RV 24V System

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Suntrekker
Suntrekker Registered Users Posts: 142 ✭✭

640W 24V LiFePO4 280AH 

I jumped from the build thread (https://forum.solar-electric.com/discussion/356634/life-cell-internal-resistance#latest) and will post off grid system details, performance and experiences.

Thnx Bill/Forum members for the support!

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  • Suntrekker
    Suntrekker Registered Users Posts: 142 ✭✭
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    System hardware under the bunk.
  • Suntrekker
    Suntrekker Registered Users Posts: 142 ✭✭
    edited September 2022 #3
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    I’m dry camping in national forest, northern Arizona.  Off grid system has power to spare, running all appliances including AC (no generator).  I’m a happy camper!  : )

    And 24V battery is clicking on all cells (credit the active cell balancer), it floats under 27V (90%+ SoC).

    The only issue was a 60A fuse meltdown between the SCC and battery. …my fault, I installed an audio fuse. 


  • BB.
    BB. Super Moderators, Administrators Posts: 33,478 admin
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    Yep... "Good/Solid" fuse blocks and fuses usually "bolt on" are not cheap (for high current systems).

    MRBF holders and fuses are relatively small form factor--If space is an issue:

    https://www.bluesea.com/products/category/16/72/Fuse_Blocks/Terminal_Fuse_Blocks



    Also, I don't remember your actual battery charging current (maximum/continuous)--I like to always suggest that battery charging circuits (wiring/breakers/fuses) be rated for 1.25x (1/0.80 or 1/80%) of charging current. For example, if you are really charging at 60 amps, suggest:
    • 60 Amps * 1.25 for NEC continuous current derating = 75 Amp or larger wiring/current protection device (CPD)
    For North American fuses/breakers they are generally rated to "trip" at 100% or greater current, and "not trip" at 80% or less of rated current.

    When charging batteries--A well discharged battery can usually accept maximum/rated charger current (i.e., 60 amp charger) for "hours" (600 AH bank @ 10% rate of charge = 60 amps)... And a 50% discharged bank can take that current for upwards of 5 hours continuous rated current flow. A fuse/breaker (and wiring) running at 100% of rated current (or for example 60 amp fuse * 0.80 NEC derating = 48 amps suggested max continuous current flow) is going to run hot and possibly trip after hours of rated current flow.

    You could also replace the fuse with a breaker (with manual trip) and have the OCP and "switch" function too (turn off for service, winter storage, etc.).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Suntrekker
    Suntrekker Registered Users Posts: 142 ✭✭
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    Bill, good info (as always)!
    Yeah I installed another fuse and happy to report all’s good.

  • Suntrekker
    Suntrekker Registered Users Posts: 142 ✭✭
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    Off grid hardware:

    REC 320NP mono 320W panel (2)

    Tamarack tilt kit

    Outback FM60 SCC

    Aims 3K pure sine wave inverter 

    Aims remote LCD display 

    DC converter 60A

    LiFePO4 24V 280AH battery bank 

    Active cell balancer 

    Cole Hersee solenoid 24V 200A

    PowerMon smart battery monitor

    Perko main disconnect switch 250A

    Assorted breakers, fuses

  • Suntrekker
    Suntrekker Registered Users Posts: 142 ✭✭
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    Love Off Grid - away from the hubbub.


  • Suntrekker
    Suntrekker Registered Users Posts: 142 ✭✭
    edited March 2023 #8
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    Hi Bill and fellow members, update after a year.  All’s good, the lithium 24V battery performs well!


  • BB.
    BB. Super Moderators, Administrators Posts: 33,478 admin
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    Thank you for your updates... Always wonderful to read about successful solar installations.

    Take care,
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Suntrekker
    Suntrekker Registered Users Posts: 142 ✭✭
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     :) 
  • JRHill
    JRHill Registered Users Posts: 293 ✭✭✭
    edited March 2023 #11
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    Whether boondocking or just plain living off grid in the middle-of-nowhere is something many do not desire or relate. Ask a city or urban dweller the last time they stopped and listened to snow flakes hitting the trees. You'd have to pull the ear buds out.

    BTW, nice set up. TY  for the beautiful pictures.
    Off Grid. Two systems: 1) 2925w panels, OB VFXR3648, FM80, FNDC, Victron BMV-712, Mate3s, 240 xformer, four SimpliPHI 3.8; 2) 780w, Morningstar 30a, Grundfos switch, controller and AC/DC pump, 8 T105. Honda EU7000is w/AGS. Champion 3100. HF 4550, Miller Bobcat.
  • Horsefly
    Horsefly Registered Users Posts: 472 ✭✭✭✭
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    Very nice pics!  I'm still amazed that you don't have a BMS, but it seems to be working for you.

    Be aware that I had that exact active balancer and something went haywire on it while I was testing. One side (around 50% of the capacitors) got too hot to touch, and the board was draining one of my cells pretty quickly. That cell would have been destroyed had I not checked on the system when I did. Since then I only plug in the active balancer when the cells look out of balance, which I can see on my BMS Bluetooth app. I unplug it again a few hours later after it's done its job.
    Off-grid cabin: 6 x Canadian Solar CSK-280M PV panels, Schneider XW-MPPT60-150 Charge Controller, Schneider CSW4024 Inverter/Charger, Schneider SCP, 8S (25.6V), 230Ah Eve LiFePO4 battery in a custom insulated and heated case.
  • Suntrekker
    Suntrekker Registered Users Posts: 142 ✭✭
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    JRHill  :)

    Thnx Horsefly for mentioning the active balancer, I’ll keep it in mind.  Battery performance is monitored by phone (Bluetooth).  All looks good!

    And I’ll post more pics of my surroundings, BLM land and Prescott National Forest.  

    …phone/internet service is spotty but I’m not complaining  ;)

  • Suntrekker
    Suntrekker Registered Users Posts: 142 ✭✭
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    Rare snowstorm in the desert.

  • Suntrekker
    Suntrekker Registered Users Posts: 142 ✭✭
    edited March 2023 #15
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    Cold nights (20°) have prevented solar charging until the battery warms up.  I didn’t foresee camping in low temps (or take the necessary precautions).  …charging has been reduced to 4 hours/day.

  • Suntrekker
    Suntrekker Registered Users Posts: 142 ✭✭
    edited July 2023 #16
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    System performance exceeds expectations. On a typical day sun powers all loads (fridge and AC), battery SOC 90%.

  • Marc Kurth
    Marc Kurth Solar Expert Posts: 1,145 ✭✭✭✭
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    System performance exceeds expectations. On a typical day sun powers all loads (fridge and AC), battery SOC 90%.



    Nice! This is rare in the RV world.



    I always have more questions than answers. That's the nature of life.
  • Suntrekker
    Suntrekker Registered Users Posts: 142 ✭✭
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    System performance exceeds expectations. On a typical day sun powers all loads (fridge and AC), battery SOC 90%.



    Nice! This is rare in the RV world.

    So far so good!  Boondocking 1-1/2 yrs and all systems go!  I did replace cheap split wire loom (on the roof) with RoHS UV rated stuff. 

  • scrubjaysnesttoo
    scrubjaysnesttoo Registered Users Posts: 5
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    I use cordmate II and paint it with krylon.
  • Suntrekker
    Suntrekker Registered Users Posts: 142 ✭✭
    edited March 4 #20
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    The new UV rated split wire loom should last at least 3 years (and easy to replace).  Anyway I inspect the RV roof every year.

    Also two years rving and the 24V LiFePO4 battery performs as designed. …very pleased!