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Author Topic: Use frame for negative run  (Read 3475 times)

supermanotorious

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Use frame for negative run
« on: February 06, 2017, 05:30:50 PM »
In case I run out of cable, I could use what I have for the fused positive run, then use the frame to carry the negative from battery bank to inverter. Anyone see why this wouldn't work?
« Last Edit: February 06, 2017, 05:33:13 PM by supermanotorious »
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xrated

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Re: Use frame for negative run
« Reply #1 on: February 06, 2017, 05:46:32 PM »
It's been working in cars and trucks for the last 100 years or so.  Having said that, you have to make sure that ALL of your ground connections are made on bare metal....and I mean bare!  Files, emory cloth, small dremel bit, whatever you need to take the grounding locations down to bare metal.  It wouldn't hurt to apply a dab of di-electric grease to the connection point also, just don't overdue it.
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Cant Wait

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Re: Use frame for negative run
« Reply #2 on: February 06, 2017, 05:55:52 PM »
If you look close to the wiring diagram you your unit I 'd bet you'll find that 90% of all negative runs use the frame instead of wasting the wire.
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supermanotorious

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Re: Use frame for negative run
« Reply #3 on: February 06, 2017, 05:56:17 PM »
that's what I was thinking too, although I've heard you want equal length runs for inverters
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Isaac-1

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Re: Use frame for negative run
« Reply #4 on: February 06, 2017, 08:00:55 PM »
It depends on how big the inverter is,  It is much better to have a direct run of copper wire if it is a large inverter (over 800 watts or so)
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supermanotorious

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Re: Use frame for negative run
« Reply #5 on: February 06, 2017, 08:44:24 PM »
it is bigger, this is the 2,000 watt (4,000 peak) pure sine wave "solar" inverter
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HappyWanderer

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Re: Use frame for negative run
« Reply #6 on: February 06, 2017, 09:01:54 PM »
Connections should be made directly to the battery, not dependent on chassis components to complete the circuit. Weird things start to happen when grounds are compromised. It's simply not worth saving the few bucks it takes to do it right.

Lou Schneider

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Re: Use frame for negative run
« Reply #7 on: February 06, 2017, 11:27:08 PM »
A 2,000 watt inverter can draw up to 200 amps from the 12 volt batteries (400 amps during the 4000 watt peaks).

Are you absolutely sure your chassis connections can carry this load?  How about any welds or joints between the connection points?

The other factor is voltage drop along the chassis rail.  When the inverter draws lots of current through the chassis it will send voltage surges into other equipment that's also tied to the chassis rail.  Things like the engine computer, radio, etc.

Arc welders use similar currents and can create the same kind of voltage surges, so it's common to disconnect the negative battery cable to protect the electronics before welding on a chassis.

All of the above is why you need to run both positive and negative cables from the inverter to the battery and leave the chassis out of the inverter's current path.  And keep them short - even the largest wire will lose too much voltage if there's more than a few feet between the batteries and inverter.
« Last Edit: February 06, 2017, 11:38:07 PM by Lou Schneider »

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Re: Use frame for negative run
« Reply #8 on: February 07, 2017, 04:48:32 AM »
In case I run out of cable, I could use what I have for the fused positive run, then use the frame to carry the negative from battery bank to inverter. Anyone see why this wouldn't work?

I totally missed where you are wanting to use the frame for the negative conductor for an inverter circuit.  I definitely would not do that.  It's a high current circuit and needs the proper size wire and the shortest distance possible from end to end to prevent voltage drop.  Take Lou Schneiders advice.
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AStravelers

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Re: Use frame for negative run
« Reply #9 on: February 07, 2017, 08:37:33 AM »
As already stated, you want the absolutely least amount of voltage drop in the connection between the battery pack and the inverter.  Use the proper copper wire size for the negative connection.
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AStravelers

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Re: Use frame for negative run
« Reply #10 on: February 07, 2017, 08:44:59 AM »
You also really need to install a battery monitor which displays the total AH (Amp Hours) going out of you battery pack and being put replaces by whatever charging method you use.

Use a Trimetric or something like it:  http://www.bogartengineering.com/products/trimetrics/

Without a battery monitor like this you will not know just how far discharged and how close to fully charged your batteries are.  You will be flying blind w/o the monior and WILL, over time, significantly reduce your battery life.
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denmarc

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Re: Use frame for negative run
« Reply #11 on: February 07, 2017, 10:17:18 AM »
I could not agree with Lou more! Cable the inverter directly to the battery using the correct gauge cable for the distance. And keep that distance as short as possible. Keep that inverter as close to the battery as possible. Even if you have to mount it somewhere you're not keen with. You will be happier in the long run and get the most benefit from it if you do. Trust me. I boondock 100% with genny power only to run the AC and charge the battery bank. Inverter runs electronics and such during the evening when silence is wanted.

Your idea is a good one. But the amperage that may be required limits your practical options.
Mark

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supermanotorious

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Re: Use frame for negative run
« Reply #12 on: February 07, 2017, 08:51:24 PM »
well I heeded the advice, I bought some legitimate 2/0 gauge pure copper welding wire for the runs which are approximately 8' long from battery bank to inverter

I'll post pictures of the wire run on my inverter project thread

I also thought I'd experiment with this battery monitor which should arrive later this week

https://www.amazon.com/gp/product/B013PKYILS
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AStravelers

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Re: Use frame for negative run
« Reply #13 on: February 08, 2017, 09:31:40 AM »
well I heeded the advice, I bought some legitimate 2/0 gauge pure copper welding wire for the runs which are approximately 8' long from battery bank to inverter

I'll post pictures of the wire run on my inverter project thread

I also thought I'd experiment with this battery monitor which should arrive later this week

https://www.amazon.com/gp/product/B013PKYILS
I assume you noted that the battery monitor is only rated for up to 100 amps and the inverter you listed earlier can pull 160-180 amps. 
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fairway2002

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Re: Use frame for negative run
« Reply #14 on: February 08, 2017, 11:49:37 AM »
A lot of modern day equipment use the chassis ground. If that inverter went bad it could put some weird voltage on ground. Might damage other equipment.
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supermanotorious

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Re: Use frame for negative run
« Reply #15 on: February 08, 2017, 12:25:15 PM »
I assume you noted that the battery monitor is only rated for up to 100 amps and the inverter you listed earlier can pull 160-180 amps.

DOH!
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BIG JOE

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Re: Use frame for negative run
« Reply #16 on: February 08, 2017, 12:56:00 PM »
Just another .03 but...

For the purpose's of hooking up an Inverter correctly.. Connecting the Positive & Negative 12v supply leads [directly] to the Battery is the safest way to go. The Battery then becomes an RF Filter, a Heat Sink and has many other Whizo benifits. 

Being sure the Inverter's body is connected to a good chassis ground.. is important also ?


 :)
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Lou Schneider

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Re: Use frame for negative run
« Reply #17 on: February 08, 2017, 03:43:09 PM »
I assume you noted that the battery monitor is only rated for up to 100 amps and the inverter you listed earlier can pull 160-180 amps.

Not only that, but the amp-hour reading only counts up, not down.  So you can meter how many amp-hours you're putting into the batteries, or how many you're taking out but not both.

It's a design flaw in those cheap meters.  What you really want is an amp-hour meter that measures current flow both ways, in and out of the battery and keeps a cumulative count of how much remains.  Otherwise you have no way of knowing the battery's state of charge.

robertusa123

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Re: Use frame for negative run
« Reply #18 on: February 08, 2017, 04:37:03 PM »
I wouldn't cheep out on a nice inverter like that..... Do it right
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supermanotorious

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Re: Use frame for negative run
« Reply #19 on: February 08, 2017, 08:39:30 PM »
alright alright alright, I will return or resale the battery meter

now, this diagram is how the batteries will be wired, any problem with the running the negative lead as depicted on the dashed line? the arrows in the left side of the image show where the negative run would normally come from but again, I'm trying to save wire, thoughts?
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Tom_M

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Re: Use frame for negative run
« Reply #20 on: February 09, 2017, 07:00:56 AM »
Here's a meter available on eBay that measures both forward and reverse current up to 250 amp:

http://www.ebay.com/itm/DC-5-40V-0-250A-Volt-Amp-Combo-Meter-Battery-Charge-Discharge-No-Need-Power-/171557473254?hash=item27f19f4be6:g:ei0AAOxy~hdR1aFN

Other current ranges are available.
Tom
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AStravelers

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Re: Use frame for negative run
« Reply #21 on: February 09, 2017, 08:05:29 AM »
alright alright alright, I will return or resale the battery meter

now, this diagram is how the batteries will be wired, any problem with the running the negative lead as depicted on the dashed line? the arrows in the left side of the image show where the negative run would normally come from but again, I'm trying to save wire, thoughts?
I don't see anything wrong with the wiring.  No matter what you do you are going to have to have a jumper from one set of batteries going to the other.  To totally balance the wire lengths you would need to attach the + & - cables going to the inverter in the middle of the jumper.  If you had 4 sets of batteries I would want to make sure the cables to the inverter where in the center of entire battery pack. 

Here is a link to a great discussion about cabling multiple batteries together:  http://www.smartgauge.co.uk/batt_con.html 

Whether anyone agrees with or disagrees with the info in the above link, is not important.  The information given is worth considering.  We are all free to wire our batteries as we see fit.    I did not create the link or the info.  However I have seen some folks criticize some of the tiny details in the link. 
« Last Edit: February 09, 2017, 08:10:37 AM by AStravelers »
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supermanotorious

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Re: Use frame for negative run
« Reply #22 on: February 09, 2017, 09:11:55 AM »
all these configurations are parallel, I have to use series/parallel to get 12V, I know for a fact I am wiring them correctly as this isn't my first install, however the question remains, any problem linking the negative out to the right side terminal rather than the left side terminal

I don't see anything wrong with the wiring.  No matter what you do you are going to have to have a jumper from one set of batteries going to the other.  To totally balance the wire lengths you would need to attach the + & - cables going to the inverter in the middle of the jumper.  If you had 4 sets of batteries I would want to make sure the cables to the inverter where in the center of entire battery pack. 

Here is a link to a great discussion about cabling multiple batteries together:  http://www.smartgauge.co.uk/batt_con.html 

Whether anyone agrees with or disagrees with the info in the above link, is not important.  The information given is worth considering.  We are all free to wire our batteries as we see fit.    I did not create the link or the info.  However I have seen some folks criticize some of the tiny details in the link.
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supermanotorious

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Re: Use frame for negative run
« Reply #23 on: February 09, 2017, 09:22:49 AM »
I assume you noted that the battery monitor is only rated for up to 100 amps and the inverter you listed earlier can pull 160-180 amps.

wait a minute here

doesnt   Amps = Watts/Voltage  ?

so even at peak 4,000 watts / 110 volts (going low for arguments sake) = 36.36 Amps (repeating of course Leroy Jenkins)
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Lou Schneider

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Re: Use frame for negative run
« Reply #24 on: February 09, 2017, 11:29:23 AM »
wait a minute here

doesnt   Amps = Watts/Voltage  ?

so even at peak 4,000 watts / 110 volts (going low for arguments sake) = 36.36 Amps (repeating of course Leroy Jenkins)

True, but we're talking about the 12 volt input.

4,000 watts / 12 volts equals 333 amps.  At the 2000 watts continuous rating it will pull about 160-180 amps.

supermanotorious

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Re: Use frame for negative run
« Reply #25 on: February 09, 2017, 03:48:16 PM »
doggone it, I didn't even realize that, this site is great for calculating

https://www.batterystuff.com/kb/tools/ac-to-dc-amperage-conversion-run-through-an-inverter.html
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Lou Schneider

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Re: Use frame for negative run
« Reply #26 on: February 09, 2017, 06:10:11 PM »
That's why cable lengths and gauge are so critical on the 12 volt side of the inverter.  Not only do you only have 1/10th as much voltage as on the 120 volt side, but you're running 10 times as much current at 12 volts.

Take both factors into account, and the 12 volt input is 100 times more sensitive to wire loss than at 120 volts.

That's why you need short, fat cables on the inverter input and having the path to each parallel battery be as equal as possible.  This means don't hang both cables on one battery and run more wire to the second battery, but put the (+) cable on one battery and the (-) cable on the other.
« Last Edit: February 09, 2017, 06:11:44 PM by Lou Schneider »

supermanotorious

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Re: Use frame for negative run
« Reply #27 on: February 09, 2017, 08:20:35 PM »
well in our Sandstorm, I ran 2ga wire about 5' long for our 1500W inverter with no monitor and it did just fine

this rig is getting a 2000W inverter and 8' runs of 2/0ga wire
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AStravelers

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Re: Use frame for negative run
« Reply #28 on: February 10, 2017, 07:38:07 AM »
all these configurations are parallel, I have to use series/parallel to get 12V, I know for a fact I am wiring them correctly as this isn't my first install, however the question remains, any problem linking the negative out to the right side terminal rather than the left side terminal
Well, duh, yes, your 6V batteries are wired in series. This has nothing to do with whether or not this is your first install or your 20th install.   However as far as the link I provided goes, it does show parallel wiring.  Don't forget when you wire your pair of 6V batteries in series you just wind up with what in reality is a single 12V battery.  Your four 6V batteries are in reality are just treated as two 12V batteries.  If you had eight 6V batteries wired in pairs to form four 12V batteries you would match the diagrams in the link provided. 

I go back to my earlier reply:  "I don't see anything wrong with the wiring.  No matter what you do you are going to have to have a jumper from one set of batteries going to the other.  To totally balance the wire lengths you would need to attach the + & - cables going to the inverter in the middle of the jumper.  If you had 4 sets of batteries I would want to make sure the cables to the inverter where in the center of entire battery pack."
« Last Edit: February 10, 2017, 07:40:43 AM by AStravelers »
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Lou Schneider

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Re: Use frame for negative run
« Reply #29 on: February 10, 2017, 11:00:16 AM »

I go back to my earlier reply:  "I don't see anything wrong with the wiring.  No matter what you do you are going to have to have a jumper from one set of batteries going to the other.  To totally balance the wire lengths you would need to attach the + & - cables going to the inverter in the middle of the jumper.  If you had 4 sets of batteries I would want to make sure the cables to the inverter where in the center of entire battery pack."

On two parallel batteries (or two series strings of 6 volt batteries connected in parallel) wiring to opposite corners, i.e. (+) on one battery, (-) on the other, will balance the wiring.

Each set of batteries will see one jumper in the current path.  No need to split the jumpers in two to connect to the middle.

 

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