general/basic wiring questions

mshen11mshen11 Solar Expert Posts: 185 ✭✭✭✭✭
* its been said the wires to battery should be the as short as possible and same length - from battery to buss bar/inverter/etc... what if you are using 6V batteries: the interconnects should be the same length between the + and -, what about the length of interconnects compared to the wire that connects the battery to the buss bar?

* when using larger wires it is difficult to bend/shape them if they are less than 2 to 3 ft. what do you do in this case to keep the distance short. ex: my battery to buss bar is only 1 ft, but w/ 1 ft 2/0 cables, i cannot even bend it to the properly position to make the connection

* if you need to connect the fuse to the wire near the battery buss bar, should those extra distance be factored in to wire length - or is it insignificant.

* if working w/ 2/0s (and they are not flexible) how do you connect wires from inverter to fuse to buss bar? the suggestion has been to use a copper peice of large enough size (1/4" thickness 1"+ wide) as connectors, and skip the wires. that seems elegant enough - are there other solutions?

* when sizing wire you want to oversize but sometimes you cant do it more than the capacity/wire hole of the inverter/ charge controller. is there way around this? let say the outback 80amp MMPT. max wire size is 2AWG. what if you want to have a wire run a few hundred ft? the 2AWG is not enough - aka, it wont fit

Comments

  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: general/basic wiring questions
    mshen11 wrote: »
    * its been said the wires to battery should be the as short as possible and same length - from battery to buss bar/inverter/etc... what if you are using 6V batteries: the interconnects should be the same length between the + and -, what about the length of interconnects compared to the wire that connects the battery to the buss bar?

    As short as possible, but the battery-battery cross connect does not need to be the same length as the battery-bus bar wires.

    * when using larger wires it is difficult to bend/shape them if they are less than 2 to 3 ft. what do you do in this case to keep the distance short. ex: my battery to buss bar is only 1 ft, but w/ 1 ft 2/0 cables, i cannot even bend it to the properly position to make the connection

    I've always used a "Hickey" for that. It's a pipe bender for bending a tight radius in a rigid conduit. Works great for thick wire too:

    http://www.restockit.com/Hickey-1-2-Rig-%28332-508%29.html?source=froogle&Bvar5=100F1&Bvar6=100F1&Bvar7=100F1

    * if you need to connect the fuse to the wire near the battery buss bar, should those extra distance be factored in to wire length - or is it insignificant.

    Yes, consider the length of the fuse and jumper from fuse-bus bar as part of the wire length.

    * if working w/ 2/0s (and they are not flexible) how do you connect wires from inverter to fuse to buss bar? the suggestion has been to use a copper peice of large enough size (1/4" thickness 1"+ wide) as connectors, and skip the wires. that seems elegant enough - are there other solutions?

    Again, for me it's all about the hickey. Actually, I tend to usually use them in pairs. With two hickeys I can form a piece of wire (or conduit) into just about any shape I need. Sometimes you need a longer wire to get a grip on it - so you form it then chop off the extra that you don't need.

    Sometimes though, even the tightest radius that the hickey can make isn't tight enough. So, I'll take a piece of rigid pipe and clamp it in a vise. Then I take another piece and slip it over the wire. Then slip the wire into the piece of pipe in the vise. Then grab the pipe that's not in the vise with the hickey and bend the wire.

    Looks a bit like this:


    --(wire)
    ==(Pipe A)==--==(Pipe B)==

    Pipe B is in the vise, and you grab Pipe A with the hickey to put a really tight bend in the bit of wire between Pipe A and Pipe B.

    Make sure you don't cut the insulation with the pipe ends. Also there are code restrictions on how tight a radius is allowed for a given size of wire - however for a short piece used as what is considered "chassis wiring" it will normally be fine.

    A hickey is also very handy for grabbing a fat wire and wrestling it into position.

    * when sizing wire you want to oversize but sometimes you cant do it more than the capacity/wire hole of the inverter/ charge controller. is there way around this? let say the outback 80amp MMPT. max wire size is 2AWG. what if you want to have a wire run a few hundred ft? the 2AWG is not enough - aka, it wont fit

    Power distribution block. There are different sizes depending on the need. Looks like this:

    http://store.solar-electric.com/16220-1.html
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: general/basic wiring questions

    You're probably going to get a lot of different opinions on this ....

    The important factor with wire length on battery connections is to keep it equal between banks so that one bank isn't drawn/charged more than another. Wires should be sized to handle the maximum current flow over the length of the wire (see the wire size calculator).

    In my opinion battery interconnect wires should be as heavy as the leads to the inverter. I've heard others say it doesn't need to be. Personally I'm using copper bar to connect between batteries: easily good to 500 Amps.

    Unless the fuse is for some reason a really long way from the battery, a few inches extra wire on the (+) lead over the (-) won't make that much difference. Especially if the runs are kept short over-all (under 4 feet, say).

    Heavy wires should have swedged connectors on them. Not a do-it-yourself prospect unless you want to shell out the money for the special tool. You can measure your lengths and get your wires made up by the shop that sells the wire (usually).

    If the wire won't fit in the connector, as with your MPPT example, you should re-think your design. As in the output of an MX60 is 60 Amps, but at 12, 24, or 48 Volts. If your wires can't handle the current requirements you should increase the system Voltage to accommodate this.
  • mshen11mshen11 Solar Expert Posts: 185 ✭✭✭✭✭
    Re: general/basic wiring questions

    [I've always used a "Hickey" for that. It's a pipe bender for bending a tight radius in a rigid conduit. Works great for thick wire too:

    http://www.restockit.com/Hickey-1-2-...F1&Bvar7=100F1]

    doesnt a hickey damage the wire? aka, cutting of *some* flow. isnt there somethign about the wires should be as straight and short as possible?

    [Yes, consider the length of the fuse and jumper from fuse-bus bar as part of the wire length.]

    even if the total length is 3ft and the fuse/wire portion is 1+ ft? remember you are dealing w/ thick wires

    [Power distribution block. There are different sizes depending on the need. Looks like this:

    http://store.solar-electric.com/16220-1.html ]

    how do they work? let say the CC only fits 2AWG and you want to put 2/0 AWG. ok you use one of these devices to convert the sizes of wires (you can also w/ a buss bar). but the CC wont get the 2/0 AWG benefits
  • mshen11mshen11 Solar Expert Posts: 185 ✭✭✭✭✭
    Re: general/basic wiring questions

    [Heavy wires should have swedged connectors on them. Not a do-it-yourself prospect unless you want to shell out the money for the special tool. You can measure your lengths and get your wires made up by the shop that sells the wire (usually).]


    well i just buy cut wires. as for the ends i use screw lugs which is DIY and cheap for large sizes
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: general/basic wiring questions
    mshen11 wrote: »
    [I've always used a "Hickey" for that. It's a pipe bender for bending a tight radius in a rigid conduit. Works great for thick wire too:

    http://www.restockit.com/Hickey-1-2-...F1&Bvar7=100F1]

    doesnt a hickey damage the wire? aka, cutting of *some* flow. isnt there somethign about the wires should be as straight and short as possible?

    As I said, you can get away with tighter bends if the wire is considered to be "chassis wiring":

    http://www.ownerbuilderbook.com/images/journal/full/8245.jpg

    [Yes, consider the length of the fuse and jumper from fuse-bus bar as part of the wire length.]

    even if the total length is 3ft and the fuse/wire portion is 1+ ft? remember you are dealing w/ thick wires

    Correct. If you have a 3' negative wire, and your fuse+(jumper wire from fuse to bus bar) is 1', then you need 2' from the fuse to battery.

    [Power distribution block. There are different sizes depending on the need. Looks like this:

    http://store.solar-electric.com/16220-1.html ]


    how do they work? let say the CC only fits 2AWG and you want to put 2/0 AWG. ok you use one of these devices to convert the sizes of wires (you can also w/ a buss bar). but the CC wont get the 2/0 AWG benefits

    There is no "benefit" to the CC anyway.

    You asked about doing a long run of over sized wire and then reducing it to fit the terminals on the CC. The only benefit to that is to reduce the voltage drop over distance - it won't magically make the CC be able to handle a greater voltage or amperage.

    Say you use #2 from the distribution block to the CC, and 2/0 for the long run. You still have to fuse the line to protect #2. The whole setup won't handle any more amperage by using 2/0 for a section of the run.

    The voltage drop for a short run of #2 isn't going to be noticeably different than the voltage drop for a short run of 2/0. For a short run, you gain nothing by using over-sized wire.

    For a long run, you reduce voltage drop by using over-sized wire. Terminating that 2/0 in a distribution block, and then running a short run of #2 to the inverter isn't going to undo the benefit of reducing the voltage drop over a long run.
  • tallgirltallgirl Solar Expert Posts: 413 ✭✭
    Re: general/basic wiring questions
    mshen11 wrote: »
    [Heavy wires should have swedged connectors on them. Not a do-it-yourself prospect unless you want to shell out the money for the special tool. You can measure your lengths and get your wires made up by the shop that sells the wire (usually).]


    well i just buy cut wires. as for the ends i use screw lugs which is DIY and cheap for large sizes

    Screw lugs can loosen and corrode. Properly crimped on lugs produce a reliable physical and electrical connection that will last a lifetime.
  • mshen11mshen11 Solar Expert Posts: 185 ✭✭✭✭✭
    Re: general/basic wiring questions

    about corrosion - that occurs/results only in areas of high humidity right? if your area is pretty dry (and is indoors) then you should be ok?

    is it really recommended to dab vasoline on EVERYTHING?
  • WindsunWindsun Solar Expert Posts: 1,164 ✭✭
    Re: general/basic wiring questions

    We do not recommend Vaseline (or any other common grease) for ANYTHING.

    Though often touted as a corrosion inhibitor, it has problems, such as melting into a liquid in summer temperatures. If you really need something to cover the terminals, then something like silicone grease should be used, as the melting point is up well over 200F.
  • tallgirltallgirl Solar Expert Posts: 413 ✭✭
    Re: general/basic wiring questions
    Windsun wrote: »
    We do not recommend Vaseline (or any other common grease) for ANYTHING.

    Though often touted as a corrosion inhibitor, it has problems, such as melting into a liquid in summer temperatures. If you really need something to cover the terminals, then something like silicone grease should be used, as the melting point is up well over 200F.

    There are products in the electrical industry specifically designed for this purpose. I see it more in industrial / heavy commercial, rather than the lighter weight stuff I do.

    Still, it's dirt-simple to crimp a lug onto a conductor -- cut, strip, crimp, done. The "crimp" part takes a heck of a lot less time than dorking with set screws and so on. AND a crimped connector is physically smaller -- no screws or whatever protruding out in places you might not want them.
  • BB.BB. Super Moderators, Administrators Posts: 32,639 admin
    Re: general/basic wiring questions

    You can also look at Deoxit or conductive grease with anti-oxidants.

    Be careful about using silicon sprays and grease around contacts (switches, relays, etc.). Silicon does vaporize and contaminate switch contacts. When the switch operates, the arc will turn the vapor into silicon dioxide (an insulator).

    From Omron (a switch manufacturer download pdf file and search for silicon dioxide):
    If a switch is used in the atmosphere of silicon gas, arc energy may attract silicon dioxide (SiO2) to the contacts and contact failure may result. If there is silicon oil, silicon sealant, a wire covered with silicon, or any other silicon-based product near the switch, attach a contact protective circuit to suppress the arcing of the switch or eliminate the source of silicon gas generation. Even for a sealed switch, it may not be possible to prevent all of the gas from penetrating the seal rubber, and contact failure may result.
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: general/basic wiring questions

    Corrosion preventative sealer like this:

    http://www.princessauto.com/truck-trailer/electrical/trailer-wiring/8039562-ultra-seal-corrosion-preventive-sealant

    Worst problem is acid venting around batteries - which is why they tell you to charge with caps on. That stuff will corrode connections pronto.
  • mshen11mshen11 Solar Expert Posts: 185 ✭✭✭✭✭
    Re: general/basic wiring questions

    [Still, it's dirt-simple to crimp a lug onto a conductor -- cut, strip, crimp, done. The "crimp" part takes a heck of a lot less time than dorking with set screws and so on. AND a crimped connector is physically smaller -- no screws or whatever protruding out in places you might not want them. ]

    i assume you are talking about smaller size wires. how about 2AWG and thicker wires... especially 2/0 AWG plus? yeah i know there are crimpers for them but they are getting expensive. also the terminal rings are hard to find locally


    about battery corrosion. is there a way to prevent this? would putting a peice of wood over the batteries be a solution or is the discharge in such small particles it ultimately will get everything (including the car that is parked in the garage?
  • KamalaKamala Solar Expert Posts: 452 ✭✭
    Re: general/basic wiring questions

    This tool, available from NAWS, has worked well for me.

    http://http://store.solar-electric.com/hacrtoforlal.html

    Set it on a solid surface. I used a 2lb hammer. Had to give 3 good whacks. NAWS has lugs but I got mine at

    http://www.marinco.com/product/heavy-duty-lugs

    Were I to redo my cables, and I may yet, I would use the tool to crimp the lug to the cable, wrap with electrical tape and then heat shrink tubing over.
  • tallgirltallgirl Solar Expert Posts: 413 ✭✭
    Re: general/basic wiring questions
    mshen11 wrote: »
    [Still, it's dirt-simple to crimp a lug onto a conductor -- cut, strip, crimp, done. The "crimp" part takes a heck of a lot less time than dorking with set screws and so on. AND a crimped connector is physically smaller -- no screws or whatever protruding out in places you might not want them. ]

    i assume you are talking about smaller size wires. how about 2AWG and thicker wires... especially 2/0 AWG plus? yeah i know there are crimpers for them but they are getting expensive. also the terminal rings are hard to find locally


    about battery corrosion. is there a way to prevent this? would putting a peice of wood over the batteries be a solution or is the discharge in such small particles it ultimately will get everything (including the car that is parked in the garage?

    My crimpers go to 500kcmil, I think. I use them all the time for 2/0, haven't need the 4/0 dies on them yet.

    And yes, real crimpers can be spendy, but if you make friends with professional electricians they might come to your house with their crimpers and do a few for you in exchange for Adult Beverages (or loan them to you while they watch). The other thing is that real crimpers produce connections that won't wind up with an insurance company pointing fingers when they find an improper termination made with a hammer.

    I'm all for saving money, just not all that keen on doing things improperly, and a hammer is not a proper way to afix a crimp on lug, even if the tool is $300 less (mine was less than $300 in the first place, so ...)
  • nigtomdawnigtomdaw Solar Expert Posts: 705 ✭✭
    Re: general/basic wiring questions

    Have a read of this post for inexpensive hydraulic crimpers.

    http://forum.solar-electric.com/showthread.php?t=5379&highlight=hydraulic+crimper

    Nigel
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: general/basic wiring questions

    Crimps or lugs - just depends on the application. For a building install I'd say either is fine by me. For a mobile rig I prefer crimps.

    As for corrosion - again, not really an issue on most building installs. Some sure, but not most. For painting terminals I use Led-Plate. If I can't get Led-Plate (a very rare occurance as most electrical supply houses that I've been to do carry it) then Noalox is fine.

    I'm not sure Vaseline is actually recommended for anything is it? Maybe the o-rings on Mag-Lites...
  • mike95490mike95490 Solar Expert Posts: 9,582 ✭✭✭✭✭
    Re: general/basic wiring questions
    dwh wrote: »

    I'm not sure Vaseline is actually recommended for anything is it?

    painting on, over connected battery terminals ?

    Tax time ?


    I don't like using silicone except for high temp stuff: spark plug boot release. It creeps and can lift paint off metal, makes some plastic brittle.
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  • nigtomdawnigtomdaw Solar Expert Posts: 705 ✭✭
    Re: general/basic wiring questions

    Bottom line do it properly, crimp with proper gear simple end of thread or prepare for failure.

    Nigel
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