MPPT not going into float at float voltage setting.

learaviator
learaviator Registered Users Posts: 15 ✭✭
in Off Grid Solar & Battery Systems #1
I am still confused as to what switches my charge controller into float mode. I have a Victron MPPT VE Can 250/100 and in settings I have the float voltage set at 27.00. Currently my battery voltage is showing 27.35 and it is still in bulk. That reading is from Victron Connect looking at the device screen. When I go to my dashboard on the portal, the battery voltage is going back and forth between 26.96 and 27.05. Does the portal have to see the voltage above 27.00 for a certain amount of time to go to float? I apparently am not understanding what determines going into float. I am attaching a screenshot of my system. 
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  • mike_s
    mike_s Registered Users Posts: 167 ✭✭✭
    #2
    "Float voltage" is the voltage the controller will go to after switching to float mode. It has nothing to do with when that change occurs. The charging stages are well described in the manual, read it. But basically, it will charge to the set absorption voltage, stay there for some period of time and/or until the charging current drops below some level, and only then switch to float.
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  • learaviator
    learaviator Registered Users Posts: 15 ✭✭
    edited September 24 #3
    Thank you! I also heard from Jason at NAZ and he reminded of how it all works. AND helped me with some shunt settings. I am not sure how I forgot everything I have learned LOL

    Work has been so crazy, I need to spend more time at my off grid place I'm thinking LOL
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  • Jackielei
    Jackielei Registered Users Posts: 5 ✭✭
    #4

    Don't worry, this is normal behavior. The transition between charge stages is determined by the battery voltage measured locally by the controller, not the data you see on the cloud portal. Your controller reading 27.35V means it 'sees' a voltage that is indeed high.

    The system is likely still in Bulk because it hasn't yet reached your configured Absorption Voltage setting, or it has reached it but the Absorption Time hasn't elapsed yet. These two parameters are key for determining the switch to Float.

    I'd recommend checking your Absorption Voltage and Absorption Time settings in Victron Connect. Victron's algorithm is very smart and is designed to ensure your batteries are truly full before switching to Float, which is much better for their long-term health.

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  • Jackielei
    Jackielei Registered Users Posts: 5 ✭✭
    #5

     The controller uses its local reading, not the cloud, to decide. It will stay in Bulk until it finishes the Absorption stage (hits the Absorption Voltage and holds it for the Absorption Time), which is separate from the Float voltage setting.

    Your Float is set to 27.0V, but your Absorption is probably set higher (like 28.2V), which is why it's still bulk charging.

    On a related note, for a stable 48V system, using a dedicated energy storage battery can really simplify these settings and improve performance. such as the 48V batteries are designed to work perfectly with Victron gear. Feel free to take a look if you're interested: https://cmxbattery.com/product/16kwh-48v-320ah-lifepo4-lithium-off-grid-solar-battery-for-home-energy-storage/

    Hope this helps you get it all sorted!

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  • cleancurrent002
    cleancurrent002 Registered Users Posts: 13 ✭✭
    #6

    Your battery voltage is near the float level, but the controller hasn’t switched yet. MPPTs usually wait a bit above the float setpoint before entering float, and if the battery is full but current is still high, it may stay in bulk to taper safely.

    Check Victron Connect to ensure absorption voltage, absorption time, and float voltage are set correctly—sometimes a small tweak fixes it.

    You can also read more about solar charging basics here for solar use

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  • Jackielei
    Jackielei Registered Users Posts: 5 ✭✭
    #7

    That looks normal. Many MPPTs will hold bulk a bit longer if the battery is nearly full but the charge current hasn’t tapered enough. A small adjustment to absorption time or lowering the absorption voltage by 0.05–0.1V per cell can help it enter float more consistently.

    Also, if your inverter/charger supports more precise charge tuning, that can smooth things out too. I’m using a 12kW unit with flexible charge settings (this one: https://cmxbattery.com/product/12kw-18kpv-hybrid-inverter-charger-all-in-one-hybrid-inverter/ ) and it helped stabilize the transition between bulk - absorption - float.

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