UPS Battery Types 2

[Yme48]

Hello all,

I need help identifying the different types of large scale UPS (750kVA, 480V) batteries. Sealed lead acid, gell cell, wet cell, etc...

Can anyone explain the differences between them, advantages/disadvantages of each type. Perhaps a good baseline reference?

Thanks

Yme

 

[mpparent]

You could check out the IEEE orange book...

Mike

 

[busbar]

Batteries for the application are commonly manufactured in wide ranges of quality, and commensurate pricing variations.

A copy of the IEEE Battery Standards Collection may provide some guidance in the specification/selection process.

 

[jbartos]

Suggestion: The selection of the large scale UPS batteries depends on the type of load these batteries are feeding.
The DC motors will need relative low internal resistances of battery cells.

 

[wbd]

In addition to the other excellent references, try these:
IEEE Std 485 - Recommended Practice for sizing large lead storage batteries for generating stations and substations
IEEE std 484 - Recommended practice for installation design and installation of large lead storage batteris for generating stations and substations
Additonally, I'm sure there is info on the manufacturer's website and their reps would be of assistance.

 

[peebee]

Gel-cells are typically not recommended for large UPS applications.

VRLA (valve-regulated lead acid) batteries are common. They also go by other common names such as sealed-cell and immobilized electrolyte (both terms also include gel-cell) and glass-mat absorbtion. VRLA is my preferred term. Anyway, they can be usually purchased with 5, 10, or 20 year warranties, usual life is 3 to 8 years. Advantages include low maintenance (almost no maintenance), little or no hydrogen off-gassing and little hydrogen monitoring requirements, ability to locate in cabinets, small footprints, may be located in general office/data center areas, etc. Also, the glass mat tends to absorb acid like a towel, so acid spills are of relatively low concern. Low initial cost but high lifecycle cost as compared to wet cell. Good for people who have better things to do than worry about their UPS and don't mind frequent battery changes.

Wet cell batteries are the other common battery storage. Off-gas hydrogen, detection usually required. Acid spill containment required. High maintenance. 20-year warranties are common, usual life is ~18 years. Low lifecycle cost. Bigger footprint, specialized rooms. Good for sophisticated users whose primary concern is UPS availability.

Rotary storage is making a comeback as a replacement for batteries, too. I have little experience with rotary systems, though. Most data center types stick to batteries, but I've heard that many manufacturing plants are installing rotary UPS systems.

Hope this helps.

 

[peebee]

Also, see

http://www.cdtechno.com/cd/library/papers/9807/9807.htm

for an excellent comparison of various battery technologies.

 

[nukeman]

Peebee
Very good descriptions.

YME48
You might want to take a look at IEEE 1188 and IEEE 450 for the recommended maintenance for VRLA and vented lead acid batteries.

 

[Ares]

Peebee comments are right on
Additional considerations should be:
-Wet cell usually fails by shorting, failure not trivial to diagnose and may lead to catastrophic failure.
-Wet cell may short the UPS electronics if system is not floating (isolation transformers on input and output.
-Wet cell when disconnected for maintenance (fairly frequently) does not provide backup.
-Cooling fresh air (significant amount) takes energy, not cooling reduces battery life. Often this is overlooked in the economics.
-Safety a concern
-Eye wash station may be required, additional cost, additional space,

-VRLA usually fails by breaking the cct making entire string useless until repaired …BUT that can be offset by having two strings in parallel. Such failure is also trivial to detect and not to common.
-does not require maintenance, ventilation - fresh air- low operating cost

 

[tmahan]

Several companies are now producing relatively cost effective fuel cell systems as well. Initial purchase price is much higher but they do have many advantages. There is a least one that is aiming for the substation market.

I have no affiliation with Aperion (an ABB spin off) but thought they had an interesting product

 

[peebee]

I've recently heard of "flow cells". Something like a closed-loop fuel cell or battery, uses an electrolyte for energy storage. I have no details or experience with them, don't know of anywhere they've been installed, and have no idea if they'd make sense for a UPS (probably not unless you like using unproven technologies on your critical power system). I heard they are being used or might be used in the future on solar systems.

Any thoughts/experiences/information on flow cells?

 

[Shortstub]

Adding to reference materials and standards:

Don't forget "new" safety rules in NFPA 70E, covering battery rooms!

 

[Yme48]

Thanks to all for some very informative comments. My application is for a large data center. Environmental issues are certainly a concern as well as maintenance costs and overall footprint. We have had Gel Cells in place for 5 years that require replacement. Battery vendors are trying to sell me wet cells. Now I think I know why...maintenance!

I have not heard of using flow cell technology with a UPS but as peebee mentions is probably not an option.

 

[peebee]

What kind of company are you? How large is your large data center? In established companies with solid long term prospects and large equipment areas (say, 50,000 sf or more), such as many bank and government installations, the choice of wet cells is a no-brainer. Similarly, every phone company DC system I've ever seen is a wet cell system.

Dot coms, small offices, small manufacturing, securities traders, etc., typically want the low initial cost, flexibility, and low maintenance of VRLA's.

 

[eddie11]

I have 2 related questions if some kind person can provide his/her opinon.

1) Do VRLAs-based UPS and DC power systems require eye stations also?

I am wondering about a telecom datacenter application with a 30KVA UPS with VRLA batteries. Someone came through recently and dinged us as being in code viloation for not having eye rinse stations, acid resistant gloves, PPE procedures, acid spill procedures, and acid resistant cover for the hydrometer when taking specific gravity readings.

I thought all of these things are not needed with VRLA???


2) Then, I have a 48VDC wet cell DC plant in another site that has all that stuff, but does not have hydrogen detection. Is that always mandatory?

Any comments are appreciated. Thanks!! I do not have an expert of my own to consult so I want to get a little better educated before I re-engage with the critics.

 

[peebee]

I'm not sure what code drives eye protection.

Acid spill is generally not much of a concern with VRLA's (or gel cels), that's the whole point of the glass mat (or gel) -- if you drop the battery and the case breaks, the mat acts like a towel and sucks up the acid (or the gel just sits there like Jello).

Specific gravity readings?!? On a VRLA ?!? I didn't think that was necessary, or even possible on a VRLA, they're SEALED cells. . . . Are you sure they're not wet cells? Did "someone" have any idea what they were looking at?

NEC 480.9 requires ventillation sufficient to prevent the buildup of hydrogen. Some local AHJ's also require hydrogen detection (and sometimes even Div 2 XP construction) -- but they are the exception.

 

[PowerfulStuff]

Hi,
Coming from a different area of the world, most substations and high criticality supplies are pocket plate Nickel Cadmium - Lead Acid of any construction wouldn't be considered. This is in part due to the rapid life shortening that occurs above around 25 degrees for lead acid batteries. Are they part of your considerations? Saft are a common supplier but there are others as well.

 

[itsmoked]

YME48;

You should seriously consider rotating storage and a generator. It is becoming more common because it makes a LOT of sense. The rotating storage carries the system while the generator gets up and stable. This avoids batteries entirely, their gases, maintenance, space, creeping capacity limit, growing disposal hassles and the fact that they WILL go dead in a power failure, then require a lengthy recharge period. A generator lets one easily provide power for extended periods, days! Also it only costs slightly more to provide power for the entire facility, instead of just the data processing equipment with the generator. A generator can also cover long term utility problems. Where I live we have had two multi-day power failures. One was an earthquake trashing the switchyards another was a failed transmission line. These are just examples of outages that a UPS doesn't even begin to address. A generator can also allow you to save a small fortune by signing up with your utility to allow them to drop you to prevent brownouts. You will see that they have a tiered price system that allows you monthly savings that go up exponentially based on how little notice they need to give you when they want to drop you. With the above system they can pull the plug anytime with only the house lights blinking. Generators also have outstanding salvage value. UPS's with batteries have truly zilch resale value.

 

[lengould]

You might consider investigating the "flow battery" at VRBPower

http://www.vrbpower.com/vrb_power.html

. They've recently joined with Regenesys and look like they've gotten some strong financial backing, but it is quite new technology.


Pechez les vaches.

 

[ScottyUK]

Hi itsmoked,

Your comments contain some truth, but it sounds like you are suggesting that only a rotary UPS can be used with a generator... which is total nonsense. Rotating storage systems of the type marketed by Caterpillar and (I think) Merlin Gerin have their own problems, so while they address many of the shortcomings of battery-based systems they also introduce a whole load of their own troubles. Rotary energy stores need time to recover too, and store a lot less energy than a battery system. The standby generator HAS to start pretty much first time with a rotary system, or the load is flat.

You overlooked one of the greatest weaknesses of both battery systems and rotary storage systems, which is their lousy capacity to clear faults by tripping a load breaker when the load is powered from stored energy through the power electronic converter. Try explaining that the UPS didn't clear a 16A circuit breaker, and dumped an entire trading floor as a result. An employer or two ago, our client's engineers had to do just that and I bet it was an interesting exchange between engineering and management. We were called in as independent consultants to referee the fight!

I'm a big fan of the integrated rotary UPS systems which employ a special electrical machine and a diesel engine close coupled on a common bedplate through a clutch, but they just aren't available in small sizes and they are expensive.

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