DC to DC charger

I am wanting to replace my Group 24 lead acid with a Group 27 lithium in my 2017 320. I understand it will not fully charge as-is. To charge the battery while driving, I was considering the Victron Orion-Tr Smart 12/12-30A isolated DC to DC charger. To charge from house current a LiTime Smart LiFePO4 charger. Does this sound correct and what am I missing. I think I need fuses at the + for each battery and maybe a disconnect on the DC to DC for when I use the LiTime charger. If anyone has a schematic it would be greatly appreciated. The TV is a 2015 Lexus RX with tow package that includes an upgraded alternator. 

Comments

  • qhumberdqhumberd Administrator, Moderator Posts: 674
    @Alan57 I recently changed out my AGM batteries for the 230 Amp hour LiTime battery in my 400. Really a game changer. I considered two things that I since have decided I did not need.

    First, for use with mostly shore power camping, an upgrade to the WFCO converter was really not needed. In my case if boondocking for a prolonged period my rig has a solar port and my portable panel has a charge controller and a Lithium setting, so it will charge the batter to 100% and balance the cells. I use a small LiTime 10amp lithium charger that fits next to the battery and can plug in the the cargo area, so when on shore power I can disconnect the battery and fully charge overnight.

    Second, on my TV it seemed a lot of work to connect a DC-DC charger. And it is not cheap. We get a small trickle charge of around 2.5 amps when driving on the current 7 pin connector. That results in a net minus 2.5 amps when the frig is running while driving and over 2 drive days to Florida recently it cost me only 10% of my new lithium battery.

    So for needs the DC-DC system was overkill and I saved a lot of time not wiring up something I can't say would provide any benefit. Your needs, of course may be different.

    2019  T@B400 Boondock Lite "Todd"

    2016 Toyota Tundra 5.7 Crew Cab
  • MarcelineMarceline Member Posts: 1,706
    qhumberd said:

    Second, on my TV it seemed a lot of work to connect a DC-DC charger. And it is not cheap. We get a small trickle charge of around 2.5 amps when driving on the current 7 pin connector. That results in a net minus 2.5 amps when the frig is running while driving and over 2 drive days to Florida recently it cost me only 10% of my new lithium battery.

    So for needs the DC-DC system was overkill and I saved a lot of time not wiring up something I can't say would provide any benefit. Your needs, of course may be different.
    The OP is expecting to have many long days on the road so would benefit from a DC-DC charger (arguably even more than solar). 
    San Francisco Bay Area
    2013 CS-S us@gi
    2015 Toyota Tacoma PreRunner Double Cab
  • Alan57Alan57 Member Posts: 24
    I am new to camping and anxious to begin our across country trip. Thanks to this forum and a special thanks to FishDoctor, I have a solid plan for adding solar in the Spring. Thank you Marceline for mentioning that I will be do long drives from my previous post, as I forgot to mention and it lends relevance to adding DC to DC. I used ChatGPT and received the following code:

    [Lexus Starter Battery +]
       └── (≤12") 50A ANL fuse
            └── 6 AWG +
                 └── Anderson SB50 (+)
                     └── 6 AWG +
                          └── [DC-DC Charger INPUT +]
    [Chassis ground not used for current return]

    [Lexus Starter Battery –]
       └── 6 AWG –
            └── Anderson SB50 (–)
                 └── 6 AWG –
                      └── [DC-DC Charger INPUT –]

    [Ignition/Remote lead]
       └── Add-a-fuse to ACC circuit
            └── Charger Remote/D+ input

    [DC-DC Charger OUTPUT +]
       └── (≤12") 40A ANL fuse
            └── 6–8 AWG +
                 └── [House (LiFePO₄) Battery +]

    [DC-DC Charger OUTPUT –]
       └── 6–8 AWG –
            └── [House (LiFePO₄) Battery –]

    I was hoping to hear from someone that had done the installation as opposed to going with an AI generated schematic. I will also search YouTube videos. 
  • HoriganHorigan Member Posts: 795
    @Alan57, I can't remember if you have a 400 or 320, which plays a role in battery location and wire runs.  The key to making a DC DC work is having sufficiently thick wires from the TV battery, thru the DC DC converter, to the trailer battery, as highlighted by the AI response.  Most 7 pin connectors are rated to 20A, and this is reflected in the wire sizing going to the connector.  You could do it if you had 8AWG wires from the TV battery all the way to the trailer battery, with a unique connector to the trailer that could handle 30A.

    A consideration is how smart the alternator is.  Will it provide full current when you want it?  Do you have to turn the headlights on?  Something to research.

    Another consideration is that the Orion DC DC 30A is inefficient.  If not adequately cooled it will derate due to over temperature and lower the output current, by half.  I'm experiencing this on my boat and am about to switch to their more efficient, smaller XS 50A version.
    Rich
    2019 T@b 400
    2013 Toyota Highlander 3.5L V6
    Bellingham WA
  • FishDoctorFishDoctor Member Posts: 74
    If you are putting rooftop solar on the trailer, you might not need the DC-DC charger. I find my 200W rooftop solar with a 100V/30A charge controller easily replenishes my overnight battery usage during a 4 or 5 hour daytime drive, even when there is not fully clear sky. Of course, if it was very cloudy or rainy that wouldn't happen. I thought about adding a DC-DC charger, but decided to hold off until I found out whether I needed it. As someone mentioned, it is a fairly involved installation and more expense, so I am glad I waited instead of jumping right in.
    Downers Grove, IL
    2017 T@B S Max, Blue and Silver -- "The Blueb@rry"

  • Alan57Alan57 Member Posts: 24
    Back to the drawing board for me. I am convinced the solar solution I had planned would be sufficient.  I just thought the DC to DC would be a quicker and easier installation. Less parts, easier to comprehend, run a couple wires to the trunk and a couple out to the tongue box. Sounds like I grossly underestimated the process. Thanks to all!
  • elbolilloelbolillo Member Posts: 530
    We have 360w of solar on the roof of our 23’ Tab400. Provides plenty of charging capability while traveling. Even with a DC to DC charger you will never get adequate charging through your 7 pin.
    _____________________________________________________
    Ken / 2023 Tab 400 “La Bolita” (29,000+ miles) / 2024 Toyota Sequoia
    2025 - 1 Trip - 25 nights - 2 National Parks
  • MarcelineMarceline Member Posts: 1,706
    edited October 14
    Alan57 said:
    Back to the drawing board for me. I am convinced the solar solution I had planned would be sufficient.  I just thought the DC to DC would be a quicker and easier installation. Less parts, easier to comprehend, run a couple wires to the trunk and a couple out to the tongue box. Sounds like I grossly underestimated the process. Thanks to all!
    I think that installing roof panels plus the solar controller is not going to be much easier than installing a DC-DC charger. I wish that someone who's actually installed a DC-DC charger would chime in here to offer advice. I know there have been a few.  You might search this forum (magnifying glass at top right). 
    If you have to choose either 1) DC-DC charger or 2) rooftop solar, you should probably think about what kind of output you expect from both systems. The solar is affected by time of year (shorter days = lower output) and weather. So you have to consider that. You also need a rough idea of how much power you're going to consume. 
    Back in your first post you said:
    New to camping and just purchased a 2017 Tab 320 Outback and planning a two month road trip traveling the States.  Most all of the time I will be staying overnights without shore power.  Ideally I would like to be able each evening to power a tv, lights, and the fan. ... Mainly need to charge when driving during the day so that I have power at night. 
    This post is why I suggested a DC-DC charger. If you're traveling in the summer and you're pretty certain that you'll have good sun, you could certainly go the solar route. 
    San Francisco Bay Area
    2013 CS-S us@gi
    2015 Toyota Tacoma PreRunner Double Cab
  • MarcelineMarceline Member Posts: 1,706
    edited October 14
    elbolillo said:
    We have 360w of solar on the roof of our 23’ Tab400. Provides plenty of charging capability while traveling. Even with a DC to DC charger you will never get adequate charging through your 7 pin.
    The OP currently has no solar at all. Any wiring for a DC-DC charger should be completely separate from the original 7-pin connection.
    San Francisco Bay Area
    2013 CS-S us@gi
    2015 Toyota Tacoma PreRunner Double Cab
  • rcarlson1957rcarlson1957 Member Posts: 239
    edited October 14
    I don't have roof solar either. I have 2 portable 120W panels and a solar battery. Have 100ah lithium battery. Also installed a Victron 100/20 solar controller in the front tub. I used 1 panel for trailer battery and 1 for solar battery with 12v frig plugged into it. Rather than get a traditional DC to DC controller I got a Bluetti Charger 1 alternator charger. Unlike a DC to DC controller the output voltage can be changed via a phone app. It's mainly designed for charging solar batteries and I use it for that sometimes to charge my Bluetti solar battery. But I mainly use it to charge my trailer battery now. I hook it up to my solar controller (the solar controller doesn't care as long as don't exceed voltage/amp rating). I get a pretty steady 200 watts of out it charging my trailer battery rain or shine when truck is running. Trailer battery is always at 100% even if it's a short trip. My Ridgeline uses typical smart alternator so I usually leave the headlights on when I'm going down the road. If I'm boondocking I can back the truck up to the trailer, plug it in and charge the trailer battery if getting low. Can also do the same for the solar battery if it's not a sunny day. And of course, I can also still use the portable panels too. 
    2018 TAB 320S Silver/Black w/100ah Lithium/Bluetti Solar Battery & Portable Solar Panels
    2020 Honda Ridgeline RTL (AWD) Lunar Silver Metallic w/Bluetti Charger 1
    North Texas - Retired Air Force/Corporate Trainer
    Trips - 48  Mileage - 63,452
    "Favorite trip will always be our next one"
  • MarcelineMarceline Member Posts: 1,706
    edited October 14
    I don't have roof solar either. I have 2 portable 120W panels and a solar battery. Have 100ah lithium battery. Also installed a Victron 100/20 solar controller in the front tub. I used 1 panel for trailer battery and 1 for solar battery with 12v frig plugged into it. Rather than get a traditional DC to DC controller I got a Bluetti Charger 1 alternator charger. Unlike a DC to DC controller the output voltage can be changed via a phone app. It's mainly designed for charging solar batteries and I use it for that sometimes to charge my Bluetti solar battery. But I mainly use it to charge my trailer battery now. I hook it up to my solar controller (the solar controller doesn't care as long as don't exceed voltage/amp rating). I get a pretty steady 200 watts of out it charging my trailer battery rain or shine when truck is running. Trailer battery is always at 100% even if it's a short trip. My Ridgeline uses typical smart alternator so I usually leave the headlights on when I'm going down the road. If I'm boondocking I can back the truck up to the trailer, plug it in and charge the trailer battery if getting low. Can also do the same for the solar battery if it's not a sunny day. And of course, I can also still use the portable panels too. 
    Portable panels aren't going to work for the OP because he says that he wants to be charging his trailer battery during his long daytime drives. If he arrives at his off-the-grid stops at dusk obviously the portable panel solution won't work for him.
    The Bluetti Charger 1 is a DC-DC charger. It's just that it's designed specifically for charging portable power stations. It's interesting that it works to charge your trailer battery via the solar controller. 
    If @Alan57 doesn't want to do all the wiring for rooftop panels or a DC-DC charger, another option would be to get a big-ish portable power station and charge it into the vehicle during his daytime drives and then plug his trailer into it at night. 
    San Francisco Bay Area
    2013 CS-S us@gi
    2015 Toyota Tacoma PreRunner Double Cab
  • WayneWWayneW Member Posts: 244
    I installed a Renogy 20A DC-DC charger in our previous tow vehicle and found it fairly straightforward.  I ran 8-ga wires directly from the battery to the rear of the truck (2007 F150) and ended near the 7-pin trailer connection.  The wires were enclosed in a black ribbed plastic loom.  I did buy aftermarket battery terminals to accommodate hooking up the wires.  I installed a 30-amp fuse in-line fuse on the positive wire.  I terminated the wiring with an SAE connection.  I know some folks here aren't impressed with the SAE fittings but I've had no problem with them.  I mounted the charger inside the tub of the trailer on the front wall.  I ran wires from the tongue of the trailer (again next to the 7-pin wiring) to the charger, enclosed in the plastic loom and zip-tied the wires to the 7-pin trailer wiring.  I then connected the charger to a bus bar for the 100 ah litime battery.  Renogy requires a 12v activation wire, so I ran a 16 ga wire from the charger to the junction box under the tongue of the trailer and hooked into the terminal for the trailer running lights.  This way I could turn the charger on or off by turning the parking lights on/off while driving.  Renogy also has an option to halve the output of the charger, so I had the option of charging at 20 amps or 10 amps, depending on how much time I was driving and what load I wanted to put on the alternator.  I installed a switch in the tub to accomplish this. 

    When I connected the trailer, I could hook up the dc-dc charger if I wanted to by plugging in the SAE connection when I hooked up the 7-pin connection.  While in route, I could turn the charger on/off by turning the running lights on/off.  I didn't have any problems with dust or water with the charger being in the tub.  All-in-all, it was a pretty easy install.  

    That being said, I didn't install the charger when I got a new truck.  The 100w panel on the roof generally keeps the batteries charged.  I also have two 100 W solar panels that I can deploy if needed at the camping site.  We mostly boondock and we've been able to keep the battery charged without much problem.  We are quite conservative in our power use, having removed the television, hardly ever using the radio, and using rechargeable Luci lights for bedtime reading.  The 12v fridge is the largest user of electricity by far.
    2021 320S BD
    2017 F-150
    Coeur d'Alene, Idaho
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