Grounding battery rack
- Thread starter deanmi
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Do you know why VRLA batteries were spec'd on your project? Low cost?
brian john
Senior Member
- Location
- Leesburg, VA
Low cost, competitive bidding, size of UPS and few customers or electrical engineers KNOW anything about batteries So the salesman decides what goes in. (Depending on project size) then there are less restrictive installation requirements, less maintenance (TO NONE by many customers).
And all of this is done without the end user realizing this battery has a 3-5 year reliability, depending on usage of course.
DM2-Inc
Senior Member
- Location
- Houston, Texas
There are plenty of manufacturers that have 10 and 20 year VRLA batteries. We're using C&D, 10 year VRLA on a project currently.
Yes they do make them, but none ever make it that long. 5 to 7 years tops for a sealed product.
brian john
Senior Member
- Location
- Leesburg, VA
1. What model?
2. Have you ever seem them provide 10 years of ACTIVE service in a UPS...NO, No, No.
Unless the load is Nothing.
DM2-Inc
Senior Member
- Location
- Houston, Texas
We're using the C&D Liberty Series...
http://www.cdstandbypower.com/product/battery/vrla/lib1000_12_373.html
A Qualified Yes...
I've been to the facility that uses them (an Oil refinery in Indiana). After looking as some of the date codes (11 years), I'd have to say that they do last for 10 years. Now there were quite a few batteries that had a date code less than 10 years, most of them 8 years, but after talking with some of the maintenance folks, they're not able to remember failures too frequently (whatever that means).
Initially I was skeptical about any battery lasting longer than 5 years. After talking with the local rep and getting a better understanding of their product, as well as looking at a few date codes on the batteries on site, I've changed my opinion.
I'll have to say that I've never worked with flooded batteries, which by your post I'm guessing you advocate and have experience.
Most of the systems we work with have less than 100 amp hour requirements. The current project I'm involved with has anywhere from 1600 amp hours to 2000 amp hours requirements. The systems we work with have a 24 hour battery backup requirement, and in some cases 90 hours.
I'm a mechanical engineer, not an electrical engineer, so whether a 24 hour design task these UPS systems more than a 4 hour design, I can't comment. I'm guessing it has more to do with how many times they're discharged, and how far they're discharged. We disconnect the batteries when they fall below 18 volts, but I'm not sure how much that help.
Regards
brian john
Senior Member
- Location
- Leesburg, VA
not sure what you mean by this?
DM2-Inc
Senior Member
- Location
- Houston, Texas
Mean by what?
It's my understanding that if you continue to draw current from batteries, until they're down to 0 Volts, it becomes much harder for the battery to recover as well as compromising they're life.
This is simply the web site for the batteries we're using. If you have a read through it, they warranty the batteries for 10 years (yes...I know...warranty doesn't always equal service life, but...). If you have a look at the C&D Endur II, they claim a 20 year warranty. I don't believe C&D uses a catalyst to aid in the longevity of battery life, as some others do. The Military has been doing this for some time now and are getting 20 years out of VRLA's.
If this is the question, my comment only implies that some chargers I've seen don't disconnect the batteries at all when they're drawing power from the batteries due to primary power loss. Our designs disconnect the batteries when the voltage falls below 18 volts if the AC to the charger is not present.
It's my understanding that if you continue to draw current from batteries, until they're down to 0 Volts, it becomes much harder for the battery to recover as well as compromising they're life.
weressl
Esteemed Member
Yes and no, some will and some won't and therein lies the problem.
UPS battery banks are a series connection of batteries, that can range into the hundreds if single cells are used. Sealed batteries utilize mulitple cells in a single jar.
Most common failure mode of a cell is an open circuit. What it means in practical terms that a single cell failure can make your entire bank unavailable. So while your UPS elctronics have 60-120 years MTBF, your battery bank often has less than a year. The kicker is that the battery failure is often not evident until you are impressing a load on it and then the failing cell will open and shut your UPS down when it is really needed.
There are various ways to remedy this shortcoming, but it is really getting away from the topic, so if somebody is interested, start a thread and invite me to contribute.
(I am in the process of writing of our Battery Maintenance Procedure.):smile:
ItsHot
Senior Member
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- A little piece of heaven!
guarding?
guarding?
A little " op", but is there a requirement for protection on these large ups's? I ran into a very large new ups last week. Tons of batteris on 3 levels, no type of guards! The digital voltage read was about 520 volts!! What is the nec requirements on this? Sorry to the op, I am not trying to reail your thread!
guarding?
A little " op", but is there a requirement for protection on these large ups's? I ran into a very large new ups last week. Tons of batteris on 3 levels, no type of guards! The digital voltage read was about 520 volts!! What is the nec requirements on this? Sorry to the op, I am not trying to reail your thread!
brian john
Senior Member
- Location
- Leesburg, VA
In a lead acid battery if you draw current below 1.5 VPC (volts per cell) you will trash the battery.
It is better to talk volts per cell or let us know the string voltage I assume your 18 volt system is a nominal 24 VDC battery floating around 27 volts DC.
In my opinion a with a sealed battery and if you are using a long discharge period a higher voltage (above 18) would do less damage to the cell life.
brian john
Senior Member
- Location
- Leesburg, VA
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