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
replyIt 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.
replyI 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.
replyCurrent 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.
replytemperature is also a problem
replyTemperature probes shouldn't require disconnecting cells, though.
reply