Charging Through the 7 Pin Cable

[pfm41]

We recently picked up our 2023 16X which has the solar option and 1 100AH Battleborn lithium battery. Our tow vehicle is a 2022 Nissan Frontier. Our first big trip will be to Alaska in May where we will have some overcast days and maybe a snow day. I am going to install a DC-DC convertor to make use of the available charging through the 7 pin and more importantly to protect my TV from the possible 14+ volts of feedback. I'm not interested in adding additional wiring to max out the charging capability but just use what is there to augment the solar. It looks like about the only choice is the Renogy 20 amp with the current limiter set for 10 amp. We will probably boon dock a lot with a full day a driving in between. I'm also considering a second battery to guard against that possible snow or site seeing day. Thoughts on my logic please. Thanks

[Silvr_Bullet]

I read on an Electrical Forum that most modern vehicles protect against back feeding, I can’t say that that’s true, but maybe something to check with your TV manufacturer or dealership. That bit in your post jogged my memory with back feedings, thought I would pass it on FWIW.

[Ndcctrucks]

Backfeeding (current traveling from the trailer battery to loads in the TV) can be prevented with a single diode. Non need for a dc-dc converter between the trailer and the Towing Vehicle.

You could select a diode which is rated for twice the voltage and twice the largest fuse in the 7-pin plug circuit that you’re using.

I charge through my 7-pin and simply unplug it from the TV at the campsite after setting up the trailer.

-Ken

[pfm41]

Please let me clarify my post; I want the proper charging capability and at the same time eliminate the possibility of damaging feedback. What I am wanting in feedback from those that have installed a dc-dc converter in the stock wiring and what are the results. Thanks

[bobzdar]

Originally Posted by pfm41

Please let me clarify my post; I want the proper charging capability and at the same time eliminate the possibility of damaging feedback. What I am wanting in feedback from those that have installed a dc-dc converter in the stock wiring and what are the results. Thanks

The diode solution above will do exactly that without the need for a DC-DC converter - diode only lets current flow in one direction, so if the trailer has a higher voltage than the TV, nothing will flow. If it's lower and needs a charge, current will flow from the TV to the trailer. DC-DC will allow the TV to charge the trailer even when it's close to fully charged, so that's the only real benefit (imo).

[vanderwielen]

Originally Posted by pfm41

Please let me clarify my post; I want the proper charging capability and at the same time eliminate the possibility of damaging feedback. What I am wanting in feedback from those that have installed a dc-dc converter in the stock wiring and what are the results. Thanks

I've done this. Get the Victron DC to DC charger. You can use either the 18A or 30A model. Technically, the load from this unit will draw down the 12v from your tow vehicle substantially, but don't worry. The DC to DC can take a voltage as low as 8v and elevate it to the exact charging profile needed for your lithiums.

A 'Diode' simply doesn't work. Additionally, it drops 0.7v additional volts.

The unit also can auto detect if your vehicle is running and only draw a charge when it is. However, my F150 only powers the 7 pin while the truck is running, the doors are shut and it has detected the trailer.

Functionally, you should get 100-150 watts of charge.

If you don't already have a victron shunt installed to measure your state of charge, invest in that.

good luck.

[kscherzi]

Originally Posted by bobzdar

The diode solution above will do exactly that without the need for a DC-DC converter - diode only lets current flow in one direction, so if the trailer has a higher voltage than the TV, nothing will flow. If it's lower and needs a charge, current will flow from the TV to the trailer. DC-DC will allow the TV to charge the trailer even when it's close to fully charged, so that's the only real benefit (imo).

Not sure about that. His lithium battery needs a charge voltage somewhere in the 14.4 volt range. The voltage coming from the 7 pin plug is probably less, maybe 13.5 volts or so. Possibly less due to line loss. The diode just stops electricity from flowing from the trailer into the truck when there's a voltage difference.

[Al and Missy]

Originally Posted by Ndcctrucks

Backfeeding (current traveling from the trailer battery to loads in the TV) can be prevented with a single diode. Non need for a dc-dc converter between the trailer and the Towing Vehicle.

You could select a diode which is rated for twice the voltage and twice the largest fuse in the 7-pin plug circuit that you’re using.

I charge through my 7-pin and simply unplug it from the TV at the campsite after setting up the trailer.

-Ken

A standard silicon diode has a forward drop of 0.6 volts which would probably negate any utility for charging Lithium batteries. Even a Schotty Barrier diode would drop about 0.2 volts. In my opinion, a diode is not a viable option.

[vanderwielen]

Originally Posted by bobzdar

The diode solution above will do exactly that without the need for a DC-DC converter - diode only lets current flow in one direction, so if the trailer has a higher voltage than the TV, nothing will flow. If it's lower and needs a charge, current will flow from the TV to the trailer. DC-DC will allow the TV to charge the trailer even when it's close to fully charged, so that's the only real benefit (imo).

This won't work, as a depleted lithium battery will appear as a direct short unless there is either a BIM or DC to DC charger in line. The diode you're recommending would need to be massive to overcome this. Additionally, a diode solution does not have any knowledge of the correct charging profile to correctly top off Lithiums. You are simply connecting dissimilar chemistries.

Victron's DC to DC orion was created to prevent this and should be integrated as a solution.

[field & stream]

Absolutely not an expert on this subject but for whatever it might be worth I will share our experience. We have a 16’ trailer, no rooftop solar, a single 100Ah Battleborn GC2, a dc-dc converter, and a Victron 712. The TV is a 2001 Yukon Denali XL with a fairly new alternator.

We get very little charging from the TV while driving — maybe 5-10 Ah per long day of driving. Maybe less. It starts off charging at 5-8 amps, but drops to a trickle after a short amount of time. My uneducated amateur guess is that once the TV battery reaches full charge, whatever controller is associated with the alternator drops the charging rate.

My advice: don’t count on much, get the second battery, install a dc-dc converter, add a shunt based battery monitor so you know what is going on, and get real good at conservation.

[ROBERT CROSS]

Originally Posted by pfm41

We recently picked up our 2023 16X which has the solar option and 1 100AH Battleborn lithium battery. Our tow vehicle is a 2022 Nissan Frontier. Our first big trip will be to Alaska in May where we will have some overcast days and maybe a snow day. I am going to install a DC-DC convertor to make use of the available charging through the 7 pin and more importantly to protect my TV from the possible 14+ volts of feedback. I'm not interested in adding additional wiring to max out the charging capability but just use what is there to augment the solar. It looks like about the only choice is the Renogy 20 amp with the current limiter set for 10 amp. We will probably boon dock a lot with a full day a driving in between. I'm also considering a second battery to guard against that possible snow or site seeing day. Thoughts on my logic please. Thanks

You won't charge any significant amount charging thru the 7-pin while driving.

POI...We do charge two Zamp 160w panels thru the 7-pin.

Bob
🇺🇸

[JBBeaubeaux]

We installed the Victron 12/12/18 DC to DC Charger, https://livinginbeauty.net/product/v...-dc-converter/

[bobzdar]

Originally Posted by vanderwielen

This won't work, as a depleted lithium battery will appear as a direct short unless there is either a BIM or DC to DC charger in line. The diode you're recommending would need to be massive to overcome this. Additionally, a diode solution does not have any knowledge of the correct charging profile to correctly top off Lithiums. You are simply connecting dissimilar chemistries.

Victron's DC to DC orion was created to prevent this and should be integrated as a solution.

I believe the 7 plug connection is limited to 10A max. A 18vPIV, 15A diode should work. If the current isn't limited by the TV it might blow the fuse, though.

Agree, for proper charging to 100%, a DC-DC converter or proper charge controller would be needed. However, at 0% Lithium should be 10V and at 13V should be around 30% charged (which is roughly what you'd get from the TV at 13.6V with a .6V drop from the diode). With .2V drop you'd get 13.4V which would put the Lithium at 99% charge. You won't get 100% with a diode, but should get to 30% minimum. The diode will protect the TV if you charge the Lithium to 100% with shore power or solar and then plug it in. As most vehicle alternators put out 15V max, it should charge the Lithium to full or close to it.

But you can do it many ways, and using a DC-DC converter gets rid of all variables in vehicle alternator output etc.

edit: that doesn't factor in charge times, the closer to the Lithium charge voltage you get, the slower it will charge, so if the battery sees 13.6V it might take days to get to 99% charge, but should get to 20-30% pretty fast. If full charge from the TV is wanted in minimal time, then yeah, proper converter is needed.

[uncle_bob]

Hi

First off, you very much want a DC/DC with a programable current limit. You might find that your cabling will get you to 15A, you might find that 10A is about as far as it will go. It will be a "try it and see" sort of thing once you get the device installed.

In May, heading up to AK snow by the side of the road will be a very real possibility. Getting enough show fall to significantly interfere with solar is unlikely. You will be into "lots of daylight" time in May so that will help your solar production.

The Victron buck/boost DC/DC is what Airstream uses on some vans. It's not cheap, but it works very well.

https://shop.pkys.com/Programmable-D...ers_c_791.html

Bob

[field & stream]

An afterthought addition to my advice in post #10 above: to add some additional charging you may want to add a 100w portable solar to you setup, even after adding a second lithium battery. Those electric-only fridges draw a lot of power.

[Hn387]

Call battleborn, who is an authorized Victron dealer. They will tell you not to bother with a DC to DC converter because the wiring won’t even allow significant current.

Just unplug the 7 pin if you plan to leave the trailer hooked up more than 24 hours

[pteck]

Looks like there's a spectrum of hearsay and experience.

I can tell you for my own trailer, I have a Renogy 20amp DC-DC charger running on the 7-pin, from my Lexus LX570 (aka Land Cruiser). Charges great and delivers a legit 20 amps over the stock cabling, confirmed by a shunt.

It works with my solar just fine in-route and I get significant charging between the two. Enough that I can easily run the fridge off that power, through an inverter, and still be charging the batts.

I also have a Victron 18amp DC-DC in my TV charging another lithium batt in-vehicle (for overlanding). At least comparing the Victron to Renogy, they both deliver. The Victron might be the better choice for its more compact dimensions, BT interface and voltage readout, and being 18amp, be a bit more likely to work for most tow vehicles.

[uncle_bob]

Originally Posted by bobzdar

I believe the 7 plug connection is limited to 10A max. A 18vPIV, 15A diode should work. If the current isn't limited by the TV it might blow the fuse, though.

Agree, for proper charging to 100%, a DC-DC converter or proper charge controller would be needed. However, at 0% Lithium should be 10V and at 13V should be around 30% charged (which is roughly what you'd get from the TV at 13.6V with a .6V drop from the diode). With .2V drop you'd get 13.4V which would put the Lithium at 99% charge. You won't get 100% with a diode, but should get to 30% minimum. The diode will protect the TV if you charge the Lithium to 100% with shore power or solar and then plug it in. As most vehicle alternators put out 15V max, it should charge the Lithium to full or close to it.

But you can do it many ways, and using a DC-DC converter gets rid of all variables in vehicle alternator output etc.

edit: that doesn't factor in charge times, the closer to the Lithium charge voltage you get, the slower it will charge, so if the battery sees 13.6V it might take days to get to 99% charge, but should get to 20-30% pretty fast. If full charge from the TV is wanted in minimal time, then yeah, proper converter is needed.

Hi

The typical 7 pin is limited by a slow blow fuse at 30A. Your 15A diode will be long gone before that fuse gets into the act. Since it's not a fuse designed to protect a diode, you will need a diode rated to well over 30A to have any chance of it surviving. How much over depends a bit on how big a heatsink you put it on and maybe how big a fan there is on that heatsink. If you have a diode that is rated to drop 1V ( check that spec sheet !!! ) at full current. It will dump 30W at 30A. That's a lot of heat.

Why do we talk about 10A of charge current on the 7 pin? The battery only accepts current above a certain voltage. You can't hook a 12V battery to a 6V source and expect it to charge. The wiring drops voltage as the current goes up. In the typical case ( alternator at this, battery in that range ) you get 5 to 10 A.

... but ... hook up a near dead battery and you can get a *lot* more current. Flip on a load of some sort ( that power jack on the front of the trailer ....) and you get a pretty good current hit. Your poor diode needs to survive all that.

Bob

[cctx27]

i upgraded my vehicle charging per the attached link:
https://www.adventurousway.com/blog/...trical-upgrade
I disconnected the charging wire on the 7 pin. It requires a heavy duty alternator and a 2awg wire from the battery to the TV hitch.
I can charge at a minimum of 50 amps while traveling.

[vanderwielen]

Originally Posted by Hn387

Call battleborn, who is an authorized Victron dealer. They will tell you not to bother with a DC to DC converter because the wiring won’t even allow significant current.

Just unplug the 7 pin if you plan to leave the trailer hooked up more than 24 hours

Battleborn is in conflict with their integrators, such as me, who can attest to the fact that you can absorb 100-150 watts via a Victron Orion DC to DC converter even with the factory wire. It is also not necessary to unplug your 7 pin with or without a DC to DC converter since most current tow vehicles have a qualifying circuit that only provide power to the charge wire while running...among other qualifiers.