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DC to DC Charger

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  • DC to DC Charger

    2019 Reflection 295RL
    2015 Chevy 2500 Duramax

    Hello,

    I purchased a Lion Safari UT 1300 lithium battery at Costco a few days ago. I currently have two 6V golf cart batteries with 220 amp hours that I'll be removing. As I've researched usage of the Lithium battery, learned I need to be careful when the trailer is hooked up to my truck such that I don't fry the alternator. Called Lion this morning and they told me they recommend using the Renogy DC to DC charger.

    Here's my use case; We're full time and initially I'm doing this for weight savings, the flat power curve and longevity of the Lithium battery. May eventually end up adding Solar and more Lithium batteries, yet budget doesn't allow that yet. Plan to use stock converter. I understand won't fully charge Lithium battery and won't charge nearly as fast as a Lithium converter. Plan to add the Lithium converter next month or two. We boondock about a quarter of the time.


    Two questions:

    1) The Renogy DC to DC charger comes in several Amp configurations. Which one do I need?
    2) How do I wire up the charger. Mounting it in the front basement near the Lithium battery seems like a good choice, yet how do I get to the truck alternator?

  • #2
    Originally posted by bhickman2 View Post
    2019 Reflection 295RL
    2015 Chevy 2500 Duramax

    Hello,

    I purchased a Lion Safari UT 1300 lithium battery at Costco a few days ago. I currently have two 6V golf cart batteries with 220 amp hours that I'll be removing. As I've researched usage of the Lithium battery, learned I need to be careful when the trailer is hooked up to my truck such that I don't fry the alternator. Called Lion this morning and they told me they recommend using the Renogy DC to DC charger.

    Here's my use case; We're full time and initially I'm doing this for weight savings, the flat power curve and longevity of the Lithium battery. May eventually end up adding Solar and more Lithium batteries, yet budget doesn't allow that yet. Plan to use stock converter. I understand won't fully charge Lithium battery and won't charge nearly as fast as a Lithium converter. Plan to add the Lithium converter next month or two. We boondock about a quarter of the time.


    Two questions:

    1) The Renogy DC to DC charger comes in several Amp configurations. Which one do I need?
    2) How do I wire up the charger. Mounting it in the front basement near the Lithium battery seems like a good choice, yet how do I get to the truck alternator?
    Wow--you came to the right forum. Check out https://gdrvowners.com/forum/operati...e-battle-borns

    I tend to be quite verbose (sorry) as I document as I go, mistakes and all. My purpose is to give the reader a complete insight into what works (and what doesn't).

    Give the thread a read and hit me up if you have any questions. MidwestCamper (Jim) also has a setup that uses the stock truck wiring--much less expensive. Hopefully he'll chime in here when he sees the tag.

    Since you're new, also check out the Welcome Letter to New Members at https://gdrvowners.com/forum/main-fo...to-new-members

    Howard
    Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

    Howard, 2017 Ford F-350 DRW, '19 315RLTSPlus

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    • #3
      Originally posted by bhickman2 View Post
      2019 Reflection 295RL
      2015 Chevy 2500 Duramax

      Hello,

      I purchased a Lion Safari UT 1300 lithium battery at Costco a few days ago. I currently have two 6V golf cart batteries with 220 amp hours that I'll be removing. As I've researched usage of the Lithium battery, learned I need to be careful when the trailer is hooked up to my truck such that I don't fry the alternator. Called Lion this morning and they told me they recommend using the Renogy DC to DC charger.

      Here's my use case; We're full time and initially I'm doing this for weight savings, the flat power curve and longevity of the Lithium battery. May eventually end up adding Solar and more Lithium batteries, yet budget doesn't allow that yet. Plan to use stock converter. I understand won't fully charge Lithium battery and won't charge nearly as fast as a Lithium converter. Plan to add the Lithium converter next month or two. We boondock about a quarter of the time.


      Two questions:

      1) The Renogy DC to DC charger comes in several Amp configurations. Which one do I need?
      2) How do I wire up the charger. Mounting it in the front basement near the Lithium battery seems like a good choice, yet how do I get to the truck alternator?
      I used to have 4 Lion Energy batteries (now six), and run the same Renogy 40 amp as Howard. Its phenomenal and even with my solar has come in handy a ton on rainy drive days. That said I ran mine for a year with the stock wiring and no DC to DC charger and never had a problem with my alternator. The computer controlled alternators in modern trucks never see the draw from the trailer as enough to crank up the alternator output. That coupled with the wire size going to the trailer batteries meant even when mostly depleted and capable of taking 130 amps of charge, my stock charging wire would only put out 7-10 amps. So I made the upgrade to get more charging power out of my trucks dual alternators rather than to avoid damaging them.

      Howards write up should answer most of your questions, but to address them directly, I got the 40 amp version and mounted it in my front bay near the batteries. I ran 4 AWG cable from the truck batteries back to an Anderson connector I mounted in the bed next to the light cable.
      Neil Citro
      2018 Reflection 28bh
      2019 F350 6.7L Long Bed Crew Cab

      Comment


      • #4
        I greatly appreciate all of Howson's write-ups. More than he could ever imagine. I recently purchased a 2021 Reflection 315RLTS like Howson and study all of his posts. :-)

        I have purchased, but not yet installed, the Renogy 60 amp DC-DC charger, and will do something similar to Howson, but with a bunch of changes. My old truck alternator would not be up to the task, so I'm installing a Mechman 320 amp alternator. This will be to charge 4 to 6 Battleborn batteries (still not sure how many I can fit under the bedroom drawers).
        Fairfax, Virginia
        2021 Grand Design Reflection 315RLTS Travel Trailer
        2002 Ford F350 7.3 Diesel 4X4 SRW

        Comment


        • #5
          The DC DC charger is a nice way to keep the RV battery topped off while traveling since they can be charged very rapidly. A few key points.

          1) Its not efficient to mix battery technologies. Lithium batteries operate at a higher voltage and with a lower internal resistance. Higher charge voltage is needed to top balance the battery.
          2) A couple battery manufacturers will tell you that these batteries can be mixed, where no damage will occur, but the Lithium will not top balance in this way where it is critical to occasionally charge off AC.
          3) A fully charged Lithium connected to a TV lead acid battery will actually back-feed to the truck since the TV battery operates at a lower voltage. So the TV should be disconnected when not running.

          Lastly:
          Alternator concerns are real where vehicle manufacturers can protect the alternator to some level but this is a secondary concern IMO. The main concern is to be able to re-start the vehicle and as a result they will do whats called load shedding to turn off secondary systems such as heated seats and so on when the TV battery voltage becomes low. Also high loads at idle are an emissions concern and as a result they do not like to charge at high rates at idle. I spoke with the folks at Denso who confirmed that diode overheating could be an issue with high loads at idle where cooling is lacking. Also calibration is not done by them. So to use a DC DC charger to isolate the two batteries and turn on the DC DC only while underway to avoid overheating of the alternator should be considered. There are no thermal measurements in an alternator where modeling would be used to determine temperature. Its unlikely manufactures are modeling with an unknown load from 1-4 lithium batteries at idle while pulling current from the TV. Once they become in tune with lithium technology, I suspect they would also use a DC DC converter, or a dual alternator system designed specifically for this purpose which most likely would involve a DC DC converter since I do not see them bearing the responsibility for an add on system with unknown battery technology.

          I'm using the 20amp Renogy on my truck while being powered through the 7 way connector since I have one battery in the rig. Care must be taken to be sure the TV circuit can handle up to 27amp start up loads from the Renogy.

          Hope this helps,

          Jim
          2017 Imagine 2600RB
          2015 GMC Sierra 4x4

          Comment


          • #6
            Another nice feature in wiring up a Renogy DC DC is connecting the TV charge wire only to the Renogy is to also connect the TPMS to this input. As a result, the TPMS only operates when the TV is connected to the trailer either with a dedicated plug like Howard has installed or via the 7 way connector that I use. The Renogy can be activated from the TV by connecting the trigger lead (also referred to as D+) to the marker lights. This way the charger can be turned off when not needed with the caveat that its daylight or that your TV lights are manually turned off. No choice for night driving.

            Jim
            2017 Imagine 2600RB
            2015 GMC Sierra 4x4

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