Sorry if this is not the place for this I was unsure which section to put it.

I bought a APC ups pro-1000 a while back, the batteries died. I went to the store to get some new ones and they had a APC smt750rm2uc for a really good deal with new batteries. The first ups I had worked fine with the built in ups settings. I have tried every way I can think of and the new one will not work. I can not get it to recognize that it is a different one. I do not want to do a nut server, I may not really understand how they work. If the power goes out the switch would die then the nut server would be worthless, correct.

Can anyone tell me how I can get the new one to be recognized?
When I turn the option back on it says it has lost connection.

Any help would be greatly appreciated.

If you have a questions please ask and I will do my best to answer them.

Thanks in advance

Not sure I understand your issue, but I'm going to assume you are connecting the USB cable like you had before with the 1000 and it's not reading anything from the UPS?

If that is the case, go into the menu on the APC UPS and go to the configuration menu, there you will find an option called "Menu Type", if that is set to "Standard", change it to "Advanced". Now you will have additional options in the configuration menu. One of the new options on the configuration menu will be an item to enable ModBus, this is a protocol that is used over the USB connection from the UPS. Once that is enabled, in UnRaid, go to the UPS settings and set the "UPS cable" to "USB" and the "UPS type" to "ModBus". See if that helps.

You may notice that among other things, once the menu is set to advanced you can also modify the voltages that the UPS will switch at, in case you need it.

Edited October 30, 2025Oct 30 by WizADSL

Dang that didn't work. I changed the settings on the ups like you suggested. The serial-modbus was disabled, I enabled it. Defiantly lot of options I don't need to be messing with lol. I don't know if it is possible but it seems like the original ups is in some configuration somewhere. When I plug the new one in and turn it on it is not overwriting the old. That is probably not right.

Yes I did not explain it very well, I hooked it up the exact same way.

Do you mean that the settings in unraid, after you save them, aren't overwriting the previous settings? Also, you're using a USB cable I assume, if the new UPS came with one use that one rather the the old one (it shouldn't matter but I've had issues with cables)

Install the NUT plugin and try that (not a NUT server)

7 hours ago, MowMdown said:

Install the NUT plugin and try that (not a NUT server)

If I install the nut plug in and hook it up that way, does the ups have to be hooked up to the network?

If it helps at all, this is what my settings page looks like:

Yours should look very similar, would you mind posting a screenshot?

3 hours ago, Silver_30 said:

If I install the nut plug in and hook it up that way, does the ups have to be hooked up to the network?

No. It has nothing to do with internet or servers, it runs a daemon that communicates to your UPS.

What plug type in cable end which connect to new UPS ? RJ45 ?

For smt750rm2uc, it look like you should use type A to type A USB cable.

20 hours ago, MowMdown said:

No. It has nothing to do with internet or servers, it runs a daemon that communicates to your UPS.

Sorry like the op says I don't really understand how nut works. Do you know a good video or place to learn about it. The only videos I can really find are installing and don't really explain hook up etc.

21 hours ago, WizADSL said:

If it helps at all, this is what my settings page looks like:

Yours should look very similar, would you mind posting a screenshot?

Just now, Silver_30 said:

The first one is the the original ups and the second is the new one.

11 hours ago, Vr2Io said:

What plug type in cable end which connect to new UPS ? RJ45 ?

For smt750rm2uc, it look like you should use type A to type A USB cable.

I will try it. That maybe the problem. I assumed the serial cable from the original unit would work. It has a rj45 looking plug on one end and a usb on the other.

If this is accurate to what the back of your unit looks like:

then @Vr2Io is right and what you want is the USB port, hopefully the cable is included because they are doing a VERY non-standard thing by putting a USB-A plug at both ends. The RJ45 connector is clearly labeled as serial so you don't want to use that (if, as you describe the cable is RJ45 at one end and USB on the other, it most likely contains a serial-to-USB converter and is not what you want to use).

Actually, APC most common cable are USB to RJ50 ( it look like RJ45 but has 10 pin instead 8 pin ), it support USB and Serial in same RJ50 port.

But different UPS model will be different, and smt750rm2uc should have stranded RJ45 network port ( most right side ) it native support Ethernet access.

If you can found UPS in USB device list then it is not connection issue, otherwise you need try different cable to got UPS detect first.

Edited November 1, 2025Nov 1 by Vr2Io

I'm aware of that. My current UPS uses that cable and it is carrying a USB signal. However, the documentation for the UPS mentioned here clearly states it's a serial interface with a separate port for USB. If the UPS doesn't match that Port layout then that's another story. But the documentation is very clear.

1 hour ago, WizADSL said:

I'm aware of that. My current UPS uses that cable and it is carrying a USB signal. However, the documentation for the UPS mentioned here clearly states it's a serial interface with a separate port for USB. If the UPS doesn't match that Port layout then that's another story. But the documentation is very clear.

I haven't deeply go through the manual, but APC doc's always not detail.

Most cable are USB only, but the RJ50 port may support USB+Serial, my old rack APC UPS have DB9 COM port and RJ50 port, you can use Serial in either DB9 COM port or RJ50 port, but USB only on RJ50.

That's not if have DB9 COM, then RJ50 is USB only.

That's why I said if use common cable ( USB only ) haven't detect thr USB device then it is connection issue. There a question does OP's UPS RJ50 port also support Serial+USB or USB only or Serial only.

Edited November 1, 2025Nov 1 by Vr2Io

If this is still an issue id suggest trying to set the ups up on say your laptop - this is counter intuitive - lets find out what port you need. I'm leaning to the |o|o| (serial port). I run an Eaton 5PX ups and it is a USB to the RJ interface for the serial interface.

suggest installing the APC Power chute software to your computer then plugging it in. the green port is for the cloud management software. if you are running a windows vm on your server you could pass that usb port through to it to do this testing.

i dont have an APC smart to test with but it looks like 7.2.3 has an APCsmart in the drop down as well.