APC UPS Smart-UPS 1400VA (SU1400RMNET)


An old unit but getting 12-month warranty for the battery and for the price of 130 € including an SNMP communications card.

These are also simple and easy to fix if they go wrong.

It is the same model as one that I have had on my eBay watchlist for a year, but haven’t bought it because of 200€+ price. This is locally available so no postage. Pure sinewave, which is the only one to really consider.

Expecting the new infrastructure take perhaps 420 watts, which would give maybe 20 minutes. More than enough to save everything and even wait for the power to come back.


I have a halogen lamp hooked to the device and the light level is clearly oscillating. So either it isn’t pure sinewave, or it is doing poor job regulating. Could be old caps. But I don’t have tools to diagnose the problem so for now I just have to trust that the power is good. That’s a poor predicament but what can I do.

Charges at 75W so definitely not happy with that. At that rate it will take 10 hours, or so, to recharge. Perhaps this is the way all UPS work but that feels like poor performance. Perhaps it has something to do with battery design or longevity of the batteries, or the battery technology.

Installation succeeded

First of all I must say that whenever you can: get a dual PSU machines; there were no distractions to my main server when the UPS was plugged between the machine and the wall outlet, while another server with single power supply suffered from me not being even close fast enough in switching the power.

But this UPS isn’t for keeping the machines up and running for a long time, that is for sure. The batteries were completely drained after only maybe three minutes. So either the batteries aren’t the best or time went by really fast. But I will be doing complete test down to 1 bar of capacity once the batteries have recharged. Also seriously considering to get another one since the man said he has plenty of these. And the price is on the spot.

More about the current setup

So the way I have set things up is like this, looking from the wall outlet onwards:

  1. Ground fault circuit interrupter
  2. Power meter
  3. Overcurrent protector
  4. UPS
  5. Sensitive devices

So the idea is that if there is current leaking to wrong places, then the ground fault circuit interrupter will save lives and hopefully prevent fires, and when everything works correctly, the power meter will measure the power usage, the overcurrent protector will protect the UPS, and the UPS will protect the devices (secondary function) and provide them power if utility power fails.

The location of power meter is probably wrong because it is now receptive to overcurrent, and could in such situation cause fire. So it will be moved between the overcurrent protector and the rest of the system.

The power usage of this model, by the way, is about 40W idle. AFAIK it is line-interactive and not online so not sure where it puts all that power. 40W is quite a bit.

The noise is practically non-existent. Maybe if you have 100% silent setup, then the noise might be overpowering, but for anyone buying devices like these then no, not really a concern.


At about 420W load the runtime with full batteries is only 6 minutes and 45 seconds; to complete power-off undervoltage shutdown. So the batteries have only about 50% of their capacity left. It should have lasted at least twice as long, as it is 950W device and the runtimes for those are usually about 5 minutes at full load. But I am not going to bitch about it to the man who sold it because the price is fair even with less than ideal batteries, and new batteries will only cost about 100 € anyways.

The condition

I opened up the device to check the batteries out and glad I did because one battery had leaked something and one connector was so oxidized that it is a wonder that any current passed through that connection. So the poor testing results could partly be explained by the connector, because it certainly dropped some voltage, and the UPS may have had trouble pulling the current out of the batteries.

But the leaking battery is a bigger problem because it is likely that it won’t stop leaking just because I hope so. So new batteries are in order sometime near.

After testing it again, the oxidized connector wasn’t the problem because I got practically identical runtime with new connector in place. So the batteries are poor. One is marked as 2012 so I expect the rest to be that same era.

$50 pure sine wave inverter?

Amazing how these old UPS can be reconditioned and reconfigured to do the work of 1000 € devices:

Check the whole series. Real hardware hacking.

Also the guy knows a lot about inverters and a lot of that seems to apply to UPS as well, and just like cheap inverters; cheap UPS too provide modified sine wave which can even be damaging to sensitive electronics and motors.

So if I ever want to get an UPS I will make sure to get one of these rack/professional units which are of higher quality.

Eaton Evolution 1550 Rack 1U


Found this 1550VA/1100W UPS for 190 € incl. shipping. But it’s 2013/08 and batteries are dead, according to local Eaton representative.

He suggested to charge the batteries for 48 hours and the see if they had hold any charge, and told 6 months is usually the guaranteed period the batteries can stand still until they start degrading.

And as far as I understood when lead-acid battery once sulfates then it cannot be restored. Long charging may help but never up to their original condition.

And new battery packs trading easily at or around 100 € I have to pass this one. New Eatons go for 500 € so at 300 € total cost after restoration it probably isn’t worth it.

Definition of Volt-amperes, true power, phantom power, reactive power and apparent power

I tried to once find a good explanation what Volt-amperes used in UPS systems truly are or how they differ from power.

Wikipedia has very poor explanation or at least I was not able to truly comprehend the differencies.

Yesterday I found this by accident and it finally started to make sense.

We know that reactive loads such as inductors and capacitors dissipate zero power, yet the fact that they drop voltage and draw current gives the deceptive impression that they actually do dissipate power. This “phantom power” is called reactive power, and it is measured in a unit called Volt-Amps-Reactive (VAR), rather than watts. The mathematical symbol for reactive power is (unfortunately) the capital letter Q. The actual amount of power being used, or dissipated, in a circuit is called true power, and it is measured in watts (symbolized by the capital letter P, as always). The combination of reactive power and true power is called apparent power, and it is the product of a circuit’s voltage and current, without reference to phase angle. Apparent power is measured in the unit of Volt-Amps (VA) and is symbolized by the capital letter S.