The Gates of Delirium (Dec 06 2012)

N9JFE wrote

I'd say, once they've run themselves down once, replace them -- they won't give anything like the same amount of run time for the next outage.

But what was the expected lifetime of the cells you were using?

A lead-acid cell (jell or liquid electrolyte) has several failure mechanisms. Some are age-related, some cycle related. Generally, UPS cells are maintained under trickle-charge conditions for years at a time and may occasionally be required to deliver charge. The age-related parameters dominate.

In other words: test and replace cells on a fixed timetable. Unless you're having brownouts every other week, the shelf-life parameters are going to dominate.
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Just a thought and it seems to be somewhat suggested earlier, but every UPS I have used, uses a 12 volt battery which trickle charges when maim line power is in use. I seems to me you might be able to use a deep cycle marine battery or one of the optimum dry cell batteries to supply the power in the case of a power outage. Should give a substantially longer time before shutdown is mandatory and might have saved things in this situation.
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FYI everything that is now downloading to my system is comming up with computation error
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Thanks. Actually I had installed an Nvidia GTX 690 during the time seti was down. Appreciate the advice.
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My two cents on the batteries..

I have always heard, and personally experienced both at home and at work, that a brand new battery tends to only last 2-3 years in a unit. Doesn't matter if it gets discharged between 25-75% once per month or only once or twice in a 3-year period.

I brought home three 1400VA carcasses from work that had bad batteries and got new batteries for them. All the batteries came from the same lot# from the manufacturer and in one unit, it ran on battery maybe 12 hours total across two years before deciding one day to just stop working entirely (that's the one that caused my laptop to lose power).

The other unit lasted an additional 15 months and had more load on it when it was running on battery, and it usually ran down until it shut itself off.

The third one had a 35% load on it 24/7 and it is the one my main cruncher is on. When the power would go out, I would shut everything down and usually just leave this one running for my router and modem.

A couple of weeks ago, I guess the power flickered and both the second and third one stopped functioning simultaneously. The next day when I started opening all of my UPSes up, I noticed a common pattern amongst all of them: every single battery had gotten so warm and swelled so much, that the plastic casing cracked on them, and the white powdery stuff inside (I'm assuming that is dried-up acid gel) was crumbling and falling out.

I have heard that if you cycle them once per month and run them down to about 25% remaining, it can extend the life of them, and I did that for the first six months on the third one, but since the second one survived just as long, I don't think that's conclusive.


TL;DR.. batteries won't last forever. Age is usually a problem. 2-3 years is all you will get out of a battery, usually regardless of use. From the sounds of it, their units were functioning just fine, they just don't have much run-time, but you're not supposed to. UPSes are only supposed to do three things: get you through a flicker or very short loss, last long enough for the back-up generator to come online, and give you enough time for a graceful shutdown. An automated generator system will take less than 30 seconds to come online. A 3000VA unit at full load will still give you ~4 minutes which is enough time for `umount /remote/*' and `init 0'.
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Linux laptop uptime: 1484d 22h 42m
Ended due to UPS failure, found 14 hours after the fact

every single battery had gotten so warm and swelled so much, that the plastic casing cracked on them, and the white powdery stuff inside (I'm assuming that is dried-up acid gel) was crumbling and falling out.

I have heard that if you cycle them once per month and run them down to about 25% remaining, it can extend the life of them, and I did that for the first six months on the third one, but since the second one survived just as long, I don't think that's conclusive.

UPSes are only supposed to do three things: get you through a flicker or very short loss, last long enough for the back-up generator to come online, and give you enough time for a graceful shutdown.

The gel batteries and AGM batteries (as well as many other low maintenance/no maintenance batteries) are a calcium battery. These batteries have about 0.5% of the battery grids (the structures forming the battery plates) being calcium. One known wear-out mechanism of calcium batteries is plate growth even when the charging current is fine. Plate growth will makes batteries bulge and swell to the point of cracking. Overcharging can cause the battery to gas resulting in a pressure build-up within a cell with similar results.

A part of battery safety testing investigates the battery operation with pressure build-up. Batteries are intentionally overcharged to make the battery gas and build up internal pressure until the pressure is relieved or other failure stops test. Acceptable results from the test are for a single operation vent to relieve pressure or multiple operation vent to open and close. A single operation vent may be a plug popping out or a controlled cracking of a case. The objective is for the vent to operate without the case exploding and creating shrapnel.

There are other factors that can affect battery life including temperature, cycling, vibration, and how long a battery sits discharged. These are topics for other lengthy discussions.
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They do not like to be severely discharged (take them down to 10V & you can consider them deceased).

I'd like a 3kVA online (i think they call them double conversion now) unit, but they're way out of my price range. So it's 2 very cheap 1500kVA units, with a couple of car batteries on one of them. At 45% load it's good for about 6-8 hours. I tried running both systems on it, which is about 85% load- but when running on batteries it gets so hot i'd expect it to fail within 20mins (after just 5 minutes i could smell it cooking).
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Grant
Darwin NT.

I'd like a 3kVA online (i think they call them double conversion now) unit, but they're way out of my price range. So it's 2 very cheap 1500kVA units, with a couple of car batteries on one of them. At 45% load it's good for about 6-8 hours. I tried running both systems on it, which is about 85% load- but when running on batteries it gets so hot i'd expect it to fail within 20mins (after just 5 minutes i could smell it cooking).

It's better if you pay a few extra dollars for deep cycle batteries. Regular auto batteries will fail early if you deep discharge them but deep cycle are designed to withstand the abuse of of dry camping or electric powered boat motors.

The problem with car batteries is hydrogen production. Doesn't happen often, but when it does it's very nasty.

A computer store I worked at had car batteries connected to the server UPS. The source of the fire that wiped out the building was located to that room.

The problem with car batteries is hydrogen production. Doesn't happen often, but when it does it's very nasty.

A computer store I worked at had car batteries connected to the server UPS. The source of the fire that wiped out the building was located to that room.