Battery Wire Gauge

[RubyDog]

Looking to increase my battery capacity and am wondering about battery wire. My 2014 FC 25FB has 6 gauge wire. I know a thicker gauge is desirable for a host of reasons even with the OEM Interstates but is it necessary? Trojan recommends specific gauges based on Ah. I assume they use conservative recommendations. I just want my batteries to last longer. I do not see my load changing. Does that mean my 6 gauge wire remains both adequate and safe? Assuming no other appliances are added such as a toaster etc. I assume the 6 gauge be adequate even if someone runs the 1000 watt inverter given you can do that now with the OEM configuration. In short increasing battery capacity has no impact on my maximum draw, correct? If I do decide to upgrade the wire how difficult is it to pull? Thanks all.

[Glenritas]

If you load is unchanged you don't need to change the wire size.

Pulling wire is a major project and in your case not necessary .

Now IF you were to add a major load it should have its own circuit starting at the battery.

[Jammer]

1000 watt inverter will typically draw 90 amps when there is a 1000 watt load connected to it.

That's marginal for 6 gauge though it may work fine if the distances are relatively short (several feet) and the cable is exposed enough that it can cool. It will also work fine if you don't connect 1000 watt loads to your inverter, because the inverter will draw less power when the loads are smaller. At, say, 600 watts you could run it all day. Or until the batteries give out, at least.

[Panama Red]

1000 watts on a 120 volt inverter only draws 8.33 amps, if it is a straight resistive load... So the draw on the dc input will be slightly higher, according to the efficiency of the inverter. Figure roughly 10-12 amps.

-red


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[idroba]

Originally Posted by Panama Red

1000 watts on a 120 volt inverter only draws 8.33 amps, if it is a straight resistive load... So the draw on the dc input will be slightly higher, according to the efficiency of the inverter. Figure roughly 10-12 amps.

-red


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Sorry Red but W = V x A.

At120 volts the 1000 watt load may only be 8.3 amps, but the input will be ten times that much, or 83 amps.

1000/12 = 83

[dznf0g]

I think Jammer is correct on this....It's north of 83 amps 12V DC, with losses, it's around 90 amps.

[Panama Red]

Originally Posted by idroba

Sorry Red but W = V x A.



At120 volts the 1000 watt load may only be 8.3 amps, but the input will be ten times that much, or 83 amps.



1000/12 = 83

You're right. Sorry, brain farted for a second there..

-Red, been out of school too long...

[Panama Red]

I maintain a large Uninterruptible Power Supply on my job, 100kW three phase thing, and I totally went off of current in vs current out on my system when I started thinking on this problem. I totally bypassed the battery portion in my thinking... And, the sun was in my eyes, the dog ate my papers, and someone distracted me...

-Red, thinking up excuses...

[dznf0g]

"-Red, thinking up excuses..." If we are to accept the aforementioned excuses, the price is one beer.

[Panama Red]

Originally Posted by dznf0g

"-Red, thinking up excuses..." If we are to accept the aforementioned excuses, the price is one beer.

DEAL!!!!

-Red, never thinking he'd get off that cheap...

[idroba]

Red, we all do it, no apology necessary and some humor helps us get through the day. I laugh at myself often. Keeps me sane more or less.

Some may argue that last few words.

[dznf0g]

Hey! !!! You're endangering my negotiated free beer!

[Panama Red]

Originally Posted by dznf0g

Hey! !!! You're endangering my negotiated free beer!

Wait, you wanted the beer? I totally misunderstood and drank that thing last night...

-Red, slow on the uptake, quick on the chugdown...

[dznf0g]

Nice! I bet they'll make more.

[Panama Red]

Originally Posted by dznf0g

Nice! I bet they'll make more.

Sure they'll make more, but that one was yours... Man, I feel bad, but there's nothing to be done about it now.

-Red, being purposely obtuse...

[dznf0g]

geez, ya learn something new about people every day!

[Panama Red]

Tell you what, since I drank yours, my cooler will be open for you at Canopener 2016... it's the least I can do. Literally...

-Red, making amends with limited liability...

[dznf0g]

Wish I could be there.....Save it and you can have it then....but not till then!

[Panama Red]

Originally Posted by dznf0g

Wish I could be there.....Save it and you can have it then....but not till then!

Man! Thanks! Not everybody would so willingly give up their beer like that...

Sorry for the thread hijack. I'll quit now.

-Red, sensing skunky beer in his distant future...

[switz]

The wire size is important for longer distances due to voltage drop caused by internal resistance of the wire. An analogy is a ¼" water hose out 25 feet and a ⅝" water hose out 25 feet. Obviously the larger hose delivers more volume but at also closer to input water pressure (volts) as compared to the pressure drop in the small diameter hose.

In a perfect world, the wires from the batteries to the inverter should be adequate sized per the National Electric Code for the inrush current imposed be an device with a motor. Resistive loads like a toaster are constant power draw from turn on to turn off.

There are usually only 15 amp rated 120Vac outlets in a trailer, the factory #12 wire is rated 20 amps and is usually on a 20 amp breaker, so that reduces the voltage drop and allows for more devices to run at the same time (up to 20 amps momentary use, but that #12 wire is rated by the NEC for 16 amps continuous load).

We have a 400 amp fuse between our battery bank and the Magnum MS-2812 inverter/charger that is capable of creating 2,800 watts of AC power (can even start and run the rear air conditioner for awhile). The wire size is 2-0 copper or about the diameter of my thumb.

That is why all inverter installation manuals prefer the shortest possible wire runs of larger wire size from the battery bank to the inverter.