APC Back-UPS 1300 not charging battery

[sambul83]

I have APC Back-UPS XS 1300 LCD for 5 years powering home PCs. The battery pack is almost new, was replaced a year ago. Battery voltages are 14.5V and 14.4V, total 28.9V .

Its recently started shutting down power to battery outlets, while surge outlets remain powered. I did some measurements and found that during daytime input utility voltage stays at 116-117V, and at that voltage the UPS doesn't charge the battery anymore. Charging voltage on terminals is 17V with battery disconnected at no load. At night utility voltage raises to 118-120V, and the UPS charges batteries OK overnight to full capacity. Charging voltage on terminals at night is 28.9V raising within 3-5 min to 30.9-31V at no load, and stabilizing.

APC support said, when batteries aren't charging due to lower power voltage from wall outlet, they're continuously slowly discharging by design (probably due to supplying power to UPS PCB?), even if connected to UPS battery outlets equipment still drains power from utility, and not from batteries. Once the battery is fully discharges in about 8 hours, the UPS switches off power to battery outlets. Other than that, the UPS doesn't report any failures or problems at all, and all its functions like sound alarms etc. work OK.

If some tech guys are still willing to provide any meaningful help on this forum, pls advice what caps or other PCB elements I can test and replace to fix this aging UPS? What software I can use for failed components diagnostics (PowerChute doesn't do that)? Pls don't suggest obvious things like "time to buy a new one", unless you're an APC rep. This equipment can be relatively easily repaired, and "repair" is not limited to battery replacement.

Also, could someone point to a proper procedure for UPS Battery calibration, or software for it compatible with APC UPS line? Can it be that APC sets a time bomb in firmware that degrades UPS specs after 4-5 years so it stops working normally and must be "upgraded"? Their older models were reported to work for 8-15 years, but now APC seems to dominate UPS market to the extent when product durability is no longer a factor.

[sambul83]

Re: APC Back-UPS 1300 not charging battery

Update

I disconnected the battery pack from the UPS. Its LCD and front button leds went down. It was still providing utility power to surge outlets. After an hour utility power went up from 116V to 118V. The UPS suddenly switch on, front buttons Led got red. I can switch LCD on with batteries still disconnected, and it blinks "no battery" and beeps. Charging voltage on terminals now measures 30.9V at no load.

Can you guys point to its schematics link? What aging PCB component can trigger such symptoms - no charging at 117V utility power, and normal work at 118V up? The UPS sensitivity is set to Medium. How to fully reset its memory and preferences? I can't do it by simply disconnecting it from the wall, detaching batteries and discharging residual current by pressing Power button. It still shows "battery empty" and "battery half-charge" periodically, obviously taking it from memory, since the battery is disconnected. That's why it more looks like a firmware "time bomb".

[budm]

Re: APC Back-UPS 1300 not charging battery

Per APC:
Input voltage range for main operations 88 - 139V
So to have nominal AC INPUT operating Voltage to drop from 120VAC to 116V and cause the charging Voltage to drop from 28VDC (no batteries connected) to 17VDC (no batteries connected) is extreme so you do have charging circuit problem.
We will need good clear pictures of the circuit boards, both top and bottom sides to start with to identify the circuit function on the board.

[budm]

Re: APC Back-UPS 1300 not charging battery

BTW, once the batteries are charged up, how long does it run when you remove the plug from the AC outlets a with loads (pc, monitors, etc) connected?
:Charging voltage on terminals now measures 30.9V at no load." That is too high.

[sambul83]

Re: APC Back-UPS 1300 not charging battery

I'll take some PCB pics, and also try to fully discharge the battery with load connected later. Now its half-charged.

You say that 30.9V charging is too high, but fully charged battery voltage is 28.9V - does it mean its overcharged? The pack looks normal and doesn't smell. Would UPS be still able to charge it if charging voltage drops to 28V? APC support says it should be 25.2-27.6V.

Another issue I already mentioned: when battery is disconnected, its front panel buttons and LCD are switched off. So it looks like PCB was previously powered by the battery. But after some time (15-30 min) the front buttons and LCD are lit again, now powered by utility. Does it hint anything?

The other thing they said is to use True RMS Converter to measure voltages on terminals. I've Vichi VC9808+ Multimeter. Is their a way to calibrate it, may be it gives some voltage error? I checked it with small batteries, and it gives 9.8V for new 9v, and 1.4-1.8V for various rechargeable 1.5V, but may be they are at that voltage.

[budm]

Re: APC Back-UPS 1300 not charging battery

12V batteries charging Voltage is 13.75~14V, so for two batteries is series, it should be around 27.5~28V range.
Most UPS when the batteries is not connected, when you first turn on the UPS, it will go into self test, if the batteries are not present then it will not run, if the batteries are connected, it will go into battery mode to verify that the load is not overload (too many device connected the to UPS backup outlets), if it is overloaded then it will beep at you and shutdown.
Learn more about batteries here:
http://batteryuniversity.com/

Also see #9 in the owner manual

[sambul83]

Re: APC Back-UPS 1300 not charging battery

They are marked as 12V batteries, but in fact show 14.5V half-to-fully charged.

I hooked yesterday a small 1500W heater to the battery outlet. It beeped, shown battery overload while connected to utility, but kept working for 2 min on utility power with no battery drain. Then I switched off the heater. So this circuit seems working OK.

Do you know, why batteries are slowly (within 6-8 hours) being fully discharged by the UPS from fully charged state at no load connected and UPS hooked to utility?

It now beeps continuously but keeps showing me that the battery is being charged (growing bar count from 2 to 4 overtime) despite the battery is disconnected already for 2 hours, and I switched the UPS off outlet after that and fully discharged, then hooked back to the outlet again.

[budm]

Re: APC Back-UPS 1300 not charging battery

"Do you know, why batteries are slowly (within 6-8 hours) being fully discharged from fully charged state by the UPS when not being charged due to low charging voltage, at no load connected and UPS hooked to utility?" That is why we need to locate the charging circuit, most charging circuit (regulated switching power supply is used these days) in the UPS are regulated, meaning that it can take the AC input from around 90VAC ~130VAC and can still maintain the charging Voltage.
For example in the Cyber power:
https://www.badcaps.net/forum/showth...ght=cyberpower

Typical charging circuit:
https://www.badcaps.net/forum/attach...5&d=1420777425

[sambul83]

Re: APC Back-UPS 1300 not charging battery

Thanks for the links. For some reason I expected modern lead-acid batteries to have some PCB inside and be more "intelligent" to limit overcharging like Li-Po batteries are.

I now think to have misinterpreted the voltage readings. I mean that difference in charging voltages may not be related entirely to utility voltage. When I hook the UPS to wall outlet with battery disconnected, it stays in Standby mode, and charging voltage shows 17V. But... within 15min it switches to Normal mode (while battery is still disconnected), and charging voltage raises to 30.9-31V. So this raise is probably not dependant on utility voltage, but on the UPS current mode. Not sure though, why it needs to power its PCB (but not external load) from batteries leading to their slow discharge, despite connected to utility?

[budm]

Re: APC Back-UPS 1300 not charging battery

So then, do the batteries still take the charge over night (16 Hr per APC) and get to full charge?

[sambul83]

Re: APC Back-UPS 1300 not charging battery

Above charging voltages were measured with batteries disconnected. Re charging overnight, I now recall that 3 days ago overnight the pack went from 3 bars charged to 1 bar charged. Next night it went from 1 bar charged to 5 bars fully charged. Following night it went from 3 bar charged to 5 bar charged. So I don't know if utility voltage variations at night affected it... or UPS issues.

Another thing I now think about... The batteries were staying at 3 bars charged for about 4 months continuously without visibly being charging up or down - it started after some storm and power outage, but the UPS worked OK, so I didn't bother. Only when the UPS went to Standby and shut down battery outlets due to full battery discharge, I had to deal with it.

My assumption was, the batteries might have a "bad memory" now and need some re-training to charge-discharge several times to fully expose their capacity and start fully charging again. Now they fully charge every night, but may be utility voltage got more stable at night... not sure. Again, I need to drain them at some load with UPS hooked off the wall to see residual capacity as you suggested.

Will disassemble this thing again and post some pics. I already looked at this PCB 2 days ago, no visible damage signs.

[budm]

Re: APC Back-UPS 1300 not charging battery

It sounds like the batteries is not taking the charge well. They are brand new batteries and was not sitting in the shelf for a long time before selling to you? May be you can look at the date code on the batteries.
You may be able to exercise batteries by running the UPS in BATT mode until it stops running, charge it over night and do it again a couple of times to see if it improved.
Most of the Low end UPS does not have smart charging circuit that when the batteries is fully charge it should then go into float charging mode.
As you can see what happen when one of the cell shorted out inside the batteries, the charge just keeps pumping in the charging current and get themal run away.
I exercise my UPS about every 3 months.

[sambul83]

Re: APC Back-UPS 1300 not charging battery

May be I should start exercising them too. Can't find battery dates, they were replacements sent by APC. As always, the sticker is covered on top with APC sticker, but I can see Kung Long Batteries sticker below it. Barcode says APCRBC109, do you know how to interpret APC battery 12-digit S/N for any date hints?

I now think, another reason for such erratic conduct may be the UPS went into a "programming shock" after recent utility power burst taking it into Standby mode with no charging, so I had to detach the battery and take the UPS apart. It get back alive, but may be firmware doesn't function properly after that. Now I tried to reprogram it from Medium Sensitivity to High and back, and re-hooked to wall outlet using the manual you posted. The LCD battery status is now more reasonable, it doesn't show charging when battery is out. So may be I need to observe today if it fixed the issue... I may still take it apart and post its PCB pics later, if that doesn't fix the issue.

For guys who wonder how to take this thing apart, you need to remove the batteries, disconnect from wall outlet, and then gently detach plastic front panel clips by pushing in a thin screwdriver along the line btw front and side panels. Once front panel is detached, you'll see several screws on both sides holding side panels to the base. Unscrew, remove one side panel, and then gently remove the main board. Be careful, wiring is too short for easy handling.

[budm]

Re: APC Back-UPS 1300 not charging battery

FYI: about batteries date code:
http://forums.apc.com/spaces/4/back-...tery-date-code

Kung Long battery:
http://www.klb.com.tw/en/tech-3.html

[sambul83]

Re: APC Back-UPS 1300 not charging battery

Thanks again. APC barcode shows 1323 (June 2013), and King Long's LK25PC (Nov. 2012) that sounds strange given Angela's claim that APC has batteries shortage.

Charging voltage stays at 31V @ 118V utility. How higher charging voltage affects battery life assuming its not damaged yet internally? Why it goes higher with UPS age, and how such problem is usually fixed on the board? The UPS has now charged the battery to "full" 5 bars from 3 bars, with no sign of discharging. Will see how it goes if utility voltage drops a bit tonight.

[budm]

Re: APC Back-UPS 1300 not charging battery

http://batteryuniversity.com/learn/a...d_acid_battery
http://www.powerstream.com/SLA.htm
http://www.zbattery.com/Overcharging-SLA-Batteries

http://www.batteriesplus.com/t-sla-g...practices.aspx
http://www.atbatt.com/sealed-lead-acid-batteries/faq
http://upgi.com/dynamicContentPage.a...batteryarticle

[sambul83]

Re: APC Back-UPS 1300 not charging battery

Most of the Low end UPS does not have smart charging circuit that when the batteries is fully charge it should then go into float charging mode.

I take it, this is considered a low end UPS? Does it mean, it keeps the battery charged indefinitely long under constant charging voltage, even when UPS works on utility power for months? Why than the battery doesn't usually blow up?

[budm]

Re: APC Back-UPS 1300 not charging battery

The charging is active 24/7 even when the UPS is not turned on, so it will keep charging the batteries as long as nothing goes wrong with batteries and the heat is dissipated, and local surround temperature is normal base on 25c.
Your ups is also line interactive type, meaning that the inverter circuit that converts the DC from batteries to AC will only run when the UPS detects the loss of incoming AC or when the line Voltage go below 90V or above 130V, the Voltage in that range is being regulated with the buck-boost switching tabs of the auto-transformer.
So basically the batteries is not really being used at all when the AC is normal.
The True-on line UPS, the inverter circuit is always running and there is no transfer time involve like the line interactive that the transfer relay has to kick in when it is on battery mode.
So just hope that the batteries does not go bad and cause real bad problem when it happen.
If you put DC Amp meter in series with batteries then you can see if the current is being drawn from batteries or being fed into the batteries when UPS is not in Batteries Backup mode.

[budm]

Re: APC Back-UPS 1300 not charging battery

BTW, I wonder what APC has to say about their batteries charging topology used in your UPS, what kind of protection does it have if the batteries are over heat, shorted cells, failed charging circuits, etc.

[sambul83]

Re: APC Back-UPS 1300 not charging battery

If you put DC Amp meter in series with batteries then you can see if the current is being drawn from batteries or being fed into the batteries when UPS is not in Batteries Backup mode.

I assume if the battery is visibly discharging based on UPS LCD's readings, the current is drawn from it. APC support guy said their units are designed that way: if the battery isn't charging, it supplies power to PCB (but not to connected load) when UPS is hooked to outlet and on utility power, even at no load. I assume, the battery would stop discharging so fast, if one disconnects UPS from the wall outlet and load, and switches it off (if it can be switched off with batteries connected instead of dropping to Standby).

As to why the batteries don't blow up eventually due to continuous charging, I don't think APC 1st level support can answer such in-depth questions except saying "its by design", but may try to ask next time. Generally I'd expect ANY support troubleshooting call to APC inevitably end up with conclusion your UPS "upgrade" is long overdue.