Difference in Battery Cable Sizes/designations

Willhound

When I added a second house battery wired parallel a few years ago I placed it on the opposite side of the hull for weight distribution. I picked up a set of gently used cables from a local dealer as $$ were tight when I just purchased the boat and although they've worked OK, I think there might be some rot setting in and want to change them. About a 9 foot run to account for routing around the engine bay.
My first question is, what is the difference between wire marked 1/0 AWG as in this link: https://ca.binnacle.com/Electrical-Ancor-Marine-Grade-Wire/c58_206/p8849/Ancor-Marine-Battery-Cable-1/0-AWG-Per-Foot/product_info.html

And just 1 AWG as in this link: https://ca.binnacle.com/Electrical-Ancor-Marine-Grade-Wire/c58_206/p2451/Ancor-Marine-Battery-Cable-1-AWG-Per-Foot/product_info.html
Both are listed as battery cables.

Also, my current set up uses 2 AWG for the parallel connector as well as the wire from the original house battery to the battery switch. 
So is there any need, or advantage to using 1 AWG for my new wire, or just stick with #2 ?

Ian

The 1AWG is 20% smaller in area so has a lower current carrying capacity. Given the extra distance I’d go for the larger (over 2 also) to avoid any loss.

Willhound

Something was twigging in my brain, and I think I just remembered the answer to my first question. If I remember right, the 1/0 is "1 Aught" to signify 1 past zero gauge.
So in order of lightest to heaviest gauge it would be 2, 1, 1/0, 2/0 correct?

Ian

I believe you are correct, where I am from we use a method where a bigger number means a bigger wire, not the other way around, 24 “gauge” as such is a bus bar, not a phone line!

Dream_Inn

Will hound, you are correct.  The larger is better for less resistance and more amp carrying. 9ft is a pretty good distance for a battery cable.

Willhound

I understand the heavier cable, the less resistance. Given that my cable from second house battery to battery switch is 2 AWG, is there still any advantage to going with a heavier 1 AWG from battery to battery? 

aero3113

I would think bigger the better, just when the wire gets too big it’s harder to work with. I also think the bigger cable is good for long runs to compensate for voltage drop. Also the bigger the cable the more expensive it gets.

Ian

As @aero3113 said...

Willhound

I see the point and understand  the heavier gauge from battery to battery allows better current flow between them, but then it chokes down to 2 AWG from the second house battery to battery switch and rest of the boat, so is it really accomplishing much? Not asking to be contrary, and there's not much difference in price, more of an academic exercise. I probably overestimated the distance a bit, thinking about it there's about the same distance from battery 1 to 2 as there is from battery 2 to the switch.

aero3113

@Willhound , would you order the wires with terminals already swaged on or will you cut and install the terminals yourself? When I replaced my 242 cables, I bought a hydraulic crimper for the terminals, really no other way to do it other than soldering them on.

LaRea

Willhound said:

... there's about the same distance from battery 1 to 2 as there is from battery 2 to the switch.

If you're not really changing the cable length, you can use the same size (2 AWG).  

In general, if you double the length and want to keep the same voltage drop, you should double the cross-section area.  That means going up three sizes (from 2 to 2/0).  

Willhound

Makes sense guys, thanks. @aero3113 I have access to a swaging tool at work. Could solder them too. In either case I'll also seal them with heat shrink.

aero3113

Get the heat shrink with the sealant in it, will make them somewhat water resistant.

Aqua_Aura

aero3113 said:

Get the heat shrink with the sealant in it, will make them somewhat water resistant.

Yes highly agree. I actually started selling the heat shrink tube and heat shrink crimp connectors with glue in them last year and it is far superior to the old crimp connectors. 

Willhound

Agree. I've always used those type of connectors. Pro tip: do NOT let it drip on your skin....don't ask how I know.😨

Dream_Inn

Being that it is wired in parallel with another battery, I would go with one size larger.  I do agree you'd be ok 2AWG though.  Also, I'm betting you are tapping back to the boat off of one battery?  Not using the negative off of one and positive off of the other?  If that is the case, then you definitely want less resistance, go with larger wire.

Willhound

@Dream_Inn you are correct. The original house battery is connected to the switch, the second one I added I simply wired parallel with that one.