Help! APC 1500 Smart UPS went up in SMOKE! - Page 1
Forum section: electronics / repair

author: thekidkevin93
author_rank: Contributor
timestamp: May 08, 2023, 02:56:55 pm
content: I was careless, it's on me. I was tidying up my external battery bank I had wired into a black APC Smart 1500 UPS, upgrading the end of the extension wire with proper lugs,the cabinet with the giant 12v wheelchair/mobility scooter FLA batteries was dark, I run the UPS on this 24v bank, I hadn't had my morning coffee, I just wanted to get it over with and start my day....my blind ass hooked up the lines BACKWARDS. from the UPS: BOOOOOM!........SMOKE.........beep-beep-beep.After a lot of mother F's and GD's and holy S's! I sucked down some coffee, and opened up the UPS to see the damage I did. Exploded all 8 STP140NF55 MOSFETS, three 25v 330MF caps near the heatsink are bulged. On the underside a thin trace got hot enough (but not burnt) to shed its coating and reveal copper.24v cooling fan is OK.I looked on ebay, no replacement boards, called the local college looking to buy decommissioned UPS hardware, in the age after the year 2010 even if you offer money, liability, red tape, bluh bluh bluh,they wouldn't play ball. Looked up the MOSFETS on digikey and Mouser....out of stock until 2024.I remember back in 2010 living in another town, I bought two Dell Pentium III Xeon servers from the local college and they bright it to my home in a truck. $80. The deal was, $60 for one or pay $80 and I get two. Yeah you read it right. Those were the days.This thing is my primary battery backup here in my home, my backup UPS to my primary is a black APC Smart 1000 UPS.Guys, what do I do? what damage have I done to stupidly hook this up backwards? What other components have I fried? Should I try to replace what things I can see and hope thats all that fried?What is a proper substitute for the (80A?) STP140NF55? I get conflicting opinions.....one site even spit at me a number for a MOSFET that was thirty Amps! For a MOSFET that is 80 Amps!???Help help help! Please!

author: bdunham7
author_rank: Super Contributor
timestamp: May 08, 2023, 03:30:50 pm
content: Quote from: thekidkevin93 on May 08, 2023, 02:56:55 pmIf you take it apart and inspect the circuit board closely you are likely going to find all sorts of other small components and even circuit traces that have been burned, exploded and so forth. These are simply not protected against shorting or reverse polarity. I know this from experience...Your best solution is to fire up eBay and start looking for someone selling one cheap without batteries. What exact model is yours? I just acquired an SMT1500 w/o batteries, sold "as is for parts" for $49 shipped. I installed batteries and it seems to be working fine. I can't guarantee you'll find that good of a deal, especially in Canada, but I can promise you that any APC SmartUPS that has blown main power MOSFETs is going to look very ugly when you have a closer look.

author: thekidkevin93
author_rank: Contributor
timestamp: May 08, 2023, 04:13:21 pm
content: UPDATE: I removed all four heatsinks, desoldered all eight blown MOSFETS, and desoldered all three of the blown 330mF caps.I had to use my Weller model 8200 gun (old school model 8200, not the newer crappier one with the same model number) to take the heatsinks off,I had to DRILL OUT all the torx screws holding each MOSFET in. No idea why they were seized and turned so slowly than blam they stripped, but I drilled all of them out.Than I used my temperature controlled soldering iron at 370 oC to remove the fried MOSFETS.

author: thekidkevin93
author_rank: Contributor
timestamp: May 08, 2023, 04:19:51 pm
content: It is a model SMT1500 AS1027121495. It's a black case standalone model (non rack type). It's made by APC and its a smart UPS, which after what I did to it this morning;I think its probably a lot smarter than I am.That's the first thing I looked for was an APC 1500 with no batteries. I saw similar models for BIG money, than I looked for just the PCB, no results. Now I'm willing to try to replace the compoents and try to fix what I got. Now here I am with my hat in hand.

author: Algoma
author_rank: Frequent Contributor
timestamp: May 08, 2023, 04:24:16 pm
content: I did just tear apart a old SMT1500 for recycling, Most of its gone, but I only keet a few of the more useful ICs from the board. And kept the transformer for scrap copper. There are many differnt model years.That whole PCB is unlikely to ever be reliable again considering how much feedback and monitoring is within a SmartUPS compared to APC's BackUPS products, any bits out of tolerance and that controller is designed always refuse to output any power (Beeping Alarm).. Given APC used to have a quarter million connected equipment coverage guarentee on those units when they're new.I've got a few of the chips from one (OpAmps / PWM controller .. etc), but repair is likely not practical.

author: thekidkevin93
author_rank: Contributor
timestamp: May 08, 2023, 04:47:55 pm
content: I washed off the soot and it was just smoke residue around the mosfets. I brushed it away with a toothbrush and mild cleaner and discovered another trace that got hot and shed its coating.

author: bdunham7
author_rank: Super Contributor
timestamp: May 08, 2023, 04:51:26 pm
content: Quote from: thekidkevin93 on May 08, 2023, 04:19:51 pmI'm seeing complete units for ~$175 USD and circuit boards for ~$80, of course in Canada and CAD it will likely be more. To get a deal like I did you'll have to stalk eBay for awhile, most sellers know what their stuff is worth.If you want to fix it, perhaps take some high-resolution pictures of both sides of your circuit board and let us have a look. If you have trouble posting photos just ask for help, the forum is a bit tricky with attached files and posting external photo links has other downsides.

author: thekidkevin93
author_rank: Contributor
timestamp: May 08, 2023, 04:55:07 pm
content: The million dollar question gents is: what is an appropriate substitute for the eight 55v 80A P140NF55 MOSFETS I fried?Something Digikey or Mouser have on hand right NOW and isn't $30 a piece. Obviously I want to get a ten piece tube of these MOSFETS.

author: thekidkevin93
author_rank: Contributor
timestamp: May 08, 2023, 04:56:48 pm
content: Quote from: thekidkevin93 on May 08, 2023, 04:55:07 pmOK i'm new here so i'm figuring out how I can share photos but I will take some hi res photos and figure out later how to send them.

author: bdunham7
author_rank: Super Contributor
timestamp: May 08, 2023, 05:01:08 pm
content: https://www.mouser.com/datasheet/2/196/Infineon_IRF1405Z_DataSheet_v01_01_EN-3165877.pdf

author: thekidkevin93
author_rank: Contributor
timestamp: May 08, 2023, 05:09:24 pm
content: OK I couldn't find my good Canon digital camera, so here are some photos I took with my 2012 phone.https://ibb.co/cxDhjSrhttps://ibb.co/Q9rjXdnhttps://ibb.co/L8ghTD6https://ibb.co/9HZ9rZzhttps://ibb.co/nPy2WxHhttps://ibb.co/vdXTgcT

author: thekidkevin93
author_rank: Contributor
timestamp: May 08, 2023, 05:27:36 pm
content: For ten IRF1405ZPBF MOSFETs Mouser wants $54.60 total....... They want $20 to ship ten little transistors.Somebody put me back in the fridge.Update: Digikey wants $35 CAN for 8x MOSFETS and 3x 330 mF 35v caps. Thats more reasonable....wait shipping.....$8.000 yeah that figures.....grand total $47.74 dollary-doos.Wow.

author: bdunham7
author_rank: Super Contributor
timestamp: May 08, 2023, 06:31:10 pm
content: I'm not sure what your price expectations are based on, but if you must go cheap just try eBay.https://www.ebay.com/itm/303945085787I can't see anything else obviously blown up in your photos, but I still wouldn't give particularly good odds that a new set of MOSFETs will revive it.

author: Algoma
author_rank: Frequent Contributor
timestamp: May 08, 2023, 06:35:14 pm
content: There is a very good chance as those mosfet's body diode melted internally some of the voltage could have fed back through the gates a blew out the driver chips / pwm controller too.

author: thekidkevin93
author_rank: Contributor
timestamp: May 08, 2023, 06:36:27 pm
content: Quote from: bdunham7 on May 08, 2023, 06:31:10 pmI'm not trying to be a tight wad here, but $35 for some MOSFETS and $20 to ship it is moon talk. The link you posted leads to exactly what I hoped for but vvvrrrrpppp.....Does not ship to Canada.What, my moneys not good here?

author: thekidkevin93
author_rank: Contributor
timestamp: May 08, 2023, 06:41:56 pm
content: Quote from: thekidkevin93 on May 08, 2023, 06:36:27 pmYes and I doubt that it would be visible to the naked eye. I don't know what to do.

author: Algoma
author_rank: Frequent Contributor
timestamp: May 08, 2023, 06:46:20 pm
content: Test for short circuts to ground now that you've got the dammaged parts out.. low resistances between various chips VCC and GND.Diode test on a multimeter and test for expected values across various diodes and fets. its a pretty short path between the battery terminals, so dammage wouldn't have spread far with only 24V, likely the drivers could withstand that voltage level by design, there looks to be plenty of protection diodes around them.

author: thekidkevin93
author_rank: Contributor
timestamp: May 08, 2023, 06:52:08 pm
content: I find it fascinating that not one of these MOSFETS had any thermal paste on them. ZERO.

author: thekidkevin93
author_rank: Contributor
timestamp: May 08, 2023, 06:56:19 pm
content: It was only hooked up for a few seconds but there is a chance the chips and such survived while the MOSFETS and the electrolytics nearby melted down.I don't know. $50 for some MOSFETS , than replace them, and its possible they can all fry up because the MOSFET driver stage is bad.

author: thekidkevin93
author_rank: Contributor
timestamp: May 08, 2023, 07:00:52 pm
content: Man I feel bad. And I feel ashamed. This thing worked like a champ since 2009 and I got it last year from a scrap yard. It worked like a champ all the time I owned it.And in one moment of carelessness I blew it all up. I should have known better.I have strong feeling that this is going to turn out to be an expensive lesson if I want to get the same or similar spec hardware to replace the one I nuked.

author: Algoma
author_rank: Frequent Contributor
timestamp: May 08, 2023, 07:02:01 pm
content: All the gates had resistors on them, Worst case is IC18 or IC19 took a hit. but likely the resistors protected them.I have those chips (salvaged) if needed.. Digikey has them too. Looks repairable so far, you've done well cleaning it up.

author: thekidkevin93
author_rank: Contributor
timestamp: May 08, 2023, 07:10:49 pm
content: Quote from: Algoma on May 08, 2023, 07:02:01 pmThanks, I've never removed MOSFETS before or did a damage control on a PCB before. If you salvaged a bunch a these kind of MOSFETS, what you like for eight or ten of them?I live in Belleville.

author: Algoma
author_rank: Frequent Contributor
timestamp: May 08, 2023, 07:23:18 pm
content: They're actuall in there with Hex screws (small allen's key) through the hollow center. I only kept a few (3) because many were dammaged upon removal and I didn't need a drawer full of used mosfets, Just a good variety of known working ones.

author: bdunham7
author_rank: Super Contributor
timestamp: May 08, 2023, 07:23:56 pm
content: Quote from: Algoma on May 08, 2023, 07:02:01 pmI'm not up on the detailed internal architecture of these, but they can be cold-booted from battery so the onboard control electronics has to run from 24V somehow. Is that all protected somehow from reverse polarity? I have a blown up SUA1000 board here that has obvious additional damage beyond the MOSFETs, including a few SOIC8 packages with their tops blown.Also, perhaps he could test it with the MOSFETs out? (I'm not sure, but if anyone knows...) If the display and control work maybe has a chance.

author: Algoma
author_rank: Frequent Contributor
timestamp: May 08, 2023, 07:26:48 pm
content: Yes there appears to be a battery tap through that F1 Fuse. (Check if that is blown).. any dammage downstream would have blown that fuse.There appears to be a reverse protection diode there. (D45)But Q45 and Q46A would be ones to check if they survived.

author: thekidkevin93
author_rank: Contributor
timestamp: May 08, 2023, 07:27:27 pm
content: I'm going to ask a potentially dumb ass question here. But as far as I'm concerned I still feel like im on stage with my pants down for hooking up a UPS BACKWARDS!!!!I'm looking at the board and I GET that this unit is a good sinewave inverter, with a big iron transformer with multiple taps for compinsating for brownouts, but it is also a battery charger.Now I GET that when this is hooked to mains and after the power comes back on and the batterys are drained a bit, in charge mode the transformer is backfed mains AC and rectified to recharge the batteries.Fine. But my question is: where are the big FAT rectifiers for the back fed AC coming out of the transformer? I cant see them anywhere.

author: thekidkevin93
author_rank: Contributor
timestamp: May 08, 2023, 07:33:40 pm
content: Quote from: Algoma on May 08, 2023, 07:26:48 pmThere is a big spade terminal  that is being used as a jumper. There was supposed to be twin choke coils side by side but they cheeped out and put one coil and a jumper.Same with C7 and C8. There was supposed to be two big bat 40v capacitors but they left one pad blank and the other, oh boy its not even a good quality brand its Janghei or something, not a Rubycon or a Nichicon. Shame on you APC. This thing wasn't cheap in 2009.

author: thekidkevin93
author_rank: Contributor
timestamp: May 08, 2023, 07:37:55 pm
content: Well, before I pulled all the plugs and smoke was rolling out, the relays were click clacking and the control panel was beeping.The thing was turned away from me so I couldn't SEE what the LCD was displaying. It was probably saying "why master??? Why have you done this to meeee?"

author: Algoma
author_rank: Frequent Contributor
timestamp: May 08, 2023, 07:38:13 pm
content: Those smaller capacitors in your first image looks kind of bulged and crusty on top. Likely they're in poor condition and should also be replaced while you're in there.Edit: Never mind.. I see you already took them out.

author: thekidkevin93
author_rank: Contributor
timestamp: May 08, 2023, 07:49:31 pm
content: Hang on a minute. The ACP Smart 1500 UPS is rated flat out at 1000w and runs on 24v.1000w divided by 24v equals only 41Amps. The original eight MOSFETS were rated at 80A a piece.It looks like its set up for two banks containing four 80A MOSFETS each in parallel. Like two 320A MOSFETS?One leg of the transformer primary it hooked to one bank and the other to the other bank.I'm lost, can't just four MOSFETS, one in each row work?

author: thekidkevin93
author_rank: Contributor
timestamp: May 08, 2023, 07:51:44 pm
content: Yeah they blew their tops. I desoldered them along with the MOSFETS, I showed that in the last picture.https://ibb.co/nPy2WxH

author: bdunham7
author_rank: Super Contributor
timestamp: May 08, 2023, 08:23:37 pm
content: Quote from: thekidkevin93 on May 08, 2023, 07:49:31 pmThe setup is an H-bridge and each of the heatsinks has two MOSFETs in parallel, so yes one MOSFET per bank would work until it doesn't, I suppose. The 80A specification is just one parameter, the goal would be to have the lowest possible RDS(on)to minimize heating and also some safety margin. Add in the fact that the current is not steady so your peak and RMS currents will be much higher than the 41A DC average current you calculated and you'll see that the original specified MOSFETs were probably not much of an overkill at all.As far as other 'missing' parts and 'cheaping out', this board was used with a number of models so the parts count will vary. You'll see space for 4 MOSFETs per heat sink, for example. That large electrolytic is a specific very low ESR model even if it brand doesn't impress you. Your model doesn't need 2 of them.QuoteThe MOSFETs...

author: asis
author_rank: Frequent Contributor
timestamp: May 08, 2023, 08:25:30 pm
content: Hi,From the photo I see PCB: 640-3076-Z-REV 06 MAIN 4.5 GEN SMART UPS.I once had a repair of similar UPS and I will be guided by PCB: 640-3081J-Z-001 Tg=170.The platforms are very similar, right down to component indexing.These UPSs used MOSFET's:STM1500 RMI2U - P140NF55 8(16)pcsSTM3000 RMI2U - FDP3651U N-ch 100V 80A 18mOm x16pcsSTM3000 - IRFB4710 (IRFB4410)R77,R95,R76,R97,R74,R96,R75,R94 MOSFET's gate resistors (20 Ohm).First of all check IC12 TL3843 (PWM for main voltages +12V,+5V)IC9,IC600+C87 dropout 12V->5V to power MPU 89C51RC-UM and other logic !!D37,D23,Q36Buy IC18 Intersil i4082IBZC - MOSFET's control driver.It is possible that IC21 (ASIC 361-0025V2 ONsemi) is damaged - it can only be found from a donor.Check:Q45 NTD2955 P-chQ914(6NF10)Q904,D901,Q11,Q18,D61,Q23,Q1,Q2,Q5,(D44+C102=12V) - relay control components RY900,RY1,RY2,RY5,(RY4,RY6)Q46,Q46Adiodes in the charger(~27V): D702, D32optocoupler U700 pin1-2Fuse: F1,(F1A,F1B),F701.ECAP C7(C8) - check.

author: thekidkevin93
author_rank: Contributor
timestamp: May 08, 2023, 08:40:35 pm
content: Quote from: bdunham7 on May 08, 2023, 08:23:37 pmWell this gives me a lot to think about, I looked up what an H-bridge is and i'm getting myself comfy with how that works.

author: asis
author_rank: Frequent Contributor
timestamp: May 08, 2023, 08:55:28 pm
content: https://www.eevblog.com/forum/repair/apc-smartups-overload/...what you see is what you get... pdf at the bottom

author: thekidkevin93
author_rank: Contributor
timestamp: May 08, 2023, 09:09:17 pm
content: In the name of science I put the UPS all back together without the MOSFETS and the three caps. Hooked up AC.....nothing......hooked up the battery bank, got a little spark like it always did to charge that big capacitor, n the screen....no responce to button pressing or cursewords out of my mouth......no beeping.

author: thekidkevin93
author_rank: Contributor
timestamp: May 08, 2023, 09:23:59 pm
content: Oh god. If my UPS is as similar as this one in the PDF, than the IC was instantly fried the second I hooked it up backwards.In the PDF the IC  has no protection what so ever.All I got now is a steel case containing a 24v a non center-tapped stepup transformer, some power outlet sockets, and a 24v DC fan.What a waste. I sure learned a lot and I'm going to learn more the right way by reading.Any ideas what I could make out of this thing guys???But I wonder if the reason the screen is dead is because the transformer is suposed to be providing power to the board and its obviously disconnected.The only thing is to try with some mosfetts and see what happens. But to find eight of them for about $20 would be good.

author: asis
author_rank: Frequent Contributor
timestamp: May 08, 2023, 09:38:53 pm
content: Remove the transformer and power it ~ 220V, get, on the order of 28V AC for spot welding.

author: bdunham7
author_rank: Super Contributor
timestamp: May 08, 2023, 09:41:55 pm
content: Quote from: thekidkevin93 on May 08, 2023, 09:23:59 pmYou have a huge, decent-quality transformer that would make a pretty robust linear power supply. And some other doodads of not much interest.As I mentioned, the UPS can be booted from the battery alone. And IIRC, the UPS won't boot with mains power if there is no battery and the capacitor is discharged. This makes me think that the transformer and MOSFETs don't have anything to do (directly) with powering the control electronics. But I don't know the exact design setup and haven't looked all that closely.

author: thekidkevin93
author_rank: Contributor
timestamp: May 08, 2023, 10:03:17 pm
content: Can somebody please explain to me how a transistor that is no bigger than my thumb nail with leads that are like 28 gauge nothings is rated to switch 80 AMPS!!??

author: bdunham7
author_rank: Super Contributor
timestamp: May 08, 2023, 10:10:59 pm
content: Quote from: thekidkevin93 on May 08, 2023, 10:03:17 pmRDS(on)is rated at less than 8 mR (0.008 ohms) so at 80A the voltage across that is 0.64V and the power is 51.2W. The thermal resistance from junction to case is 0.5C/W, so all you have to do is keep the case under about 145C and Tjwon't exceed its 175C rating. It's even easier if you derate them a bit.

author: thekidkevin93
author_rank: Contributor
timestamp: May 08, 2023, 10:20:30 pm
content: Quote from: bdunham7 on May 08, 2023, 10:10:59 pmInteresting! Huh that explains why the heatsinks are so small. And I take back what I said about there being no thermal paste. I forgot the heat sinks are part of the circuit too.But the leads...they are so thin I can't see them being thick enough to pass 8 amps let along 80! How is that feat pulled off?

author: thekidkevin93
author_rank: Contributor
timestamp: May 08, 2023, 11:21:11 pm
content: OK to hell with this. The board is done, the board is TRASH. If I open up my wallet and buy a pack of nice MOSFETS there is a very good chance they will all go POP. Even if it doesn't I see the reality that after what I did I put a lot of strain on alot of the circuitry that is already almost 15 years old (2009).I don't feel like turning this carcass into anything else like a big hairy old school battery charger, or a big linear power supply, or even a bucking transformer to run stuff down at 100v.I already own big hairy 24v industrial grade battery chargers, plenty of power supplies made by Astron, the switch mode kind and the nice heavy irons, and such.I needed that APC 1500 smart ASS to power my essentials in my apartment in a blackout, and to work hand in hand with my 7ft solar panel system.I'm on a strict shoestring budget this damn thing is the heart of my operation.Now shout out to forum.....and your buddies........I live in Belleville Ontario,does anybody have the board from an APC 1400 Smart UPS they want to part with for a reasonable price?

author: thekidkevin93
author_rank: Contributor
timestamp: May 09, 2023, 12:55:36 am
content: We got signs of life gentlemen! I noticed a fuse on the board, it doesn't look like a fuse but it is, I jumped it with a thin wire, put it all back together;bear in mind.....no mosfets, those three bulged 330mF caps are removed and the transformer heavy 24v winding wire are hanging in the air. I looked deeper, and outside AC gets to the board not JUST through the transformer.Now the LED display panel lights up. But now it displays the words fault state overload.

author: Algoma
author_rank: Frequent Contributor
timestamp: May 09, 2023, 12:56:14 am
content: UPS units are often taken out of service and recycled, their batteries often only have a nominal lifespan of 5 years. I've removed so many from service that they've got to pretty common. Could always ask a local E-waste recycling center if they have any in their scrap pile. Its rare to find used units online, because it costs more to ship than an an unit is worth.Call local installers that deal with business and datacenters and they'll likely have an entire stack of old units waiting to be picked up for recycling you can haul away if you want. They really don't care who picks them up, as long as they stop taking up space in the corner of the warehouse. Data center units are usually 240V rackmount .. where the 1500VA is typically the highest 120V. Most tend to be storm damaged, or the batteries were left in place so long they puffed up, and become very difficult to extract without destructive prying.

author: thekidkevin93
author_rank: Contributor
timestamp: May 09, 2023, 01:21:39 am
content: Now when I plug it into AC and the battery it says "warning state: charger" , but I hold down the power button and now it consistently says "AVR Relay Weld".If I hold down the button and reset it it will cycle through its motions, click the relay, and it will eventually say 0% load 17% battery level. I don't have any AC loads hooked to it.I think it might be a symptom of the three capacitors being absent.It will also flash for a second something like misc fault.

author: thekidkevin93
author_rank: Contributor
timestamp: May 09, 2023, 01:27:39 am
content: Quote from: Algoma on May 09, 2023, 12:56:14 amThis is great advice and just what I needed to hear, but I wouldn't know where specifically to look, who exactly to call. Would you please give a me a clue?I feel when I call places they clam up and start babbling "liability" and "we can't really do that", and you need to bid on this or that on such and such site somewhere else.Look, all I want is my pick of what I like from a skid of old junk and I'll slid a twenty dollar bill in your pocket. Why is this so hard?

author: thekidkevin93
author_rank: Contributor
timestamp: May 09, 2023, 01:30:49 am
content: m going to get some kind of thin copper wire like a strand of ethernet cable and repair those traces that got hot enough to shed their coating.

author: Algoma
author_rank: Frequent Contributor
timestamp: May 09, 2023, 03:27:06 am
content: We recycle our bulk business E-waste through Habitat for Humanity. They gain the collection fees to build homes:https://habitat4home.ca/restore/e-waste/https://habitat4home.ca/restore/shop-online-2/https://habitatpeh.org/is in Bellville.. perhaps they may have a lead on a few scrap UPS units.They're actually inclined to redirect scrap items in trade for donations through their ReStore locations and tend to receive quite a few business class items through their pickup collections.

author: thekidkevin93
author_rank: Contributor
timestamp: May 10, 2023, 12:04:46 am
content: I found four ITF260R MOSFETS but they physically bigger than the ones that fried up. I'm thinking I can take the four and put one in each row to atleast get this old pig on its feet, mount the MOSFETS upside down and use solid wire.Can anybody warn me off subbing four ITF260R's for the eight P140NF55's if I'm about to screw up??

author: BradC
author_rank: Super Contributor
timestamp: May 10, 2023, 01:33:15 am
content: A lot has already been said but in general for every APC SmartUPS I've looked at :- The screws holding the MOSFETS in are hex head not torx. You can remove them by removing one row at a time, then passing the allen key through the holes to get to the next row without de-soldering the heatsinks.- There's no heatsink compound because you want maximum electrical conductivity to the heatsink- You *may* have damaged the MOSFET driver circuit, but that should use off the shelf parts.- The rest of the circuitry is usually powered by a small 24V->12V/5V SMPS. You may have damaged that converter, but odds on the downstream stuff has survived.- The charging circuit uses the MOSFETs as diodes, but also relies on the inductance of the transformers to operate as a boost converter. It's pretty clever.- You will very likely have smoked the main 24V rail filter cap. These are special, super low impedance electros and if you replace it with something "off the shelf" it's likely it'll die quickly under load.The voltage divider that measures the battery voltage might have damaged the H-Bridge controller ASIC, but it's pretty high impedance so you might have gotten away with it.To test it, I'd be applying mains through a dim-bulb tester (maybe a 40W light bulb in series with the input) rather than powering it from the DC side. You could then look at the waveforms on the MOSFETs and associated driver chip with a scope to see if the PWM ASIC has survived. If that's dead then it's scrap.I had an old SU2200 fail where the MOSFET driver shorted and caused all the high side MOSFETs to release the magic smoke, but that was through-hole with discrete high side drivers and I could rebuild it piece by piece. Yours is a lot newer and uses the integrated MOSFET driver.There's a schematic around somewhere for the "Grey Wolf", which is slightly older, but the topology is usually the same. See if you can find the schematic for an E1732-E5. It's an early SUA 1500 model, but they don't seem to change much in the actual inverter.

author: thekidkevin93
author_rank: Contributor
timestamp: May 10, 2023, 02:26:58 pm
content: Thanks everybody for being patient with me and pitching in with advice

author: MartinZ
author_rank: Newbie
timestamp: December 20, 2023, 03:42:33 am
content: I have several APC SMT1500 UPSs and use them with large external AGM batteries. I currently have a large 400 amp 240V rectifier to prevent the UPSs from charging the batteries. But, this causes a 0.7V voltage drop. Can anyone tell me how to disable the battery charging circuit? I do have a proper AGM battery charger and maintainer, and a 24V generator.I also had two previous generations of these 1500's catch fire. The SMT1500 I'm pleased with except the 980W limit, my refrigerator defrost cycle will trip it. What makes these SMT1500's acceptable is running 3 of them off a pair of very large AGM batteries.