Why did Skylla drive voltage higher than the setting?

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patr asked Mar 25, '22

Why did Skylla drive voltage higher than the setting?

On a recent night I was woken up by an alarm on my CCGX saying the voltage was over my alarm setting of 14.8v.

My two Skylla IP44s are set for:

Charge algorithm: 7 (for my 1200Ah of Relion LiFePO batteries)

Absorption voltage: 14.2

Float voltage: 13.5

My system also has two MultiPlus 3000 inverters (master / slave) but they were not connected to shore power. I also have 1500 watts of solar panels. But this was at night. The Skyllas were plugged in to shore power. I cut off shore power and the alarm cleared.

Looking at the VRM history, I can see that one of the Skylla's (Sky2)was outputting significant current, spiking at the time and the output voltage going up to 15.03. The other Skylla did not appear to be outputting any current and had an output voltage of 14.83. Both Skyllas had been in Absorption mode and went to Off when shore power was cut.

This has not happened since, but I have not been using shore power much.

Any ideas why this happened?

thanks

Pat

Skylla overvoltage

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Answer 1 · 2022-03-26T07:43:37Z

wkirby answered · Mar 26, 2022 at 07:43 AM

My thought is that Sky2 is having a problem with temperature compensation. It might be somehow measuring a lower temperature than the actual battery temperature and so the compensated charge Voltage would be higher than Sky1.

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patr commented · Mar 29, 2022 at 08:29 PM

Why would that make it go 0.63v over the set limit?

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