MPPT and a DC to DC charger

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DaveJ
DaveJ Registered Users Posts: 1 ✭
in Solar Beginners Corner #1
Hi Everyone, I have 400w of PV and a Epever MPPT controller on my campervan. All is good until winter. So was was thinking of adding a DC to DC charger to charge from the main battery to the leisure batteries. Would I need to disconnect the MPPT before switching in the DC to DC? I'd rather they were both connected to avoid the MPPT shutting down as it will not have power. My worry is that the DC to DC charger will damage the MPPT when charging the sealed lead acid batteries.
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    edited December 2019 #2
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    Welcome aboard @DaveJ

    Having two charging sources on a single battery is generally not an issue but it must be remembered that the one with the highest potential will take priority if the other is unable to supply adequate voltage, therefore both need to be set with the same charging profile for optimum performance. Should the MPPT not be able to provide sufficient output, equal to the DC to DC charging source, it will simply cease charging until such time it is able to do so, therefore disconnection is unnecessary as reverse current protection is inherent to charge controllers.

    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • RoyB
    RoyB Registered Users Posts: 2 ✭
    #3
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    What McGiver said.......I just got my Renogy 40A DC to DC charger to install in my truck to charge the Toy Hauler batteries while driving.
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  • mike_s
    mike_s Registered Users Posts: 155 ✭✭
    #4
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    If the charging profiles of the batteries are anywhere close, I'd consider just getting a <$50 battery isolator.
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