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07-04-2016, 09:08 PM
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#1
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Junior Member
Join Date: Feb 2016
Location: Lebanon, Illinois
Trailer: 2010 Escape 19
Posts: 8
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DC Wiring Changes
Hi, all. I've done some forum searching, but haven't been able to find an exact answer for a wiring question I have.
I'm making changes to some DC wiring in my 2010 Escape 19' to accommodate an inverter and a battery monitor. The current DC wiring appears to have all negative-side connections from the battery and DC circuits going to chassis ground. In order for my battery monitor to work accurately, I have to run all DC loads (I'm using the negative side for this) to the load side of the shunt and then run the battery side of the shunt to the negative battery terminal.
Right now the negative battery cable is attached to a metal junction box and that box is grounded to the chassis. The negative-side DC wires all connect to a hub post on the back of the distribution panel along with a cable that grounds to the chassis.
My question is this: Can I effectively take the chassis ground cable from the hub post on the distribution panel and connect it to the load side of the shunt, and disconnect the negative battery cable from the junction box and connect it to the battery side of the shunt? This should theoretically satisfy the needs of my battery monitor, but then all of the DC circuits would terminate at the battery negative post and not chassis ground. I have read that low voltage DC circuits don't necessarily need to be "grounded." I'm not sure, however, if I would then need to run a grounding cable from the negative battery post to the chassis to complete the circuit for the trailer running lights (which will remain grounded to the chassis).
Any constructive input from someone with RV wiring experience will be much appreciated!
Regards.
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07-04-2016, 10:54 PM
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#2
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Senior Member
Join Date: Dec 2012
Location: Edmonton, Alberta
Trailer: 1979 Boler B1700
Posts: 14,935
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Quote:
Originally Posted by michaelt0120
Can I effectively take the chassis ground cable from the hub post on the distribution panel and connect it to the load side of the shunt, and disconnect the negative battery cable from the junction box and connect it to the battery side of the shunt? This should theoretically satisfy the needs of my battery monitor...
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This makes sense to me, and eliminates the frame connections as part of the operating circuit. I don't have any issue with putting lots of current through the frame (that's normal for motor vehicles), but the connection points to the frame can be problematic (the way they're done in a typical car is carefully designed and unlike the method used in a trailer, including an Escape).
Remember that the cable and connections from battery negative to shunt and shunt to any connection hub must take all the current delivered by the battery - with an inverter that could be very large (about 130 amps for a 1500 watt inverter at full load, plus whatever is going through other circuits). Escape usually runs separate positive and negative cables to the battery in inverter-equipped trailers.
Quote:
Originally Posted by michaelt0120
... but then all of the DC circuits would terminate at the battery negative post and not chassis ground. I have read that low voltage DC circuits don't necessarily need to be "grounded." I'm not sure, however, if I would then need to run a grounding cable from the negative battery post to the chassis to complete the circuit for the trailer running lights (which will remain grounded to the chassis).
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I would connect the battery negative to the frame... in this case the original connection as built by Escape could be used (and a new cable used for the battery-to-shunt connection).
Do the running lights really use the frame as part of their return of their circuit? I hadn't heard of that being done by Escape, and in any case the running lights are not run by the trailer's battery. Normally the only connection between running lights and other trailer wiring is sharing a "ground" wire to the tow vehicle (which does connect to the trailer frame), and while many trailers use the frame as part of the running lighting circuits, I would rather avoid that due to the issue of frame connections (not the flow of current in the frame).
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07-05-2016, 01:06 AM
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#3
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Senior Member
Join Date: Jan 2014
Location: North Van., British Columbia
Trailer: 2014 Escape 19, sold; 2019 Escape 21, Sept. 2019
Posts: 8,743
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Quote:
Originally Posted by Brian B-P
Do the running lights really use the frame as part of their return of their circuit? I hadn't heard of that being done by Escape, and in any case the running lights are not run by the trailer's battery.
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Well the brakes certainly do. No negative ground to the frame, no brakes.
I've gone on about this in previous posts and this would be a good opportunity to improve the grounding system while doing the inverter/monitor mod.
Things I'd check are the multiple ground points. Each axle has a ground to the frame as well as a couple of others up front where it goes battery to ground on the frame, then a foot away another ground connection up to converter. I tied all my grounds together with a copper buss cable.
Ron
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07-05-2016, 09:43 AM
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#4
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Senior Member
Join Date: Mar 2016
Location: Burlington Twp., New Jersey
Trailer: 2010 Escape 19
Posts: 7,126
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Quote:
Originally Posted by Brian B-P
Remember that the cable and connections from battery negative to shunt and shunt to any connection hub must take all the current delivered by the battery - with an inverter that could be very large (about 130 amps for a 1500 watt inverter at full load, plus whatever is going through other circuits). Escape usually runs separate positive and negative cables to the battery in inverter-equipped trailers.
I would connect the battery negative to the frame... in this case the original connection as built by Escape could be used (and a new cable used for the battery-to-shunt connection).
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I just got done wiring in a small battery monitor the other night on a 2010 19' so I'm very familiar with the wiring arrangement that michaelt0120 refers to. I agree that the monitor wiring could be approached in the fashion described, but there is no mention to the size of the inverter and the added load. I would presume it is of a decent size and agree with Brian B-P that the wiring of an inverter should involve wiring directly to the battery. We do not have an onboard inverter so I cannot speak to how Escape wires it. I do know that the gauge of the ground wire from the common ground post on the distribution panel to the frame was fairly small. For my install I simply intercepted the ground wire that came into the trailer junction box directly from the battery and wired my battery monitor inline, but I was not adding any load to the DC system and was ok with the current grounding arrangement (for now).
I know some users get into the very complex and expensive battery monitors, but for those out there that are looking for a simple, yet powerful device in a small package you might consider the Doc Wattson battery monitor. It gives you amps, watts, voltage, amp-hours (Ah), kilowatt-hours (Kwh) and peak amps and minimum voltage in a nice little package (only 2.8" L x 1.7" W x 0.83" D). I wired this up to measure draw from the battery but it can also be wired inline with a generation device (i.e. solar panel) to measure what is going into a battery.
www.rc-electronics-usa.com/ammeters/rv-battery-monitor.html
Picture is from install in a Scamp.
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07-05-2016, 10:07 AM
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#5
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Junior Member
Join Date: Feb 2016
Location: Lebanon, Illinois
Trailer: 2010 Escape 19
Posts: 8
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Thanks for the input so far, guys! The inverter I'm installing is a GoPower 300 watt pure sine, so it's not a huge inverter. I think the maximum draw from it is not expected to exceed 40 amps.
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