Distance from inverter and battery bank : Some questions.

[RanchyRanch]

Hi there,

I'm going to replace my inverter with a pure sine wave one and was wanting to relocate the inverter upstairs from it's existing position in the basement so I can monitor it and have easier access to it. I have no interest however in relocating the battery bank however. Are there any issues with having the inverter located about 30-40ft away from the battery bank? What gauge wire should be used to complete this safely and effeciently?

I am uncertain if it matters/how it plays into it, but I am using (2X) 100 Watt 12v panels that are charging (6X) 6v, 65aH batteries.

[Sunking]

Are there any issues with having the inverter located about 30-40ft away from the battery bank? What gauge wire should be used to complete this safely and effeciently?

Extremely serious issues like cost and safety.

The Issue is Power Loss is extreme with low voltages once you get past 5 to 8 feet 1-way distance, and very high currents required for low voltage. For example let's say that is a cheap 400 watt Inverter @ 12 volts drawing 40 amps at full power. If located within 5 feet would requires #8-10 AWG copper wire to maintain 3% power loss. Move out to 40 feet requires 400 MCM which is about as large as your wrist, weighing 120 pounds worth of copper. You would have no way to Terminate the cable or Connect it. Not to mention cost $6/foot.

Convinced to move the batteries now?

[SunEagle]

Hi there,

I'm going to replace my inverter with a pure sine wave one and was wanting to relocate the inverter upstairs from it's existing position in the basement so I can monitor it and have easier access to it. I have no interest however in relocating the battery bank however. Are there any issues with having the inverter located about 30-40ft away from the battery bank? What gauge wire should be used to complete this safely and effeciently?

I am uncertain if it matters/how it plays into it, but I am using (2X) 100 Watt 12v panels that are charging (6X) 6v, 65aH batteries.

Due to wire size & cost and potential fire hazard it is better to keep your inverter within 5 feet of your battery bank.

Another area to be concerned it having more than 2 strings of batteries wired in parallel. It is hard to get a balanced charge and discharge equally across all of the batteries which results in one or more getting over worked.

[bridaus]

There are a number of remote monitoring solutions that are so much more interesting and worthwhile than moving the inverter. This would be like moving a car engine into the passenger compartment to read the rpms. Leave the engine in the basement and get a TED or remote display. Cost less than the cable.

[Bucho]

Convinced to move the batteries now?

Or he could just set up an on/off switch for the inverter and a display upstairs.

[Sunking]

Or he could just set up an on/off switch for the inverter and a display upstairs.

Yes but I doubt he is coming back.

[Fiddler]

For example let's say that is a cheap 400 watt Inverter @ 12 volts drawing 40 amps at full power. If located within 5 feet would requires #8-10 AWG copper wire to maintain 3% power loss. Move out to 40 feet requires 400 MCM which is about as large as your wrist, weighing 120 pounds worth of copper. You would have no way to Terminate the cable or Connect it. Not to mention cost $6/foot.

You say 12V 40A 40 ft 3% drop requires 400 MCM yet this calculator http://www.southwire.com/support/vol...calculator.htm states a #2/0 would keep the loss to less than 3%.

Am I missing something? I'm trying to determine if I can have my MidNite Solar MNB17 on my living room wall and my batteries in a shed 20 feet away.

Thanks!
Jim

[max2k]

You say 12V 40A 40 ft 3% drop requires 400 MCM yet this calculator http://www.southwire.com/support/vol...calculator.htm states a #2/0 would keep the loss to less than 3%.

Am I missing something? I'm trying to determine if I can have my MidNite Solar MNB17 on my living room wall and my batteries in a shed 20 feet away.

Thanks!
Jim

the calculator is correct- #2/0 over 20' run will have 0.29V drop over both wires in total: 0.145V one wire and the same- another. This is less than 3% (2.4%) of the voltage drop or power loss.

[sensij]

the calculator is correct- #2/0 over 20' run will have 0.29V drop over both wires in total: 0.145V one wire and the same- another. This is less than 3% (2.4%) of the voltage drop or power loss.

If anything, that Southwire calculator is conservative, including an AC reactance component, and assuming the conductor is at 75 deg C (167 deg F). You could use a more basic calculator, or even a chart for 12 V systems like what Blue Sea Systems publishes, showing <3% drop for 40 A over 40 ft round trip distance could be achieved with 2 AWG.

[Fiddler]

Thanks to the both of you.
Jim

[Sunking]

You say 12V 40A 40 ft 3% drop requires 400 MCM yet this calculator http://www.southwire.com/support/vol...calculator.htm states a #2/0 would keep the loss to less than 3%.

Am I missing something? I'm trying to determine if I can have my MidNite Solar MNB17 on my living room wall and my batteries in a shed 20 feet away.

Thanks!
Jim

My bad, been to long to remember what numbers I used. Obviously a mistake on my part, I think I might of used 400 feet. 2 AWG at 40-feet one-way with 40 amps.

[Fiddler]

Ah, OK. Mistakes happen! Just wanted to make sure I wasn't doing something wrong.