APC Back-UPS XS1500 LCD (BX1500LCD) Not Charging - Page 1
Forum section: electronics / repair

author: UnexpectedBill
author_rank: Newbie
timestamp: August 09, 2015, 11:11:10 pm
content: I have an APC Back-UPS XS 1500 that I bought new several years ago. Its factory supplied batteries failed several years later, and upon replacing them with brand new ones, I noticed that the unit was not charging them. I put it aside, what with being busy and having a working spare from a garage sale handy.Now I've hauled it out again and given it an inspection to try and figure out what's ailing it. I found one slightly bloated 400V 22uF CapXon capacitor and replaced several others from known "low end" brands. There is still no charging taking place.I'm not entirely sure how the charging circuit in this unit is designed to work. It looks to possibly use a high frequency pulsed charging approach. There is a simple LM317 linear regular onboard that I initially thought might be used for charging, but to my surprise, its input is not actually connected to anything! This was verified with a strong light shown through the PCB. Only the output and adjustment pins actually have traces leading away from their through holes, making me wonder what exactly APC is doing with this part. Metering the output pin showed no voltage coming to it.Of the four protective fuses I found on the unit's circuit board, none are blown. Nothing on the board is obviously smoked or distressed. So long as charged batteries are attached, the unit will power itself up normally, go through its self test and run from AC line power as though nothing is wrong. The inverter also runs perfectly when the plug is pulled. Its built in display shows the expected values for AC line input.I've taken current draw measurements from the attached batteries. With the unit's power "off" and the cord plugged in, it is pulling about 71 milliamps from the batteries (instead of charging). Powered up and idling, it is drawing somewhere around 160-200 milliamps.This unit leaves its power and alarm silence buttons illuminated when it is connected to line power, even with the output turned off. I believe that when it was working normally, the buttons would light up as soon as AC power was connected. It does not work that way now. I have to touch the power button briefly before they'll light up with the cord connected. Then they stay illuminated as they should.When unplugged from the wall outlet, the two lighted buttons turn off after a few seconds, just as they did when it worked normally. Current drawn from the batteries drops to zero.Pictures of the unit's primary printed circuit board can be supplied upon request. It is a multilayer board, which makes tracing it sometimes difficult.

author: TheElectricChicken
author_rank: Frequent Contributor
timestamp: August 12, 2015, 10:26:08 am
content: I'd be curious to see pics of the not connected part. sometimes 2 out of 3 pins are enough when you're after a voltage drop or temperature reading, but maybe it is connected through another layer somehow, or corroded, or a fly lead came off.

author: UnexpectedBill
author_rank: Newbie
timestamp: August 14, 2015, 05:55:15 am
content: Quote from: TheElectricChicken on August 12, 2015, 10:26:08 amHere you go:Now there's something I didn't notice before. Pins 2 and 3 aretied together! Unless there's something I've missed, that would render the regulator's existence totally moot. So what's it doing there? There's no evidence of rework, flying leads or anything else on another working example of this UPS.Please don't cane me too much over the sloppy soldering job. I swapped the regulator to verify that it did or didn't work, and the drop in (known working but not pretty) has been a lot of action at this point.

author: TheElectricChicken
author_rank: Frequent Contributor
timestamp: August 14, 2015, 08:57:52 am
content: when you desoldered it, or if you do, did you continuity test the hole and see if or where it goes, that might shed light on it.

author: UnexpectedBill
author_rank: Newbie
timestamp: August 14, 2015, 10:37:07 pm
content: Quote from: TheElectricChicken on August 14, 2015, 08:57:52 amThe pictures above reflect a bright light being shone through the PCB. If there's a trace running to pin one of that regulator, I'd expect it to be visible as a result.

author: TheElectricChicken
author_rank: Frequent Contributor
timestamp: August 15, 2015, 04:21:19 am
content: Quote from: UnexpectedBill on August 14, 2015, 10:37:07 pmmmm, possibly, still, if it is quite small there seems darkness between pins, continuity test defines being sure. Just a thought.

author: sunnyhighway
author_rank: Frequent Contributor
timestamp: August 15, 2015, 08:01:51 am
content: Quote from: UnexpectedBill on August 14, 2015, 10:37:07 pmMy guess you used a large light-source instead of a small light source.The traces you think you see between the pins, look like partial shadow of the pads to me.

author: APCPROBLEMGUY
author_rank: Newbie
timestamp: February 10, 2020, 06:36:43 pm
content: Hi Unexpected BillI saw your old post on your APC UPS XS1500 problem, to my surprise I have the same APC model and the same problem. All your problems are the same right down to the letter that my APC back up does. Even the bulged cap on the same location on the board. My unit will drain the new bats also, so I have been charging them on a 12v battery charger then go back to testing the unit. I have replaced all the electrolyte caps with stick through leads on the board, also the charging rectifier you had pictures of. I also replaced the IC chip which is an oscillator I believe for the 60 Hz out put from the batteries which is right by the MOSET on the small aluminum heat sink, and it uses these when in the run on battery mode. My unit works just fine and so does the LCD display, it just won't charge, and will drain the batteries. My question, did you ever find out what was wrong with yours, and what did you replace to make it run right? I would guess it must be in an smd part on the board, oh I also changed all three relays on the board. I hope you find this message for it would sure help me out. Thanks Bill