedia (AWG page), 4 guage is less than 100A, and 2 guage is little more than 100A. If you want to protect wire with a 200A fuse, you should use 'triple aught', 000.

10m of wire (5 there, 5 back) in 4 guage would drop 1.6v at 200A, which is probably too big a chunk of 12v. In 000, it would be 0.4v, which is better. Best would be to mount the inverter under the hood next to the battery.

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  • \$\begingroup\$ Yes, it should go under the hood, there is much better ventilation there than in the trunk. And when it catches fire chances are you can leave the car before it's too late, as the engine compartment is usually at least a bit protected against fire harzards. \$\endgroup\$
    – Janka
    Nov 6, 2016 at 16:24
  • \$\begingroup\$ 200 Amps is what I got from reading online. Would it be better to use less amps? Also the inverter says to keep it away from water. Would it be safe to mount it under to hood? \$\endgroup\$
    – Austin
    Nov 6, 2016 at 16:39
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    \$\begingroup\$ Janka thinks it would be safer under the hood, and I agree. How much water do you keep under there, if that's a worry to you? If you want to power something using 2kW, then you're going to need those 200A. It might be prudent to start your car before boiling your 2kW kettle. \$\endgroup\$
    – Neil_UK
    Nov 6, 2016 at 16:48
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    \$\begingroup\$ I've done a bit engineering for cars ten years ago. Water protection is a must in the engine compartment. If your inverter isn't properly protected (e.g. open ventilation ducts) you can't mount it there. But most times this is merily a cautious vendor who doesn't want to be held reliable by coffee-cup-spilling-then-litigating people. \$\endgroup\$
    – Janka
    Nov 6, 2016 at 16:56
  • \$\begingroup\$ Oh, and water-protection can also mean: let the water drops rinse down quickly, so they cannot accumulate to a puddle. That's something you have to make sure of by choosing the correct mounting. \$\endgroup\$
    – Janka
    Nov 6, 2016 at 16:59

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