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andy-baird asked

Can’t equalize with 75/15 solar controller

I have a pair of Lifeline AGM batteries that I want to equalize/condition, as they’ve been sitting unused for a while. Lifeline recommends doing this periodically, as follows:

“First go through the normal charge cycle to bring the battery to full charge. The conditioning charge should then be applied by charging for 8 hours. At 77°F (25°C), the conditioning voltage should be set at 2.58 VPC (15.5 volts for a 12 volt battery).”

(There follows a temperature compensation chart. At my ambient temperature, 15.6 V is what they recommend.)

The gist of my problem is this: I have been unable to get my 75/15 to put out anywhere near 15.6 V in equalization mode, or to equalize for more than an hour at a time, regardless of what settings I choose in the VictronConnect app. I’ve read and reread the 75/15 manual, but it doesn’t cover manual equalization, or any of the “Expert Mode” settings available in the Victron app.

Here’s my hardware setup:

* Two 100 W solar panels, tilted and aimed at the sun, under clear Arizona skies. They’re connected in series and are putting out more than 40 V. From past experience I know I can get at least 180 watts from them under these conditions.

* Victron 75/15 solar controller (firmware v1.42), with settings controlled by the VictronConnect app (v5.11) running on an iPhone (iOS 13.1.3).

* Two Lifeline GPL-6CT batteries connected in series, for 300 amp-hours at 12 V.

Again, my goal is 15.6 V for 8 hours, as the battery manufacturer recommends. So I go into the VictronConnect app’s battery settings. I choose “Expert Mode.” I set the equalization voltage to 15.6 V. I set the equalization stop mode to “fixed”, and the equalization duration to 8 hours. I tap the button to start manual equalization. That’s where things go wrong.

First I get a warning that equalization will be limited to 1 hour. And indeed it is: regardless of settings, I have to manually restart the process every hour. What happened to my 8-hour fixed time setting?

Worse, the controller never puts out more than 15.2 volts, despite the fact that I set it to provide 15.6 V in equalization mode. It has plenty of power available from the panels, but is only drawing 19 watts. 15.2 V is obviously not enough to do the job, per Lifeline’s recommendations.

What am I missing here? Why can’t I get the 75/15 to do what its settings say it will do? Any help will be much appreciated.

battery charging
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klim8skeptic avatar image klim8skeptic ♦ commented ·

For a one time 8 hour battery refresh, you could set the absorption voltage 15.6 volts and 8 hours.

I would not leave the battery unattended though. Dont forget to reset the absorption values once finished.

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andy-baird answered ·

Thanks, Klim8skeptic. That may be worth a try as a temporary workaround, assuming the 75/15 will actually put out 15.6 V in absorb mode--I haven't tried it yet. But obviously the long run, I'd like to get it to obey the equalization settings that the VictronConnect app lets me choose. Does anyone else have any ideas on how to achieve that?

(Victron has suggested that maybe I need more power into the solar controller, but really--200 watts in bright Arizona sun isn't enough to generate a couple of amps at 15.6 V? I find that hard to believe.)

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