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Thread: Electrical System Set-Ups
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06-01-2015, 09:02 AM #41james quinnGuest
Jim
I have a fiver ? Huh. Actually thought about that as well but liked the idea of counter weight as well as taking weight out of payload in back of truck.
Rob,
You may be right, I haven't actually checked measurement yet ... just had the idea driving home from Toronto last night. I had already figured I would have to fashion a sturdier base with stops to prevent battery from sliding around.
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06-01-2015, 09:33 AM #42
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Sorry James. I see you have a 313. I've got 5ers on the brain.
Jim & Georgianne
N. California
2016 Reflection 29RS
2008 Ford F-250 Super Duty PSD
B&W Companion hitch
Rubber turtle with no name
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06-01-2015, 10:49 AM #43
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Jim, we could go back and forth all day on this. Table 310.16 is a basic starting point for any circuit regardless of voltage. Current is current. Granted you do calculate for for a higher voltage drop in a 12VDC circuit just simply due to the nature of such a low voltage and as you pointed out low transmission rate that cost Edison lots of money. The 3% tolerance is not always applicable either, There are actually two calculations that can be used by ABYC standards which are critical and non critical at 3% and 10%. Now is that 3% drop calculated at nominal, fully charged, fully discharged, 50% discharged under full load? There are certainly a lot of variables and 100 tables all giving different information. While I would never use #14 for 20 amps by any standard (NEC puts it in at 15 amps) the ABYC standards actually says its good for 20 amps for a distance of 6 ft for critical loads and 20 feet for non critical. Now lets get practical, what in the RV pulls 20 amps of current? Pretty much nothing but the leveling gear and generator start that's upwards of 95 amps that isn't even in the linked table but by the calculations it provides would require a #2 wire for less than 6ft. Next closest is the blower motor for the furnace at 12 amps. I dont even think my main feeder off the battery is #2. Then there is demand factor that none of these tables take into account. By the tables a car starter would have a 500 MCM starter cable and it just isn't so as its de-rated for demand factor.
Just for comparison and to show how far apart one table reference is from the other on the exact same subject here is the ABYC table.
http://assets.bluesea.com/files/reso...on_chartlg.jpg
In the end, wire it how you like as there are no standards governing RVs
I dont typically deal with 12V DC systems on a daily basis, my DC applications run upwards of 800 VDC with 4000 AMP discharge rates.2015 Reflection 323 BHS #589
Still working Electrical Engineer
Rob, Maureen, Dakota, Jacob and Murphy the Lab
JustinThyme (Just In Time) is a forum handle
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06-01-2015, 11:13 AM #44
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Glad you got a chance to research ABYC electrical standards. That's what I'm familiar with and that's how I base my recommendations. Your primary battery cable is probably 6 AWG like mine. Well within "Industry" standards I'm sure.
Jim & Georgianne
N. California
2016 Reflection 29RS
2008 Ford F-250 Super Duty PSD
B&W Companion hitch
Rubber turtle with no name
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06-01-2015, 11:50 AM #45
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I'm with you that I'm typically one to over do things but it seems as time goes on, more comes into the calculations. Right about now it's more about money and space in the electrical business. The market calls for the biggest punch in the smallest and most cost effective package. Copper is expensive and the risk of other metals as conductors is completely out the question whether it be from lack of conductive properties such as aluminum or cost is way out of reach like platinum. It's getting so bad in the industry that mistakes are being made that eventually costs millions of $$ to correct all in the name of savings a few $$ per unit by doing something playing with tin instead of nickel. Google "tin whiskers". Sometimes it's just a short circuit on a PC board, others they do this on 480V 4000 amp switch gear with disastrous consequences.
2015 Reflection 323 BHS #589
Still working Electrical Engineer
Rob, Maureen, Dakota, Jacob and Murphy the Lab
JustinThyme (Just In Time) is a forum handle
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06-01-2015, 12:39 PM #46
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Good to know that when playing my nickel plated banjo the only whiskers will be on the player. 😉
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