Repeated Smart UPS 2200 problem?

[Anonymous user]

The comany I work for uses APC 2200's to back up networking racks in various buildings around the city (about 100 at least) and we repeatedly see similiar problems over and over.
I looked over three units (we have seen this problem in many more than three), and each had the same problem - two 1/4 watt 470 ohm resistors on the main board were burnt (R38, R43). Nothing else appeared to be compromised. I replaced the resistors with 1/2 watt parts, and installed fresh, matching batteries (because they're in series). After an initial charge time, the resistors continued to run hot (way too hot to touch), and the quescient operating power of the UPS (no load attached) was 77 watts!?

Measuring the voltage drop across the resistors showed between 45-60 volts, so the parts were dissipating about 5 watts (I realize a regular DMM will average the waveform, but this was just for a rough idea). Obviously the original design spec wasn't for these parts to handle this much current (because the original part was a 1/4 w resistor), so my question is why am I seeing this recurring problem in multiple units? Is this a known issue? What is causing it?

Message was edited by: johnszxr

[BillP]

Sounds like the SUA version is in a different league altogether as there are no SMDs in my old SU series.  I haven't heard of "APC FIX" but was able to locate something about it via a Google search.  Most of it was in Russian and I will get my wife to translate it for me.  Thanks for the tip!

[MarkGinger_apc]

Hey johnszxr,



How did these failures manifest themselves? Did the unit turn off completely? Was it acting erratically? Any info would be greatly appreciated.



Thank you!

[Anonymous user]

My SU2200RM3U has these resistors toasty as well. My unit will not switch to battery power. The batteries appear to be charged and all measure 13 volts, but if I yank the cord it never switched to battery power. It also never switches to battery power when pressing the on button like the directions say. Any ideas on how to fix this thing??

[BillP]

Just as a note, it's entirely possible to read "good" voltage on a completely toast battery. It will still charge up and keep voltage, it's just that the capacity isn't what it used to be, so it doesn't have enough runtime to sufficiently power your load for any duration and will simply turn the UPS (and equipment, of course) off. How old are the batteries?

In terms of switching to battery on power-on, if you disabled the self-test, it wouldn't do that... Are you saying it turns right back off instead?

[Anonymous user]

thank you for information repairs ups good

juju

[Anonymous user]

jevs wrote:
My SU2200RM3U has these resistors toasty as well. My unit will not switch to battery power. The batteries appear to be charged and all measure 13 volts, but if I yank the cord it never switched to battery power. It also never switches to battery power when pressing the on button like the directions say. Any ideas on how to fix this thing??

There is no way that UPS is running 12v nominal and measuring voltage across only one pack is not a good technique. I believe the entire pack is either 24 or 48v. Measure the voltage across the entire pack using a meter and continue monitoring as it goes into battery backup. If the voltage plummets instant it switches over, you have a bad battery pack that needs replacing. If it doesn't change much, but isn't switching over, it's a board issue.

This is a fairly common issue with that generation SmartUPS. It's like monitoring the RPM at idle only to have the engine stall as soon as the clutch is engaged.

Battery can fail open circuit, so its possible for them to be low in capacity one day, but completely dead the next due to a failed cell in a string. A serious problem with older SmartUPS is that when it goes into self-test and the battery "isn't there" as in open circuit failure, or it can't handle it, it will drop the load instead of jumping back to AC power and report failure, so the UPS in itself has the chance to cause a power failure.

So, this would be a good opportunity to get a newer model or an online (double conversion) model that is less prone to this.

The older SmartUPS is dumb enough that it will drop the load if you were to initiate self-test with the battery missing (which is basically what happens when battery fails open circuit from grid corrosion). I don't represent APC, but after I learned that new models have resolved this problem, I really encourage getting a newer model, because this leaves you at risk of having a "power outage" even in the presence of utility power.

[Anonymous user]

The comany I work for uses APC 2200's to back up networking racks in various buildings around the city (about 100 at least) and we repeatedly see similiar problems over and over.
I looked over three units (we have seen this problem in many more than three), and each had the same problem - two 1/4 watt 470 ohm resistors on the main board were burnt (R38, R43). Nothing else appeared to be compromised. I replaced the resistors with 1/2 watt parts, and installed fresh, matching batteries (because they're in series). After an initial charge time, the resistors continued to run hot (way too hot to touch), and the quescient operating power of the UPS (no load attached) was 77 watts!?

Measuring the voltage drop across the resistors showed between 45-60 volts, so the parts were dissipating about 5 watts (I realize a regular DMM will average the waveform, but this was just for a rough idea). Obviously the original design spec wasn't for these parts to handle this much current (because the original part was a 1/4 w resistor), so my question is why am I seeing this recurring problem in multiple units? Is this a known issue? What is causing it?

Message was edited by: johnszxr

[Anonymous user]

I replaced the two 470 ohm 1/4 watt resistors with 1/2 watt parts, which helped. Also, I lowered the float voltage on one of my test units from 54.9 to 54.5.

[hkpolice_apc]

Very informative post, thanks to all involved.

Did anyone try adjusting the float voltage by using the Serial cable + Hyperterminal and using "PROG" mode? Or is the R118/R119 mod the only way for SUA2200 units?

[BillP]

I was never able to get the battery voltage to change using the "PROG" mode and replacement of the resistors was what did it for me.

[Anonymous user]

I have an out of warranty 2200 that has exactly the same issues....No power/response when plugged in, and R38/R43 appear to be fried.

Has anyone had long-term luck replacing these two resistors? If so, how do I determine the correct values...they are too burned to read the bands. ( board is: 640-0734K Rev 13)

...and are there other components that should be replaced?

Thanks,

Dave

[Anonymous user]

I agree. I don't know why expensive equipment like this is not supported by schematics. This stuff is not that complex electrically.

[BillP]

thanks to johnszxr, i found R38 and R43 "cooked"on my non-functioning su2200net

i was wondering what happened to my smart-ups -- it looks to me this is a design flaw

[BillP]

an SU2200NET is an older generation UPS and as far as I know. has anyone seen this on an SUA2200 which is the current generation?

[Anonymous user]

Is anyone from APC/Schneider still tracking this thread? I just joined up so
I could participate, and have a couple of units [2200, 1400XL] with the
same issue. I would agree that it's a design problem, which only manifests
itself when the unit is on wall power and the hot parts in question run at
a normal cool level when the inverter is drawing on the battery.

Let's assume that schematics are available on the net by now. They are,
with a little creative searching. So now we can talk grubby design details.

In the high-side drivers, C34 and its equivalent C35 are used to bootstrap
the "downstream" of D13/D14 to a much higher voltage that comes from
the transformer. Q31 is held on, so the low side of R38 is grounded.
So you've got as much as 50+ volts across R38 [well, it actually varies
per the switching waveform] which is making it have to dissipate on
the order of 2 watts. No wonder it [and R43, same situation] get warm.

The path by which the high voltage reaches R38 in the first place seems
to be via forward bias between the collector and base of Q29 -- I can't
see any other way current would flow when the XFMR1 lead is high.
You aren't supposed to do that to a transistor, last I thought... so it really
looks like an unintended consequence in a high-side driver that someone
thought was simply going to be 100% shut down when the unit is in
battery-charging mode. But at this point I'm sort of guessing.

I'll let y'all cook on this one a bit and hopefully there will be more
input once those who are interested can get a better look at what's
going on. Well, if APC doesn't come along and just delete my post.
When their support people in the Phillipines simply hang up on you
when you simply want to talk to a tech, it wouldn't surprise me.

_H*

[BillP]

Null

Message was edited by: Wwallender

[Anonymous user]

Could someone tell me how to change the float voltage parameters?

In 1980s UPSs, various parameters were set with a potentiometer. Anything newer, including the Generation 3 SmartUPS, these calibration constants are stored in EEPROM and the parameters are proprietary.

Such things include float voltage, volt meter reading,etc.

Back in the days, a technician would measure the voltage using a calibrated DVM, then adjust the pot so that the reported value or float voltage are correct.

Now, computerized DVMs take the measurements, then adjust the EEPROM through the RS-232c interface using a proprietary software. Very production friendly, very DIY unfriendly

[Anonymous user]

I have a similar problem, I do not have any technnical information about this equipment, like schematic, devices list, nothing at all. The same resistors were burned, such do not see the original colors. Getting information about these resistors of other UPS APC SU2200NET, the resistors are of 1K ohm, 1/4 Watt. But the original mainboard where the resistor were burned is 6400734K Rev 13 (1996) , and where I got the information is 6400734-E Rev5 (1995). I do not know if is correct to suppouse the two mainboards are almost the same and the resistors too, because the printed circuit are light diferent, but basically both are the same. You said the resistors are of 470 ohms, value very diferent of the resistors I found. Where are the wrong in the values of the resistors? Which number of mainboard do you have? Thanks a lot for your attention, I will be so grateful of recive your answer.
Jose Francisco Castillo A.
jcastilloa@costarricense.cr
or
fcastillo@iplsistemas.com

[Anonymous user]

I think is a bad, very bad political of the APC and others companies do not give any information about theirs products, at least a block diagram could give. Others makers do the same, like TrippLite, but searching and searching something I got of the WEB. I suggest never recomend one Brand like the I have mentioned. So, I guess we have to join us to sharing all the information I colud get of any ways.
I have 2 SU2200NET damaged, one is death and the other produce a noise inusual and begin to smeel to burn, so i turn off inmediatly.
What can I do? Some suggestion? Thanks.

[Anonymous user]

I agree with you, but what can we do? The only one I think is not suggest buy brands like this. Do you?

[Anonymous user]

I have the same problem with a couple of different RM Smart UPS 3000XLs
My main unit turned off and will not power on. No sign of life at all. No lights, no clicks, nuthin'
I examined it and found R38 and R43 burned up.
I was planning to replace them but couldn't determine the values.

So I decided I would look at another working unit to figure out the values.
To my surprise, on a working unit, the same pair of resistors were also toasted too badly to read the color codes.

If I replace these will they just burn up again quickly? Is there some other part that has failed that's causing these resistors to fry?
Perhaps not since they seem to be toasting even on a working unit.

It looks like a design flaw to me since the same pair of resistors are fried on many units.
I gather from previous posts in this thread that these resistors should be 470 Ohms, or perhaps they are 1K Oms.
Anyone know for sure?
See attached pics for photos of the resistors.
I'm going to go ahead and replace them with beefier 1/2 watt or larger resistors and hope for the best.

If anyone has had any success with fixing this please post your results.
If anyone has a source for schematics, please PM me.

Message was edited by: CAHutch

[Anonymous user]

I have had 3 of these units. 2 of them have failed. They failed in the same way. After a couple of years if you unplug the until for a certain length of time, the unit will fail to operate after that. You can put new batteries in it or charge the old one, but unit will not operate. Personally, I believe they have put a timing circuit in the unit so as to time out after a couple of years. I have no proof that this is true, but logic would conclude that if you have 2 units that fail the same way, they refuse to give out schematic on the unit and if the unit cannot self correct itself my their instruction on the phone; well, then, they will give you 300 dollars trade in for "new" one. That's the way it happened with me.

I wish you the best. I hope you get your unit going again.

chuck

PS. Oh, by the way, the third one is still running only because it has never been off line.

[Anonymous user]

Update:
FYI, when I removed those resistors they weren't open. Still reading ~480 Ohms.
So they were toasty but not burned open and apparently not the cause of my problem.

I've tried checking points on the board with power applied and I'm getting AC voltage after the transformer(s).
It's not something simple like an open fuse or open transformer.
It looks like a multi layer board though and without schematics I'm shooting in the dark.

If anyone has found a source for schematics, please let me know.

[Anonymous user]

I have two 2200's as well - both are 640-734K Rev 13 boards. Given that the schematics on Rev 12 indicate 1K ohm resistors, but 470 ohm resistors were used on my rev 13 boards (DMM confirmed - too scorched to read the actual colors), this seems to be a design tweak with unintended consequences. By comparison, I have 2 Smart 1000's with 1K resistors, and they show no signs of overheating. It seems plausable that APC did a quick design fix to address an issue and made a mess of it. (I mean really, if you're chopping resistance in half you should spend 5 mins thinking about how the power is now flowing in the new circuit). Anyway, replacing them with 2 watt 470 ohm resistors seems to be a reasonable band-aid type fix for now, although wasting that much power for no good reason isn't ideal.

That fix and replacing R118 and R119 with trim pots (100k,10k respectively in the smart 2200, 100k, 22.1k respectively in the smart 1000) to control the charging voltage (one acts as a coarse adjustment, the other is fine) seems to address the more urgent shortcomings of the design. Then it's just a matter of setting a reasonable charge voltage that won't gas off too much water, cracking open and refilling the cells every 12 months and doing an equalization / de-sulfation charge.

Final parting thought: you can get 7 years out of a car battery if you don't abuse it. I'm not sure why 2-3 years should be considered acceptable in UPS's that just sit there with minimal use. I know APC has (supposedly) improved the charging circuit in later models, but if they're not gettting well over 5 years on light use then there's obviously more they (and other manufacturers) should be doing. It's probably time they did it properly and started counting coulombs or something like that. Just make a proper charging ASIC once and be done with it.

[BillP]

nobody from APC can really comment as to the internal components of the UPS and the specs on them since the internal schematics are proprietary. we also dont support opening the UPS and replacing the components but of course if the unit is out of warranty, you can realistically do whatever you want.

though, i can see what I am able to find out for you, if anything, on this subject. do you have the serial numbers on these devices and exact model numbers? if you want, you can PM them to me rather than posting so i can investigate.

we generally dont open these up and repair them ourselves in tech support but i can say that from my standpoint, i am not aware of any "known issues" with the 2200 having a problem like this (assuming these are the 'SU' models).

what are the external symptoms you saw? overheating, smoking, etc?

[Anonymous user]

The model number is SU2200NET.
They are out of warranty.
I have sent you a PM w/ more information.
I realize that schematics are proprietary, and don't expect any of that information to be divulged, but I do suspect that this problem has occured for others as well. I'm suspecting there is a known fix. Without a schematic finding the fix is much more difficult.

[BillP]

i will follow up with you via PM.

[Anonymous user]

johnszxr, you've got a PM

Stew

[Anonymous user]

Should be a law about this. Without a circuit diag. I'm trying to find a needle in a haystack.
I replaced the two 470R's to no avail. Ruddy thing powered up for a second or so then no go again, not even a glimmer from the front cont. panel.
Somethings stopping the relays coming on, looks like a problem around the optical sensor in the mains input.
Any ideas folks where I can get a peek at a circuit diagram?
--Gary

[Anonymous user]

Ive got a SU3000 with the same burned resistors and rev13 board. My unit shows ~480 ohms each. The schematics that are out on the web show that they are supposed to be 1k.

On my unit, when plugged in, no signs of life what so ever. If the batteries are connected, it moans with all the lights dim. No response from the buttons. I can get it to work if I jump start it. Once I do this, it will function just like always. But, if it ever goes to battery and they run down completely, I have to jump start it again.

Here is my jump start procedure. I am in no way responsible for any damage or injury to yourself. Do at your own risk. Do not taunt an unhappy SmartUPS. This procedure requires playing with 120VAC. Dont do it unless you are stupid enough to try it.

Ok, that aside. Locate C99. Its the large poly film cap next to the connectors that go to the large transformers. Removing the smartslot helps a great deal. You must connect to the "XFR-HOT" side. This is the side that is next to the connectors, also the side with the batteries. If you connect it to the wrong side, bad things will happen. Plug in your unit turn on the main breaker. Clip a wire to the C99 lead mentioned previously and touch the other end to the main hot screw on the breaker. The unit will groan, maybe beep and squawk then hush. Depending on the last settings, it may turn on, it may be in standby/off. DO NOT LEAVE THE LEAD CONNECTED!! Doing so will short out smart trim and boost taps. If all goes well, you should be able to start the unit normally. On my SU3000, I put a momentary push button on the front panel to do this.

Again, I recommend that you do not do this. If you want to, that's up to you and your risk.

[BillP · Accepted solution]

Thank you for reiterating the potential dangers and unintended consequences of working on or modifying any piece of electronic equipment.  It may be worthwhile to consider revising forum rules to not allow posts such as mine that cannot be condoned by APC/Schneider Electric or are otherwise potentially dangerous.

[BillP]

I just want to reiterate that these APC Smart UPS units are not user serviceable by design.

The same goes for Back UPS and single phase UPSs in general. I also want to make sure everyone is clear and understands that any instructions in this post are to be followed at your own risk and could potentially be extremely dangerous, hazardous, or even life threatening. Please make sure that you take all proper precautions before attempting to service your technically "unserviceable" unit.

I don't want to remove this type of information from the forum for users that are qualified to do this type of work but I can't stress enough that these types of modifications and work are extremely dangerous. I want our users to be safe and essentially understand APC or Schneider Electric cannot support any of it for liability reasons - that is why the units are not designed to be user serviceable  If the units are out of warranty though, you have the right to proceed at your own risk.

You should verify that your units are completely de-energized before doing any type of work at your own risk. Make sure to remove the unit from AC power and disconnect all batteries properly.

[Anonymous user]

I agree that doing something blindly and if you are inexperienced with component level repair work can be hazardous.  But, on the balance apparently a great many users are having the same sort of issue.  Hence the reason people keep coming on this thread.

For those of us with years of experience doing repair work of this type it seems silly to toss out a perfectly good device because $3 worth of parts failed.  Before I got here I looked around and was unable to fine a schematic or final testing procedures to ensure that the UPS is in good working order.  If APC were to release the schematics for sale on older out of warranty units similar to the way TV schematics were released in days gone by (SAMS manual) it would go a long way to making things easier and safer.  Your average person who smells the "magic blue smoke" isn't going to crack the case and even try a repair.  And your electronics tech or hobby person is always going to regardless of what they can find documentation wise.

In a nutshell this type modification (higher wattage resistors, and trimmers to get the exact values the circuit was designed for) results in broken equipment going back into service and batteries being recycled.  And, I'm more likely to buy equipment that could be marketed as more "green" because it is repairable verse thrown away or scrapped when I next choose a vendor.  But that is a whole different topic.

Just my 2 cents worth.

[BillP]

BlueSky - while I would like to avoid posts like these, I do know that users such as Robert B find them helpful. I have added some disclaimers, like seen at the bottom of the page, but I just wanted to re-state it. I hate to remove them because eventually they'll just start up again and I know some people that are qualified to do this type of work will find it useful. Even if we offered our schematics (which as you probably know is not my decision), I still think we'd see threads like this.

[Anonymous user]

In addition to replacement resistor, the unit must also caliberation through hyper terminal in windows, because there is a reset of the eeprom

[BillP]

That is true.  I was able to get the information for the calibration directly from a chat I had with an APC technical support representative.

[Anonymous user]

Hi,

Just had my SUA2200 bulge the batteries and heat them up very very hot... anyways, found the thread and checked things... of course my R38 and R43 are overheated as described.  It is a rev 13 board, and on one of them I can still read the color codes at 470 ohms... so I'll replace them with the larger wattage and that will be good.

Question,   I plan to replace the R118 and R119 with the trimmers and adjust the charge voltage... but I can't seem to locate them on the board... can you give me an idea of where they are in relation to the burned resistors?  And can they be seen without removing the board from the unit?  I was planning to just solder in the new 2watt resistors without pulling it...

Thanks,

Robert

[BillP]

They are between IC14 and IC16 and, if I can add an image, I will attach it here.  They can be seen without removing the board as I recall but I'd recommend that the board be pulled and the offending resistors being properly desoldered.  They can be seen below (to the south) of R38 and R43

[Anonymous user]

AH, thanks...

I didn't realize the board came out as easy as it does, I'll for sure remove it to do a proper job of it.  I was thinking it was going to take a while to remove and I would be able to just use some desolder braid and get the job done... But, 2 screws and the board is loose with just the electrical connections to be tagged and removed.

I appreciate the pictures..

Robert

[BillP]

You bet!  Good luck with your restoration.

[Anonymous user]

I've got a unit that's been sitting here unused for awhile because it wouldn't power up. Decided to tear into it today and it looks like the same issue as everyone else. Bad resistors on a 640-734K Rev 13 board.

This worries me, as we have several other units that are powered on but that we might not be able to rely on.

[BillP]

Hi, I need to try and keep this thread alive as I am trying to keep an old (1999) SU2200NET. I haven't opened it up to check for burned resistors, etc., but my issues are with the float voltage and the fact that the unit will only charge to about 94%-95% and never get to 100%. The battery voltage is 54.05 total and I believe it should be a bit higher to make 100%. I have read that the charging circuits in these units don't age very well and, more times than not, results in overcharge and bulging batteries, etc. I read that the charger could also age the other way and reduce the battery's charge level as is the case in my unit.

Johnszxr indicated that he was able to adjust the float voltage and I sure would appreciate knowing what he did to reset the float and to what float he set it to.

Any help and guidance would be greatly appreciated!

[BillP]

I took alex870's advice. I have a rev.7 board that has 1kohm parts for R38 and R43. Although not completely chared, I decided to replace them with new, 2 watt, parts. Incidentally, the old resistors both measured about 950 ohms.

I also replaced R118 and R119 with 25-turn, 1/2 watt, trimmers. After removal, the original 100k part was reading 113k and the 10 part was reading 11.7k. I set the trimmers to 10k and 100k prior to installation.

As measured across the battery terminal, I have 55.0 vdc. As reported by the AP9617 NMC, I am reading 55.05 and the battery charge indicator is now sitting at 100%.

Thanks to everyone who have had input into this thread for allowing me to restore my trusty SU2000NET to full service! I am indeed a happy camper!!

Message was edited by: BlueSky

Message was edited by: BlueSky

[Anonymous user]

I have not checked this for a while, but considering the number of responses it is no surprise to me that other people have had the same problem. I do want to say that I appreciate that this thread has been allowed to remain alive so that others may share this information. Better here where the manufacturer can easily get feedback than on discrete websites which also address this issue.

With that said, the APC 2200's that we have (last count about 250+) have been a good case study as to what happens to these units (and batteries of course) over time. We utilize 2200's, 1400's and 700's - most of which are the 2200's & 700's. Primary problems are with the 2200's, which is what started this thread.

As for adjusting the float voltage (from memory here), I set it to about 54.5 volts (what is the manufacturer spec?). The adjustment was not with pots (which is probably a good idea if a high quality pot is used), but by putting another high value resistor in parallel with either R118 or R119 (don't recall which reduced it). What I probably did was measure the float voltage, then temporarily drop a 4.7Meg or so across R118, then note the float voltage change. Repeat for R119 to see how a slight change in value of each resistor affected the float voltage (and by how much). I did it this way as to maintain the total series resistance of the voltage divider. A moment with a calculator and the correct resistance to put in parallel can be figured.

[Anonymous user]

HI,

I replaced the burned resistors today and put in a nice fresh set of batteries.  I ended up not doing the R118/R119 replacement.  Had trouble getting the proper parts to do it and since the board is easy enough to pull I figured I'd just leave them for now and measure the charge voltage and see what it is.

Ended up using 1-watt resistors verse the 2-watt version called out above.  Same supply problem... i.e. local electronics shop was out of stock.  Going to just watch them and see if they are getting to hot then order the 2-watt version if I need to.  The infrared thermometer says around 120 degrees F once they leveled off...  Soldered them in high and away from other components.   There were minor burn marks on the board where they were mounted.  Checked and they are each dropping 12.9vdc... so 27ma... so 0.354 watts roughly, which should be fine in the long run... it also explains why the original 1/4watt resistors cooked. 

Also, interesting note both of them were reading somewhere around 670 ohms after I removed them.  I could still clearly read the color code on one of them and it indicated 470ohm... so either it changed values due to the cook-factor or apc got a bad batch of these.... I am thinking bad batch since they were both exactly the same and if they had changed on their own I'd have figured they wouldn't match... just speculation on my part.

If I recall my Navy days dealing with battery packs, lead acid batteries drag down the voltage and suck up the current when charging, and once fully charged they limit current and the voltage levels off.  Assuming of course it isn't being overcharged by to high a voltage.  Which means until the pack is fully charged the only way I would be able to read the charge voltage would be to disconnect it live... which would be in the "Hazardous and life threatening" stupid category Angela mentioned.... in her disclaimer...i.e. NEVER work on live circuits unless you have the proper training, experience and equipment... or you can die.

Left the meter hooked up across the battery pack to watch the voltage as it charged, recorded the readings at 15 minute intervals:

(note, my meter hasn't been calibrated in years so these could be off a bit, but should be close enough)

0min - 53.9~54.0vdc  - 1 bar charge indicated

15min - 54.0~54.1vdc - 2 bars charge indicated

30min - 54.0~54.1vdc - 3 bars charge indicated

45min - 54.1~54.2vdc - 4 bars charge indicated

60min - 54.1~54.2vdc - 4 bars charge indicated

According to the labels on the battery they should be running (13.6vdc~13.8vdc x 4) 54.4~55.2 for standby use... i.e. kept topped off and occasionally discharged/recharged...

SO, I am in wait and see mode... once the pack is fully charged I'll check the voltage and see where it is at and if I need to make an adjustment.

Anyways, Thank you for all the help.

Robert

[BillP]

With changing R118/R119, my batteries float at 55.05 VDC which may be a little on the high side but I'll continue to watch, smell and feel them   Also, I purchased my parts from Allied Electronics and they have been in business for eons!  Good luck!

[Anonymous user]

Well,

Pack fully charged and my voltage is still 54.1~54.2...to keep it that steady the charge circuit must have a huge overcapacity I am thinking.... well done...

Net result is I am a happy camper... obviously that is high enough to make the charge happen, but not high enough to do any harm to the batteries...   Incidentally, I went with the 12v22ah batteries ...  $20 difference in price for the 4 of them ($5 each), but should result in a longer hang time.. 

I saw mention of calibrating it earlier in the thread, is that procedure referenced anywhere? And what exactly is being calibrated?  Just the reported percent until it fails so it can send a shutdown signal?

[BillP]

I found the information here:

APC UPS replacement batteries may appear to have a lower capacity and not last as long

The calibration number (in hex) is specific to each individual APC UPS.  In my case, SU2200NET, the number I obtained via a chat with APC tech support was "AF".

Hope this helps.

[Anonymous user]

I would like to offer the community a semi-official fix for the hot

R38 / R43 issue.  I say semi-official because I've had an interesting

discussion with some of the long-timers at Schneider and the concensus

after quite a bit of head-scratching on all sides is to simply beef

up the resistors in question to higher wattage versions.  The APC

folks don't seem to mind us discussing these things on the forums but

let me emphasize as a third-party participant outside of Schneider

that this is not a specifically supported mod, and anyone tackling the

process is strictly on their own with all the associated safety and

liability caveats.

It turned out that my earlier theory about a minor design flaw was

correct, and there's much more information at my "resolution" webpage

about the adventure that this has been:

   http://techno-fandom.org/~hobbit/power/dumbups/res.html

Hopefully this will allow owners to keep these otherwise very robust

units going for that much longer.

H*