BE600M1 cycles on and off battery

[lmacmil]

My BE600M1 which was built in December 2025 and purchased and installed in April 2026 has started switching on and off battery several times a day.  I can hear the clicks.  It is only on battery for 1 to 4 seconds.  There haven't been any power outages and my other BE600M1 which is older but with a new battery has not exhibited this behavior.  The logs show the line voltage has never dipped below 121v and varies from 121-125v.  I have just changed the sensitivity from medium to low to see if that will solve the issue but I'm concerned that maybe the unit is defective.  Log files attached.

[lmacmil]

After switching the sensitivity from medium to low, the on-battery/off-battery event has only occurred once in the last 24 hours so it has reduced but not eliminated the issue.

[Teken]

For the benefit of others and you some extra high level information regarding basic UPS Technology.

Changing the sensitivity setting on the unit is a good first step in troubleshooting to see the results and behaviour.

Doing so in no way addresses the electrical condition(s) at the site / home. If dirty power is the culprit there are very few options for the average person / consumer to do without throwing a whole lot of finances toward it.

There are four types of (common) UPS Topologies available for the consumer three of which are the most common: Standby, Line Interactive, OnLine (Double Conversion).

Technically there are five types of UPS Topologies but the last two are so rare you won’t find them for sale at any Best Buy’s etc.

Think military applications . . . 

There are also three types of voltage output most commonly used in UPS’s: PWM, Modified, Sine Wave. A pure Sine wave output is what comes from the local utility and into the home.

For clarity sake PWM is (NOT) the same as Modified Sine Wave! On the surface the stepped wave appears to be the same but I assure you the output is not. 

Higher end models also incorporate a AVR (Automatic Voltage Regulation) circuit that taps into the secondary / primary transformer windings. This circuit allows the system to step up / down the output voltage to the connected devices within its programmed / design limits.

This is called buck / boost from a technical term but normally named (labeled) on various NMS as trim / boost.

Should the input voltage exceed the user defined threshold the system will engage the battery only circuit.

When in this inverter mode all devices connected to the output of the UPS are powered by the RBC (Replacement Battery Cartridge) or battery.

Your specific model UPS is a standby model that uses a stepped modified sine wave or modified. Your unit does not incorporate an AVR circuit as such can only change from Line to Battery (Inverter) mode.

If you review the user manual for defining the sensitivity level. Changing this setting forces the unit to accept a wider input voltage.

As such it’s imperative that all your connected devices are capable and designed to operate in this wider voltage range.

If not expect shorter service life and on the extreme to see the magic smoke puff out!

NOTE: In 2026 the vast majority of electronics are designed for dual voltage / frequency. As such they are more than capable of operating in higher voltages say 120 / 240 VAC 50/60 Hz.

Keeping in mind when voltage decreases current increases. This is when electronics draw more power and current (amps). 

This is why a typical Brown Out or what the industry terms as a voltage sag (lull) is often times more dangerous then a voltage rise.

Questions Ask . . . 👍

[lmacmil]

As the older lawyer joke goes "Everything you said is perfectly true, but you've given me no useful information."  The BE600M1 was put into service in April 2026.  The on/off battery cycling just started in the last couple weeks.  Prior to the current unit, I had another BE600M1 on the same circuit with the same connections (PC, monitor, cable modem and router) for 5 years and never experienced this issue.  Nothing in my house has changed and I doubt that the electrical grid reliability has changed in the last 2 weeks.  If you looked at the logs, you would have seen that the voltage never dropped below 121v which should not have tripped the unit into battery mode.  I think the unit may be defective and I need some information that will either confirm or refute that.

[Teken · Accepted solution]

At a high level if everything was created equal you could compare the two identical units and come to the conclusion one of the units is defective.

But, you can’t because neither devices have been built using the same components and firmware.

If you have the proper diagnostic tools you can confirm the power quality at your location. If not it will be extremely difficult to validate the same.

As it relates to what the logs captured being 121 VAC. The data presented is a brief window of time which doesn’t accurately reflect live monitoring. The interval to see *Dirty Power* is measured in milliseconds / microseconds not seconds and certainly not minutes as the system currently tracks and monitors.

Also note (Dirty Power) is not limited to voltage but related to fast voltage transients, voltage swings, frequency, and THD. The system can detect these disturbances (within a limited design window) and react to them.

As such this is the primary cause for the unit to behave as you describe. If you’re in doubt at all you can submit a service request and have APC Technician Support decide.

Given, the incident of switch over has decreased points to a power quality issue being present.

Questions Ask . . . 👍

[lmacmil]

It sounds like you're saying the PowerChute software can't really detect the kind of power issues I may have been having that caused the unit to go on battery for a second or three.  I might as well uninstall it then since it's not giving me any useful information. 

The unit hasn't switched to battery in 3 days so I'm going to put the sensitivity back to medium.  If it continues to operate normally then I will assume your diagnosis of a day or two of "dirty power" was correct.

[Teken]

The power chute application is primarily designed to connect to a target computer system and provide a controlled graceful shutdown.

It also provides a general means to setup and define user features and options. It provides a high level ability to monitor, track, and recall operations and faults.

It is not designed as a power quality monitor as other dedicated and products do.

Make the change and let me know the outcome. Dirty power is and can be transient or very persistent depending upon where you live.

Questions Ask . . . 👍

[lmacmil]

No issues since changing sensitivity back to medium.  Thanks for your help.

[Teken]

Appreciate the follow up and outcome.

Rock On . . . 🤘