SmartSolar 75/15 Absorption Voltage Higher than Set

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jaeger asked Mar 23, '19

SmartSolar 75/15 Absorption Voltage Higher than Set

Finally have a clear cold day and am able to test my SmartSolar 75/15 installation. I have a pair of new 100ah 12v AGM deep cycle batteries that were only slightly discharged and a 100 watt 20v solar panel supplying the charge.

To the point, the configuration screen of the charge controller shows the absorption voltage set to 14.4 volts, but the app shows the actual voltage being produced is a consistent 14.67-14.68 volts. My BMV-712 Battery Monitor confirms the voltage as 14.65 volts which is close enough. Reading voltage at the batteries with my older voltmeter shows 14.58 volts.

My concern is the battery manufacturer says 14.7 volts is the high end of the absorption range and I don't want the controller to ever exceed that. Since the controller is already exceeding its own configured voltage, I'd really like to know if there's a risk of the voltage going even higher.

Thanks.

@Jaeger

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boekel answered · Mar 23, 2019 at 03:22 PM

This question comes by every day, it is probably due to the temperature compensation. Colder = higher voltage.

Your battery manufacturer also states a temperature (usually 20-25 degrees C) where the maximum voltage is stated.

Maybe the Manual can be made more clear on this? (@Guy Stewart (Victron Energy Staff) ?)

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mvader (Victron Energy) ♦♦ commented · Mar 23, 2019 at 05:15 PM

Yes; and the app. We’ll work on that; thanks!

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jaeger commented · Mar 23, 2019 at 07:30 PM

The math works out almost exactly. The temperature during the test was about 2 degrees C and based on a standard 25 degree setting, 23 times the voltage adjustment resulted in almost the exact voltage shown. Thanks!

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Answer 1 · 2020-08-13T04:13:08Z

mark2 answered · Aug 13, 2020 at 04:13 AM

I wanted to bump this as I have a similar issue after having LiFePo4 batteries installed yesterday. Absorption voltage is set to 57.6 as per manufacture recommendation, however the BMV and CGGX both display voltage of 57.9 at the end of bulk. The charger is set to 'Lithium' battery type which should disable temperature compensation. In any case, the temperature yesterday was around 20 degrees C.

I am concerned that I could be overcharging them - should I reduce the absorption setting by 0.3V?

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