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cruz-in's avatar
cruz-in
Explorer
Aug 23, 2019

Isolating TT's Lithium from TV's Lead Acid Batteries

Hi Team,

I am installing Lithium batteries on our TT. To provide isolation between TT's Lithium and TV's Lead Acid batteries, I plan to install a Renogy DC-to-DC converter. It is kind of neat. Has three stage charging and supports Lithium. Here is a link to them:

20 Amp and 40 Amp DC-to-DC charger

TV has 30 AMP fuse for the power line to the Trailer Plug. I assume I need to stay below 30 Amps so am I stuck with the 20 Amp Model?

Would be nice to use the whole available 30 amps.

Thanks
Dan

28 Replies

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  • CA_Traveler's avatar
    CA_Traveler
    Explorer III
    Aug 24, 2019
    Charging is important for boondock to boondock travel and very important for the trailer battery for the brakes to work correctly . I'd want adequate charging availability while driving.
  • grizzzman's avatar
    grizzzman
    Explorer
    Aug 24, 2019
    I have the 40 amp DC to DC charger. With 20 foot of 4 awg copper wire
    I still see a bit of a voltage drop. To get 40 amps out it takes 50 amps from the truck. I would advise at least 6 awg from the tow rig to the trailer. Here is my post on it

    What type lfp? How are you going to shut off the charger when the bank is full?
  • BFL13's avatar
    BFL13
    Explorer II
    Aug 24, 2019
    You don't need the little bit of charging you get from the TV to the TT while driving.

    Just pull the truck's fuse for pin #4 (Chev it is Stud 1--whatever for other trucks--Ford has a relay to disconnect.)
  • CA_Traveler's avatar
    CA_Traveler
    Explorer III
    Aug 24, 2019
    The 30A TV fuse is to protect the TV wiring. The TT wiring may not be adequate for 30A, hopefully for the 20A model.

    Consider new wiring, connector and fuses for the 40A model. Plus is the TV alternator adequate for an additional 40A load? Likely more than 40A due to wiring losses.
  • CA_Traveler's avatar
    CA_Traveler
    Explorer III
    Aug 23, 2019
    pianotuna wrote:
    Dan,

    Think about beefing up the charging wire to meet the 40 amp requirement?
    X2 Wire length, amps and volts all factor into what size wire to use. Maybe the manual has some guidelines?
  • garym114's avatar
    garym114
    Explorer II
    Aug 23, 2019
    You are going to need a larger gauge wire from the TV battery to the TT converter.
    The 12 gauge wire in the 7 way and probably the other wire in the trip is not large enough for even a 5 amp load.
    See the voltage drop calculator at the bottom of this page.
    http://www.powerstream.com/Wire_Size.htm
  • pianotuna's avatar
    pianotuna
    Nomad III
    Aug 23, 2019
    Dan,

    Think about beefing up the charging wire to meet the 40 amp requirement?

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