Circuit breaker vs fuse

[galladanb]

John it says max terminal size is 8awg for the cmd-20,
So, I assume that means 4awg won't fit...?

The 2awg vs 2/0awg, wow... I saw those before but didn't pay attention.

Looking it up now...

The kit came with four wires, two with what I'm assuming are panel connectors, and two
Very stiff, but about the same sized wires with ring terminals...
I think they call them tray cables? Not sure where these go or are used for, yet...

[font=Arial, sans-serif]Overview:[/font]
[font=Arial, sans-serif]Renogy Premium Kits are created with efficiency and safety in mind. Equipped with the highest quality Renogy products, this fully stocked off-grid kit is ideal for various off-grid applications such as for an RV, boat, or camper.[/font]
[font=Arial, sans-serif]Includes:[/font]
[font=Arial, sans-serif](2) Renogy Eclipse Solar Panels.[/font]
[font=Arial, sans-serif](2) Renogy Z-brackets.[/font]
[font=Arial, sans-serif](1) Commander 20 amp MPPT Controller.[/font]
[font=Arial, sans-serif](1) 20ft 10AWG Adaptor Kit.[/font]
[font=Arial, sans-serif](1) 2ft 8AWG Fuse Cable.[/font]
[font=Arial, sans-serif](1) 8ft 8AWG Tray Cable.[/font]
[font=Arial, sans-serif](1) MT-5 Tracer Meter.[/font]
[font=Arial, sans-serif](1) 10 amp In-Line Fuse.[/font]
[font=Arial, sans-serif](1) 20 amp ANL Fuse.[/font]

 

[highdesertranger]

with most solar controllers if you disconnect the battery(switch it off) while the panel is out putting(sun's up) you will fry the controller. that's why you put a switch, fuse, or breaker between the panel and controller. highdesertranger

 

[Optimistic Paranoid]

John it says max terminal size is 8awg for the cmd-20,
So, I assume that means 4awg won't fit...?

Correct.  Just use the 8 gauge wire supplied with the kit.

 

[Spaceman Spiff]

Brad,

 Why do you need a breaker between panels and mppt?   And why would you need to shut the power off there?

I understood the need for a large fuse between mppt and battery. ... I thought 60 was large enough??

I put a fuse between panels and controller because:

1. controller instructions specified it, in my case a 60 amp fuse for a 45 amps controller (and wire that will handle 60+ amps).
2. it is an easy way to disconnect panels from controller.  Instructions say to disconnect solar input first if I want to disconnect the batteries.

Mainesail recommends using the largest fuse that will protect the wire (less voltage drop), not using cheap fuses (dangerous failure modes), and using ANL, Class T, or MRBF fuses at batteries.

http://www.pbase.com/mainecruising/battery_fusing

 -- Spiff

 

[MrNoodly]

I'm not an electrical genius, but if you have circuits blow so often that a breaker seems like a better idea than replacing fuses all the time, how about correcting what's wrong with the circuit?

 

[MrNoodly]

1. it is an easy way to disconnect panels from controller.  Instructions say to disconnect solar input first if I want to disconnect the batteries.

Because disconnecting MC4 connectors is so hard?

 

[Spaceman Spiff]

Because disconnecting MC4 connectors is so hard?

Yes.  They are up on the roof, tied down under the panels.  Fuse is right next to the controller.

 -- Spiff

 

[galladanb]

Ok, so in summary...
4awg from alternator/isolator to 60 amp fuse to cutoff switch to house battery positive buss.
2/0awg from Tripp-lite charger to 60 amp fuse to cutoff to house battery positive buss.
2/0awg from house battery positive buss to positive terminal on battery.
4awg from house battery positive buss to 60 amp? fuse to cutoff to dc input on power distribution panel.
4awg from solar controller to blade type 20amp fuse to house battery positive buss.
inline fuse between panel positive  and controller.

Repeat using same wire sizes for grounds or return side, but with out fuses.
And put the meter shunt after the ground buss but before ground to frame.

And for clarity...
(1) 20ft 10AWG Adapter Kit. Use these for the panels to controller?
(1) 2ft 8AWG Fuse Cable. Has ring terminal on each end, Use between big inline 20 amp fuse and positive side of battery?
(1) 8ft 8AWG Tray Cable. Has ring terminal on one end, stripped on other end. Use between controller and fuse going to battery?
(1) 10 amp In-Line Fuse. Use between the panel positive and controller input?
(1) 20 amp ANL Fuse. Use between Controller and positive side of battery?

Just don't wanna screw anything up....

Also, do the panels hook up to each other? I ask because there are only two wires in the kit with a male and a female connector...
I know there are four wires at the panels, right?

About ready to go shopping for wires and connectors locally.
Going to an car audio place first (to see what large fuses, holders and connectors they have),
then Lowes ( to see what wire I can get there),
then a welding supply shop for cables.

SO Confusing, but SUCH FUN!!!!

 

[Optimistic Paranoid]

Dan, please re-read #18 in this thread.  A 60 amp fuse is NOT big enough for the Triplite.

 

[galladanb]

Oops, John, my mistake!

I was putting all of that together and got distracted...

Your right, I meant to say 125 amp or bigger! Sorry for the confusion!

I found some 2/0 welding cable, very heavy, flexible, and only 3 bucks a foot.
So I bought 12 feet, and I think I have a plan...

 

[user 37446]

My right trigger finger is tired from clicking "thanks" on this thread...

I appreciate the answers to the OP's questions and have learned some more for my soon to be solar.  :idea:
I am wondering why many bigger amperage charge controllers limit the wire size they will accept to like 8 AWG. Not all obviously, but the lower priced PWM ones often do.   :huh:   Economics?

Also, does each fuze block/fuze holder in a line cause a voltage drop (even if "properly done")?  Would all these connections add up to half a volt or so? Does it even matter? I am aware that many 12v nominal panels are sending about 18-19v to the controller, so it's what the controller is sending to the batteries through any fuzes/breakers which is where the voltage drop would be, right? Then outflow from batteries to the power distribution panel adds more connections.

An aside question, (not solar), on the alternator to the c.d. solenoid, there's a couple additional connections for potential voltage drop as well, correct? Fuze, solenoid, fitting to battery...

 

[SternWake]

Fuses do cause some voltage drop, Not much can be done except using the fuse rating for the wire.

My solar controller calls for a 30 amp fuse, but I use 4awg wire which is good for 136 amps. I should be able to fuse for 130 amps for less voltage drop, but the controller says 30 amps, so it has a ****** 30 amp circuit breaker that warms up drops voltage and in general pisses me off.

So be it. I used 8 awg cable for a 32 foot total run from 130 watt panel to controller to get more voltage there. My 68 watt panel has its own 10AWG run. The resistance in the fuse between controller and battery is made up for on the thicker cable from panel to controller.

Every electrical connection adds resistance, and the more amps that try to flow, the more resistance will be added, casuing more heat in the connector, causing more resistance, causing more heat. It is why I harp on the importance of good wire/cable terminations, and using products likethose from Caig DeOxit on connections to keep electrical resistance to a mininum at connections.

With batteries, how much voltage that reaches the battery terminals affects how much the amperage the batteries ask for, so regular voltage drop calculators are not so great for determining the wire size required. Works/acceptable/ideal are far from each other in this regard. Minimizing possible voltage drop is a good route to go, but wire sizes thicker than 2 or 1 gauge are usually overkill, dependding on circuit length from alternator to house battery.

 

[galladanb]

Ok, I'm running into a few roadblocks...

I found the 2/0 wire, no problem.
I can't find a fuse holder with fuses for that large wire?
Of course, I want the screw and hole type not the post or stud kind.
Because, getting ring terminals of that size are also hard to find, not to mention, I have no way to crimp that big of a termanation.

And I like the look of the push in and screw kind, not to mention, I can custom size the length, like 3.5 inches not six, etc...

I can find 1/0 or 1 gauge both on Amazon and locally, but not 2/0.

I beginning to think I need to drop back to 1 gauge.

I did find some buss bar with push and screw 2/0 connections.

Any ideas or links for me?

 

[highdesertranger]

the type that you put the wire in and screw a screw down to hold the wire in are not very good for mobile applications, plus they are not meant for stranded wire. for 2/0 wire you need to go with a larger fuse and holder like this,

https://www.bluesea.com/products/5001/MEGA___AMG_Fuse_Block_-_100-300A_with_Cover .
https://www.bluesea.com/products/5502/Class_T_Fuse_Block_with_Insulating_Cover_-_225_to_400A
https://www.bluesea.com/products/5503/ANL_Fuse_Block_with_Insulating_Cover_-_35_to_750A

what type of terminal are you looking for 2/0 to ? highdesertranger

 

[galladanb]

Thx, hdr! All three of those will require ring terminals.
Which, as I stated, I'm having trouble finding, and even if I could find them, I will have no way to crimp them.

 

[Optimistic Paranoid]

Thx, hdr! All three of those will require ring terminals.
Which, as I stated, I'm having trouble finding, and even if I could find them, I will have no way to crimp them.

This guy can make you any cable you want.  Or he can sell you the ring terminals.  They could be soldered.  (That statement is GUARANTEED to start a huge debate)

http://custombatterycables.com/parts/just_parts.htm

 

[SternWake]

Do not buy budget wire terminations, especially those for serious cables.
http://www.genuinedealz.com/marine-electrical-supply/wire-connectors/heavy-wall-lugs?cat=205
Soldering thin wire or thick cable, properly, cleanly, effectively, is a skill requiring the right tools.
The same can be said for crimping.
Both can be done well, both can be done horribly unacceptable.  Some unacceptable might 'appear' otherwise.
Having to buy the right tool to do a job correctly is not unheard of.
I have used a grinder and file  to shape some of myhydraulic crimper's undersized dies to fit cable/thick walled ring terminals larger than 4awg, but wish I spent more on a better tool in the first place.
While Genuine dealz makes custom cables too.  I have one report that the cables in the 2/0 size appear to be crimped with some sort of hammer crimp, rather than a hexagonal crimper.  This earns a seriously loud 'Boooooooooo!' in my book.
http://www.pbase.com/mainecruising/battery_cables
Low resistance long lasting crimps are not made with a hammer crimp.

 

[Weight]

I have 2/0 cables from Genuinedealz. Plus some smaller wire. At least 20 crimps. They are all hexagonal pressure crimps. No hammer crimps. Yours is the first complaint I have seen about this.

 

[galladanb]

John, that will be a great resource for the 2/0 cables with the lengths and connectors I need.

THANK YOU!!!

Now, before I place my order, where does the cutoff switch go?
Battery to fuse to cutoff switch to charger?
Or as I show here, battery to cutoff switch to fuse to charger?

It matters because the cutoff has 3/8 terminals and the fuse holders have 5/16, I believe...?
So that will determine how I get the cables made up.



Also do I need a cutoff switch between the solar panels and the controller, maybe for future maintainace issues?

Does it matter if I use the battery post, the 5/16 stud, or both...
I Want the best possible ground and wiring simplicity...

 

[Optimistic Paranoid]

Best practice is to have the fuse close to the battery.  On boats, Coast Guard regulations require the main fuse to be located within a foot or so of the battery bank.

BTW, since the manual says it can draw 125 amps, I would fuse it a bit more, say an 150 amp fuse.  Fuses should never routinely carry more current than about 80% of their rating.

As for the solar panels, there are people here who know more about that than I do.  I will note that I have never seen a so-called "complete solar panel kit"  that included switches, which leads me to believe that a lot of solar systems don't have them.  That said, I can't think of any reason that putting a switch in would hurt anything, other than the obvious fact that it would be one more potential failure point, and thus violates the KISS principle.  If you do put a switch in, spend the money for a GOOD, high-quality one.