Cable and Fuse Sizing

[freeagent]

Originally Posted by Dirk Mitchell

I am running this wire I picked up off Amazon from the starter battery back to the house battery.
SoundBox Connected 0 Gauge It is CCA but has really good coating and is flexible. I have used a lot of CCA wire in AC applications with no issues so I wasn't to concerned about that.

One note to make about Copper Clad Aluminum is the difference in using it in AC versus DC power applications. CCA is more effective in AC applications due to the skin effect where a majority of the electrons are flowing in the outer portion of the wire where the copper cladding is. Since the skin effect is a by-product of alternating current, it doesn't happen with DC. In DC, the electron flow is more evenly distributed throughout the entire cross section of the wire.

Since there is no skin effect in DC applications, the electrons are flowing through the aluminum in a CCA wire (as opposed to the copper "skin") and the ampacity of aluminum is less than copper. If you have 4 AWG in copper and 4 AWG in aluminum, the aluminum doesn't have the same current carrying capacity because it is a less efficient conductor.

So, if you choose to use CCA in any application especially DC, I would suggest upsizing your wire to accommodate your desired ampacity. There are a bunch of ampacity charts on the internet showing copper vs aluminum for appropriate wire sizing. Here is one example (scroll down the page):

Wire Sizing Charts - Affordable Solar

With all of that being said, if you're connecting your house battery to the start battery just for charging purposes then I think you're fine with 1/0 CCA unless you have a really long run. However, for those considering the 4 gauge CCA in an earlier post, I would certainly recommend consulting an ampacity chart and going with a bigger size to make sure you're getting what you need.

[Scalf77]

Originally Posted by larrie

Re fuses: IIRC it is not the house load that you have to size the breaker for. It is the short circuit amps. The Blue Sea calculator has you input the battery CCA so it can size the fuse.

You actually size the wire for you loads, and size the fuse/breaker to protect the wire. The battery CCA (Cold Cranking Amps) does come into play when picking a fuse/breaker as you will want to pick one with the correct AIC rating for your battery bank. This will be based off of the size of your battery bank , and if the fuse/breaker is a main/branch circuit.

Essentially, if your battery cable going to the house loads was shorted to ground, you need to have a fuse/breaker that can handle the full power of your battery to ground. A lower AIC fuse/breaker may still destroy itself and present a fire issue.

-greg

[86Scotty]

Just a quick disclaimer here for those unaware. Two different CCA's are being used in this discussion. Above in post 31 freeagent is discussing copper-clad aluminum wire (CCA) and in post 32 Greg (Scalf) is discussing cold cranking amps (CCA).

Hope that helps someone, as I was confused for a second, but I'm on my first cup of coffee.

[Scalf77]

Eric,
Good point, I edited my post.

-greg

[Flux]

Copper Clad Cold Cranking Aluminum Amps??

Not showing up on a google search....

[Flux]

Last night I figured I better sit down and start working this stuff out. Leaving everything in my head is a recipe for disaster.

My concern on this thread was sizing the Main line of my circuit. The one that goes from battery to battery through the 7622. The solar and house loads are really branches so to speak.

Scalf provided me sound reasoning. The mystery to me is how many amps the house battery would pull when drained. Really, it won't be able to pull more than the alternator could provide. So we could easily assume 150 Amps, but likely much less because the Van is using some to run the engine etc. Even upgrading to a 200 Amp alternator would likely never really give me 200 amps, more like the 150 amps or even less.



So being generous on the Blue Sea Circuit Wiz with 3% loss and 23 ft length we have:

100 Amps AWG 2 (210 Amps Capacity)
150 Amps AWG 1/0 (285 Amps Capacity)
200 Amps AWG 2/0 (330 Amps Capacity)

Now these come directly from the Blue Sea Calculator and I believe their Cable is a bit superior to SAE cable as far as ampacity etc.

Everything in Green is still a bit of a mystery.....

[boywonder]

FWIW, I used a pair of 150A breakers in the locations that you are showing next to each battery....

...not sure what the upper switch in the diagram is for?? Doesn't the 7622 have a separator switch built in?

...not sure the other switches are needed either......if I want to mess with my solar controller or disconnect it from the battery, I just pull the fuse between the controller and the panel.

..and not sure what the breaker in the solar panel negative would do.....

Have you purchased a 4D battery yet? I'm assuming that you are familiar with the Lucent-Alcatel blem batteries that are available in San Diego...

BTW, when my house batteries are low I've seen a max of about 20A or so flowing from the alternator when looking at my battery monitor...I expected more....

[Flux]

Originally Posted by boywonder

FWIW, I used a pair of 150A breakers in the locations that you are showing next to each battery....

Probably a better alternative. I will look into the differences in how they trip v a fuse blowing.

...not sure what the upper switch in the diagram is for?? Doesn't the 7622 have a separator switch built in?

You are correct. That switch would be redundant. Only upside would be that it's

...not sure the other switches are needed either......if I want to mess with my solar controller or disconnect it from the battery, I just pull the fuse between the controller and the panel.

The switch below the top switch would act to isolate the solar and battery. That way I could let solar do the float charging of the battery while on lengthy cruises.

..and not sure what the breaker in the solar panel negative would do.....

LOL, Me neither. I looked at the schematics from the midnite solar site on the Kid. Don't think it's necessary other than to completely isolate the panels from the charger.

Have you purchased a 4D battery yet? I'm assuming that you are familiar with the Lucent-Alcatel blem batteries that are available in San Diego...

No, not yet. I have a local dealer in Palmdale and might go through them for warranty sake. Gotta see what they have and what they are asking for them.

BTW, when my house batteries are low I've seen a max of about 20A or so flowing from the alternator when looking at my battery monitor...I expected more....

This is what haunts me right now. How many actual amps will be heading to the house battery

Thanks for looking that Diagram over!

[Flux]

The kindness of strangers once again prevails around here. Scalf77 took some time with me and gave me some pointers as well as linked me up to his presentation.

THANKS Scalf77!!! The Oregon crew is top notch!

So I made a few revisions and will keep banging away.




So a few changes are that we agreed that 2 AWG would suffice from the starter back to the Inside Panel. Well I ended up scoring a super deal on ebay for 1/0 Ancor so I am gonna stick with that. Gonna use 2/0 from the house to the panel, future consideration for an inverter. Found a good deal on 2/0 as well.

Gonna move the 7622 ACR to the Panel as well as add in a 7700 RBS. Battery side fuses will move in there as well.

Gonna size for the alternator max, 150 amps. Probably never see that.

Battery Fuses will be Type-T or Terminal fuses. Ancor Type-T's aren't available until next month but the next best AIC rating is the terminal types. 20k vs 10k. Still not sure about the solar and house fuses/breakers. But will work that out soon.

The addition of the 7700 RBS allows me to cut the everything away from the Solar and Battery. This way, on a long cruise, I can switch em off and let the solar properly float the house battery and let the alternator deal with the starter and house. I was originally going to use a switch, but they are not rated for switching with the motor on, the 7622 and 7700 are. Put the remotes up next to my upfitters and good to go!! I found a 7700 on ebay for 99 bucks so I had to do it!

Other nice thing about these is I can possible use them like terminal posts and limit the number of connections needed overall.

Just getting my homework done before 2017.

Cheers and Happy New Year!!

[boywonder]

Where's the charger and inverter? You may also want a transfer switch for shore power..there are a few options for wiring that. I bought a transfer switch but never installed it.