Battery voltage varying 0.0 to 14 volts daily

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mhenricks asked May 2, '24

Battery voltage varying 0.0 to 14 volts daily

I have a SmartSolar 75/15 and a 200ah LifePO battery. The Victron app shows rapid and large changes in the voltage of the battery. For instance, I checked it an hour ago and it showed 0.0 volts. Now it shows 14.18 volts. The screenshot shows voltages ranging from 0.0 to 14-plus daily. This seems unlikely to be accurate. It has been too cloudy to get any solar power from the 100-watt rooftop panel. But I have it plugged into shore power. Any idea what could be going on? Bad battery? Loose connection somewhere? Thanks!

Lithium Battery voltage

victron.png (99.8 KiB)

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mhenricks commented · May 05 at 12:59 PM

I am following up to let anyone interested know that I apparently found and fixed the problem. I went to check the fuse in the Victron controller, as one answer suggested, and found I'd installed the controller incorrectly. I had connected the leads from the battery to the connectors for the load. Swapping these apparently fixed the problem. The controller immediately started showing a steady 13.29 volts charge on the battery. That was yesterday. This morning the reported charge was a steady 13.26 volts and the history showed the charge for today had varied only between 13.27 volts and 13.26 volts. There is still too much cloud cover for any solar charging. We'll see how that goes. For now, all good. Thanks!

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Answer 1 · 2024-05-02T15:31:26Z

prein answered · May 02 at 03:31 PM

Over voltage protection causing shut downs? Which battery do you have?

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mhenricks commented · May 03 at 02:58 PM

Prein, it's a Lossigy 200ah LifePo battery. I've had it for two years. Do you have any idea how to tell if it's overcharging causing a shutdown and, it so, what do about this. Thanks for your help on this.

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Answer 2 · 2024-05-02T16:23:56Z

Justin Cook answered · May 02 at 04:23 PM

Most likely bad connection, blown fuse, that sort of thing. If you see 0v at the battery reported by the controller, that either means the battery has shut down or isn't connected to the controller at all, which is usually a matter of wiring or fuse/breaker.

The 14+v that you're seeing reported by the controller is also very likely not from the battery, but from the controller's own output on the line.

Check all your wiring, fuses, etc - grab the multimeter!

Also, as a note, your solar voltage isn't high enough to charge a 12vNom lithium battery in any case - remember, PV input voltage must be 5v higher than battery voltage for the controller to turn on and start charging (as noted in the manual, datasheet, etc) so you'd need a minimum of around 19v from the panel to have a hope of starting to charge an LFP battery that usually rests between 13.3v and 13.6v.

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mhenricks commented · May 03 at 03:07 PM

Thanks, Justin Cook. So you're saying the battery has gotten disconnected from the Victron controller somehow, likely due to a wiring fault or blown fuse? Is that right? I guess that might explain the 0.0 volts reading.

I was not aware that the controller output any voltage but that might explain the 14+ volt reading that seems to happen every day, regardless of whether the sun is shining, the trailer is on shore power or the battery disconnect switch is even flipped on. Is there any way to check the controller output? Perhaps if I disconnect the battery by removing the cables from the battery posts? If I did that and the controller was still showing voltage on the line, that might indicate it's coming from the controller.

I was aware that the panels have to be putting out a minimum voltage of 18 volts or so to charge the battery and it's not even close to that due to heavy cloud cover. It's plugged in to shore power, however, so the battery would normally be fully charged unless there's some problem with the converter. Right now the app is showing about the battery is charged to about 13 volts. Thanks again for your help on this.

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Matthias Lange - DE ♦ mhenricks commented · May 03 at 03:13 PM

I'm 99% sure that it's just a blown fuse. You should check that first, there is also a fuse directly at the bottom of the MPPT.

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mhenricks Matthias Lange - DE ♦ commented · May 03 at 03:20 PM

Thanks, Matthias! I will check fuses and let you know what I learn. Much appreciate your help on this.

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