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Comment by peesem | Hacker News Reader

i'm confused, why would a system simply checking its own power state be taking so much electricity as to show up on grid measurements? unless they mean that the systems are choosing to start charging the batteries, but then it's a continuous load and not a spike at the start of the minute, right?

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The Frequency is actually increasing at every event which means grid load is reduced for a short while every minute. Those UPS installations basically briefly switch to Battery every Minute to test Capacity/internal resistance and so on. This so called "load dump" is visible in grid frequency since a lot of these systems work synchronous thanks to NTP

It can be that part of battery is disconnected, to estimate cells voltage. You can not measure voltage while another source is chsrging battery. Or capacitors are charging.

I think you can. RC toys do that all the time. Maybe the measurement is less precise, but you usually don't need super precise voltage, especially if you know your capacitance and measure current.

Current doesn't tell you if the battery is leaking charge, or otherwise failing to store it though. Vastly increased losses could be a sign of failure, for example. In any case it's important to be sure.

temperature is also a problem

Temperature probes shouldn't require disconnecting cells, though.

no the temperature changes the voltage reading

A few microvolts difference, well under 1 milli-volt. I'm pretty sure power grid storage doesn't need that precision.

That wouldn't require dropping from power network, just disconnecting battery from load/charging

If they are checking the charging at exactly the minute, then start of charge will happen then too, which will create a spike if it's synchronized with many others doing the same thing.

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