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Old 05-30-2014, 11:53 AM   #1
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Calling all electrical experts!!!!

I'm not sure of the gauge, but the cables that connect our house bats together and also the main "bus" cables are HUGE (like as big as my thumb).

I bought an extra to install my battery monitor and all NAPA had (in a short length) were "starter" cables. I figured that most starters pull up to 250 AMPS (or more), so thought I'd be OK.

Now I'm pretty sure the new cable is NOT large enough; it's smaller than my little finger. It is not getting warm to the touch, but it might someday.

So, question is should I replace the added cable with one the same size as the original cables..... And is so, where do I get something that huge??

Boowho??
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Old 05-30-2014, 12:38 PM   #2
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Stay with the current (ok, pun intended) wire gauge, probably a 2 or 4 right now. The one you bought is maybe a 6 or 8 ga so considerably smaller. Smaller number, bigger wire. There is a guide sheet, not at my fingertips, which shows what you need for length of run vs volts/amps needed for the application. Go with what is currently in place and you should not have any problems.
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Old 05-30-2014, 12:50 PM   #3
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What you will need is welding cable. There are many websites that will guide you to the right size
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Old 05-30-2014, 12:59 PM   #4
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Not sure what type of ends you want - but here is a source for pre-made battery cables. They go up to 2/0, which is probably large enough. Or if you just want plain wire w/o the ends - they go up to 4/0.

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Old 05-30-2014, 01:13 PM   #5
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Quote:
Originally Posted by boowho View Post
I bought an extra to install my battery monitor and all NAPA had (in a short length) were "starter" cables. I figured that most starters pull up to 250 AMPS (or more), so thought I'd be OK.
Not sure what the extra cable is for but if your battery monitor is more or
less a volt meter that tells you the amount of charge remaining in your
batteries- just about any size wire will work. IF the extra wire you need
is passing the total CURRENT to/from your batteries then it needs to be
big.
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Old 05-30-2014, 01:16 PM   #6
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If the monitor has a shunt you need the same size cable.
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Old 05-30-2014, 01:19 PM   #7
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Quote:
Originally Posted by KyDan View Post
Not sure what the extra cable is for but if your battery monitor is more or
less a volt meter that tells you the amount of charge remaining in your
batteries- just about any size wire will work. IF the extra wire you need
is passing the total CURRENT to/from your batteries then it needs to be
big.
I am with you on this...I can't imagine why the OP needs this type of wire for a "monitor". Normally some 16 gauge would work fine to monitor the volts on the battery. If he were going to measure current, he should be installing a "shunt" in line with the batteries and then measure the millivolts produced across the shunt and convert to current flow.
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Old 05-30-2014, 01:26 PM   #8
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I don't quite understand you are adding a battery display monitor, something to read what your voltage is in your battery bank? If that is what you are talking about what you bought would be fine. I agree with KYDAN.
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Old 05-30-2014, 06:42 PM   #9
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Background: this is what Boohoo did concerning the question he posed. More info to follow:

Just finished installing the Battery Monitoring module for the Magnum 1212. Install was quite easy; mostly plug and play.





It took the system right at 20 hours to get an accurate reading on State of Charge. While waiting the display simply reads "Thinkin'" !!





Paid $170 for the kit (with shunt), but almost $60 additional for stuff they do NOT include.





Going to experiment/test it out over the next week or so, to determine exactly how much good it does for me. Initially, I think it will be a great asset.
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Old 05-30-2014, 06:43 PM   #10
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Clarification

I should have posted this earlier, but here's a drawing, both before and after. The before pic is one top. After on bottom.

The number 1-4 indicate the pos and neg of TWO output circuits; one to the house 12 volt circuit, the other to the Inverter.

The after after drawing shows how I added the shunt to the negative. While not a shunt, I added a terminal block to the positive side. All the wires in the before drawing are the "huge" ones ( 0/4, I believe ). All in the after drawing are the same EXCEPT the two attached DIRECTLY to the posts.

In other words the black wire from the bat to one side of the shunt PLUS the red wire from the bat to the terminal block are the lighter gauge ( 4 ).

Thanks for the replies so far.

Boowho??
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Old 05-30-2014, 07:02 PM   #11
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An actual photo would also help.

AS an FYI - Here is a photo of my shunt and monitor wires. Remember the shunt goes DIRECTLY to the farthest negative terminal of your battery bank (directly opposite of your farthest positive terminal). That way all current going to the battery bank is monitored by the shunt.

The battery wiring diagram if for 6 - 6 volt batteries; not 4.
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Old 05-30-2014, 07:19 PM   #12
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Quote:
Originally Posted by Mmnsc View Post
What you will need is welding cable. There are many websites that will guide you to the right size
My jumper cables are made out of 0 gage welding lead.

If I wanted to redo the trailer I would use 4 gage.
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Old 05-30-2014, 11:13 PM   #13
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You might wanna use a caliper to measure the thickness of your existing positive cable so you can match it. 2/0 cable is probably what you need and you'll probably need a custom cut length with lugs swaged on.
Cross section of WIRE no insulation measurements:
00 (2/0) 0.3648 INCHES
000....0.4096
0000...0.4600
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Old 05-31-2014, 06:15 AM   #14
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I'm still confused.
Does a battery monitor act like an AMPmeter?? Does all the current that
is used go THROUGH the monitor??
Another way to ask-- is the monitor hooked to the batteries in
series or parallel?
(Just trying to get my head around this.....)
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Old 05-31-2014, 07:50 AM   #15
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Quote:
Originally Posted by KyDan View Post
I'm still confused.
Does a battery monitor act like an AMPmeter?? Does all the current that
is used go THROUGH the monitor??
Another way to ask-- is the monitor hooked to the batteries in
series or parallel?
(Just trying to get my head around this.....)
1. Yes...it will show you amps in and amps out. It will also calculate remaining battery capacity and time remaining at PRESENT amp draw. Not just by +/- amp draw but by using Peukerts formula and knowing battery bank size which you enter. Of course it will also show voltage readings which is useful as you are charging...and it will show state of charge during charging so you know when you finally got to 100%. Also ...when you actually get to 50% it will show that rather than a ficticious voltage in use display...so you know when to recharge.

2. Almost NONE of the current goes through the monitor...it all goes through the shunt which the battery monitor telephone wire type cable plugs into. All negative wires go to the shunt. Then they pass through the small monitoring circuit which diverts a small amount of current ...then on to the other end of the shunt which a battery cable attaches to the negative battery post. The only wires which go to the monitor itself are the telephone type wire and a small red wire to the positive battery post for power.

If you are always plugged in somewhere, theres little need for this...but if you boondock it is the most useful tool you have to plan for your needs and charging routine and save your batteries from unmeditated murder!

Here's a picture of a nice clean install with the shunt on the top right.
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Old 05-31-2014, 11:06 AM   #16
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OK, here's a pic. Note TWO original cables on the left side of the shunt. One of these feeds the inverter, the other feeds all the 12 volt accs in the coach.

The right side of the shunt has the cable I added; it goes directly to the negative battery post. Note how much smaller it is. That is my question; will that smaller cable be a problem??

I have an identical setup on the positive leads, just using a huge terminal block instead of a shunt. Also, for further clarification: I have all cables that tie the 4 bats together in the proper configuration and the single positive and negative (new) cables are attached to diagonally opposite posts on the bat stack (as they should be).

The orange and blue wires are the battery monitoring "sense" wires.

Boowho??
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Old 05-31-2014, 12:20 PM   #17
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Quote:
Originally Posted by boowho View Post
OK, here's a pic. Note TWO original cables on the left side of the shunt. One of these feeds the inverter, the other feeds all the 12 volt accs in the coach.

The right side of the shunt has the cable I added; it goes directly to the negative battery post. Note how much smaller it is. That is my question; will that smaller cable be a problem??

I have an identical setup on the positive leads, just using a huge terminal block instead of a shunt. Also, for further clarification: I have all cables that tie the 4 bats together in the proper configuration and the single positive and negative (new) cables are attached to diagonally opposite posts on the bat stack (as they should be).

The orange and blue wires are the battery monitoring "sense" wires.

Boowho??
I really do not see anything wrong with that for just a monitor. Unless I'm missing something, is it working?
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Old 05-31-2014, 12:42 PM   #18
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YES IT IS A HUGE AND DANGEROUS PROBLEM. GET A CABLE the SAME SIZE as you are putting on the other end of the shunt.

GLJ...EVERY amp and volt bit of electric use is going through that shunt!! The monitor only sees a tiny bit through the blue wire....but must monitor all of it. Downsizing the cable is the equivilent of downsizing ALL the existing cables...like the ones at the other end of the shunt.
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Old 05-31-2014, 12:55 PM   #19
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Originally Posted by camaraderie View Post
YES IT IS A HUGE AND DANGEROUS PROBLEM. GET A CABLE the SAME SIZE as you are putting on the other end of the shunt.

GLJ...EVERY amp and volt bit of electric use is going through that shunt!! The monitor only sees a tiny bit through the blue wire....but must monitor all of it. Downsizing the cable is the equivilent of downsizing ALL the existing cables...like the ones at the other end of the shunt.
X2 Think of it like water, you have a three quarter inch hoe that delivers say 5 gallons a minute, you then add a tree eighths hose, how are you going to get that 5 gallons a minute. in the case of the reduced sized cable it will heat up and could eventually burn because it is over loaded, reducing cable size is never a great idea.
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Old 05-31-2014, 02:34 PM   #20
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Originally Posted by camaraderie View Post
YES IT IS A HUGE AND DANGEROUS PROBLEM. GET A CABLE the SAME SIZE as you are putting on the other end of the shunt.

GLJ...EVERY amp and volt bit of electric use is going through that shunt!! The monitor only sees a tiny bit through the blue wire....but must monitor all of it. Downsizing the cable is the equivilent of downsizing ALL the existing cables...like the ones at the other end of the shunt.
Okay Thanks Cam I can go for that. I thought it just showed his battery power left or charging. How come he just can't add it to the battery post? It's monitor if I understand it. But I guess I don't thanks for the correction and info as always...
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