Constant voltage trim with APC UPS - Page 1
Forum section: electronics / beginners

author: Hammer8
author_rank: Newbie
timestamp: July 16, 2022, 03:09:16 pm
content: Hi, I have a APC Smart UPS 3000, similar to the one shown in video #504 - UPS Tutorial and Teardown. Thank you for that video. My unit is rated for 208V operation, however, being in the US, the electric service to my home is 120/240 V. So, when I use this UPS, AVR/Voltage Trim is always on. My question is will this degrade the service life of either the batteries or the UPS itself? What is seems to be doing, per PowerChute software, is reducing the input voltage from 244.8V to 217.4V on the output.Watching the video, which is excellent, it sounds like this UPS is designed to run off the mains/utility power mostly, and will only switch to using the transformers when there is an under or over-voltage situation which in my case, is constant. And hence my question of reliability.Thank you!

author: m k
author_rank: Super Contributor
timestamp: July 19, 2022, 01:45:47 pm
content: Rule of thumb would be batteries yes and other stuff no, if they are correctly designed.Generally UPS is for grid power breaks so yes, only for short terms at the time.Its not even for maintaining power but only keeping it on for as long as it takes to take the load off in a controlled manner.Lead acid batteries then generally don't like to be empty, or discharged deeply so that will shorten their life.https://www.power-sonic.com/wp-content/uploads/2021/02/Line-Interactive-Vs-Online-UPS.pdf

author: Hammer8
author_rank: Newbie
timestamp: July 21, 2022, 04:57:39 pm
content: Thanks…do you mean because it is always trimming down the voltage that it is effectively running in Line Interactive mode all the time, which it is not designed to do, and hence will wear out the batteries quicker?

author: ejeffrey
author_rank: Super Contributor
timestamp: July 21, 2022, 05:16:34 pm
content: It should not be discharging the battery. Line interactive UPSes use an auto-transformer to correct the voltage when power is present but slightly out of spec.

author: Hammer8
author_rank: Newbie
timestamp: July 21, 2022, 06:11:36 pm
content: Thanks…that’s what I was hoping and so I’m just wondering if it constantly has to use the auto transformer to step down the voltage, will that reduce the life of the unit? Eg., the unit is designed for 208V and I feeding it 240V.

author: james_s
author_rank: Super Contributor
timestamp: July 21, 2022, 09:38:06 pm
content: It shouldn't, although some UPS's that have this auto-regulation feature bypass it to improve efficiency when the input voltage is within the correct range. Are you sure it is not selectable between 208 and 240V? 208V is typically found in industrial and commercial buildings that are fed by 3 phase. Many apartment buildings are also 120/208V as the building has a 3 phase feed and then two phases go to each unit.

author: MrAl
author_rank: Super Contributor
timestamp: July 23, 2022, 03:32:11 am
content: Quote from: Hammer8 on July 16, 2022, 03:09:16 pmHi,Not sure what power level you are operating at, but if you are that worried you can always purchase a step down transformer and use that to reduce the input level to the UPS system. That would put the strain, if any, on the external transformer and you can choose it to suite your needs independently of the UPS system.Alternately, if you can contact APC you might get some help there. I went to school with one of the managers that worked there some years ago.

author: Hammer8
author_rank: Newbie
timestamp: July 23, 2022, 09:30:56 am
content: Yes, I think the unit was designed for datacenter use where they have 3 phase. Since I am using it in a regular house, I only have 120/240. The exterior of the unit does not have any voltage selector and neither does the control software. I have contacted APC, but I got the general/standard "if it's not meant for 240V, then it will wear out the unit." So, I'm just trying to figure out if that is technically true. The unit in video #504 is almost identical to mine and so I figured I'd ask here...

author: MrAl
author_rank: Super Contributor
timestamp: July 23, 2022, 10:03:53 am
content: Quote from: Hammer8 on July 23, 2022, 09:30:56 amHi,Oh yes i see what you are looking for.You could do your own tests maybe. Check to see if the battery is being used during any time. If it is, then it is wearing faster than it would be if not used. That's the simplest test because batteries always wear faster when charged and discharged. SLA batteries one of the worst. The less you charge and discharge it, the longer it lasts. That's especially with deep discharge where life can be much shorter.To check any transformer, see how hot it gets during regular use. If it does not get hot it will probably last a long time. If it gets warm or moderately hot it will still probably last a long time. If it gets very hot then it could see a limited life, but generally transformers are not very prone to failure unless they are used in applications that do not respect their ratings very well, and that means the hot ones.Also, if you are not using it at full power, you can rest a little easier too, and you shouldnt be using any system at full power anyway.I actually worked in this industry for several years in design and test. In the lab we had a saying about using a converter (which includes a UPS system). That was, we called full load "fool load" (ha ha). I still have to laugh about that today. It was meant to remind us that systems that are run at full load are prone to early failures. One of the rules of thumb was that if you need 1000 watts, buy a 2000 watt converter because only a fool would use one at the full rated load power continuously.Hope that helps shed some light on this issue.

author: darkspr1te
author_rank: Frequent Contributor
timestamp: July 23, 2022, 10:45:10 am
content: Quote from: Hammer8 on July 16, 2022, 03:09:16 pmYou can actually change these value so it's not in trim mode all the time.https://networkupstools.org/protocols/apcsmart.htmlshould be " ^V A" or "^V I"you can also set some values to remain like set a 240 unit to 120, this wont matter though as the transformers are what control this and they are fixed at what ever you got the unit country for but you might end up in overload cycle , to bypass this power up on battery and then switch the value back.darkspr1te

author: Hammer8
author_rank: Newbie
timestamp: July 23, 2022, 09:58:26 pm
content: Thanks everyone. The load will be very light relative to the 3000 VA capacity, so knowing that helps to prolong the life is great info. The batteries are $150 per set so I’d hate to keep having to replace them.On the serial commands, that’s also super helpful info although I am having a hard time connecting using Putty on a Windows box.Thanks you!

author: darkspr1te
author_rank: Frequent Contributor
timestamp: July 25, 2022, 07:32:02 am
content: Quote from: Hammer8 on July 23, 2022, 09:58:26 pmUse realterm, some of the commands you have to send cannot be sent via normal TTY serial connection and may require hex commands sent first. also some of the responses will send commands back in hex that will be interpreated by the serial software and may clear screen and other odd things, to get around this you use the HEX+ANSI display option in realtermNB: using the reset battery date, battery snapshot values etc will alter the systems apparent battery cap, this is normal and is part of the inhouse tools APC use to reset a serviced UPS. This is also required when you replace the battery , most users didnt know they needed to reset the battery cap after changing the batterydarkspr1te

author: wraper
author_rank: Unknown
timestamp: July 25, 2022, 07:50:01 am
content: This will reduce efficiency, therefore somewhat increase your electric bill. Dunno if it's possible to adjust its calibration by altering calibration constants but it should be possible to replace some resistor in voltage divider to adjust its voltage sensing.

author: m k
author_rank: Super Contributor
timestamp: July 25, 2022, 04:00:40 pm
content: Quote from: Hammer8 on July 23, 2022, 09:58:26 pmCable hacking is missing 4 DSR, I'd say it's more important than 1 CD.So 4-6 instead of 4-1, 1-4-6 is no harm either.Lowest Putty Category is Serial, if Flow control there is None or XON/XOFF only UPS connected 3 wires should be enough.Smart Protocol Modelstring ^A is Caret notation of single value of 1, ^B is 2 and so on.Caret here is Ctrl-key, so Ctrl-A, Ctrl-B and so on, here character is not case sensitive.Run in bypass mode ^ is that character, 0x7F is a hex notation and a single value of 127.Despite Windows codepage all characters will be sent using their correct values.If keyboard has no character available alternative method is pressing Alt-key down and typing character's decimal value using keypad numbers, character is produced when Alt-key is released.This is a Windows feature so nothing to do with Putty.