APC Back-UPS battery - Page 1
Forum section: electronics / repair

author: PlainName
author_rank: Super Contributor
timestamp: January 27, 2021, 02:03:47 am
content: Got an APC Back-UPS 1400 which doesn't do anything. It did before I left it in a corner for 3 or 4 years, and that occurred because the owner complained that it sometimes turned the PC off.So, thinking I would sort it out I have it apart and see a battery pack comprising two batteries en bloc connected in series. No markings to identify what the batteries are. There is 14V across them: one is measuring 10V and the other 4V. So 12V batteries and the charger would be putting around 24V into them.Power up the UPS without the batteries and look at the battery leads. There is 13VAC there, which suggest the batteris are 6V each! But... a 6v battery can't read 10V so that seems a pretty solid clue. But 13V is just too close to being a decent 12V battery charge (bit low, perhaps, but it's AC) and where APC uses 12V batteries they are usually in parallel, so without the 10V reading I would have gone for 6V batteries.Anyone know either what the batteries should be, or how to tell if they are 6V or 12V?

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: January 27, 2021, 02:08:38 am
content: Is this it?https://www.apc.com/shop/my/en/products/APC-Back-UPS-1400VA-230V-AVR-Universal-and-IEC-Sockets/P-BX1400U-MShttps://www.apc.com/shop/my/en/products/APC-Replacement-Battery-Cartridge-113/P-APCRBC113

author: gnuarm
author_rank: Super Contributor
timestamp: January 27, 2021, 02:33:37 am
content: Ed's photos show the caps on each cell. So the ones in his links are 12V, 6 cells x 2V each. Do your batteries have the six caps?But you should not be measuring AC on the battery leads. What is that about???I recently worked on a lead acid charger and the chip we had picked sensed when the battery was too low to be charged at full rate, then it would trickle charge at a very low current until the voltage came up. I'm sure 14V is too low to be charged at full rate. Since you are measuring with no battery connected they may be pulsing the power. If the power to the battery is truly AC, going positive and negative, I'd say your charging circuit it bad.

author: Monkeh
author_rank: Super Contributor
timestamp: January 27, 2021, 02:37:29 am
content: Quote from: gnuarm on January 27, 2021, 02:33:37 amLack of smoothing. Rectified and slammed into the batteries without a care in the world. It's a cheap APC UPS after all, their business is in selling batteries.

author: gnuarm
author_rank: Super Contributor
timestamp: January 27, 2021, 02:48:32 am
content: Quote from: Monkeh on January 27, 2021, 02:37:29 amIf that's what he is seeing fine, but that's not AC. It's DC with an AC component.

author: pqass
author_rank: Super Contributor
timestamp: January 27, 2021, 03:11:46 am
content: Alternate source for RBC113:https://www.upsbatterycenter.com/apc-rbc113-compatible-replacement-battery-packYou can confirm the correct battery for your unit by choosing "UPS BATTERIES" menu, "APC Back-UPS" item, and drill-down from there.Be sure to use the name on the front of your unit. eg. Back-UPS XS 1300

author: Klondike Mike
author_rank: Newbie
timestamp: January 27, 2021, 05:33:18 am
content: DON'Tcheap out and buy a non-APC branded battery. Just like buyingANYTHINGChinese, you risk burning down your house. Spend the extra required for the brand name and have peace of mind that it won't catch fire and burn down your home with you in it.

author: wraper
author_rank: Unknown
timestamp: January 27, 2021, 05:36:00 am
content: Quote from: Klondike Mike on January 27, 2021, 05:33:18 amCertainly buy non APC branded battery. As they usually are cheap Chinese crap as Kung Long sold at 4x the price. You will get overpriced CSB if lucky. Buy CSB, Yuasa, Panasonic or whatever good quality battery you can get at reasonable price.

author: Monkeh
author_rank: Super Contributor
timestamp: January 27, 2021, 05:36:32 am
content: Quote from: Klondike Mike on January 27, 2021, 05:33:18 amDon't be daft. There are many good battery manufacturers andAPC aren't even a manufacturer.

author: james_s
author_rank: Super Contributor
timestamp: January 27, 2021, 06:18:27 am
content: Quote from: Klondike Mike on January 27, 2021, 05:33:18 amIf you peel the APC sticker off of the battery, you'll find it's whatever cheap brand they could get that week. The only reason to buy an APC batter is if you've got money to burn and are feeling charitable to APC. I've had reasonably good luck with Power Sonic batteries, there are only a few companies that actually make small SLA batteries though, they get labeled with dozens of different brands.I've fixed probably 20 UPS's and every single one of them just had bad batteries and nothing else wrong with it. Every one I've fixed also had 12V batteries, either one or a series pair.As far as safety, UPS's can be dangerous, but if it's going to burn your house down it's not going to be the battery that causes that. I've seen the MOVs catch fire more than once, power surges are rare here and MOVs are marginally useful under the best of circumstances so I usually remove them.

author: pqass
author_rank: Super Contributor
timestamp: January 27, 2021, 08:24:53 am
content: If you peel the sticker off you won't likely find an ampere-hour rating. I've never seen one on APC branded batteries.It will probably state its nominal voltage and chemistry (sealed lead-acid).Then measure the size (length width height) of your battery and compare it to other sealed lead-acid batteries of the same size.From that, you'll get the ampere-hour rating. And don't forget the terminal/lug size too.Then go buy a battery from your choice of vender. Good brands: Yuasa, Panasonic, Interstate.I've also used lesser brands: Power Patrol

author: natman69
author_rank: Regular Contributor
timestamp: January 27, 2021, 11:59:25 am
content: They are two 12V 9Ah sealed lead acid batteries in series, with 6.3mm connectors. I am sure because I have done manteinance to this UPS in the past.I can suggest to replace with a battery that can supply high current for short period, designed for UPS application. I use FIAMM 12FGH36 but you can use any brand with same specs.

author: PlainName
author_rank: Super Contributor
timestamp: January 27, 2021, 02:34:48 pm
content: Quote from: Ed.Kloonk on January 27, 2021, 02:08:38 amYes, that's the one. And that's the cartridge. But whatisthe cartridge?

author: PlainName
author_rank: Super Contributor
timestamp: January 27, 2021, 02:39:23 pm
content: QuoteYes, same. They don't appear to be actual caps so I figured they could be just molding marks and didn't want to rely on them.

author: PlainName
author_rank: Super Contributor
timestamp: January 27, 2021, 02:50:08 pm
content: Quote from: gnuarm on January 27, 2021, 02:48:32 amConfession time: that's not what I'm seeing. At least, not now.I had inadvertently removed the battery power connector after dismantling (forgot at the start), so the negative lead of the meter was floating. No power gave no reading and turning the mains on showed 13VAC. Duh.Fixed that now and I get an actual DC reading of 4V. However, I get that with no mains too, so not sure wtf is going on - perhaps some capacitor holding a charge, but why bother when there's a BFO battery at the end of the wire? Whatever, it makes much more sense now (in the way it doesn't change). Sorry to have laid a false trail...

author: PlainName
author_rank: Super Contributor
timestamp: January 27, 2021, 02:51:22 pm
content: Quote from: natman69 on January 27, 2021, 11:59:25 amThanks very much

author: james_s
author_rank: Super Contributor
timestamp: January 27, 2021, 07:44:27 pm
content: I actually have a dead APC battery cartridge right here that I saved for rebuilding with new batteries so you can see exactly what they are. Oddly they don't have the Ah rating but this physical size is standard and comes in 7.5 and 9Ah variants. Note the "HR" in the part number, that indicates High Rate, although one battery manufacture I contacted a while back stated that all of their batteries are built as HR, so who knows. If you look up the datasheet for a reputable brand like Power Sonic you'll see that the ratings are pretty much worthless in a UPS application. At the full rated load you'll get only a small fraction of the stated Ah capacity and even at more sensible levels you will get nowhere close. The capacity printed on the battery is assuming something like a 10 hour discharge which you will never get, even with no load plugged into the UPS at all. They abuse the hell out of the batteries even under the most ideal of conditions.

author: madires
author_rank: Super Contributor
timestamp: January 27, 2021, 07:59:46 pm
content: Quote from: wraper on January 27, 2021, 05:36:00 amLong time ago APC used also Panasonic SLAs in their battery packs. Only the standard types, not the ones specifically designed for UPSs.

author: EHT
author_rank: Frequent Contributor
timestamp: January 27, 2021, 07:59:57 pm
content: The only thing slightly tricky, at least in the Smart-UPS 750s that I have is that the 'cartridge' is two batteries glued together with a wiring harness & fuse. Often the UPS is eBayed without the battery for obvious reasons, but then you might be missing the wiring harness. It has a special plug which allows the pair of batteries to side into the connector on the UPS chassis. Might be a bit of a pain if you don't have one off the old batteries...FYI, I used Yuasa Y7-12 for the Smart-UPS 750. Decent brand and *way* cheaper

author: james_s
author_rank: Super Contributor
timestamp: January 27, 2021, 08:04:45 pm
content: Quote from: EHT on January 27, 2021, 07:59:57 pmThat's the reason I saved this dead cartridge I have, it's the most convenient way to store the other bits. If you are buying a used UPS it's worth asking the seller if they're willing to yank the hardware and wiring off of the batteries, otherwise you might have to buy an OEM cartridge and then re-cell it next time around. I'm not a fan of the cartridge format in general, it makes swapping batteries by non-skilled users marginally easier but most people seem to just buy a new UPS anyway judging by the number of perfectly good ones with dead batteries that I've been given.

author: m k
author_rank: Super Contributor
timestamp: January 28, 2021, 09:17:28 am
content: My experiment is that differences start showing when batteries are in "wrong" orientation.Some models last pretty short time.

author: james_s
author_rank: Super Contributor
timestamp: January 28, 2021, 07:41:22 pm
content: A lot of UPS's really cook the batteries too, they charge them aggressively to get the low cycle time, and they use batteries that are grossly undersized for the stated rating of the UPS. I've also had some batteries that were defective right out of the box.

author: CJay
author_rank: Super Contributor
timestamp: January 28, 2021, 09:50:09 pm
content: Quote from: james_s on January 28, 2021, 07:41:22 pmThat's been my experience, if you have an outage that lasts long enough to result in scripted shutdown (I.E. takes a decent amount of charge out of the batteries) the kind of size UPS you would fit in a rack with the servers tend to cook the batteries while recharging.They don't survive many cycles of that.The building UPS on the other hand...

author: james_s
author_rank: Super Contributor
timestamp: January 28, 2021, 09:55:27 pm
content: I think at some point we'll start seeing a lot more UPS's using lithium iron phosphate batteries. Those are far more tolerant of the sort of high discharge rate experienced by the typical UPS. A LiFePO4 battery with half the rated capacity of the Pb counterpart will likely provide higher real world capacity in that application in addition to much greater cycle life. IIRC with a 30 minute discharge a SLA battery gives only about 50% of the rated Ah capacity which is specified for something like a 10 hour discharge. You'll NEVER get a 10 hour discharge with a consumer UPS.

author: CJay
author_rank: Super Contributor
timestamp: January 28, 2021, 10:17:16 pm
content: Quote from: james_s on January 28, 2021, 09:55:27 pmThey're out there but they're *expensive*.The design goal for most UPS isn't to run stuff for hours, just long enough to get everything down safely or to get your standby genny up to speed.

author: wraper
author_rank: Unknown
timestamp: January 28, 2021, 10:38:39 pm
content: Quote from: CJay on January 28, 2021, 10:17:16 pmSuch as APC with 850VA power rating, 12V 7.2Ah battery and 1 minute run time spec under full load. Discharging battery in 1 minute while wasting the vast majority of power, if this is not an abuse, then dunno what is.

author: floobydust
author_rank: Super Contributor
timestamp: January 28, 2021, 11:21:02 pm
content: It became a numbers game with the run time and VA rating, so the batteries are exploited to the absolute max.I've found APC UPS are not great, cheaper to throw them out and buy another on sale lol, than replace the batteries. The electronics has almost nothing for cooling because it's intended to only run for a few minutes. They have crappy charging algorithms, a shorted cell makes it roast the pack, thanks for no alert. High float voltage to give a better recovery time spec with the wimpy charger. So it constantly wastes several watts doing nothing, which heats up the batteries and cheap electrolytics. Put a thermal-imaging camera on one, they are terrible offenders.LiFePO4 doesn't (calendar) last kept at 100% SoC all the time. I think you'd have to derate to 50-60% capacity.

author: CJay
author_rank: Super Contributor
timestamp: January 28, 2021, 11:33:00 pm
content: Quote from: wraper on January 28, 2021, 10:38:39 pmBuy cheap shit and you get crap performance, an 850VA UPS is a toy.APC aren't bad when you get around 3KVA rack sizes, better still when you get to server room stuff but there are better brands.

author: wraper
author_rank: Unknown
timestamp: January 28, 2021, 11:55:13 pm
content: Quote from: CJay on January 28, 2021, 11:33:00 pmStill utter shit compared with others at the same price.

author: james_s
author_rank: Super Contributor
timestamp: January 29, 2021, 12:11:52 am
content: Quote from: CJay on January 28, 2021, 10:17:16 pmThat doesn't have to be true. There are lots of applications for a UPS that is smaller than that even, and that doesn't mandate it being a toy, only consumer pricing does. I have absolutely no use for a UPS as large as 3kVA however I would like it if more of the small UPS's had much larger batteries. 3-4 hour run times are useful to me in the event that I'm not at home when the power goes out, longer would be nice but budget and volume becomes an issue. My UPS's are small units that are distributed around the house powering specific loads. They're great during wind storms where there can be a lot of power glitches just long enough to reboot things, and if there is a longer outage the lamps that are plugged into some of them stay on and I can go get out the generator and get that set up up without rushing.

author: james_s
author_rank: Super Contributor
timestamp: January 29, 2021, 12:15:50 am
content: Quote from: CJay on January 28, 2021, 10:17:16 pmUnderstood, but I think the cost differences will keep shrinking, and the advantages of Li are greater for short run times than they are for Pb which is fine if you want to run something for hours but really gets murdered if you load them heavily and drain them in a few minutes, treatment that LiFePO4 tolerates quite nicely. The greater cycle life (as in more charge/discharge cycles) between battery replacements further favors Li, and the lower shipping cost due to smaller and lighter weight. Even at current prices Li could pay for itself eventually given it's not that unusual for a typical SLA battery to be toast after just a year or two of UPS service.

author: PlainName
author_rank: Super Contributor
timestamp: January 29, 2021, 01:25:17 am
content: QuoteYeah, I always seem to find that out just before a major outage.Having said that, my rack has a APC Smart-UPS 3000 RM and that tells me the battery was replaced in 2018 (and I checked my receipts to make sure it wasn't fibbing). Also says I have 125mins runtime, but I usually I let it run for 10 mins to see if the power is coming back, then get the generator out to take over (or do a manual shutdown). Can't remember how many times we've had to do that - sometimes it goes for years without an issue and then we get a series over a month or two - but I know we had a biggy a couple of months back.

author: TheMG
author_rank: Frequent Contributor
timestamp: January 29, 2021, 02:46:39 am
content: Quote from: CJay on January 28, 2021, 11:33:00 pmHas nothing to do with size/capacity. UPS aimed at the general consumer market (APC Back-UPS series falls into that category), are indeed pretty crappy as they are designed for minimal cost rather than reliability. Your average consumer for a home or small office scenario doesn't usually want to pay a small fortune for a UPS, and isn't too concerned with runtime.APC and other manufacturers do make some pretty decent UPS aimed at the business/enterprise sector as small as 700VA or 1000VA capacity, with such features as expandable battery capacity (via additional external battery modules).While the early model APC Smart-UPS line did eat through batteries pretty quick, the newer versions they sell these days seem to fare much better.Battery life in UPS has a lot to do with the charging method and temperatures. Consumer-grade UPS tend to have plastic cases with relatively poor ventilation, keeping the batteries at an elevated temperature. They also tend to have simplistic charging circuits, also not very good for battery life.

author: james_s
author_rank: Super Contributor
timestamp: January 29, 2021, 03:38:59 am
content: There are lots of contributing factors, but I really think the discharge loading is the biggest factor for the cheaper units. I did some testing a while back and it seems like I was measuring around 35A being drawn from the poor little 9Ah SLA with a test load of incandescent lamps approaching the nameplate rating of the UPS. Of course this current also continued to increase as the battery voltage sagged which further increases the rate of sag so if it runs until the unit shuts down due to low voltage, the battery is heavily overloaded at that point. It's hard to find datasheets for small SLA batteries but the ones I did find didn't even show a discharge curve for such a heavy load, and the highest loaded curves they did show were around half or less the rated capacity. SLA batteries, even those optimized for high rate were never designed to deliver their entire charge over just a few minutes. Properly specified Li cells can do this no problem, I have RC airplanes that will drain the battery flat in 4 minutes if you hold the throttle to the stop the entire flight and they don't seem to mind that a bit.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: January 29, 2021, 05:24:07 am
content: 7 & 9Ah SLA batteries were fine for alarm system backups.The plug-in, portable type UPS initially came with one, maybe two outlets. The idea was to protect, say, the computer from work loss. But not the monitor, printer, active speakers, desklamp..

author: james_s
author_rank: Super Contributor
timestamp: January 29, 2021, 06:09:05 am
content: The old desktop PCs could easily draw 200-250W from the wall just for the system unit, even just that is more load than those little SLA batteries were designed to carry.

author: CJay
author_rank: Super Contributor
timestamp: January 29, 2021, 09:38:11 am
content: Quote from: wraper on January 28, 2021, 11:55:13 pmNot my experience, there are better and there are worse, APC are a decent mainstream brand, yeah, they rip you off for batteries, guess what, all UPS brands do.FWIW, I've been working in and around server rooms, data centers etc. for >20 years, part of my job was maintenance checks which included UPS testing, scheduled battery replacement etc.We did some analysis of reliability, we repair/replace more APC UPS because there are more of them in service, they're about even for reliability with most common brands, there are some stand out winners where reliability is excellent but, guess what, the price reflects that.Small, cheap 'desktop' UPS are a joke no matter what the brand, nobody wants to pay for a well designed/engineered good quality one.

author: CJay
author_rank: Super Contributor
timestamp: January 29, 2021, 09:41:19 am
content: Quote from: TheMG on January 29, 2021, 02:46:39 amWhich is entirely my point. Consumer grade is cheap shit.

author: gnuarm
author_rank: Super Contributor
timestamp: January 29, 2021, 05:11:39 pm
content: Quote from: dunkemhigh on January 27, 2021, 02:34:48 pmEach of the six circles on the top of the battery are a cell. 6 x 2 = 12V.

author: gnuarm
author_rank: Super Contributor
timestamp: January 29, 2021, 05:14:00 pm
content: Quote from: dunkemhigh on January 27, 2021, 02:39:23 pmThey are cell caps. Do you think they mold the battery with the electrolyte inside? Each cell has to be isolated, so 6 separate compartments.

author: gnuarm
author_rank: Super Contributor
timestamp: January 29, 2021, 05:16:18 pm
content: Quote from: dunkemhigh on January 27, 2021, 02:50:08 pmThe charger might not deliver current if the battery voltage is too low to be detected as a battery. Or the charger could be broken.

author: PlainName
author_rank: Super Contributor
timestamp: January 29, 2021, 07:24:42 pm
content: QuoteThat's a possibility, but surely the front LED would say that battery is duff then. Everything remains blank, so I am inclined to think it's actually broken.Still, there's a quick way to find out...

author: PlainName
author_rank: Super Contributor
timestamp: January 29, 2021, 07:30:23 pm
content: QuoteIs that a pukka question or a put-down?I don't have any experience of how these things are made (ones I buy for my motor typically need the electrolyte shoving in and then the caps sealing, but they are obviously caps afterwards), and for all I know the outside may just be a case to hold the real thing away from prying fingers/eyes, perhaps just made to look like a traditional battery and/or to fit in a standard battery space.

author: james_s
author_rank: Super Contributor
timestamp: January 29, 2021, 10:31:22 pm
content: Quote from: dunkemhigh on January 29, 2021, 07:30:23 pmEvery SLA battery I've seen has either round plastic discs or a cover plate that is glued on, if you pull that off there are rubber vent caps for each cell under it. These vent caps act as one-way valves, allowing gas produced if the cell is overcharged to vent out. The electrolyte is absorbed into felt-like pads between the plates. I've been able to partially resurrect dead ones by adding a bit of distilled water and letting it soak into the pads. It's an interesting experiment but I have never gained enough to really be worthwhile. During manufacture the cells are made dry, then the electrolyte is filled through the vent holes, the caps put in place and the panel or cover discs glued over the top.

author: PlainName
author_rank: Super Contributor
timestamp: January 29, 2021, 11:56:30 pm
content: QuoteWhy would there need to be the shape of the caps in the top cover? I mean, if it's a separate cover, surely just a flat thing is perfectly OK and less tricky to make (although the indents wouldn't need to be accurate, of course).Also, batteries I know have the fillers all in a row. I've never seen a car battery or bike battery with them in two rows, so a quick look at these without knowing anything further would suggest there is actually 3 cells rather than 6 (the two circular marks being for terminals, perhaps).However, thanks for enlightening me. I can feel the urge to dig out some YouTube stuff...

author: PlainName
author_rank: Super Contributor
timestamp: January 30, 2021, 02:22:12 am
content: Quote from: dunkemhigh on January 29, 2021, 07:24:42 pmYep, battery is borked. One side will charge and t'other won't - shove 14V in and there is 0mA, so presumably a break somewhere.Putting 24V into the battery leads gets the front panel lit up, and then applying mains sees 28V over the leads. So clearly it needs a functioning battery to even say the battery is non-functioning...Presumably a safety measure: you wouldn't want to be charging something that is obviously duff. However, it would surely be possible to flash the red LED is mains is applied and there is an issue.

author: gnuarm
author_rank: Super Contributor
timestamp: January 30, 2021, 02:23:06 am
content: Quote from: dunkemhigh on January 29, 2021, 07:30:23 pmSorry if that sounded rude. I didn't mean to be rude.QuoteThe batteries in cars and such are a bit different. These are called "sealed" lead acid batteries because they literally are sealed and never lose water unless they are badly mistreated. Car batteries used to need water from time to time, but with the addition of cadmium I think it is, they manage to nearly eliminate that.I have to say I don't know how they put these things together either. I just know the buttons on top do correspond to the number of cells. Look at some pictures of 6V batteries. You will only see three cells. I also know they have to fill them after making the case.

author: gnuarm
author_rank: Super Contributor
timestamp: January 30, 2021, 02:27:52 am
content: Quote from: dunkemhigh on January 29, 2021, 11:56:30 pmThat top may look solid, but the caps have to open under pressure to allow the gasses to escape or it will explode. Not good. The battery is duff after that, but at least it's still in one piece.As an experiment you can rip open the dead battery and see just how they do it.

author: PlainName
author_rank: Super Contributor
timestamp: January 30, 2021, 02:50:11 am
content: Thinking about replacements, I found the Duracell equivalent:https://www.duracelldirect.co.uk/pno/dr7-12.htmlSeems not all have visible plugs. Anyway, that got me thinking about a replacement - Duracell aren't high on my list (in fact I'm not sure they make the list at all). Yuasa are pretty cheap - are they too cheap to be any good?Sample prices (delivered):RBC113 @ £56GP 1272 F2 @ £41 or £42 (from the same place - first is found searching for UPS, second searching for RBC113)Yuasa @ £37

author: wraper
author_rank: Unknown
timestamp: January 30, 2021, 03:00:49 am
content: Quote from: dunkemhigh on January 30, 2021, 02:50:11 amThat's some bullshit price.It should cost below £20, £15-16 for a good deal.EDIT:https://www.hardwarexpress.co.uk/csb-gp1272-f2-battery-12v-72ah-452-p.aspAnd they have a very good price for Yuasa (which I would prefer even without price advantage)https://www.hardwarexpress.co.uk/np7-12l-yuasa-12v-7ah-sealed-lead-acid-battery-1333-p.aspEDIT2: I guess you meant price for 2 batteries since you compared it with RBC113

author: PlainName
author_rank: Super Contributor
timestamp: January 30, 2021, 03:13:25 am
content: QuoteYep(and don't forget to add shipping - £6 from there)Thanks for the recommend re Yuasa. I've used them previously but only in non-UPS kit (alarms and bikes).

author: james_s
author_rank: Super Contributor
timestamp: January 30, 2021, 06:40:16 am
content: Quote from: dunkemhigh on January 29, 2021, 11:56:30 pmYou'd have to ask the engineers who designed it, I don't know why they chose to do it the way they did, I just know what they look like. There are different layouts but the typical 12V SLA that's about the size of a brick has three groups of two side by side cells wired in a U shape from one terminal down one side from cell to cell, across at the other end and back up to the other terminal giving six cells in series. The caps are in the same layout, each one has a rubber vent valve/cap over a tubular stem that sticks up and then the cover is glued over the top otherwise those rubber caps would pop off instead of acting as a one-way vent. As I said, they're either six individual little round covers, or a single large rectangular panel. Either one is easy to pop off using a knife, putty blade or small screwdriver. There's no liquid sloshing in these things and the dead ones are usually bone dry so go ahead and pry the lid off one of the old ones and take a look. If you pull off the rubber caps you can peer down inside with a flashlight and see the top of the plates.

author: james_s
author_rank: Super Contributor
timestamp: January 30, 2021, 06:50:15 am
content: As the saying goes, a picture is worth a thousand words. This is a small Power Sonic 12V SLA that was in my battery recycle box. This one is the inline configuration where all six cells are in a straight line as opposed to the style common in small UPS's that is a bit like one of these folded in half with both terminals at the same end. This is also the type with a single flat panel over the valve caps instead of individual caps over each one.

author: PlainName
author_rank: Super Contributor
timestamp: January 30, 2021, 09:31:39 am
content: Thanks