Battery interconnects with 4/0 aluminum wire?

softdown

Around here 2/0 copper is "code" though solar code is never enforced. Most of us know that bigger is better with interconnects. But 4/0 and 2/0 copper is expensive. I have several hundred feet of 4/0 aluminum wire. Leaning towards using it for battery interconnects. It would transfer energy significantly more efficiently than the #2 AWG copper currently being used. Aluminum is poorly effected by heat, this causes much of its negative rap. My battery room never exceeds 80F. Average temp if 50F year round.

BB.

How would you plan on "terminating" your cable ends? The sure way is with AL rated crimped and sealed terminal lugs--I am not sure what is out there these days to make good quality aluminum terminations.

I think you can get aluminum to copper transition crimp connectors... Run copper for battery to battery and run aluminum on the longer runs?

-Bill

softdown

There is a special grease to be used when connecting aluminum to copper. Widely available from Home Depot etc.

BB.

Yes, but, I believe, the "connectors" need to be designed for use with aluminum too (aluminum behaves different under pressure vs copper--Aluminum tends to "creep" more--Gets hot, creeps out under load, gets cold, and shrinks from pressure points).

Not sure--But if you want to try, why not as long as you keep an eye on the connection(s). It can take days/weeks/years before the problem becomes visible.

Some basic information on making aluminum connections:

http://ecmweb.com/contractor/timeless-tips-terminating-aluminum-cables

-Bill

kaipo_boy

softdown wrote: »

There is a special grease to be used when connecting aluminum to copper. Widely available from Home Depot etc.

WOW! wish I had known this earlier. I thought it was a very rare beast and ordered some online at a hugely ridiculous cost ($40 for a tube about twice as big as a normal toothpaste sized container, as I recall) for a stupid welding project that never materialized where the welding arc had to maintain itself on the part that was rotating while welding, so I needed a conductive grease.

Vic

softdown wrote: »

There is a special grease to be used when connecting aluminum to copper. Widely available from Home Depot etc.

Noalox(r by Ideal), is commonly used for this purpose. It IS available in the US at many of the BigBox retailers, and is about $1.50/oz in small squeeze-applicator "bottles". It is often in connecting aluminum to aluminum, as well as to copper.

IMO, there are few places where AL conductors make sense, BUT, battery interconnects or connections would be about the absolute last place that I'd want to use AL. This comment will not very popular, ... probably.

FWIW, Making friends, Vic

softdown

No way. Nobody has ever been taken via online sales. Ever.

/s

Yep...$40 is crazy. think it was $4 at Home Depot.

kaipo_boy wrote: »

WOW! wish I had known this earlier. I thought it was a very rare beast and ordered some online at a hugely ridiculous cost ($40 for a tube about twice as big as a normal toothpaste sized container, as I recall) for a stupid welding project that never materialized where the welding arc had to maintain itself on the part that was rotating while welding, so I needed a conductive grease.

Mountain Don

COPALUM* Sealed Terminals and Splices

Ethan Brush

softdown wrote: »

Around here 2/0 copper is "code" though solar code is never enforced. Most of us know that bigger is better with interconnects. But 4/0 and 2/0 copper is expensive. I have several hundred feet of 4/0 aluminum wire. Leaning towards using it for battery interconnects. It would transfer energy significantly more efficiently than the #2 AWG copper currently being used. Aluminum is poorly effected by heat, this causes much of its negative rap. My battery room never exceeds 80F. Average temp if 50F year round.

I see no issue at all. I use aluminum conductors all the time for 800 and 1000 amp services and use AL on my batteries with set screw lugs. Any major brand lug is tin coated, no issue with aluminum, no deox necessary, although for battery service I would coat the lugs with deox to keep the electrolyte vapor off them. Is there some theory out there that AL cant handle DC or what???

BB.

Here are some details (from an aluminum wiring mfg):

http://www.southwire.com/commercial/AluminumBuildingWireHistory.htm (more at link)

In 1968 Southwire Company led the way in aluminum building wire technology with the advent of triple e® aluminum alloy, resulting in the very first AA-8000 series aluminum alloy. This change resulted in the higher aluminum standards that are still observed today. Starting with a clean slate, metallurgists developed an aluminum alloy that possessed the characteristics desirable in an aluminum building wire. In 1972, and for the first time, aluminum building wire was manufactured with its own metal, not a poor fitting hand-me-down from electrical utility applications. One alloy does not fit all! This new aluminum alloy, developed and patented by Southwire, bridged the gap in key metal characteristics between copper and aluminum. In AA-8000 series aluminum alloy characteristics such as elongation, thermal stability, compressive creep and flexibility were much closer to that of copper. In addition to a new aluminum alloy, aluminum building wire and devices were being tested and listed for compatibility. The use of compatible materials, proper testing and listing resulted in a reliable aluminum electrical wiring method. In 1981, the NEC® began requiring aluminum alloy conductors for 12, 10 and 8 gauge conductors. In 1987 NEC® began requiring AA-8000 series aluminum conductors. This has remained unchanged and can be found in the 2008 NEC® Section 310.14. AA-8000 series aluminum alloy conductors have properties that are significantly different from the old AA-1350 aluminum conductors. To confirm your cable has these conductors, look for the designation “AA-8176” on Southwire’s cable print legend. For other aluminum building wire products, make sure there is an “AA-8…” followed by three other digits.
In addition, copper/aluminum compatible (CO/ALR) devices were required for aluminum wire branch circuits and listed by UL. These devices were developed to be compatible with 10 and 12 AWG aluminum conductors. Due to the cost of these connectors and devices, it is no longer economical to use these sizes in aluminum.

-Bill

Vic

Ethan Brush wrote: »

... Is there some theory out there that AL cant handle DC or what???

Hi Ethan,

All of the AL cable that I have seen is not very flexible. Generally there seems to be fewer conductors in AL cable, and these conductors seem considerably less flexible than standard THHN copper conductors. So, for the AL cables that I have seen, they seem less flexible than THHN in 19 or 37 conductor stranding.

Customarily, battery interconnects and inverter cables are Fine-Stranded cables, which are much more flexible than THHN cables, with traditional stranding for the specific cable size.

Seems to me, that just considering thermal cycling on AL conductors used in battery interconnects that AL might not be as robust. Thermal cycling cam cause connecting hardware to loosen over a period of time. There is a reason than battery interconnects and inverter cables are generally fine-stranded copper, IMO.

Batteries can produce huge fault currents, and, personally, am just not that comfortable with AL cable handling these potentially huge currents.

And, as you noted, Flooded batteries can produce electrolyte vapor, which can cause additional corrosion of AL.

IMO, using copper cables is an investment in the system. They have a history of good service over extended periods of time. If well made, these cables will serve many decades, and, quite possibly on several different battery banks.

But, I am NO expert. FWIW, Vic

mike95490

kaipo_boy wrote: »

WOW! wish I had known this earlier. I thought it was a very rare beast and ordered some online at a hugely ridiculous cost ($40 for a tube about twice as big as a normal toothpaste sized container, as I recall) for a stupid welding project that never materialized where the welding arc had to maintain itself on the part that was rotating while welding, so I needed a conductive grease.

The aluminum connector grease, is NOT conductive. It is an oxygen barrier and has sharp little crystals in it that get massaged into the wire to cut through the surface oxide before the contact is tightened down. It's NOT the same as conductive copper grease as used on large fuses, industrial power lugs and such.

inetdog

softdown wrote: »

Around here 2/0 copper is "code" though solar code is never enforced. Most of us know that bigger is better with interconnects. But 4/0 and 2/0 copper is expensive. I have several hundred feet of 4/0 aluminum wire. Leaning towards using it for battery interconnects. It would transfer energy significantly more efficiently than the #2 AWG copper currently being used. Aluminum is poorly effected by heat, this causes much of its negative rap. My battery room never exceeds 80F. Average temp if 50F year round.

If you are getting away with #2 copper right now, then 2/0 copper is definitely overkill.
FWIW, if you are going to load the conductors to their maximum allowed insulation temperature, 4/0 aluminum is roughly equivalent to 2/0 copper, so your are correct in that.

softdown

How does one know if their interconnects are truly large enough? I replaced them with 4/0 copper fine strand yesterday. Bit of a project. Was generally unable to fit 100% of the strands into the lugs. So a little trimming was needed.

Used about 40' of 4/0 yesterday. Could have been pretty expensive without a deal. But I had found a good enough deal to warrant buying 200' of 4/0 fine strand. Still think it is a bit of overkill for most interconnects.

inetdog wrote: »

If you are getting away with #2 copper right now, then 2/0 copper is definitely overkill.
FWIW, if you are going to load the conductors to their maximum allowed insulation temperature, 4/0 aluminum is roughly equivalent to 2/0 copper, so your are correct in that.

softdown

FWIW....my 4/0 aluminum is pretty darned flexible. Much more so than copper...unless you get the fine stranded copper.

Vic wrote: »

Hi Ethan,

All of the AL cable that I have seen is not very flexible. Generally there seems to be fewer conductors in AL cable, and these conductors seem considerably less flexible than standard THHN copper conductors. So, for the AL cables that I have seen, they seem less flexible than THHN in 19 or 37 conductor stranding.

Customarily, battery interconnects and inverter cables are Fine-Stranded cables, which are much more flexible than THHN cables, with traditional stranding for the specific cable size.

Seems to me, that just considering thermal cycling on AL conductors used in battery interconnects that AL might not be as robust. Thermal cycling cam cause connecting hardware to loosen over a period of time. There is a reason than battery interconnects and inverter cables are generally fine-stranded copper, IMO.

Batteries can produce huge fault currents, and, personally, am just not that comfortable with AL cable handling these potentially huge currents.

And, as you noted, Flooded batteries can produce electrolyte vapor, which can cause additional corrosion of AL.

IMO, using copper cables is an investment in the system. They have a history of good service over extended periods of time. If well made, these cables will serve many decades, and, quite possibly on several different battery banks.

But, I am NO expert. FWIW, Vic

Ethan Brush

Vic wrote: »

Hi Ethan,

All of the AL cable that I have seen is not very flexible. Generally there seems to be fewer conductors in AL cable, and these conductors seem considerably less flexible than standard THHN copper conductors. So, for the AL cables that I have seen, they seem less flexible than THHN in 19 or 37 conductor stranding.

Customarily, battery interconnects and inverter cables are Fine-Stranded cables, which are much more flexible than THHN cables, with traditional stranding for the specific cable size.

Seems to me, that just considering thermal cycling on AL conductors used in battery interconnects that AL might not be as robust. Thermal cycling cam cause connecting hardware to loosen over a period of time. There is a reason than battery interconnects and inverter cables are generally fine-stranded copper, IMO.

Batteries can produce huge fault currents, and, personally, am just not that comfortable with AL cable handling these potentially huge currents.

And, as you noted, Flooded batteries can produce electrolyte vapor, which can cause additional corrosion of AL.

IMO, using copper cables is an investment in the system. They have a history of good service over extended periods of time. If well made, these cables will serve many decades, and, quite possibly on several different battery banks.

But, I am NO expert. FWIW, Vic

Vic,

Fine stranded copper is certainly super flexible and a pleasure to work with. I find compact stranded AL easier to work with than standard 19 strand CU however - it is lighter and stays where you bend it. Us electricians subject AL conductors to cycling currents and temperatures and high fault currents all the time with no issues. I just have not see any practical or industry evidence of modern and correct AL terminations being any less dependable and rubust than CU. I think any connection will suffer greatly from exposure to electrolyte but I dont know for sure if AL suffers more than CU or not.

Photowhit

Ethan Brush wrote: »

Us electricians subject AL conductors to cycling currents and temperatures and high fault currents all the time with no issues. I just have not see any practical or industry evidence of modern and correct AL terminations being any less dependable and rubust than CU.

I guess you have heard about Mobile homes and aluminum wiring? I understand we're talking about different alloys these days, but perhaps the expansion problems with connections would be scary enough.

Ritchie26

Aluminum wiring has traditionally been used in homes built between the 1960’s and early 1970’s It is estimated that there are over 450,000 homes in Canada that are wired entirely with aluminum wiring. Around the mid-1970’s, aluminum wiring was labelled a fire hazard and was replaced with copper wiring. Today only copper wiring is used in building construction.

mike95490

kaipo_boy said:

softdown wrote: »

There is a special grease to be used when connecting aluminum to copper. Widely available from Home Depot etc.

WOW! wish I had known this earlier. I thought it was a very rare beast and ordered some online at a hugely ridiculous cost ($40 for a tube about twice as big as a normal toothpaste sized container, as I recall) for a stupid welding project that never materialized where the welding arc had to maintain itself on the part that was rotating while welding, so I needed a conductive grease.

Conductive welding grease is NOT the same as the anti-corrosion aluminum cable greases. 

NEVER use one for the other purpose.


anti-corrosion aluminum grease is NON-conductive, it has oxygen blocking grease, and razor sharp micro-particles to break up the aluminum oxide layer that ruins the connections.  Then it must be properly terminated, after the grease has been abraded & rubbed into the strands of the cable.