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lwdoss asked

Float settings for concurrent charging on shorepower

While on shorepower, my motorhome’s 12V parallel AGM batteries (400A total) are being charged concurrently by a XANTREX Freedom SW 3012 inverter/charger and 990w parallel solar panels via BlueSolar MPPT 150/100. The SOC (for solar only) is managed through a Venus GX & BMV-712. The inverter/charger typically remains in a float condition throughout the day while plugged in to external power, maintaining the batteries at 100% SOC. There may be a few intermittent loads on the batteries throughout the day because the inverter/charger has a load mgmt system that supplements any insufficient power from shore (or generator) such as heavy start-up loads; however, the SOC typically remains at 100%. Upon daylight, the MPPT automatically enters absorption then float modes. I am not sure if both systems will recognize the other and adjust their float settings accordingly, possibly reducing battery life, and I am concerned that the batteries may be overcharged or damaged by keeping the inverter/charger and MPPT powered concurrently.
Question: To extend battery life, should I disable the MPPT while on shorepower; or should I disable the inverter/charger’s float function so that the batteries are not being charged concurrently from 2 separate sources? Or should I even be concerned about a system with 2 concurrent charging arrangements?

battery charging
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2 Answers
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boekel answered ·

What voltages are you seeing? generally in 'float' the voltage should be at a level the batteries are safe.

the trick to use as much solar as possible is to set charging parameters in the inverter/charger a couple of tenths lower than the solar charger.

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lwdoss avatar image lwdoss commented ·

The float voltage rapidly fluctuates between 13.9 and 14.1, as if the 2 units are fighting each other. That is what prompted my question. While on shorepower, I'm afraid to set the inverter/charger float voltage lower, because one/both chargers will attempt to "catch-up" in the morning and thereby use up cycles, correct?

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boekel avatar image boekel ♦ lwdoss commented ·

I find that quite high for float voltage, I'd set the shore power charger at 13,5 and the solar at 13,6-13,7 so solar is used first if available.

U don't 'use up' cycles by hovering around float voltage.

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lwdoss answered ·

The float voltage fluctuates between 13.9 and 14.1V

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