What type and guage wire fits in KID battery out terminal?

Started by NewSolarUser, January 16, 2017, 06:13:00 PM

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NewSolarUser

I've spent some time researching this and I'm running in circles chasing my tail  now. What I've got is a vehicle-mounted portable solar panel array feeding a KID, which in turn feeds four 104Ah 12V AGM batteries in a 2x2 24V array. I run an IRIS 1800/2800W inverter off of that. My question is, what wire should I run from the KID to the battery array? I temp wired it with 12ga THHN for the initial tests because it's what I happened to have on hand. The cable run from the KID to the battery posts is about 5'. I didn't run much in the way of loads for the test and the batteries were already fully charged so I didn't see any heating of the wire. I did a quick calculation using the panel array's theoretical max output of 520W and assumed 100% efficiency in the KID to get 21.7A as the max possible current to the batteries. Looking at http://www.powerstream.com/Wire_Size.htm I see that I need to run around 6ga wire, but that wire size doesn't physically fit in the KID's battery out terminals. So, what wire do I need to use? My only requirement is that it be flexible. This system will be installed and run maybe 4 times a year for two to three days each time.

ClassicCrazy

You should probably use 10 gauge which is rated at 30 amps from Kid output to batteries. Not sure what size blade fuses came in your Kid - but if they are 40 amp you can use 8 gauge. 12 gauge is only rated at 20 amps so not a good choice .  The larger wire size will give you less voltage drop so is usually the best choice. You can look it up but at the short distance you are talking about probably not a big factor.
Use a wire loss calculator like this one - there are lots of others . You want a low voltage drop 2% or under for that  run.
http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=3.277&voltage=24&phase=dc&noofconductor=1&distance=5&distanceunit=feet&amperes=30&x=59&y=3

Voltage drop: 0.30
Voltage drop percentage: 1.25%
Voltage at the end: 23.7

Put different numbers in and see what you get. You want to fuse according to your wire size.

The important thing about wiring the Kid is that the PV  negative input and the Battery negative output can not be connected together anywhere  - they have to be isolated.

Just to be sure - you have your inverter connected directly to the battery with appropriate sized breaker or fuse and not going through the Kid load terminals ?

Larry

system 1
Classic 150 , 5s3p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system 2
 5s 135w Kyocero , 3s3p 270w Kyocera  to Classic 150 ,   8s Kyocera 225w to Hawkes Bay Jakiper 48v 15kwh LiFePO4 , Outback VFX 3648 inverter
system 3
KID / Brat portable

NewSolarUser

Correct, the battery out terminals on the KID are connected directly to the battery array at this time. The batteries are set up as two series pairs in parallel, with 80A fuses between the batteries in each pair and a 150A fuse on one leg to the inverter. The two 260W Canadian Solar panels are wired in series with a 20A fuse, and I have a 30A fuse between the KID and the battery array. I chose 30A since the calculated max is about 22A.

What brought this wiring question up is that I ordered first 6ga and then 8ga cable and neither would physically fit in the terminal block on the KID. I originally wanted welding cable because of its high-temp jacket and flexibility, but apparently after perusing threads here there are issues with the fine stranding on that cable WRT terminals. THHN is designed for raceway use so has a fairly thin sheath, since my application requires the cable be out in the open I'll have to look at something like SOOW or SJOW cord instead. FWIW what I plan on doing is taking my vehicle to swap meets where I can provide power to demo the things I sell and courtesy power for people to charge up their phones and test things they've bought. Since this only occurs a few times a year I'll remove the system when it's not actually being used for that purpose. That's why the KID and related wiring is not permanently wired as it would be in a boat or structure.

ClassicCrazy

#3
Yeah go with the 10 gauge if it fits in.  There is a difference between diameters of that flexible fine stranded cable and the types with less bigger strands.  You can always go from those flexible stranded types using a rated lug that is well crimped and then use some kind of transition terminal block from that to the other type of cable that will fit in the Kid . So you could keep the 30 amp fuse but run larger gauge cable would be okay . You just can't do it the other way around and use larger fuse on smaller gauge cable.

You have done your research well. If you are setting up and taking down some of those connections frequently  you may consider some kind of suitable plug that will handle the current.  There are Anderson Power Poles but I have been using Radio Control type plugs these days which handle more current and are easier to install .

I use the XT type they come in different ratings
http://www.tjinguytech.com/reviews/rc-connectors

Larry



system 1
Classic 150 , 5s3p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system 2
 5s 135w Kyocero , 3s3p 270w Kyocera  to Classic 150 ,   8s Kyocera 225w to Hawkes Bay Jakiper 48v 15kwh LiFePO4 , Outback VFX 3648 inverter
system 3
KID / Brat portable

Vic

Agree with Larry,   the power terminals on the KID are designed for #10 AWG cable  --  THHN building wire (19 strand).    NOT finely-stranded cable.   SO Cord is somewhat finely stranded:
http://www.southwire.com/ProductCatalog/proddetail.jsp?htmlpreview=true&token=282&desc=Viper

IMO,  you will want a DC rated circuit breaker on the input and the output of the KID.   This will can be an important safety function,  as well as a convenience.

If you want SO cord,  you could place a breaker box,   like the MidNite BigBaby,  or the MN DC Quad box.   At this box,  you could change from #10 THHN,  to whatever gauge SO cord that you choose.   Although,  technically,   almost any breaker,  screw terminal strip or screw-type busbar is NOT rated for any finely stranded cable.

If you used Panel Mount breakers,   the kind that the MN DC Quad box uses,  you could find a proper crimp lug for most any fine-strand cable.

It is good practice to use properly rated DC breakers for CC PV input,   CC output to the battery,   and for DC cables to/from the inverter.   Because a disconnecting means is an important safety function (IMO).

Just my opinions,   Vic
Off Grid - Sys 1: 2ea SW+ 5548, Surrette 4KS25 1280 AH, 5.25 KW PV, Classic 150,WB, Beta Barcelona, Beta KID
Sys 2: SW+ 5548s, 4KS25s, 5.88 KW PV, 2 ea. Classic 150, WB, HB CC-needs remote Monitoring/Control, site=remote.
 MN Bkrs/Bxs/Combiners. Thanks MN for Great Products/Svc/Support&This Forum!!

WizBandit

This new KID wall mount is available from Midnite as well. #8 awg terminals with #10 awg jumpers to the KID included.
PROS: Larger wire and easy to wire.
CONS: USB for firmware update not easy to get to, requires the KID to be unbolted. Suggest roll up and leave a cable in the mount.

Vic

Hi WizBandit,

Thank you for the reminder about this important accessory for the KID,   knew that MN had been working on it,   but did not even know that it was shipping.

Are you saying that the KID's  USB cable could remain connected to the KID,   but rolled up for use,  when needed?   That would be nice if it is the case.

Thanks again,   Vic
Off Grid - Sys 1: 2ea SW+ 5548, Surrette 4KS25 1280 AH, 5.25 KW PV, Classic 150,WB, Beta Barcelona, Beta KID
Sys 2: SW+ 5548s, 4KS25s, 5.88 KW PV, 2 ea. Classic 150, WB, HB CC-needs remote Monitoring/Control, site=remote.
 MN Bkrs/Bxs/Combiners. Thanks MN for Great Products/Svc/Support&This Forum!!