SMT2200IC occasional critical errors and loads disconnected

[captainslow]

My SmartUPS 2200 has started throwing occasional critical errors and dropping power to the outlets, which is unhelpful...

About a month ago I got a B.12 "Battery voltage sense error" (0x01BB) error and it dropped power to the outlets Turning off the utility power and the UPS and turning it on again cleared it.

Yesterday I got a "A backfeed relay fault exists." (0x016B) error and it dropped power to the outlets. Again, turning off utility power and the UPS and turning it on again cleared it.

The UPS passes a full self-test. It's a second hand unit, which I've had for a year or so, and has been reliable up to now. It's on the latest firmware (18.0 for ID1015). It's only got a low load (around 120W or so).

The fault log is below:

Number Time (ms) Event Code Event
0 04/02/2026 16:16:47.792 205 Green relay open
1 04/02/2026 16:16:40.850 205 Green relay open
2 04/02/2026 16:14:02.817 137 Backfeed Relay Open Fault
3 03/19/2026 18:36:51.649 207 Battery voltage sense mismatch

The batteries are probably the original ones, but I think they've had an easy life, and before I spend $$$ on new batteries, does anyone know if the above errors indicate something terminal with the UPS electronics itself? Certainly I don't trust it at the moment...

Thanks!

[Teken]

What is the serial number of the UPS and production date of the RBC (White Sticker) vs battery installation date listed in the system?!?

Perform the following action item(s) and report the outcome:

RBC: Disconnect the Anderson connector from RBC that feeds the system and report the results. Expected behaviour is the system will continue to operate but declare a RBC disconnected fault.

Upon reconnection of the Anderson connector the system will prompt you to confirm if this is a new RBC. Affirm (No) for now and complete the next action item listed below.

Static Load Test: Disconnect all connected loads from the unit. Disconnect AC Mains from the system and report the outcome. Expected behaviour is the system will operate fine and declare a loss of AC Power. The unit should operate for several hours in this state without issues before shutting down based on the user defined settings.

Dynamic Load Test: Disconnect AC Mains from the system and report the outcome. Expected behaviour is the system will continue to operate and support the connected load and declare a loss of AC Power.

The system should continue to operate like this until the user defined shutdown has been met then power off.

Time how long the system operates for and compare that to the (Online) APC Runtime Calculator based on the attached load.

If the system drops the load and powers down immediately the RBC is expired and needs to be replaced. 

The OEM RBC has a service life of 2-5 years based on usage, temperature, and environmental conditions. The RBC is designed to sustain 260 cycles subject to the same caveats listed above.

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[captainslow]

Thank you for the suggestions and tips, it took a couple of days before I could disconnect critical loads to run these tests.

The UPS performs normally - disconnecting mains power with or without load results in a normal switch to battery, the battery runtime is as expected (several hours for a load of ~100W on a 2200VA system). Disconnecting the battery Andersen connector results in a battery disconnected fault but normal operation otherwise.

The unit is around 5 years old (manufacturing date 09/2020)  and I purchased it second-hand, but I'm reasonably sure it's had a quiet life - in a biotech lab - before I got it. 

Any other suggestions welcome... I'll keep an eye on it, but the random dropping of loads and erroring until hard rebooted by hand is not my preferred way of running IT kit... 😕

[Teken]

You haven’t provided the RBC installation / production date of the RBC for review.

Regardless, you may consider the following action items to see if the problem goes away or remains:

Green Mode: Disable this feature via LCD, NMC, Power Chute.

Brain Dead: You may complete this task during a scheduled maintenance window:

https://www.se.com/us/en/faqs/FA156611/

Generally speaking the active fault / error points to failing internal component(s) within the unit. In rare cases a drop in output is caused by a faulty connected device but the system would normally declare a output short. If a connected device is just in the beginning stages of failing it would not trip the output short circuit but mimic what you see now.

You may also complete the following tasks to obtain more information and data:

AC Input: Measure the incoming VAC and compare it to the displayed value from the system via LCD, NMC, Power Chute.

AC Output: Measure the VAC at the rear outputs and compare it to the LCD, NMC, Power Chute. Ensure the AC measurements are taken by a True RMS Meter.

DC Output: Back probe the Anderson connector at the RBC. Document the output DC voltage coming out of the systems Anderson connector.

RBC: Disconnect the Anderson connector from the system and measure RBC DC voltage and document. The voltage will be the same initially as what you measured while it was connected.

72 Hours: Leave the RBC disconnected for a minimum of 72 hours. Measure the DC voltage from the Anderson connector and report the value here.

A healthy RBC will hold its resting charge after the initial float / charge voltage has dissipated.

Meaning a drop in 0.1 VDC vs 1 ~ 3.XX VDC. Typically a person will find one or more cells are failing and thus pulling down the rest.

As such it’s imperative to inspect all the individual cells for swelling, bulging, cracks, corrosion, and heat.

When the series / parallel wiring in the RBC has been removed. It’s much easier to identify a failed cell.

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