Wire size for battery bank

[Texas_Two_Stepp]

If you've got 4-6v Trojan t105 batteries wired for 12v with 2/0 wire between them would 2/0 be the proper size to run back to your converter/charger which is 12' away? And I guess the hot wire would need to b fused somewhere near the batteries? This is not for me so don't assume anything from my signature.

[larry_cad]

Texas Two Steppers wrote:
I am the op and want to thank everyone for the information. My friend has a 50 amp Excel but I am not sure about the converter size. I also asked if the hoy leg from the converter would need to be fused???

Fuses are almost always a good idea. Not too expensive and extra safety.

[2oldman]

RJsfishin wrote:
What is the difference between diameter and cross section ? I guess I just need the definition of "cross section"

I use rectangular metal bars to interconnect my batteries. The cross section is the area of the rectangle.

[mena661]

Redsky wrote:

If your charger charges your batteries on shore power in 3 hours with 3% current loss (97% of current is getting through) then going to smaller gauge wiring with 10% current loss (90% of available current is getting through) is only going to take an extra 12 minutes of charging time.

Long, thin wire equals more VOLTAGE drop not current drop. With 12V, you can easily lose quite a bit. If we were all running 24 or 48V systems, it wouldn't be that big of a deal. And really, it's only a big deal with these POS converters that we use that either don't go into boost or drop out of boost too early because of that undersized wire. With the PD's you can force them to boost but they'll still drop out too early. Yeah, yeah I know, some people don't really care because it's good enough but I like to get every dollars worth of money out of my purchases so it needs to work EXACTLY as it should.

[Texas_Two_Stepp]

I am the op and want to thank everyone for the information. My friend has a 50 amp Excel but I am not sure about the converter size. I also asked if the hoy leg from the converter would need to be fused???

[RJsfishin]

Quote:
FYI it is not the diameter of the wire but the area of the cross section of the wire that determines how much current it can pass and how much loss there will be
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What is the difference between diameter and cross section ? I guess I just need the definition of "cross section"

[Redsky]

You could get by with 8ga but 4ga is still not terribly difficult to run and you will have less current loss. Where people go off the rails is in looking at charts for cable sizing based on less than 3% current loss as though this is of critical importance.

If your charger charges your batteries on shore power in 3 hours with 3% current loss (97% of current is getting through) then going to smaller gauge wiring with 10% current loss (90% of available current is getting through) is only going to take an extra 12 minutes of charging time.

The wire from the tow vehicle's alternator to a trailer or from the truck alternator to a camper is going to be 8ga in most situations and it is going a much greater distance to the batteries but it works well enough.

FYI it is not the diameter of the wire but the area of the cross section of the wire that determines how much current it can pass and how much loss there will be. Take a 20' run (40' in total) and using 2ga wire the voltage drop is 0.53% and going with 4ga the drop is 0.85% and going to 8ga the drop is still only 2.15%.

[mena661]

Thanks Larry for clearing that up. Went back and reread the OP. For a standard converter (like 55 amps), 2/0 would be a bit overkill for a 12 foot run. I'd go with #1 or even #2. If you're getting the 2/0 cheap or just don't mind spending on that size then 2/0 is just fine. You'll probably have to trim the end to fit in the converters lugs.

[larry_cad]

Folks, read the original post. The OP has a magnum, but he is asking for someone else. The someone else does not have a Magnum, they have a converter charger. BIG difference. BIG difference.

The Magnum is an inverter also and can draw a huge amount of amps FROM the battery bank. The converter/charger does NOT draw amps from the battery bank, it only sends amps TO the battery bank. The amount of amps it sends to the battery bank is small compared to the amount an inverter can draw from the battery bank, thus the big difference.

As someone commented, a typical converter/charger can put out 60 or maybe 80 amps of CHARGING amps to the battery bank. The 12' run should be able to handle that current. 6AWG is good for at least 60 amps. 4 is good for at least 85 amps. The voltage drop over a 12' length is minimal.

[Clay_L]

smkettner wrote:
Here

Use the quote function to review the syntax

Looks like the URL is a bit truncated on my link.
Anyhoo sometimes the URL has a code that confuses the RV.net system.
Costco.com is notorious for this.

Okay copied yours above that works. Here it is Here

EDIT
That worked for me also.
What is odd is that the url copied from the site is "http://www.rvforum.net/joomla/index.php?option=com_content&view=article&id=289%20img%20src=#1131008883119568674" and it works when pasted into the browser as does the one you used and the one I had first used and it is not the same as either of the other two. All three take you to the same site but only two work as a LINK.

I have a headache.... I think it is happy hour time. 🙂

[time2roll]

Here

Use the quote function to review the syntax

Looks like the URL is a bit truncated on my link.
Anyhoo somtimes the URL has a code that confuses the RV.net system.
Costco.com is notorious for this.

[Clay_L]

2oldman wrote:

Clay L wrote:
Not sure why the clicky function is showing like that.

Because colon-b, 😛 is that face.

Yeah but it should show "HERE" not part of the url. I have made a post on the web site help section.

[mena661]

2/0 can do 330 amps (105C insulation). I doubt he'll go over that. Running the MW on that might drop the voltage down .3V but since it's a short period of time, running into the inverter alarm shouldn't happen (unless the batteries are pretty low in SOC).

[mrekim]

Texas Two Steppers wrote:
If you've got 4-6v Trojan t105 batteries wired for 12v with 2/0 wire between them would 2/0 be the proper size to run back to your converter/charger which is 12' away? And I guess the hot wire would need to b fused somewhere near the batteries? This is not for me so don't assume anything from my signature.

I think you need to know the max current flow from the batteries in order to properly size the 12' cable run.

[2oldman]

Clay L wrote:
Not sure why the clicky function is showing like that.

Because colon-b, 😛 is that face.