2019 F-150 7 pin charging potential - Fiberglass RV
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Old 10-23-2019, 09:10 PM   #1
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2019 F-150 7 pin charging potential

In another thread I asked about driving in the cold. A lot of issues were brought up and the one about how much your truck will charge the RV battery caught my attention. I decided a little experiment would be interesting.

I disconnected my RV from shore power and hooked up a multimeter to the battery. I had 12.7 volts. I then turned on all of my lights , radio, 2 fans the furnace, and left them on. I also put an amp meter on my ground cable and saw a draw of about 7 amps. When the voltage was down to about 12.0 I connected the 7 pin connector to the truck......and nothing happened.

What is going on? My brand new truck is broke? I had no power at the socket. I won't bore you with the details but after jumping to conclusions and running in circles I found out the truck is too smart for its own good. It seems the truck will not apply power to the B+ terminal until the truck is running, the plug is connected, and the brakes have been applied.

So after all of that I brought the motor up to 2000 rpm and checked on my gauges. The voltage was up to 13.25 and I was at +5 amps. The truck was putting 12 amps into the RV and as the voltage came up the amps dropped to just above zero. The truck has a 25 amp fuse in that line so I am quite confidant it could supply 20 amps or so to the RV battery. I don't have a reliable loading device so I couldn't do a real proper test on the circuit.

I would guess that any late model ford "2015 up ?" with a tow package would be like this.
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Old 10-23-2019, 10:01 PM   #2
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F150 Charge line ……

Is not much of a charge line. It is a regulated voltage; I have a 2016 and the solar panel and the converter both charge to a higher voltage than the truck. Normally that’s OK, but if you are parked for a few days with rain, it’s nice to start with a full charge. I asked the dealer to set it higher, but it is not independent from the main battery.
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Old 10-24-2019, 10:51 AM   #3
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I have a fused 10 gauge wire from my battery to he connector. I've done this for over thirty years on assorted vehicles. I've never had a problem. You need to have both batteries in good condition.
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Old 10-24-2019, 11:38 AM   #4
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Low voltage

Large wire is important, but on my f150 the voltage is a regulated operating voltage, not a charging voltage. I need more than 13.2 volts. I'd like to see 13.9 - 14.0 to charge my two large 6 volt batteries. Then when I park for the night the batteries will measure about 13.6 ,common for the auto industry, to start and still be above 12 vdc at the end of 3 days.
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Old 10-24-2019, 01:36 PM   #5
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The ability to charge is only as good as its weakest link. In most older vehicles, the limiting factor is wire gauge, bad grounding or a bad connection.

I guess on newer vehicles you get to deal with more complicated problems...
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Old 10-24-2019, 05:09 PM   #6
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I had a 2015 F150 tow vehicle and now a 2019 F150 tow vehicle and I can tell you with confidence - the charge wire is way too small. After 2 hours with the fridge on DC the dash light said the trailer was disconnected. This means the trailer battery was dead. I stopped and sure enough it was dead. I turned the fridge off and drove for a few miles and the warning light on the dash went away. Scary thing is - there is NO trailer brakes if the house battery is dead. The truck is NOT up to the challenge of running the fridge while towing even with a fully charged house battery to start out with.
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Old 10-24-2019, 05:14 PM   #7
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Brake voltage.

"Scary thing is - there is NO trailer brakes if the house battery is dead."
On mine the brakes have all been power from the tow vehicle. The break away (if there is one) still needs the house battery.
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Old 10-24-2019, 05:50 PM   #8
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Originally Posted by bsedwebt View Post
...Scary thing is - there is NO trailer brakes if the house battery is dead. ....
If this is correct (and I have my doubts that it is), then your rig is not wired properly.

Agree that the house battery is likely needed to use the brakes via a break-away switch, but in normal operation the tow vehicle supplies all the power to the brakes and a house battery is not needed or used at all.

So if you think your statement is correct, please have a shop look at it.
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Old 10-24-2019, 07:00 PM   #9
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You're definitely not going to get 20A without wire upgrades. Assuming 20 feet of 14AWG wire (pretty common for trailer power wire) between the alternator and the trailer's battery, you'll see a voltage drop from 14.1V to 12.58V at 15A. Realistically it's probably going to spend a lot of time in float at more like 13.6V. 10AWG all the way through might be enough to get closer to 20A, though.

I'm honestly surprised you were even able to get 12A through it. I guess it helps that the battery was all the way down to 12.0V.
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Old 10-25-2019, 04:26 AM   #10
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Quote:
Originally Posted by AC0GV View Post
"Scary thing is - there is NO trailer brakes if the house battery is dead."
On mine the brakes have all been power from the tow vehicle. The break away (if there is one) still needs the house battery.
Quote:
Originally Posted by gordon2 View Post
If this is correct (and I have my doubts that it is), then your rig is not wired properly.

Agree that the house battery is likely needed to use the brakes via a break-away switch, but in normal operation the tow vehicle supplies all the power to the brakes and a house battery is not needed or used at all.

So if you think your statement is correct, please have a shop look at it.
I believe Bryan knows that and simply failed to include the term “break-Away” in his post. One would have to be a complete towing novice (or real dummy) not to know that the tow vehicle provides the power and therefore the control to the trailer brakes as to when to activate. It would seem obvious that “break-away” implies that connection between the tow vehicle and the trailer, both mechanical (hitch) and electrical (umbilical cord). I am not trying to be accusatory here, but I rarely post on the forum anymore. Participation ceases to be enjoyable when there are those who will “jump” on someone’s post due to the lack of all-encompassing details. In some cases, it is meant to be helpful; in others it is purely snarky. I DO NOT believe either of the responders I quote above had snarky intentions. But I do believe that in some cases, it may come across that way to the person who is the object of the response. My favorite example is when someone posts a question about a non-functioning (hot) water heater and invariably some clown responds by saying “why would you want to heat hot water?” It’s not helpful; it’s simply sarcastic and petty. When an appliance isn’t working, the owner is focused on getting it to work, not on semantics involving the nomenclature of the item. Come on people, give others a break. Don’t assume they “need to be educated” simply because they left out a few words in a post.
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Old 10-25-2019, 05:35 AM   #11
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From what I’ve been told and read , the Ford F 150 is so advanced that when you put the vehicle in tow / haul mode the charge voltage is increased
So when you measure the charge voltage is your truck in tow/haul ?
Maybe Floyd will chime in , he is the resident Ford Guru
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Old 10-25-2019, 06:48 AM   #12
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Every vehicle with an alternator and regulator (that would be 100%) would automatically increase the output current to regulate the voltage at the point that is controlled.
Some are at the alternator some at the fused buss, some at the battery, depending on the design of the vehicle.
The f
Ford may increase this voltage, but today many systems have the same type of battery conditioning as the multistage chargers we use in our RV.
The draw from the trailer through the wire from the plug (including the voltage drop, if any, in the ground circuit, pulls down that buss voltage and the regulator automatically increases the current to compensate.
Basically no matter what the size of the charge wiring and it's voltage drop determines the percentage of the alternator charge that goes to the trailer. Well that and the current demand from the TV as well.
If you want to be able to charge the battery with the same precision at the trailer battery then an inverter step up voltage and built in charge controller would be best. The step up inverter gives the voltage increase the charger needs to be able to charge completely.
The current from the TV would be higher while the voltage would be lower due to the drop. The power transferred would be higher at that lower voltage.
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Old 10-25-2019, 08:20 AM   #13
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I often feel the same way, Carl, and try to post less because of it. But then I remember that it's life. There are all sorts of people, and spending my time trying to avoid them isn't really the best strategy. Especially when I remember that I'm the problem sometimes as often as they are...

I agree that the things people are willing to call you out on online, they would never (at least most of them, I hope) do in a face to face conversation. It's just easy to pick apart what people say in writing. In person, they'd never get far in a conversation before the other person walked away.

Back on topic...
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Old 10-25-2019, 08:24 AM   #14
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Originally Posted by CPW View Post
I believe Bryan knows that and simply failed to include the term “break-Away” in his post. One would have to be a complete towing novice (or real dummy) ... Come on people, give others a break. Don’t assume they “need to be educated” simply because they left out a few words in a post.
Neither should you assume that the someone simply left out a few words, because you know what happens when you ASSuMEe.

You can believe what you want, but it is what he wrote therefore you really should not automatically assume that he meant something else, especially when we are talking about such a majorly important item of safety... properly wired brakes.

Even if it is unlikely that the regular brakes would fail if the house battery is dead, any suggestion of miswired brakes is too important to ignore.

We are not talking about why you would heat hot water, which is amusing if you have a sense of humor, but a very important item that can save lives.

To Bryan... As I said, I doubt that your statement about the house battery being needed for the trailer brakes is what you meant, and I am sure you understand why this was important to double check with you. Safety first.
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Old 10-25-2019, 12:20 PM   #15
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Neither should you assume that the someone simply left out a few words, because you know what happens when you ASSuMEe.

You can believe what you want, but it is what he wrote therefore you really should not automatically assume that he meant something else, especially when we are talking about such a majorly important item of safety... properly wired brakes.

Even if it is unlikely that the regular brakes would fail if the house battery is dead, any suggestion of miswired brakes is too important to ignore.

We are not talking about why you would heat hot water, which is amusing if you have a sense of humor, but a very important item that can save lives.

To Bryan... As I said, I doubt that your statement about the house battery being needed for the trailer brakes is what you meant, and I am sure you understand why this was important to double check with you. Safety first.
If Bryan could chime in as to what he meant, AND if he meant it as you interpreted his post, I might agree with you. However, before I judiciously decided to participate less, I had far too many know-it-alls try to showcase how “brilliant” they were because I failed to “write a book” rather than a sentence or two to state the obvious. And if you have been following this forum for any time then you already know who most of these individuals are (though it is only a handful of the total and you ARE DEFINITELY NOT one of them. I once jokingly suggested to one member of the site team that we should be able “to vote certain individuals off the island.” He told me he shared my comment with the whole team and they all got a good laugh out of it. Of course, those who choose to be outright jerks cannot be restricted simply for being abrasive. And if someone wants to point out that I am assuming that Bryan was referring to a breakaway situation and that his brakes function the same as the rest of ours do, it is because that is how all currently manufactured trailers are wired. Oops, I guess I had better say that is how all currently manufactured trailers WITH ELECTRIC BRAKES work less someone take me to task for omitting the minutiae. Should you wish to stress safety, I would say that the statement that he towed with a discharged battery thereby compromising the function of the breakaway system is more of a safety issue than if he thinks the house battery provides power to the brakes 100% of the time.
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Old 10-25-2019, 01:45 PM   #16
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If Bryan could chime in as to what he meant, AND if he meant it as you interpreted his post,
Not to belabor this point but I did not interpret his post, I simple read what he wrote. You interpreted his post as meaning something different from what he wrote, by adding something about a break-away switch being involved, which was not mentioned.

Quote:
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... I am assuming that Bryan was referring to a breakaway situation and that his brakes function the same as the rest of ours do, it is because that is ... how all currently manufactured trailers WITH ELECTRIC BRAKES work...
But I have to wonder about this comment he made...

Quote:
Originally Posted by bsedwebt View Post
I had a 2015 F150 tow vehicle and now a 2019 F150 tow vehicle ... After 2 hours with the fridge on DC the dash light said the trailer was disconnected. This means the trailer battery was dead....
Is that how the F-150's work now? That the tug thinks there is no trailer if the trailer's battery is dead? I rather doubt it but perhaps the truck is smart enough to know that a break-away battery is in use but it is dead, and to let you know that. But how would it even know there is a break-away switch on the trailer... many do not have a break-away switch at all.

On my vehicle with a P3 controller the controller does not tell me the trailer is disconnected just because the house battery is dead, not present or even if there is no break-away switch or battery for one at all.

I would like to know more about how the F-150 works and until I do, I have to suspect just a little that this dash light, when the trailer was in fact connected, might indicate a wiring problem. Perhaps an intermittent one, like a faulty ground.
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Old 10-25-2019, 02:05 PM   #17
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Not to belabor this point but I did not interpret his post, I simple read what he wrote. You interpreted his post as meaning something different from what he wrote, by adding something about a break-away switch being involved, which was not mentioned.



But I have to wonder about this comment he made...



Is that how the F-150's work now? That the tug thinks there is no trailer if the trailer's battery is dead? I rather doubt it but perhaps the truck is smart enough to know that a break-away battery is in use but it is dead. and to let you know that. But how would it even know there is a break-away switch on the trailer... many do not have a break-away switch at all.

On my vehicle with a P3 controller the controller does not tell me the trailer is disconnected just because the house battery is dead, not present or even if there is no break-away switch or battery for one at all.

I would like to know more about how the F-150 works and until I do, I have to suspect just a little that this dash light when the trailer was in fact connected might indicate a wiring problem. Perhaps an intermittent one, like a faulty ground.
On my vehicle , when I first plug in my trailer I get a warning telling me that my trailer is connected to my vehicle and to set the brake controller .
If the trailer becomes disconnected whether intentionally or unintentionally I get a warning signal on my dash . Your theory about a poor connection being the cause may well be correct .
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Old 10-25-2019, 02:24 PM   #18
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Originally Posted by gordon2 View Post
Not to belabor this point but I did not interpret his post, I simple read what he wrote. You interpreted his post as meaning something different from what he wrote, by adding something about a break-away switch being involved, which was not mentioned.



But I have to wonder about this comment he made...



Is that how the F-150's work now? That the tug thinks there is no trailer if the trailer's battery is dead? I rather doubt it but perhaps the truck is smart enough to know that a break-away battery is in use but it is dead, and to let you know that. But how would it even know there is a break-away switch on the trailer... many do not have a break-away switch at all.

On my vehicle with a P3 controller the controller does not tell me the trailer is disconnected just because the house battery is dead, not present or even if there is no break-away switch or battery for one at all.

I would like to know more about how the F-150 works and until I do, I have to suspect just a little that this dash light, when the trailer was in fact connected, might indicate a wiring problem. Perhaps an intermittent one, like a faulty ground.

From my experience with a 2018 F150 Off Road, the answer is no.


I have a 9 amp DC to DC converter between the truck & the trailer battery. It acts like a diode or one way connection. My truck still knows the trailer is back there.

My reason for adding it (other than to raise the charging voltage) is to prevent the truck's AGM battery from draining the fully charged lithium batteries once the truck's electronics decide its battery is fully charged & drops to float voltage. "Full" with the lithium batteries is anywhere from 14.4 - 13.6 volts, well above the truck's float voltage.
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Old 10-25-2019, 02:45 PM   #19
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As far as the P3 is concerned the ONLY thing that the controller knows is that there is a trailer brake connected.
That is the only signal that the controller "sees"
As far as the Ford it may be looking at the light circuits on the trailer like my Touareg VW.
The Touareg detects the trailer (without knowing about the brakes) by the light loads and will report a bad light. When the trailer is connected the car knows enough to not to open the hatch except manually lifting. (That is something I plan to override in the programming, by the way).
Neither the brake controller nor the CPU in the truck can know anything about the breakaway switch as it is not in the circuit unless the plug is pulled putting the 12 volts directly on the brake lines.
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Old 10-25-2019, 03:21 PM   #20
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As far ....As far as the Ford it may be looking at the light circuits on the trailer like my Touareg VW....
Thats exactly what I Thought. A "trailer disconnected" indicator probably indicates some sort of a disconnection, rather than a dead trailer battery.

BTW, The hatch lockout is interesting.. darn cars getting too smart for us.
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