Question: Splicing / Connecting 4/0 welding wire

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Hairfarm
Hairfarm Solar Expert Posts: 225 ✭✭✭
in Off Grid Solar & Battery Systems #1
I have two 3-foot sections of 4/0 welding wire for a battery to inverter run. I'm thinking I can bolt the two ring terminals together to create a 6 foot section of wire that I need to span the distance from the batts to the inverter.

Is it ok to bolt the two ring terminals together with a 3/8ths stainless steel nut and bolt. Or is that type of connection not sufficient enough to handle 300 amps, based on the size of the fuse I'll be using on the DC positive wire. I don't want the spliced connection to get too hot. If acceptable, I would cut the excess bolt off and put shrink tubing on it afterwards to insulate it.

FYI, my inverter is 12v @ 2000 watts with 4500 surge (for 5 seconds).

Or do I need to use a more traditional crimping style connector?

See pic:

Attachment not found.


thanks!
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #2
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    Re: Question: Splicing / Connecting 4/0 welding wire

    I think it's fine, I'd use a lock washer or a nylock nut. I usually slide a piece of 1 " heat shrink over the connection. If it's wrong, forgive me, cause I do it all the time without issue.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #3
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    Re: Question: Splicing / Connecting 4/0 welding wire

    Nothing wrong with it. If the lugs can take the current when connected to a post on a battery, fuse, breaker, or inverter then they can take it bolted to each other.

    BC04's advice to use lock nut/washer is important too; you don't want it loosening.

    If this is the positive cable it's a perfect place to put the fuse holder. If it's the negative cable, the monitor shunt. :D
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #4
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    Re: Question: Splicing / Connecting 4/0 welding wire

    There is copper filled conductive grease to A) improve conductivity B) reduces oxidation of the part. With tinned lugs, not too much oxide is likely, but if you can locate the grease, I'd use it. And SS washers, loc washers, and/or a nyloc nut.

    Buy the right length bolt to begin with, don't try to cut it.

    Beware fine strand welding cable, and that you use the right lugs for it, and the right crimp tool.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
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  • stmar
    stmar Solar Expert Posts: 370 ✭✭✭
    #5
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    Re: Question: Splicing / Connecting 4/0 welding wire

    My setup is like Car said; Positive is from battery to switch/fuse to inverter, negative is from battery to shunt to inverter. Nothing wrong with your type of splice but are you fused on the positive?
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  • Hairfarm
    Hairfarm Solar Expert Posts: 225 ✭✭✭
    #6
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    Re: Question: Splicing / Connecting 4/0 welding wire
    Nothing wrong with it. If the lugs can take the current when connected to a post on a battery, fuse, breaker, or inverter then they can take it bolted to each other.

    Sounds like good ol common sense...now why hadn't I thought of that?:confused:

    Thanks all!
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  • Hairfarm
    Hairfarm Solar Expert Posts: 225 ✭✭✭
    #7
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    Re: Question: Splicing / Connecting 4/0 welding wire
    Nothing wrong with your type of splice but are you fused on the positive?

    Yes. There is a 300A fuse in place along with a 350A cutoff switch on the positive.
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  • jcheil
    jcheil Solar Expert Posts: 722 ✭✭✭
    #8
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    Re: Question: Splicing / Connecting 4/0 welding wire
    Hairfarm wrote: »
    Yes. There is a 300A fuse in place along with a 350A cutoff switch on the positive.

    Must be a MONSTER switch to handle 350a...
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #9
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    Re: Question: Splicing / Connecting 4/0 welding wire
    jcheil wrote: »
    Must be a MONSTER switch to handle 350a...

    Blue Sea makes such a switch. http://www.solar-electric.com/blseabaswon3.html
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #10
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    Re: Question: Splicing / Connecting 4/0 welding wire

    I came across a monster knife switch at a welding supply company a while back. Rated 750 amps. Almost bought it. Almost.
    I've forgotten the price, think around $39.
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #11
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    Re: Question: Splicing / Connecting 4/0 welding wire
    Cariboocoot wrote: »
    Blue Sea makes such a switch. http://www.solar-electric.com/blseabaswon3.html

    I saw a disturbing web page about rotary battery switches... I can't tell from the pictures on the site whether it is a Blue Sea brand switch, or some other similar looking switch:

    http://www.amplepower.com/primer/burnt_sw/index.html

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #12
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    Re: Question: Splicing / Connecting 4/0 welding wire

    Another serious objection to the "1,2, both, off" switch is that pesky "both" position. The current flowing can be amazing under some circumstances. :(
    SMA SB 3000, old BP panels.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,448 admin
    #13
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    Re: Question: Splicing / Connecting 4/0 welding wire

    I agree with both concerns.

    Rotary battery switches should only be switched when there is zero to very small amounts of current flow. If you have a fire and need to turn off the switch--Do it--But beware that the switch may be damaged.

    Regarding alternators--Putting fuses/breakers/fuse-able links in series with the alternator output will protect the wiring against shorts/over current--But are very likely to "kill" the alternator electronics if the fuse/breaker ever opens. 12 volt Automotive Alternators can easily exceed 120 VDC if they are not connected to the battery. It is the battery (bank) that actually regulates the alternator's operating voltage. The "voltage regulator" just adjusts the long term average voltage to keep the battery properly charged.

    Similar, you should not have a switch between an alternator+regulator and the battery bank--Unless you never plan on using the switch except for servicing (when the system is shut down, and you need to remove power).

    Lastly--Stuff that is rated at high current--Seems to be a little bit of fantasy going on with the marketing department. Many times, yes, they will take 250 Amps when cranking the main engine to start--But try putting 150 Amps of charging current through the switch for 2-4+ hours--There is certainly a chance the switch contacts can overheat.

    That is why charging battery banks are so "hard" on charging systems. They can take (relatively) high charging currents for 4+ hours--And most people simply do not operate their boats/cars/RVs that way. Nominally it is a short burst of current to start the motors/run the microwave, then an hour of less than rated charging current to get the batteries back to ~100%.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #14
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    Re: Question: Splicing / Connecting 4/0 welding wire

    250 Amps when cranking an engine? What engine has a 4 HP starter motor Bill? None that I've ever seen.

    Clearly A rating of 350 Amps is the maximum whether there is one battery or two. Overload any conductor or component and you will have problems. These switches are no worse than that.

    I think people here with limited battery experience are exaggerating the hazards.
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  • Tobit
    Tobit Solar Expert Posts: 41 ✭
    #15
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    Re: Question: Splicing / Connecting 4/0 welding wire

    That switch is very common on sailboats, it is Blue Sea after all. I will agree with coots, I used for for decades on my old sailboat with no issues.
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  • zoneblue
    zoneblue Solar Expert Posts: 1,220 ✭✭✭✭
    #16
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    Re: Question: Splicing / Connecting 4/0 welding wire

    Well all i can say is that pictures of melted battery switches are reasonably common.

    https://www.google.co.nz/#q=melted+battery+switches

    Give me a carling breaker any day of the week. Why spend 30 bucks on a product that may fail when you need it most, when a $40 buck product is known to be 100% robust.

    People seem to forget that we are in most cases dealing with banks that are capable of 10,000 amps.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #17
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    Re: Question: Splicing / Connecting 4/0 welding wire
    zoneblue wrote: »
    Well all i can say is that pictures of melted battery switches are reasonably common.

    https://www.google.co.nz/#q=melted+battery+switches

    Give me a carling breaker any day of the week. Why spend 30 bucks on a product that may fail when you need it most, when a $40 buck product is known to be 100% robust.

    People seem to forget that we are in most cases dealing with banks that are capable of 10,000 amps.

    Well if you think a switch is a substitute for over-current protection then you're going to have a meltdown.

    You can't damage a component without abusing it.

    Whereas breakers are suitable as an occasional disconnect device they should not be used in place of switches. Most of the time they will work for inverter systems because you usually don't have to turn them off.

    As has already been stated there are thousands of these switches being used without failures. But no manufacturer can promise 100% safeguard against stupidity.
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  • Iceni John
    Iceni John Solar Expert Posts: 103 ✭✭
    #18
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    Re: Question: Splicing / Connecting 4/0 welding wire

    My bus uses a 42MT starter: http://www.delcoremy.com/starter-models/42mt-heavy-duty-starter.aspx It can (briefly) draw many hundreds of amps from my two 8D starting batteries, hence the 4/0 cables to my isolator switch and to it: it's able to briefly produce up to 10 HP or so. I use a Cole-Hersee M-705 which seems a lot more substantial than the red plastic thing pictured in post 11 - even after long cranking the switch and cables aren't even warm. I shoot their temperatures with an IR temp gun, an easy way to find bad connections and other potential problems. I plan on getting another Cole-Hersee for switching my house batteries to my starter if the starting batteries were dead, and a third Cole-Hersee between the house batteries and main DC breaker panel. These switches are not cheap, but they seem better made than most others out there.

    Back to the original question - I have two 4/0 starting cables temporarily connected by 3/8" stainless bolts and Nylok nuts, with lots of insulation wrapped around the connection and then several plastic bags over it to keep moisture out, all Zip-Tied together with extreme prejudice. So far, again, not the slightest increase in temperature when cranking the engine with them bolted together this way.

    John

    40' Crown bus with 2kW of tiltable panels on the roof:

    Eight Sharp 255W, two Morningstar TS-MPPT-60, Magnum MS2000, Champion C46540 generator converted to propane, eight golfcart batteries, and maybe a small Exeltech inverter for the fridger.

    Southern California

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,448 admin
    #19
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    Re: Question: Splicing / Connecting 4/0 welding wire

    Sounds good (no temperature rise). Stainless Steel is a less than ideal conductor--If you can get brass/bronze type bolt+nut, it will be better.

    Also, some types of stainless steel on stainless hardware (SS nuts and SS bolts) will badly gall and seize without lubrication (you can use a brass/bronze nut and avoid the problem too). I would highly suggest next time you have them apart, you use some sort of Anti-Seize compound in the threads (can get from a local auto-parts store).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Iceni John
    Iceni John Solar Expert Posts: 103 ✭✭
    #20
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    Re: Question: Splicing / Connecting 4/0 welding wire
    BB. wrote: »
    Sounds good (no temperature rise). Stainless Steel is a less than ideal conductor--If you can get brass/bronze type bolt+nut, it will be better.

    Also, some types of stainless steel on stainless hardware (SS nuts and SS bolts) will badly gall and seize without lubrication (you can use a brass/bronze nut and avoid the problem too). I would highly suggest next time you have them apart, you use some sort of Anti-Seize compound in the threads (can get from a local auto-parts store).

    -Bill
    Yes, I know that SS isn't the best electrical conductor, but as long as I use grease or thick oil (good ol' chainsaw sprocket/bar oil is ideal for most finer threads!) I haven't had galling or seizing problems, yet. The next time I go fossicking for nuts and bolts at my favourite hardware store here I'll look for marine-grade bronze or hard brass - good idea. Years ago when I worked offshore in the North Sea, where fighting corrosion is a never-ending struggle, we used CoppaSlip on everything, including all the BIG stainless fasteners - it worked well there, but I've never found it or an equivalent here.

    Those IR temperature guns are great. I not only check my bus's electrical connections with it, but after every hour or two of driving I check tire temperatures (a casing beginning to delaminate or a tire at lower pressure will run hotter), hub bearings and brake drums, each cylinder's exhaust port (a bad injector will show that way), the radiator (I've found a cool spot which indicates an internal blockage there, so it's soon time for a recore or rodding), and cross-check the engine's temp with the temp gauge up front. Mine's just a cheapo from Harbor Fright, but so far so good. Everyone who has high-current wiring should use one.

    Thanks, John

    40' Crown bus with 2kW of tiltable panels on the roof:

    Eight Sharp 255W, two Morningstar TS-MPPT-60, Magnum MS2000, Champion C46540 generator converted to propane, eight golfcart batteries, and maybe a small Exeltech inverter for the fridger.

    Southern California

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  • zoneblue
    zoneblue Solar Expert Posts: 1,220 ✭✭✭✭
    #21
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    Re: Question: Splicing / Connecting 4/0 welding wire

    The bolt holds the lugs together, so shouldnt matter too much what its made of, so long as corosion is taken into account. Make sure the tape+bag etc is adequate electrical insulation or bolt the whole assembly onto something to stop it moving and shorting out.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


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  • Hairfarm
    Hairfarm Solar Expert Posts: 225 ✭✭✭
    #22
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    Re: Question: Splicing / Connecting 4/0 welding wire
    Must be a MONSTER switch to handle 350a...

    This is the switch I was referring to - Attachment not found.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,448 admin
    #23
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    Re: Question: Splicing / Connecting 4/0 welding wire

    Many of these "DC disconnect" switches just use the speed of you turning the knob to disconnect. Not good for breaking current.

    My Xantrex 3 kW GT inverter had an AC/DC disconnect designed this way--You could easily wrap your had around the whole switch.

    Schneider's version of the same inverter disconnect (AC mains and DC panels)--Three big knife switches, a big over center spring disconnect which took up the bottom 1/4 of the GT inverter.

    I would trust the new design to "safely and reliably" disconnect under all conditions. The original disconnect would not.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Hairfarm
    Hairfarm Solar Expert Posts: 225 ✭✭✭
    #24
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    Re: Question: Splicing / Connecting 4/0 welding wire

    Hi BB,

    Can you recommend a better DC cutoff switch rated for 350A?

    thanks!
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,448 admin
    #25
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    Re: Question: Splicing / Connecting 4/0 welding wire

    As a few folks have posted over the last few days, the Midnite lsrge capacity breakers also make very good disconnects, for not that much money.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • ramloui
    ramloui Solar Expert Posts: 109 ✭✭
    #26
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    Re: Question: Splicing / Connecting 4/0 welding wire

    OK, so I need to ask about my system. I will be installing my new Magnum inverter soon (MS-4024PAE). I also purchased the MMP panel to get a streamlined, clean installation. That MMP panel comes with a 250A DC breaker. Can it be used as a disconnect? Say everytime I leave the cabin or do maintenance (1-2 times per month). Or should I reinstall the Blue Sea switch from my current installation so it goes battery positive --> Blue Sea switch --> MMP DC breaker?

    Thanks for clarifying!
    Off-grid cabin in northern Quebec: 6 x 250 W Conergy panels, FM80, 4 x 6V CR430 in series (24V nominal), Magnum MS4024-PAE
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #27
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    Re: Question: Splicing / Connecting 4/0 welding wire
    Hairfarm wrote: »
    This is the switch I was referring to - Attachment not found.

    This is a piece of junk. I know because I've pulled more than one from failed systems. Bought at Princess Auto for $10. Not at all comparable to the Blue Sea.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #28
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    Re: Question: Splicing / Connecting 4/0 welding wire
    ramloui wrote: »
    OK, so I need to ask about my system. I will be installing my new Magnum inverter soon (MS-4024PAE). I also purchased the MMP panel to get a streamlined, clean installation. That MMP panel comes with a 250A DC breaker. Can it be used as a disconnect? Say everytime I leave the cabin or do maintenance (1-2 times per month). Or should I reinstall the Blue Sea switch from my current installation so it goes battery positive --> Blue Sea switch --> MMP DC breaker?

    Thanks for clarifying!

    Yes a breaker can be used as a disconnect.
    It's already there, provides over-current protection, and isn't going to be flicked on and off many times per day.

    The Blue Sea switches are viable when used in conjunction with fuses. This is engineering, so there's always more than one way to do the job. Which one is best for a given application is another issue. Ask two engineers one question and get five answers.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,448 admin
    #29
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    Re: Question: Splicing / Connecting 4/0 welding wire

    And an engineer will do it one way on a $1,000,000 per unit -48 VDC powered Voice Mail system, and a different way at home when it is his money. :roll:

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Hairfarm
    Hairfarm Solar Expert Posts: 225 ✭✭✭
    #30
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    Re: Question: Splicing / Connecting 4/0 welding wire
    This is a piece of junk. I know because I've pulled more than one from failed systems. Bought at Princess Auto for $10. Not at all comparable to the Blue Sea.

    That's good to know. I'll take a look at the Blue Sea product as a replacement. My 12 system was my first install so I'm not always sure what's junk and what's not.

    thanks!
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  • jcheil
    jcheil Solar Expert Posts: 722 ✭✭✭
    #31
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    Re: Question: Splicing / Connecting 4/0 welding wire
    Cariboocoot wrote: »
    This is a piece of junk. I know because I've pulled more than one from failed systems. Bought at Princess Auto for $10. Not at all comparable to the Blue Sea.

    Yup, I melted that same one on my swamp buggy in less than a year. And that was just from the starter motor current from it being started maybe 100 times that whole year. I think that would create a nice light show if you tried to operate that under any kind of a load close to its rating.
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
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