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Old 01-16-2021, 06:13 PM   #1
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2016 19' Flying Cloud
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TV drawing power from trailer

We have a 2016 19ft flying cloud and pull it with a 2019 Jeep Grand cherokee. I replaced the batteries with lithium (200amps) and added 200 watts of solar. I notice that when we drive, the battery is not charging much from the TV. Assume it's not really meant to.

Also, when Jeep is off and still plugged in to 7pin connector, I notice about 1.5-2 amps of draw on the trailer batteries. Why is Jeep drawing power from the TV batteries? Is that normal behavior? I thought power was supposed to flow to TV, not from it.

Sorry for the basic question, but still new to pulling a trailer.
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Old 01-16-2021, 07:07 PM   #2
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Originally Posted by jsmall01 View Post
We have a 2016 19ft flying cloud and pull it with a 2019 Jeep Grand cherokee. I replaced the batteries with lithium (200amps) and added 200 watts of solar. I notice that when we drive, the battery is not charging much from the TV. Assume it's not really meant to.

Also, when Jeep is off and still plugged in to 7pin connector, I notice about 1.5-2 amps of draw on the trailer batteries. Why is Jeep drawing power from the TV batteries? Is that normal behavior? I thought power was supposed to flow to TV, not from it.

Sorry for the basic question, but still new to pulling a trailer.
Yeah. That’s to be expected because lithium’s run at a higher voltage than lead acid (which is what you have in the jeep). You need to put an isolater in the line between TV and Trailer to keep this from happening.

Others may be able to recommend a specific product. I’m just starting to investigate the whole lithium upgrade thing.
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Old 01-16-2021, 07:52 PM   #3
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Originally Posted by jsmall01 View Post
We have a 2016 19ft flying cloud and pull it with a 2019 Jeep Grand cherokee. I replaced the batteries with lithium (200amps) and added 200 watts of solar. I notice that when we drive, the battery is not charging much from the TV. Assume it's not really meant to.

Also, when Jeep is off and still plugged in to 7pin connector, I notice about 1.5-2 amps of draw on the trailer batteries. Why is Jeep drawing power from the TV batteries? Is that normal behavior? I thought power was supposed to flow to TV, not from it.

Sorry for the basic question, but still new to pulling a trailer.
I've been doing the research on moving my '88 to lithium. The way I understand the 7 pin effectively puts all your batteries (including the one in your jeep) into a parallel configuration. You're batteries are trying to level themselves out. From my reading you'll need one of these: https://www.renogy.com/12v-dc-to-dc-...ttery-charger/
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Old 01-16-2021, 08:10 PM   #4
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I don't really need my truck to charge the trailer batteries, since the solar handles that fine, so I just pulled the fuse from the truck for the battery charge line.
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Old 01-17-2021, 12:38 AM   #5
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I wonder if the Jeep has a separate fuse for sending charger power to the 7pin. wiring a DC to DC charger in the Jeep in really not an option. I'm not going to do any mods that could void the Jeep warranty.
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Old 01-17-2021, 10:23 AM   #6
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I'm sure that your Jeep does have a fuse for the charging circuit. If you have no need/desire to have it charging as you drive, just pull the fuse. Hopefully, this won't set off any alerts in the car's computer. It shouldn't affect brakes, lights, etc. The other option would be to unplug the 7 pin when you stop for prolonged periods.

On some vehicles, our Ford Truck, the charging circuit turns off when the truck turns off. I understand that not all vehicles work this way. I guess there are differing opinions regarding the wisdom of that feature. I think it's a good thing.

There would also be a way to mount a solenoid somewhere that disconnects the circuit when you turn off the ignition. That would require access to a circuit that is hot only when the Jeep is running and might be of concern to you regarding warranty. This would do pretty much the same thing our Ford does automatically.

I would go with the unplug option.
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Old 01-17-2021, 10:28 AM   #7
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Originally Posted by jsmall01 View Post
I wonder if the Jeep has a separate fuse for sending charger power to the 7pin. wiring a DC to DC charger in the Jeep in really not an option. I'm not going to do any mods that could void the Jeep warranty.
Why not mount the dc/dc converter in the trailer? As long as it’s in the circuit between the trailer lithiums and the Jeep +12VDC it should work. Then the trailer is set up (electrically) for whatever tow vehicle you use.
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Old 01-17-2021, 11:01 AM   #8
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Hi

First off, this *is* a problem you need to solve one way or the other.

The simple / quick / zero cost solution is to go to the DC distribution block in the front of the trailer and disconnect the "charge wire" that comes in from the 7 pin connector. You no longer have a connection between TV and trailer ... problem solved. Works no matter what TV you might need to hook up to.

A more involved solution is to stick a DC/DC converter in the line. Victron makes a range of them that are rated for battery charging. Something in the 5 to 10 A range is what you are after.

https://shop.pkys.com/Victron-Energy...er_p_6996.html

is one solution. Set its output to 13.6V and wire it in.

Bob
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Old 01-17-2021, 04:09 PM   #9
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Correct on all of the above. An inexpensive Victron 12A dc-dc charger was my choice. I then added a Renogy 40A dc-dc charger tied to TV alternator w/ 2g wire. Get 40A charging while driving. Between that and 400w solar our 300Ahr lithium are almost always fully charged. Only used small gen occasionally.
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Old 01-17-2021, 08:30 PM   #10
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thanks all. very helpful.

so just to be clear, I can add a dc to dc charger in the AS and not do any mods to the Jeep TV?

I thought the wiring from the alternator is too small to handle the load. again, I'm not going to do any mods to the Jeep given that would void warranty.
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Old 01-17-2021, 10:05 PM   #11
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TV drawing power from trailer

If you just install a Victron 9 amp dc/dc charger in your Airstream the stock wiring should be adequate and this will allow you to provide the correct voltage to charge the lithium batteries.



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Old 01-17-2021, 11:42 PM   #12
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I apologize in advance for the dumb question but what will installing a dc to dc charger like the victron 9amp actually do for my situation?

will this prevent the TV from drawing power from my AS batteries? will it provide more power from the TV for charging the AS batteries?

I'm just really confused about DC to DC chargers and their purpose. again sorry for the ignorance here..
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Old 01-18-2021, 05:49 AM   #13
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Dc-dc charger

Two responses to your questions.
1. A dc-dc charger does two things for you; it does prevent current from flowing “backwards” to the TV (due to the higher voltage of the trailer’s lithium’s higher voltage) and it will also limit the current flowing from the TV when driving and connected (which serves to protect all components in that system).

2. If there is “back flow” protection built into your Jeep, it isn’t the fuse, it’s in another device called a relay. A relay is a switch that turns on when Jeep is running, and off when it isn’t. A study of the wiring diagram of your Jeep in your owners manual will show you. Find the trailer charging circuit in the diagram. If a relay exists, it will show it, and show you what # block in the fuse/relay “box” under the hood.
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Old 01-18-2021, 09:30 AM   #14
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will the dc to dc charger actually increase charge current to the trailer batteries? I have solar but it would be nice to have the Jeep charging the batteries between camping locations. now it really does not .

also is there both a positive and negative wire coming from the tow harness? the dc to dc charger needs both as input and output right?

anyone else on forum installed the charger in the trailer and not TV?
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Old 01-18-2021, 11:52 AM   #15
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let me clarify the question.

will adding a small dc to dc charger in line in the trailer address both the issues

a. power draw from trailer to TV while 7 pin connector is plugged in

b. increase amps from TV alternator to Trailer when TV is running

if answer to both is yes, sounds like it's worth getting a small (9amp) victron unit since they are only $60 or so..
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Old 01-18-2021, 01:03 PM   #16
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Originally Posted by jsmall01 View Post
let me clarify the question.

will adding a small dc to dc charger in line in the trailer address both the issues

a. power draw from trailer to TV while 7 pin connector is plugged in

b. increase amps from TV alternator to Trailer when TV is running

if answer to both is yes, sounds like it's worth getting a small (9amp) victron unit since they are only $60 or so..
A) yes. The dc/dc converter will act as the “isolator” I referred to in my original reply. It will prevent discharge of the trailer batteries into the TV batteries

B) Given that your existing setup provides little or no charge current to the trailer batteries from the TV, that answer would be “yes” as well. How much charging current will be provided depends on your selection of dc/dc converter, how you configure the dc/dc converter and the wire gages involved.
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Old 01-18-2021, 01:22 PM   #17
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A) yes. The dc/dc converter will act as the “isolator” I referred to in my original reply. It will prevent discharge of the trailer batteries into the TV batteries

B) Given that your existing setup provides little or no charge current to the trailer batteries from the TV, that answer would be “yes” as well. How much charging current will be provided depends on your selection of dc/dc converter, how you configure the dc/dc converter and the wire gages involved.
thanks. I'm thinking of the small victron 9amp unit. you think I can truly get 9amps using existing jeep 7 pin ? no mods to jeep
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Old 01-18-2021, 06:56 PM   #18
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Follow-up question

does any one know how to identify the power wire coming from the tow harness on the AS? I see a blue wire connected to a bus-bar under the bench, so thinking that might be the one? There's also a bunch of other wires from the harness.
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Old 01-19-2021, 08:20 AM   #19
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Follow-up question

does any one know how to identify the power wire coming from the tow harness on the AS? I see a blue wire connected to a bus-bar under the bench, so thinking that might be the one? There's also a bunch of other wires from the harness.
Hi

Your owner's manual should give you a pretty good idea of what goes where on the DC distribution block. There are various color codes used on 7 pin harnesses. The gotcha is, there is no guarantee. Most show an orange wire for the charge line.

The only way to be sure is to go to the connector and work it out from there. Before you start there will be voltage to ground on pin 4. Once you pull the correct wire, there will not be voltage there.

Mr. Google is your friend for finding all sorts of pictures of the 7 pin connector.

Bob
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Old 01-19-2021, 09:05 AM   #20
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Yes, the DC to DC converter will provide charge to the batteries while towing.
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