Auxiliary Power plug

[Yosemite Sam]

I have a 2017 Expedition EL. I wanted to use the right, rear auxiliary power plug (cigarette plug) to keep a floating charge across the battery. After connecting the float charger (13.2 VDC) to the plug I was only seeing a 12.5 VDC reading at the battery post.
My question is: why am I seeing a .7 VDC drop from the rear auxiliary power plug to the vehicle's battery post? It's almost as if it's going through a silicon diode before reaching the battery post but that doesn't make any sense because it shows a normal output voltage when measured at the plug!
Does anybody have a wiring diagram of the auxiliary plugs that would show the full physical route of the auxiliary plug?

 

[ChrisRCNY]

Depending on how long and what gauge the wires are, it might show that much while charging. It shouldn't be that much with a 1-2amp float charger, though.

Large battery banks get chargers that have separate voltage sense lines to allow the charger to compensate for losses.

 

[Yosemite Sam]

I'm using a lab quality, 50amp, low ripple power supply set at exactly 13.200 VDC. After being connected to the auxiliary power plug
for over 24 hours and indicating 0.121 amps current draw, the battery is showing 12.5 VDC.
As far as the wire gauge goes, according to the fuse that is on that line, it is rated for 20 amps which is moot at this point
since the indicated current draw is only 0.121 amps.
SOMETHING has got to be inline with the wire that feeds the auxiliary power plug and according to my feeble mind it must be a
semi-conductor which would account for the .7 VDC voltage drop.
I'm thinking the only viable way to determine what is going on with this is locate a wiring diagram of the circuit and I really hate to
spend the $$$'s for a shop manual...

 

[Yupster Dog]

I really hate to
spend the $$$'s for a shop manual...

You can learn how DC power works for free online. Or buy the manual, either way it is not going to work the way you are trying. You need to run way bigger gauge wires than are on that outlet to even attempt charging from that far away.
your alternator is right by your battery and look at the gauge of that wire. and you trying to do it from 4 to 5 times the distance with 12 -14 gauge.

There are supplemental power upgrades you can do. In fact there are threads on here about it.
Maybe if you tell the reason you are trying this someone could help you achieve your goal.

 

[Yosemite Sam]

The reason I want to do it this way is it SHOULD be simple if the auxiliary plug wire ran directly to the fuse block and thence to the battery! Apparently this is not the case but I'd like to know why; because "enquiring" minds want to know!

As far as the wire gauge goes and your expert opinion on DC power; I think I'll pass on your advice. I realize that over 50 years of education in the electronics field doesn't qualify me as an expert so I'll reserve my opinion regarding your advice on DC power education. But thanks anyway.

Just for your edification; I'm not trying to START the vehicle from the auxiliary power port, I only want to float a low current charge on it. Over TIME (rate) I could charge a car battery using very small gauge wire over long distances. The key is the RATE at which one wishes to do the charge. The reason the wire is large, running from the alternator to the battery is because it does TWO things: It has to re-charge the battery after a very high current discharge (starting the vehicle) and two, it must also supply a fairly high current to all the items in the vehicle at the same time, in which case the wire that supports those activities must be of a fairly large gauge (small gauge NUMBER).

Now, as far as your reply goes; it neither answered my questions nor contributed to an intelligent suggestion as to where I might ascertain same. I'm not quite sure why you started up being so confrontational but quite frankly I don't care. You are not my mother and I don't find it necessary to explain to you why I want to do this (or anything). I simply asked if anybody knew how that circuit was designed to function OR if anybody knew where I might locate a wiring diagram of said circuit. You provided neither.

 

[07navi]

The reason I want to do it this way is it SHOULD be simple if the auxiliary plug wire ran directly to the fuse block and thence to the battery! Apparently this is not the case but I'd like to know why; because "enquiring" minds want to know!

As far as the wire gauge goes and your expert opinion on DC power; I think I'll pass on your advice. I realize that over 50 years of education in the electronics field doesn't qualify me as an expert so I'll reserve my opinion regarding your advice on DC power education. But thanks anyway.

Just for your edification; I'm not trying to START the vehicle from the auxiliary power port, I only want to float a low current charge on it. Over TIME (rate) I could charge a car battery using very small gauge wire over long distances. The key is the RATE at which one wishes to do the charge. The reason the wire is large, running from the alternator to the battery is because it does TWO things: It has to re-charge the battery after a very high current discharge (starting the vehicle) and two, it must also supply a fairly high current to all the items in the vehicle at the same time, in which case the wire that supports those activities must be of a fairly large gauge (small gauge NUMBER).

Now, as far as your reply goes; it neither answered my questions nor contributed to an intelligent suggestion as to where I might ascertain same. I'm not quite sure why you started up being so confrontational but quite frankly I don't care. You are not my mother and I don't find it necessary to explain to you why I want to do this (or anything). I simply asked if anybody knew how that circuit was designed to function OR if anybody knew where I might locate a wiring diagram of said circuit. You provided neither.

Yuppie just wanted to zero in on exactly what you were doing to better help you and he did direct you to other threads to further assist you.

 

[Yupster Dog]

Now, as far as your reply goes; .

I am sorry you thought I was acting like your mother
Your mother did a excellent job. And I am sure she is proud of you. So no need for me to but in

It is super easy to run wiring (Especially the bigger gauge wires not the low gauge big ones) to the front of the vehicle. Probably not as fun as belittling people who are dumb (in your mind) but it will get the job done.

Now that I have ascertained where you are coming from, good luck with getting what you need and on your endeavor.

Had to look up a smart word to end with so you will think I am smart, and maybe you mother can be pruod of me too.

 

[Yupster Dog]

Yuppie just wanted to zero in on exactly what you were doing to better help you and he did direct you to other threads to further assist you.

I am touched that you would take up for me. Your like the big brother I never wanted.

Don't think this changes anything I will still be nipping at your hack comments tomorrow.

 

[Plati]

I cut a section from my 2003 wiring diagram (below) ... looks like power goes only through fuse to the the aux power point shown in this section (cigar lighter). Of course each physical connection will have an associated voltage drop as will each inch of conductor. That voltage drop in the conductor (wires) is a function of current - wire size - distance. There will be some voltage drop at each end of battery power connection to fuse, each end of fuse, each terminal, every connection along the way to final destination. Every place a wire is crimped to a terminal. But Yosemite Sam knew that so that comment is for anyone else who happens to read this.

I also was an Electrical Engineer designing ac & dc power distribution systems for minicomputers (at one point). I have no idea whats going on here mainly because I don't think I have enough information.




I know when I put my trickle charger on my Expy (directly to battery terminals) ... it doesn't instantly go to final battery voltage ... it creeps up slowly. But thats a battery charger. Not sure whats going on with that lab power supply in the OP experiment. My trickle charger does 0.7 amp.

 

[Yosemite Sam]

MrSticker..
Thank you very kindly for your reply. That's exactly what I wanted. Considering from whom I purchased this vehicle, it wouldn't surprise me to learn that there was some modification done to this leg of the 12 volt buss. There was originally an awesome electronics package installed in this vehicle.
Thanks again for the diagram. It's much appreciated.

 

[Yupster Dog]

it wouldn't surprise me to learn that there was some modification done to this leg of the 12 volt buss..

You just full of info after the fact.
And Sticker just added that connections will lower voltage and what Chris and I said (in his own words) and added a diagram of a previous generation expedition. might as well be looking at a diagram for a Tahoe.

How is that exactly what you looking for and what we said is not?

Your just grumpy. Do you need a hug? @07navi was acting nice on your thread maybe he will give you one.

 

[1970Maverick]

I have a 2017 Expedition EL. I wanted to use the right, rear auxiliary power plug (cigarette plug) to keep a floating charge across the battery. After connecting the float charger (13.2 VDC) to the plug I was only seeing a 12.5 VDC reading at the battery post.
My question is: why am I seeing a .7 VDC drop from the rear auxiliary power plug to the vehicle's battery post? It's almost as if it's going through a silicon diode before reaching the battery post but that doesn't make any sense because it shows a normal output voltage when measured at the plug!
Does anybody have a wiring diagram of the auxiliary plugs that would show the full physical route of the auxiliary plug?

Have you tried connecting the charger directly to your battery for 24 hours to see if it will charge up to 13.2 ? That would give you a clue as to whether it's a problem with the charger or something in the wiring from the aux power socket to the battery. If it works directly across the battery maybe you could wire a small 2 pole connector behind the grill.

 

[Plati]

Have you tried connecting the charger directly to your battery for 24 hours to see if it will charge up to 13.2 ? That would give you a clue as to whether it's a problem with the charger or something in the wiring from the aux power socket to the battery. If it works directly across the battery maybe you could wire a small 2 pole connector behind the grill.

Can you just simply use any old DC power supply to charge a battery anyway? I dunno, not in my wheelhouse. Me ... I would only use a battery charger since I dunno. I got an old 12V power supply I used in college to power the 67 Chevy Van 8 track player & speakers in my Dorm room. We blasted good tunes night & day. I would not use that to charge my Expy battery. Just me maybe.



MrYup. I disagree on one point. Yup it's a 2003 wiring diagram and you have to consider that the Expy in question is a later year (I think). However, some things haven't changed over the years - some have. It's info imperfect as it is but still good info. Right?

It would interesting to place a volt/ohm.meter at the rear power outlet with a long lead to the battery. This would be fun to troubleshoot. I hope we find out a final diagnosis!!

 

[Trainmaster]

I think Sticker makes the most sense. There are no electronics involved in the accessory jack circuit.

Connecting 13 volts at low amperage to a 12 volt battery isn't going to raise the battery's voltage to 13 volts instantly. Disconnect battery connector from the post, plug your charger into the rear jack and you'll see your 13 volts at the clamp.

The battery is moderating the voltage until it charges to the new value. Make sense?

Of course you can check resistance between the rear jack and the battery clamp, etc, etc.

 

[Yupster Dog]

Have you tried connecting the charger directly to your battery for 24 hours to see if it will charge up to 13.2 ? That would give you a clue as to whether it's a problem with the charger or something in the wiring from the aux power socket to the battery. If it works directly across the battery maybe you could wire a small 2 pole connector behind the grill.

Excellent idea Maverick But He won't tell what he is trying to accomplish and evidently it is some huge secret (only mother on the need to know)

@Yosemite Sam if you would say what it is you are trying to do There is no doubt in my mind someone on this forum can help. But forum members are not mind readers.

but still good info. Right?

Absolutely correct you can put up the wiring diagram from just about any vehicle on the road today and show Battery to fuse to power point. (of course I am talking about the power point that stays on after you cut the key off)

 

[ChrisRCNY]

You might try turning the supply up to 13.8, it's still a safe float voltage. I'll try hooking up my much cheaper regulated supply to the same port on my 08, see what I get.

I'm assuming you checked the voltage at the supply with the meter, just to make sure the meter agrees with the supply's measurement. Always fun to find out a $400 multimeter needs an out of warranty repair.

 

[Plati]

You might try turning the supply up to 13.8, it's still a safe float voltage. I'll try hooking up my much cheaper regulated supply to the same port on my 08, see what I get.

I'm assuming you checked the voltage at the supply with the meter, just to make sure the meter agrees with the supply's measurement. Always fun to find out a $400 multimeter needs an out of warranty repair.

How does a power supply like that determine the current to drive?
If it's a 50 amp power supply, will it try to drive 50 amps at 13.8V?
or is there an inherent resistance with the battery that determines supplied current?
I don't understand that piece of it.

update: I'll study this tonight while swilling Miller beer
https://www.itacanet.org/eng/elec/battery/battery.pdf

 

[ChrisRCNY]

The chinesium supply I used when set to the closest I could get was as follows:

12.4v .15a @ supply
12.12@ battery.

13.2v .52a @ supply
12.13 @ battery

Meter was within 0.01v of the supply, supply only gives me one digit after decimal.

 

[ChrisRCNY]

When I turned the supply up to 14.3v, I got 1.45a, and 12.15v at battery. Pretty noteworthy drop in there, somewhere.

Might be worth turning your supply up to the higher end of 6 cell lead acid float voltages. There's still a ton of drop, but it'll work.

 

[PeteinGH]

Attached is a diagram from the 2014 shop manual.




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