Apparently Spurious Low Voltage Warning

DIY
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1

Hello,

I have a fairly simple system, a Multiplus II 12/3000/120 with four LiTime 200Ah batteries in parallel for a total of 800Ah and a Cerbo GX. The system has been running well for at least a couple of years with no hardware changes. But I recently started getting Low Voltage Warnings on occasion when the voltage wasn’t low. The most recent instance showed voltage in Remote Console as 12.79 volts with a load of -158 amps. It is my understanding the settings in the ESS Assistant, which was recently updated to the latest version determines the cutoff based on load. Here’s the summary of my ESS settings. As can be seen, 12.79 volts is substantially more than the voltage listed for any of the loads. What am I missing?

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Thanks.

Jim

2

I would love to agree, i assume you mean you have not personally made changes deliberately - however hardware changes itself.

Sometimes through thermal cycling (so terminals that have become loose)

Sometimes through component aging or problems.

Check connections, and then check the batteries. They may be unhappy. Might have to rotate the end ones to the middle to give the a holiday.

That is assuming everything was programmed exactly as it was before the updates.

3

@lxonline Thanks for the response. I just happened to have checked the batteries individually a couple months ago. They’ve been cycled daily from 70-something% to 50-something% for over two years now. I get them fully charged and into float every couple of months so the cells can balance and I wanted to confirm the batteries are all still equal and they were.

I’m guessing there is a drop in voltage compared to what it would have been even a few weeks ago just because of normal battery degradation over time. So the 12.79 volts I saw when the warning went off might have been 12.81 volts just a couple weeks ago.

What I can’t find is anywhere that specifies when to send a low voltage warning and at what voltage. The dynamic cutoff in ESS specifies a cutoff, not a warning. And the voltage I saw when the warning was issued is still well above that specified anywhere else I’ve seen.

4

It is also possible the drop was much lower and the logging missed it (but the inverter obviously didn’t)

5

@lxonline I was actually watching the real-time voltage in VRM when the warning happened. Even if the voltage were much lower, I still don’t know how the “low voltage” number is either calculated or specified for the purposes of issuing a warning.

6

There isn’t a calculation. Just a reading and the matching to the C Rate voltage set.
Since its a new issue maybe adjusting the ess dynamics and then testing to see if it happens again might be worth the test.

7

So my assumption that the warning voltage is somehow determined by the ESS Dynamic Cutoff values is correct? Is that what was meant by “matching [sic] the C Rate voltage set”? If so, I’m still confused because the voltage I observed, 12.79, is still way over the cutoff voltage for even a 0.005C load at 12.25. And I just did the math and a load of -158 amps equates to just about 0.20C which would result in a Dynamic Cutoff voltage of something a little over 12.00, again nowhere near the 12.79 I observed.

P.S. Thanks for working with me on this!

8

Yes, you’re correct. I cannot remember the exact offset, but when the voltage comes within a couple hundred millivolt of the 0.005C voltage, you get a low voltage warning. You can either just ignore the warning (Settings → Devices → Multi/Quattro → Alarm Setup), or configure lower numbers on the curve.