DC - DC Charger Project

[Yoda]

Yoda Getting caught up on the forum after being on a trip for a few days. Good advice here, I have the Renogy 40A. The 60 had just come out when I bought mine and the book said to only use short wire runs with it (I think it was mainly targeted to motorhomes and vans), but I think that has since been lifted. I run 4AWG wire on mine, and ocassionally tripped the 60 amp breaker I put up by the battery. I have increased this to 100 amps (still well within the 4awg current rating) and have not had a problem since. My longbed took a lot of wire, but I had to cross laterally as well since I located the breakers and connection point by the passenger battery, and put my connection point by the 7 pin bed connector on the driver side. I think I bought 50 foot of each (red/black welding from Windy Nation on Ebay) and used it all on the truck. I then used some wire I had around the shop for the run from the pinbox back to the batteries.

I used the Andersen SB120 connectors and they have been great. I found a guy who 3d prints a panel mount, which I cut out the side of the bed for (a scary hole to cut for sure lol) and it works great.

Thanks Neil

Is this where you got the bulkhead connector? https://www.etsy.com/listing/7780785...e_recs_5&sca=1 I did have to laugh - the shipping is twice the cost of the plug

It also takes up less room than the Pollak.

I also really appreciate the pictures of how you mounted yours - very clean. Any issues cutting the hole (wiring behind?) Thanks for doing that. Whats the button above it for - the bed lights?

Have a great week
Keith

On edit - it looks like you have the spray in bed liner - how is it holding up?

[ncitro]

Yoda Yeah it took an eternity to come as well. I think maybe from Australia as I recall. Was easy to mount, the bed is aluminum so cuts easy. Once cut there was plenty of room to follow the factory wiring down. Its been a little while now since I cut the hole but I think I used a dremel to cut it.

Button is for the factory bed lights, they are great when the cover is closed. Truck came with a LineX bed liner, the dealer puts it on all their trucks rather than order them with the Ford spray in for some reason. It has held up great, I load pallets for work with a fork lift, and move a lot of equipment for work and have no problems. Only small issue is I ran my generator in the bed with the tailgate closed for several hours once. I did not realize the exhaust was pointed towards the tailgate and it discolored and softened the liner in that area. When it cooled it hardened and seems functionally fine, but looks odd and is definitely now not as thick there as it should be. Need to get it back to LineX to get it fixed but its low on the priority list.

[wygieman]

That's good for everyone to know that the 60 amp Renogy works just fine with 4 gauge wire. The Renogy manual implies that 4 gauge is only good for up to 8 feet with the 60 amp charger, not the 40 feet that we need. Of course, since the DC/DC converter bumps up any voltage drop, so the wire gauge from the truck is clearly not critical. Although I don't know if I'd want to go to a smaller wire than 4 gauge for the 60 amp.

The manual I received with unit (rev 1.3 I believe) limited the 60 amp unit as you say. Online, the latest manual rev 1.4 has the same 30 ft spec for the 60 amp as the 40 amp specifying a 90 amp breaker. Re the wire length, Keith, I didn’t want to make any holes in the truck bed (at least initially) so I ran the wire up through the the drain gap in the tailgate which is a longer run than Neil’s clean setup.

[Guest]

Been running my Renogy 20amp through my 7 pin on my GM truck without issue. One thing to point out is the connector must be kept clean by using contact cleaner, CLR etc to keep the contact running as efficient as possible.

Jim

[Ascrone]

Been running my Renogy 20amp through my 7 pin on my GM truck without issue. One thing to point out is the connector must be kept clean by using contact cleaner, CLR etc to keep the contact running as efficient as possible.

Jim, Do you know how many amps of charging you are getting through this setup?

Alan

[Guest]

Jim, Do you know how many amps of charging you are getting through this setup?

Alan

Yes I tested the system on the driveway before installing it in the rig and I am getting the full 20 amps. System draw on the TV was about 25 amps with a startup current at around 27 amps. My truck is factory fused to 30 amp with a circuit design to 35amps from looking at the schematics.
Something I noticed after running this system for some time is warmth felt at the 7way connector, so I believe its important to keep this connection clean as we would with any plug in connection.

To keep resistance as low as possible. the Renogy was mounted in the passthrough next to my AIMs 100ah Lithium battery where 8ga marine grade wire was used from the trailer termination on the frame to the Renogy. The Renogy is activated through the marker lights on the rig.

Early on I would monitor the Renogy from my truck while driving with the Victron BMV712.

Jim

[Yoda]

Yes I tested the system on the driveway before installing it in the rig and I am getting the full 20 amps. System draw on the TV was about 25 amps with a startup current at around 27 amps. My truck is factory fused to 30 amp with a circuit design to 35amps from looking at the schematics.
Something I noticed after running this system for some time is warmth felt at the 7way connector, so I believe its important to keep this connection clean as we would with any plug in connection.

To keep resistance as low as possible. the Renogy was mounted in the passthrough next to my AIMs 100ah Lithium battery where 8ga marine grade wire was used from the trailer termination on the frame to the Renogy. The Renogy is activated through the marker lights on the rig.

Early on I would monitor the Renogy from my truck while driving with the Victron BMV712.

Jim

Jim - your set up just came to the top of my list. I found out the charge circuit on my new (yet to be delivered) F350 is 30 amp. I have no idea of the wiring gauge or what is on the power cord to the trailer, or the trailer wiring to the battery - I guess I need to look.
Victron has this unit
https://www.victronenergy.com/dc-dc-...t-non-isolated
and Renogy
https://www.renogy.com/12v-20a-dc-to...ttery-charger/

Both should work. If I may ask what wiring size did you use for the connections? Any pictures? Also do you remember the color of the wire in the trailer cord corresponding to the charge wire - I guess I can look that up.

Thanks
Keith

[Guest]

Keith,

Finding the charge wire is easy where you can follow the battery lead to the trailer junction box. I do not recall the color of the wire but I'm certain it can be found with a quick search on the forum. From the trailer junction box, I ran 8ga marine wire to the Renogy input. This was overkill but I was working to keep overall resistance as low as possible. I should also mention the charge wire from the TV is only ran to the Renogy so Its isolated from other circuits in the rig until the Renogy is activated. The D+ or activation wire on the Renogy was tied into the marker lights of the Imagine which is White/Red in color. I remember the color of that wire.
For my TV wiring, I did not look at it but rather had an inside look at the schematics where the circuit was rated for 35amp and protected at 30amp.

Jim

[wygieman]

Jim - your set up just came to the top of my list. I found out the charge circuit on my new (yet to be delivered) F350 is 30 amp. I have no idea of the wiring gauge or what is on the power cord to the trailer, or the trailer wiring to the battery - I guess I need to look.
Victron has this unit
https://www.victronenergy.com/dc-dc-...t-non-isolated
and Renogy
https://www.renogy.com/12v-20a-dc-to...ttery-charger/

Both should work. If I may ask what wiring size did you use for the connections? Any pictures? Also do you remember the color of the wire in the trailer cord corresponding to the charge wire - I guess I can look that up.

Thanks
Keith

Be careful assuming that the newer trucks pass the same current that was available on the older trucks. The current, I believe, is regulated electronically, not by the fusing. I have never seen more than 7 amps available on my 2017 F350 at the trailer. I believe others have confirmed the same thing. I ran 4 awg wire to get 60 amps from a renogy charger.

[Guest]

Be careful assuming that the newer trucks pass the same current that was available on the older trucks. The current, I believe, is regulated electronically, not by the fusing. I have never seen more than 7 amps available on my 2017 F350 at the trailer. I believe others have confirmed the same thing. I ran 4 awg wire to get 60 amps from a renogy charger.

The trailer charge circuit may be activated or de-activated but is not directly controlled by the alternator. The reason a lead acid battery will not receive a high current load is due to the batteries high internal resistance. The lithium battery has very low internal resistance and will draw more current from the TV connection. The reason its recommended to use a DC-DC converter is to avoid connecting two different battery technologies in parallel where each requires different charge voltages. The smart alternator in the TV cannot discern a direct parallel path but will respond to a large draw from the DC-DC converter and low internal resistance of a lithium battery. It will respond to the draw on the overall system and not solely on the 7 way connector. With the 20amp Renogy, you will get 20amp charging if the TV circuit can handle a 27amp startup and 25amp running current. A larger DC-DC unit should not be connected to the 7 way connector.

Also with Keiths bank of 4 FLA batteries, he will get the 20amps he is after from the Renogy 20amp DC-DC unit.

Jim

[steve&renee]

... I'm using the Keyline Iso-Pro 140 battery isolator which is connected to ground through a switch on the dash in my truck. I don't have any solar (yet) so I wanted maximum charging of the 5 Battleborn 100ahour batteries in my RV. I'm very happy with this setup.

I'm interested in your setup. Could you expand on your design goals and provide a sketch or basic wiring diagram? Do you have two truck batteries? I assume one of your goals is to keep a your starting battery charging even when the RV battery bank is fully charged. I don't think draining the starting battery has been discussed on this forum before, but it definitely seems problematic to me.

Thanks.

-Steve

[ncitro]

I'm interested in your setup. Could you expand on your design goals and provide a sketch or basic wiring diagram? Do you have two truck batteries? I assume one of your goals is to keep a your starting battery charging even when the RV battery bank is fully charged. I don't think draining the starting battery has been discussed on this forum before, but it definitely seems problematic to me.

Thanks.

-Steve

I would think I'm the case of lithium RV batteries, draining of the starting battery should be minimal. The resting voltage of the lithium batteries is higher than the lead acid in the truck, so I would not think much current should flow from the actual truck battery to the RV battery. Not 100% on that as I use a DC to DC charger that's fed by a switched ignition source, but I think that's correct.

[Guest]

The problem with an isolator is it still has a parallel connection when both batteries are charging, so no dedicated lithium profile if lithium is a consideration. The DC-DC charger is a true isolated connection where the charge profile resides in the DC-DC charger and is independent of the TV charging strategy. Otherwise an isolator is perfect to prevent back-feeding from one battery to another.

Jim

[Yoda]

Guest
New question
I see Victron Orion-Tr Smart 12/12-30A DC-DC charger has two models Non-Isolated (3 terminals hot in, ground, hot out) and Isolated (4 terminals +/- in and +/- out with chassis ground. What is the difference and which is better? I am thing that as the only real ground between the truck and trailer is maybe a 12 gauge wire in the cord, I need the isolated so I can bring the negative cable to it.
wygieman
How is you Renolgy 60A holding up. I was reading reviews and folks are having a few random quality issues. Appreciate the input on the alternator, but the 2022 supposedly have something new where it can output more if called for, up to 30A - still reading up and need to verify the wiring.. My new order truck has the instant cab heat so will have the 397 amp alt.

[wygieman]

wygieman
How is you Renolgy 60A holding up. I was reading reviews and folks are having a few random quality issues. Appreciate the input on the alternator, but the 2022 supposedly have something new where it can output more if called for, up to 30A - still reading up and need to verify the wiring.. My new order truck has the instant cab heat so will have the 397 amp alt.

My Renogy 60A has worked as specified from installation. I can’t comment on Renogy support as I haven’t needed any. I do switch it between 30A and 60A depending on whether I have discharged batteries to be recharged while driving or if I was plugged in and just want to support the refer for the drive and stay charged up. It would be great if the new trucks can output 30A over the standard umbilical. My truck has dual alternators with plenty of available amps but is limited to ~7A over the standard connection.

Edit to add: Also note that the 30A charger will require more than 30A input to get to the correct charge voltage. In my case, the charger draws over 35A to supply 30A to the batteries at the correct voltage and that is with 4AWG cables. If the truck is fused at 30A, I suspect you are probably close to a 20-25A max charge rate which is, of course, a substantial maintenance charge rate.