Electrical Questions

[Chainplate]

First, I'm grateful to those who sent links for a wiring diagram. Second, I hope I'm not being a PITA with all my questions - I've owned my Escape 17B for all of 10 days (already covered more than 2,800 miles!) and there are so many things I'd like to know.

From examining the wiring diagrams, a couple of questions have arisen, neither of them important but still have me curious. 1. With a 10 AWG wire running from the positive post of my tow vehicle's battery to the trailer, is anyone, besides me, concerned that it would be theoretically possible for the 12VDC load to drain the battery in the tow vehicle? 2. I had read, somewhere, that the voltage for the trailer's brakes come from the trailer's battery(ies) yet, in two of the wiring diagrams I downloaded, it shows the voltage coming from the trailer's 12VDC system to the brakes going through an 'emergency brake switch'. Is there anyone who can explain that to me?

Thanks for you help and safe travels.

 

[Lanark Camper]

There is a wire in the connector between the tow vehicle to the trailer that connects the vehicle battery to the trailer battery. If the vehicle should come off the trailer battery should apply the brakes through the emergency switch.
This wire can provide some battery charging depending on the vehicle and trailer batteries. If my batteries are low I’ve seen 22 Amps going into them from my pickup truck alternator.
If the connector is not disconnected over night you will be drawing power from both the trailer and tow vehicle batteries, if your not on shore power this could cause an issue.

Bob

 

[SRS]

First, I'm grateful to those who sent links for a wiring diagram. Second, I hope I'm not being a PITA with all my questions - I've owned my Escape 17B for all of 10 days (already covered more than 2,800 miles!) and there are so many things I'd like to know.

From examining the wiring diagrams, a couple of questions have arisen, neither of them important but still have me curious. 1. With a 10 AWG wire running from the positive post of my tow vehicle's battery to the trailer, is anyone, besides me, concerned that it would be theoretically possible for the 12VDC load to drain the battery in the tow vehicle? 2. I had read, somewhere, that the voltage for the trailer's brakes come from the trailer's battery(ies) yet, in two of the wiring diagrams I downloaded, it shows the voltage coming from the trailer's 12VDC system to the brakes going through an 'emergency brake switch'. Is there anyone who can explain that to me?

Thanks for you help and safe travels.

Answering your questions would be easier if we knew more about your trailer and TV. Thing like battery type. Do you have the lithium package. Make, model, and year of your TV. My F-150's ignition doesn't supply power to the 7 pin connector when the ignition is off. I also have a DC-DC charger that controls the charge to my two lithium batteries and also disconnects charging when the TV is off. Personally, I always disconnect the trailer plug from the TV when I camp even if it's only for one night.
The 7 pin connector does supply power to the 12 volt system and the breakaway switch as well I believe. That switch is also connect to the batteries in case the trailer breaks away from the hitch ball or the hitch fails. If the safety chains don't hold, and the breakaway pin is pulled, the trailer batteries will activate the breaks.

 

[Ron in BC]

Glad that you've already started making some memories with your new trailer.

In addition to understanding your electrical system the best thing that you can do is carry a multi-meter with you. Maybe you already do. So many of the folks that post an electrical problem could have tracked it down if they carried a multi-meter.

Ron

 

[Centex]

Regarding the emergency break-away brakes

• The emergency brake switch is the small box with a 'pull-pin' and lanyard on your trailer tongue; the lanyard should be fixed to a point on your TV (Tow Vehicle) when underway
• There is no current flow through the breakaway switch unless the 'pin is pulled' (so no current flows from the vehicle battery or the trailer battery through that switch to the brakes unless you 'pull the pin')
• Only when the 'pin is pulled', the same wire that carries current from the TV to the trailer battery for charging then carries current from the trailer battery to the brakes
• When you do your occasional 'test' of the breakaway brakes you should not be plugged-in to your TV (you want to ensure that the trailer battery-to-brakes circuit is working)

In 'normal' (non-breakaway condition) operation your trailer brakes are powered from your trailer brake controller via a totally separate circuit from that used to charge the batteries.

 

[Chainplate]

Sherby-
Thanks for the quick reply. We're towing our 17B with a 2016 Kia Sorento V6 AWD and when wiring up the 7-pin connector, I connected the positive 12V wire (10 AWG) directly to the positive post on the car's battery. Our 17B came with the lithium battery package. It makes sense to disconnect the 7-pin connector when camping - I should have thought of that.

Ron-
Good advice to carry a multimeter - I didn't on this trip but I have several and will plan on keeping one in the trailer. I did have a 12V test light but didn't need it.

Safe travels all.

 

[CharlesinGA]

Only when the 'pin is pulled', the same wire that carries current from the TV to the trailer battery for charging then carries current from the trailer battery to the brakes

I'm quite sure you know how it works, but the description does not do it justice. The 7 way's battery + is connected to the battery, how much wiring is involved on an Escape I don't know. The break away switch gets its power directly from the battery (at least it is supposed to) and connects to the trailer's brake wires (blue) at the junction box, probably where the 7 way umbilical connects to the trailer's + wiring to the brakes.

Charles

 

[alanmalk]

Sherby-
Thanks for the quick reply. We're towing our 17B with a 2016 Kia Sorento V6 AWD and when wiring up the 7-pin connector, I connected the positive 12V wire (10 AWG) directly to the positive post on the car's battery. Our 17B came with the lithium battery package. It makes sense to disconnect the 7-pin connector when camping - I should have thought of that.

Ron-
Good advice to carry a multimeter - I didn't on this trip but I have several and will plan on keeping one in the trailer. I did have a 12V test light but didn't need it.

Safe travels all.

In your case a disconnect is a good idea whenever possible since you have a lithium battery directly connected to a lead-acid car battery. But for those who didn't do their own wiring, in many cases there is a ignition switch relay that breaks the connection between the two, thus isolating the batteries while the car is not running. In that case leaving the 7-pin connector in place is not a problem.

For anyone who wants proof-positive: Temporarily disconnect your trailer battery, plug in the 7-pin connector. Can you turn on the trailer lights? Start the car - can you turn on lights (or anything 12V)? That should answer that question.

 

[sameo416]

First, I'm grateful to those who sent links for a wiring diagram. Second, I hope I'm not being a PITA with all my questions - I've owned my Escape 17B for all of 10 days (already covered more than 2,800 miles!) and there are so many things I'd like to know.

From examining the wiring diagrams, a couple of questions have arisen, neither of them important but still have me curious. 1. With a 10 AWG wire running from the positive post of my tow vehicle's battery to the trailer, is anyone, besides me, concerned that it would be theoretically possible for the 12VDC load to drain the battery in the tow vehicle? 2. I had read, somewhere, that the voltage for the trailer's brakes come from the trailer's battery(ies) yet, in two of the wiring diagrams I downloaded, it shows the voltage coming from the trailer's 12VDC system to the brakes going through an 'emergency brake switch'. Is there anyone who can explain that to me?

Thanks for you help and safe travels.

Starting in about the year we got our 5.0 (2021) Escape installed a DC/DC converter between the TV and the trailer for the lithium battery option. One of the reasons was to remove the possibility of the lithium draining the TV battery.

 

[vermilye]

Actually, it is more likely that the vehicle battery will drain the trailer lithium. The lithium floats at a higher voltage than the vehicle battery. The DC to DC converter is a one way device, ie current will not go from the trailer to the tow.

Of course, if you have a tow vehicle that disconnects the trailer charge line or yo uunplug when stopped, it will do the same thing.

 

[sameo416]

Actually, it is more likely that the vehicle battery will drain the trailer lithium. The lithium floats at a higher voltage than the vehicle battery. The DC to DC converter is a one way device, ie current will not go from the trailer to the tow.

Of course, if you have a tow vehicle that disconnects the trailer charge line or yo uunplug when stopped, it will do the same thing.

There's a number of safety & longevity issues created by direct connection of lead acid to lithium batteries, direct meaning without some form of decoupling. In the case of a TV without a cut-out switch, or a direct connection to the battery, directly connecting the TV DC network to the trailer is not something that should be considered. (overloading a variable-output alternator, the high charge currents possible with lithium, the existing ampacity of TV wiring, and the need to voltage adjust)

You can do interconnection of different battery chemistries, but it needs to be designed carefully to anticipate all the different characteristics of each type.

A 200 Ah lithium set up would not likely be drained by a 50 Ah TV lead acid.

The primary reason for the DC/DC converter is to provide that decoupling (or isolation) between the two DC networks, and additionally to condition the TV output for lithium charging.

 

[Perry Butler]

Might want to read: Can different type and age RV batteries be mixed? Can I add a lithium battery?

This was written in last weekend's RV Travel newsletter.

Food for thought,

Perry

 

[MVA]

Converting from lead-acid to LiFePO4 battery in your trailer requires a number of critical considerations in the engineering design. Unfortunately some Li battery marketers market their product as a "drop in replacement". While that may be a factual statement on the battery physical size, it is less than accurate in function. The Li open circuit voltage is about a volt higher, the charging and discharging curves are significantly different, resulting in a significantly much higher LiFePO4 charging current than Pb-acid. That in turn requires larger wiring gauges, different switches, review of charging devices (AC-DC converter, solar, etc). The trailer loads (lights, appliances, etc.) need to be reviewed to ensure they will function correctly. As Perry pointed out, backfeeding to the TV needs to be considered (impacts to the TV charging circuits and alternator). Unfortunately it is not as simple as the marketers claim.

 

[alanmalk]

Unfortunately it is not as simple as the marketers claim.

To add to the above list of considerations: LiFePO4 chemistry requires some careful attention to winter charging, discharging and storage.

That said, I just placed an order for 600 AH worth of brand-X, eBay specials (LiFePO4). Couldn't pass up "cheap". Intending these to power my compressor fridge for a week or so in cloudy weather.

So, in preparation, I have added a few more layers of "bubble wrap" (aka Reflectix) to the outside-facing walls of the battery compartment under the bench seat, which should help keep that area closer in temperature to the living space. I also boosted the output of the GoPower solar charge controller a bit with a couple of (switched) diodes between it and ground. And finally, at a date TBD, will add a boost-buck voltage stabilizer to the Maxxfan wiring to protect it from the higher charging voltage.

 

[Centex]

I also boosted the output of the GoPower solar charge controller a bit with a couple of (switched) diodes between it and ground.

Curious to learn what that involves and how it boosts charge controller output?

 

[John in Santa Cruz]

...

That said, I just placed an order for 600 AH worth of brand-X, eBay specials (LiFePO4). Couldn't pass up "cheap". Intending these to power my compressor fridge for a week or so in cloudy weather.

...

FWIW, I have 2 x 206AH LFP batteries, and have no problem running a Norcold N2175, aslong with LED lighting, ventilation fan, heater fan, and the water pump, for a week without any sun.

 

[alanmalk]

Curious to learn what that involves and how it boosts charge controller output?

Are you really sure you want to know?
Ok, I warned you...

My GoPower (2015 vintage) solar controller has 4 wire connections. Plus IN (solar panel), Plus OUT (to battery), and two GROUND (-) connections. All for roughly the same 10 Ga wire. It is the GROUND (-) connections that are interesting.

I started by verifying that the (-)s are electrically connected (0 Ohms between each other). Then I verified that they carried almost no current (a hundred MA, more or less), even when the solar was supplying 10 A. Conclusion 'A', the (-) connectors didn't need two wires. Conclusion 'B', the heavy wires could be replaced by a single light wire. And Conclusion 'C': If the now single (-) connector could be raised above battery ground (therefore, no longer correctly 'ground'), then the regulated output voltage would be raised by the same amount.

So, now bring in the diode(s). The traditional diode (not a 'lossless' diode) has a fairly well known and stable voltage drop depending on the diode chemistry. 0.7 Volts is the most common silicone diode voltage drop, and 0.4 Volts for Schottky diodes. With 2 or 3 diodes (actually have to admit I don't remember the exact combination I used), and a few switches, I can select a voltage drop from 0.4 to about 1.2. Finally, insert this selectable voltage drop in series between the GoPower and real battery ground. Voila, an adjustable GoPower solar voltage regulator, with output voltages in the proper range for LiFePO4 changing. (Actually, more correctly, 'Final Balancing'). Most of the charging could take place at the traditional 13.8 Volts but for safety and long life it is best to supply the recommended 14.4-14.6 Volts on occasion.

In the real world: 1, I used the batteries for a couple of years before getting around to making this modification, and left them in the trailer during a couple of Denver winters close to -20F (but that's another story.). And 2, I try to remember to turn off all 12V appliances and fixtures when solar charging at 14.4 so as not to burn out any electronics that are sensitive to over-voltage (are you listening Maxxfan?). Finally, you ask, why on earth did I do this? One word - diodes are cheaper than newer GoPower or MPPT regulators. (Sorry, more words than intended. "Cheapskate".)

 

[alanmalk]

FWIW, I have 2 x 206AH LFP batteries, and have no problem running a Norcold N2175, aslong with LED lighting, ventilation fan, heater fan, and the water pump, for a week without any sun.

Noted! But also noted that LiFePO4 batteries are getting cheaper, lighter and smaller, with almost all now coming equipped with a cold temperature charging shut-down BMS. So, why not go bigger and cheaper? Ouch, this cheap business is costing me a bundle of $$. And Oh-So-Tempting to get a bigger inverter that will run the AC... No self-control is at odds with cheap!

 

[John in Santa Cruz]

the + and - wire from the solar panel are both carrying the solar panel current. and the + and - wires to the battery are both carrying the battery charge current, so I don't understand your statement about minimal current at the 'ground' (negative side)

 

[Centex]

Are you really sure you want to know?
Ok, I warned you...

Yep, I asked for it, and I do appreciate you taking the time and effort to respond in detail.

Another learning experience for me (always enjoy that) with the highlight being that this seems particular to your PWM controller installation and is unlikely applicable as a 'trick' to boost output for we with later MPPT controllers.

But again, I do appreciate the learning experience you've provided and have great respect for your skills, knowledge, and innovation!

Best regards, Good Sir!