Connect 1500W inverter to 2 batteries

[mlatter]

Originally Posted by ScottBrownstein

We are both saying the same thing from opposite directions.

Agreed!

[WolfWhistle]

Originally Posted by mlatter

I agree with most of that, but engineers have produced charts of current draw vs wire gauge vs cable length, and in my case, the 4/0 is the ticket for inter-battery and to the inverter (bendable 4/0 welding cable). I run my trailer air conditioning all day long while travelling using the truck alternator and I don't have any issues with any cables heating up, etc. Perhaps thinner cables would work, but I don't think they'd work as well.

Hi M, I'm would like to know more about how you run your AC while driving. I gather that you have a capable inverter, battery bank; all cabled properly.

I would guess that your trailer's AC unit draws from 150 to 170 amps at 12 vdc., which is well within the ability of your alternator. But, the wire is long and would produce a significant voltage drop.

Did you run a heavier wire?

So, I wonder if you have taken a reading at the battery bank while the AC is running and what that is? Granted it would be higher until the TVs batteries are full and less when they are.

Or, if you have a monitor (I run a Trimetric TM2030) what it shows volts / amps and how much battery capacity (%) is left when you arrive after traveling while running the AC?
Thanks,
WW

[bubbles]

Why not use 2 or more smaller, manageable gage wires in parallel for the runs instead of dealing with those monstrous hard to bend, crimp, etc. wires.

[mlatter]

Originally Posted by WolfWhistle

Hi M, I'm would like to know more about how you run your AC while driving.

I have the Xantrex Freedom 3000 watt inverter/charger in the trailer, and a 320 amp alternator in the truck. Currently, I have #2 welding cable run from the alternator to the inverter, in parallel with the trailer's battery bank. There is also a connector in the front of the truck bed to be able to disconnect. This setup works pretty well, except on very hot days when the residential fridge and trailer air are running full out, causing a voltage drop at the inverter to ~13v which is not quite enough to properly charge the trailer battery bank. I plan to upgrade to 2/0 welding cable in the near future, which will take the voltage up to 13.9 while under the same load, and properly keep the trailer batteries topped up.

[mlatter]

Originally Posted by bubbles

Why not use 2 or more smaller, manageable gage wires in parallel for the runs instead of dealing with those monstrous hard to bend, crimp, etc. wires.

No reason.
I use stranded welding cable which I find quite easy to work with so it's no big deal... well, not including the 4/0 which is quite large and hard to handle.

[Skyliner]

Originally Posted by mlatter

I have the Xantrex Freedom 3000 watt inverter/charger in the trailer, and a 320 amp alternator in the truck. Currently, I have #2 welding cable run from the alternator to the inverter, in parallel with the trailer's battery bank. There is also a connector in the front of the truck bed to be able to disconnect. This setup works pretty well, except on very hot days when the residential fridge and trailer air are running full out, causing a voltage drop at the inverter to ~13v which is not quite enough to properly charge the trailer battery bank. I plan to upgrade to 2/0 welding cable in the near future, which will take the voltage up to 13.9 while under the same load, and properly keep the trailer batteries topped up.

That is AWESOME! I need to do something similar with the wiring from my truck's two alternators because the wiring's voltage drop is insufficient to even charge my 3 battery banks when I drive.

Do you notice much of a fuel economy drop with such a load on your alternator?

[mlatter]

Originally Posted by TonyD

Do you notice much of a fuel economy drop with such a load on your alternator?

It's hard to pinpoint how much affect the extra load has on fuel economy, but I have to think it would be less than running a separate generator.
At 200 amps, that equates to about 3.75 horsepower, so even at 50% efficiency, it's drawing maybe 7.5hp.

[WolfWhistle]

Originally Posted by bubbles

Why not use 2 or more smaller, manageable gage wires in parallel for the runs instead of dealing with those monstrous hard to bend, crimp, etc. wires.

Yes you can. I would consider this if the cost was lower for the smaller or pulling the heavier wire nearly impossible.

Keeping in mind that the rule (rule of thumb, not precisely) is that an increment of 3 in AWG numbers represents a halving of the cross-sectional area of a wire. The current capacity is directly proportional to that of the area.

This means that to create the equivalent of a wire of AWG(N), you need two strands of AWG(N+3), or three strands of AWG(N+5). Three strands of AWG(N+4) gives you some extra safety margin.
WW

[bubbles]

Originally Posted by WolfWhistle

Yes you can. I would consider this if the cost was lower for the smaller or pulling the heavier wire nearly impossible.

Keeping in mind that the rule (rule of thumb, not precisely) is that an increment of 3 in AWG numbers represents a halving of the cross-sectional area of a wire. The current capacity is directly proportional to that of the area.

This means that to create the equivalent of a wire of AWG(N), you need two strands of AWG(N+3), or three strands of AWG(N+5). Three strands of AWG(N+4) gives you some extra safety margin.
WW

I believe this may be true I was just speculating that instead of 1- 4/0 wire 2- 1/0 wires would accomplish the same thing with almost identical characteristics and be more installation friendly. It was just a thought. Maybe not a good idea and/or necessary in this application. Good day.

[WolfWhistle]

V, your speculation is absolutely accurate. Voltage drop is 0.049 (.41%) if you use 5 feet of #4/0 (12vdc 100amps) as it is with two conductors in #1/0 the same length. The smaller wire gauge is both easier to pull and many times more convenient to terminate. WW