Wire gauge recommendation

[johnm1]

To get the most efficent charging to my batteries, with cost kept in mind, what wire gauge should I use between the batteries and charger?

I have a pair of 6v gc batteries.
They're about 12-15 feet from the charger.
I have a Boondocker 75A charger.
Currently have 6awg wire with very good crimped battery lugs.

Thanks

[grizzzman]

smkettner wrote:
You are comparing diameter instead of the cross section area.
With cross section area you can compare to a copper pipe or a solid copper bar.
area = (pi)r² giving an exponential relationship between diameter and area.

Two wires next to each other one inch wide is not the same as a single one inch diameter wire.

On your chart use the area columns to add and compare.

Apples to apples I'm not talking about a pipe or a solid bar am I??

[grizzzman]

smkettner wrote:
No parallel wire when roping a house right?

I mean if you ran out of #6 or #8 for the air conditioner you don't pull 2x #10.

I understand what you are saying with the #2 and #6. Just not my style.

So..... What you are saying is the rules for 230/120 AC are the same as 12 volt DC??? Really? Stick your fingers on the power wires of a 230 or 120 AC line and if you are still alive put your finger in a 12 DC power port and tell me which one is dangerous???

[time2roll]

You are comparing diameter instead of the cross section area.
With cross section area you can compare to a copper pipe or a solid copper bar.
area = (pi)r² giving an exponential relationship between diameter and area.

Two wires next to each other one inch wide is not the same as a single one inch diameter wire.

On your chart use the area columns to add and compare.

[grizzzman]

grizzzman wrote:

smkettner wrote:

grizzzman wrote:
Crunching the numbers 14.6 volts 75 amps 14 foot (28 total using 6awg) shows a voltage drop of 5.68% (.83 volts) adding a 4awg to the 6awg would a bit larger then 2/0 awg and a voltage drop of 1.10% (.16).
It would likely be cheaper and more effective to move the converter. Can you?

2/0 133,100 cm
#6 26,600 cm
#4 42,000 cm
#2 66,500 cm

#6 + #4 looks more like #2 than 2/0.

http://www.genuinedealz.com/voltage-drop-calculator

OK how is this?

Inches. MM
#4 0.2043 5.189
#6 0.1620 4.115

0.3663 9.304

#00
2/0 0.3648 9.266


Hmmm not the same is it?

One thing is sure I would NEVER buy sub size wire from the URL you listed. Yet another source

[grizzzman]

smkettner wrote:

grizzzman wrote:
Crunching the numbers 14.6 volts 75 amps 14 foot (28 total using 6awg) shows a voltage drop of 5.68% (.83 volts) adding a 4awg to the 6awg would a bit larger then 2/0 awg and a voltage drop of 1.10% (.16).
It would likely be cheaper and more effective to move the converter. Can you?

2/0 133,100 cm
#6 26,600 cm
#4 42,000 cm
#2 66,500 cm

#6 + #4 looks more like #2 than 2/0.

http://www.genuinedealz.com/voltage-drop-calculator

OK how is this?

Inches. MM
#4 0.2043 5.189
#6 0.1620 4.115

0.3663 9.304

#00
2/0 0.3648 9.266


Hmmm not the same is it?

[time2roll]

grizzzman wrote:
Crunching the numbers 14.6 volts 75 amps 14 foot (28 total using 6awg) shows a voltage drop of 5.68% (.83 volts) adding a 4awg to the 6awg would a bit larger then 2/0 awg and a voltage drop of 1.10% (.16).
It would likely be cheaper and more effective to move the converter. Can you?

2/0 133,100 cm
#6 26,600 cm
#4 42,000 cm
#2 66,500 cm

#6 + #4 looks more like #2 than 2/0.

http://www.genuinedealz.com/voltage-drop-calculator

[time2roll]

No parallel wire when roping a house right?

I mean if you ran out of #6 or #8 for the air conditioner you don't pull 2x #10.

I understand what you are saying with the #2 and #6. Just not my style.

[grizzzman]

smkettner wrote:
I am not an electrician. Please refer to NEC but they don't always give details or explanations.
The text has been pointed out before but I cannot quote the section.

Well I'm not an electrician, But I have wired a house including the 200 amp panel. It passed inspection on the first try. This is not rocket science. With that said I AM an expert in low voltage DC systems.

[time2roll]

I am not an electrician. Please refer to NEC but they don't always give details or explanations.
The text has been pointed out before but I cannot quote the section.

[grizzzman]

smkettner wrote:
I don't recommend parallel connectors and NEC is not real excited about it either except for very large transmission lines.

Frame is fine IMO as long as the connections are done well.

Good luck getting tinned marine #2 AWG into the WFCO connectors.
Might be rated #2 but maybe bare copper or SAE would fit better.

Just have fun should be first on the list 😉

A. It can be trimmed to fit. It is the distance that creates the voltage drop issues.

B. Agreed the frame will be just just fine.

C. I disagree Using the 2awg and the 6awg will do a great job of reducing voltage drop. It's not like it is dangerous the 6awg can handle the amps any ways but is inefficient. Why would this be in any way dangerous?

[time2roll]

I don't recommend parallel connectors and NEC is not real excited about it either except for very large transmission lines.

Frame is fine IMO as long as the connections are done well.

Good luck getting tinned marine #2 AWG into the WFCO connectors.
Might be rated #2 but maybe bare copper or SAE would fit better.

Just have fun should be first on the list 😉

[MEXICOWANDERER]

Señor Johnm1 🙂

My battery philosophy for my personal use operates in the following manner...

I have an "X" size generator. Compute that with an "X" ampere hour battery bank. Running at 1,200 RPM my Kubota is going to use "X" pounds of fuel per hour, completely unloaded.

At a 2 Kw load "X" pounds of fuel...

At a 4 Kw load "X" pounds of fuel...

What is the "safe" charging level of a proposed A/H battery bank? Wattage or amperage at 14.8 volts bulk charging level.

My first thought was a unitary 12 cell bank.

Max charge level around 318 amperes at 28.8 volts or roughly 9,000 watts.

The Kubota is turbocharged, the generator laughs at a 17 Kw load.

I'm supposed to "be happy" with a generator that starts off at 50% load then squats on it's --- for the remainder of the charge cycle?

Maybe someone else, but not me.

I had Rolls twin the batteries. But I could no longer charge at max acceptance rate. I had to limit amperage to 600 amperes to keep the machinery capable of living long enough to grow gray hair and whiskers. Tens of thousands of hours.

This doubling of the battery bank allowed me to utilize 35-40% depth of discharge rather than the max of 50% depth of discharge. Check a Rolls depth of discharge / life cycle chart and gasp. Longevity was dramatically increased.

I recharge double the capacity with a measured 17% increase in fuel consumption.

Yet when push comes to hurricane, I have double the ampere hours available for emergency use. I'm going to risk $7,000.00 worth of lobster and food if the generator somehow does not operate. The doubling of the battery bank also bought me "time" twice the length, regardless of economizing the load.

I used insanely large cable from batteries to inverter. The shed is 33' in length. No way in hell was I going to confine the Trace inverter in close proximity to the 24 batteries. The inverter is nine feet and change distant. It's intake is a baffled and filtered (home furnace filter) with deflectors and drains out of the south side wall. Not only is it fan cooled, the ducting provides natural convection cooling.

Generator and various AC and DC controls are another subject entirely. I designed the system so an adult with a sixth grade education could successfully manage it with confidence. My daughter hates it, but she too can operate the system.

I used 350 MCM wiring on the D.C. Think of 0000 wiring with an added 50%. The inverter can draw 8,000 watts starting duty. I limit charging to 500 amperes except in an emergency where I load the Kubota until the turbo can be seen glowing at night. I have a belt driven 40" fan to exhaust engine and generator radiator heat out of the hatch I use as a doorway. The fan exhausts so much air, hydrogen concentration is negligible. I have a pair of 1/4 horse fans as standby units.

Not answering your question but I have lockoff drains feeding a common, that empty the engine, and C750L Luberfiner filter to fill a five gallon pail with lid and bung. Reminds me I have yet to change over the battery lighting to LED.

Recap: When the generator would be loafing charging a single bank, it is not loafing charging a parallel bank. No @#$%^&! generator of mine is going to spin at 10% duty. When it runs, it is working......period.

[johnm1]

OK, OK ... I'll go with 2 gauge (said with a smile).

I have plenty of room on the tongue and the truck, etc to handle the weight. The cost for said batteries, well, it is what it is as long as it gets me what I need/want.

Mex - are you saying that with my setup it would be "better" for the batteries if I added 2 more (for a total of 4)? Is this because they'll be depleted less or because the charger that's recharging them?

[MEXICOWANDERER]

Excessive voltage drop WILL INDEED cause ANY converter to drop out of primary high current step (voltage) faster. Even two-tenths of a volt premature is annoying to me. Number TWO cable at that length is a good choice because anything larger would be a waste of money. When any device is supposed to charge batteries, make it earn it's pay. Charging batteries costs money.

Larger battery capacity has two faces. The first one is, expense, room, and labor.

The second face is when a generator is running and a small battery bank is twiddling around at say 12.2 amperes, twice the battery capacity means 24.4 amperes. Not to mention a proportionately less deep cycling of the bank.

[johnm1]

So much info here and not everyone agrees so lets see if I'm close ...

My assumption is that I need to keep the 75A charger that I installed as it's now used electronics. It's not camped with yet but installed and powered up and as long as I'm not going to hurt my batteries, I'm OK with that.

1. Replace the 6 gauge with the 2 gauge that Mex suggested. Would keeping the factory 6 gauge be bad? That'd give me close to 3/0 cable.
2. Don't go to the frame for the Neg wire as there are to many connections and it's not a "clean" way to do it.
3. Get an infrared pyrometer (non-contact thermometer) to check battery temps. It can do double duty and used to keep an eye on the tire and hub temps as well.
4. Keep the batteries watered.
5. Check charging voltage at the charger and batteries and track what's going on to get a better feeling as to how my system is performing.
6. Add a 2nd bank of batteries if needed for dry camping longevity without running the genny.
7. After doing some, or all, of the above, have fun with the family and not worry too much about it ... we've both had cancer before age 50 and life is too **** #&%^$*%@ short!

I almost forgot the most important one - Don't forget to charge the battery BEFORE I try to start the travel trailer (toy hauler). The wife would NOT be happy with me if I voided the warranty! I might print up a label like that just for fun.

Well, how'd I do?