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  1. #31
    Site Sponsor SolarPoweredRV's Avatar
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    Quote Originally Posted by Boom 'r Bust View Post
    David,

    I agree with almost all of your points in the previous several posts. But the one about the frig using as much power as an air conditioner?

    My 12cf frig uses 360ish watts on AC power. My air conditioning uses 1200 to 1600 watts depending on which one I'm running. My 40A DC to DC charger is a perfect match for running the frig on AC while driving.

    Not sure what you are basing that opinion on...

    Boomer
    Fair point, however resistive heat is very inefficient and uses a lot of energy. Propane, on the other hand, has very high energy density and is more efficient at producing heat for the adsorption fridge when compared to the electric resistive heating element.

    If you are running your DC-DC Converter primarily to keep your fridge running you are not saving any money or Propane/Fossil Fuel because the energy it takes to operate your alternator is reducing your fuel mileage As a matter of fact, it could be argued that using Propane is more efficient because a Diesel or Gas engine only operates at ~ 30% efficiency and then you have efficiency losses in the Alternator as well as line losses going back to the camper (as well as Inverter Losses). Whereas, with Propane, more than 70% of the heat created by the flame is used by the adsorption fridge (70% is a WAG).
    David and Peggy
    2019 Ford F350 Lariat, 6.7L Diesel, Dually, Long Bed
    Running with 20k Reese Goosebox (Love It) and Ford Factory "Puck" system.
    Stopping with 8,000 lb Disc Brakes and Titan Hydraulic over Electric Brakes system.
    Powering all this fun with 1200 Watts of Solar, two Tesla, Model S, battery modules, 24 volt Victron Inverter.
    2018 Solitude 310 GK

  2. #32
    Seasoned Camper Boom 'r Bust's Avatar
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    Quote Originally Posted by SolarPoweredRV View Post
    Fair point, however resistive heat is very inefficient and uses a lot of energy. Propane, on the other hand, has very high energy density and is more efficient at producing heat for the adsorption fridge when compared to the electric resistive heating element.

    If you are running your DC-DC Converter primarily to keep your fridge running you are not saving any money or Propane/Fossil Fuel because the energy it takes to operate your alternator is reducing your fuel mileage As a matter of fact, it could be argued that using Propane is more efficient because a Diesel or Gas engine only operates at ~ 30% efficiency and then you have efficiency losses in the Alternator as well as line losses going back to the camper (as well as Inverter Losses). Whereas, with Propane, more than 70% of the heat created by the flame is used by the adsorption fridge (70% is a WAG).
    I understand your logic but respectfully disagree with that conclusion. My experience has been the same gas mileage and overall lower costs. By not running my frig on propane I save there. By arriving to my boondocking destination with full batteries I save the gas and wear and tear on my generator.

    All of 2021 I towed without DC to DC charging and recorded my mpg on each trip. All of 2022 I towed with DC charging. My mpg actually improved overall. But I attribute that to my truck engine being broken in more.

    The only downside I can not define is wear and tear on the alternator. But I accept that risk to reap the immediate benefits I experienced this year.
    2021 Winnebago 2932 5th wheel
    2020 F350 w/7.3 Godzilla
    2018 Reflection 220RK - sold 11/20
    2018 Titan XD 4x4 SL - sold 11/20

  3. #33
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    @SolarPoweredRV Thanks for the responses. Thanks also for clarifying the difference in charging Lithium Ion vs Lithium Iron. I researched a bit more and now I see the difference. The key point I now understand is that the Lithium Iron batteries need the 100% in order to fully balance the cells. I'll definitely need to address that with the new Multiplus.

    You make some valid points and I will reconsider the 80 amp DC charger. I wasn't necessarily set on that, I was just thinking that if I had the headroom with the alternators, why not. If I wanted to recharge the batteries quickly on occasion it would be handy to have the option. However, I see your point regarding the massive wires that would be required.

    You asked what my goal was, to run 80 amps continuously, and referenced running at 80 amps for 8 hours straight. Nope, just want to charge the batteries as needed using upfitter switch to control the charger. The main point about running the fridge off the inverter has nothing to do with saving propane. It's about not running on propane while driving; I would prefer to be able to close the propane tank valves while under way. Having the DC charger would enable charging as needed to run the fridge while under way, have battery reserve to use while stopping for breaks/meals, and maintain or top off batteries while driving in order to arrive at an overnight spot with full (ideally) batteries, at which point I would switch the fridge back to propane.

    I agree with Boom R Bust's comment that the fridge draw you referenced seems a bit extreme. But that's been addressed. You also referenced the furnace draw something to be concerned about. Perhaps your rig has difference appliances than mine. I have done tests to see how long our single SOK battery would last without shore power in cold weather. The temps were high 20's/low-mid 30's, running furnace, lights, 12 volt box fan (all night for white noise), 12 volt wall fan multiple hours each day to dry bath towels, etc., phones plugged in over night, etc. I had enough battery to run for 2.5 days. That's using the OEM converter so the single SOK battery was not fully charged. Naturally, an inverter will change that dynamic once we start plugging things in, but for straight 12 volt usage, my furnace does not appear to be as much of a current draw as yours appears to be.

    Thanks again for all the insight.
    Chad
    2023 23LDE 965W Solar, Victron Multiplus, Solar Controllers, Cerbo GX, 4x280AH DIY Lithium Batteries, SeeLevel Tank Monitoring, Shock Absorbers (Replaced 2022 22MLE)
    2022 F350 6.7L Superduty, Carbonized Gray, Ultimate Lariat Pkg, 4WD, Crew Cab, 160" Wheelbase, 3.55EL Rear End, 3566# Payload
    Adaptive Steering, Ultimate Camera Pkg, 20" Wheels, 397 Amp Dual Alternator, ARE Topper (Replaced 2004 F150)

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