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Peter Zawistowski

The Ups & Downs of UPSs

Peter Zawistowski
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samicksha
samicksha
3/24/2014 2:36:14 AM
User Rank
Student
Re: Chemistry test
You are right goafrit, Manufacturers supply run-time rating in minutes for packaged UPS systems. Larger systems such as for data centers require detailed calculation of the load and battery characteristics to ensure the required endurance is attained.

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goafrit2
goafrit2
3/22/2014 10:02:43 AM
User Rank
Master
Re: Chemistry test
>>   The UPS also provides transient protection which may prevent hardware failures in addition to data loss.  How expensive is a 10 minute outage on a mainframe system with 300 users not able to work while the system is restarted?

You have explained why cloud computing is becoming very attractive. If you have a technology that caches so that you never lose data as you work, a 10min power failure will not be catastrophic. Most laptops now can take you to one hour.

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goafrit2
goafrit2
3/22/2014 9:56:58 AM
User Rank
Master
Re: Chemistry test
There are many laws and knowledge base in battery technology. Yet, the problem is that many things are not known about materials, discharge and overall ways to improve efficiency. When a product is incubated by chemists for electrical engineers to deploy and use, you will notice a kind of lost knowledge base. Google papers on battery, they are everywhere. Yet, have an issue on battery design, you will notice not much is really known in some areas.

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goafrit2
goafrit2
3/22/2014 9:53:53 AM
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Master
Re: Chemistry test
>> The use of UPS systems on small computers or large datacenters and everything in between is an economic issue, and a convienence issue and not only a question of utility reliability.

UPS adoption is very low. Not many companies use it. I know in the developing world with sporadic power supply, UPS is seen as one of those things everyone must have. But you do not expect this to be part of small company budgets in U.S. They think they can count and rely on the grid.

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goafrit2
goafrit2
3/22/2014 9:51:21 AM
User Rank
Master
Re: Electrochemical noise
>> Does anyone have FFT of electrochemical noise? 

I think the best strategy will be looking at the levels of atoms and molecules to see how bonds break. FFT will not offer much in my knowledge.

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Vishal Prajapati
Vishal Prajapati
2/20/2014 12:26:03 AM
User Rank
Master
Re: Electrochemical noise
The approach gas gauging ICs are using is probably just providing marginal estimation of battery life and its charge status. But as of now we don't have any concrete approach for looking in to battery chemistry, we are spared with this only. I don't know if there is any novel approach has been invented for this.

 

If not this scenario needs complete makeover. The current approach needs to be revamped from scratch to have a proper estimation of battery capacity and its life.

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goafrit2
goafrit2
2/19/2014 6:09:25 PM
User Rank
Master
Re: Electrochemical noise
Predicting life of battery has been a very complicated subject. I have tried it using gas gauging ICs available in the market

Battery is a chemical product which is very complicated. Though it turns out that it is the basic tool for electrical engineers, there is nothing in battery that is electrical. This is chemistry at the highest level. My thinking is that you can accurately predict the life spam of a battery by looking at how the bonds in the chemicals degrade or break. So, it is chemistry that can accurately lead this prediction over circuits which end up becoming a burden on the DUT.

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Buck-on-Bass
Buck-on-Bass
1/26/2014 4:52:34 PM
User Rank
Newbie
Re: Chemistry test
Dave Fader worked for Bell Labs and was involved in the development of the "Round Cell" for the telephone industry.  Several times he commented "There was no such thing as a maintenance-free battery.  It is a maintenance-resistant battery."

I read the post and the comments.  First, I don't know of anyone that used a float voltage of 2.32 volts per cell for a flooded cell at room temperature.  If you check with those making large flooded lead acid cells for stationary applications, you will find the typical cell voltages are 2.17 volts to 2.25 volts.  For longer service life,, lower cell voltages are used.  To get greater energy storage, higher cell voltages are used.  When a group of cells connected in series start having the individual cell voltages drift apart, the battery string is typically "equalized" at around 2.33 volts per cell.  Some users will equalize after a discharge to attempt to restore the full capacity to a battery as quickly as possible.

Various alloy materials are incorporated into the battery grids to obtain some desired properties.  Calcium is used for standby batteries to reduce the float current and water usage.  Some call these batteries lead calicum batteries.  Instead of calcium, antimony is used in some batteries.  Antimony provides greater cycling capability but has higher float current and greater water usage.  Introducing other materials into batteries may adversely affect the batteries' performance.  This is why battery manufacturers provide information about what water is acceptable for adding to (watering) a battery.  This is why the noise analysis of the acid reacting to a metal plate may not be good for a continuous monitoring method.  

The use of UPS systems on small computers or large datacenters and everything in between is an economic issue, and a convienence issue and not only a question of utility reliability.  If a $200 UPS prevents the loss for 4 hours of work a year from the lights blinking in a thunder storm or a momentary interruption from other causes, that UPS have more than paid for itself in my engineering group.   The UPS also provides transient protection which may prevent hardware failures in addition to data loss.  How expensive is a 10 minute outage on a mainframe system with 300 users not able to work while the system is restarted?  What about the data loss?  Maybe a $10,000 UPS is a viable way to avoid those interruptions.  If you are selling online services, what is the impact on customers?  Look at cloud service providers to see what interruptions do to their businesses.

All the applications I have mentioned so far are considered to be stationary battery applications.  Batteries used for forklifts and similar applications are considered to be industrial battery applications.  In these applications the batteries discharged in the applications then recharged over several hours, typically 8 hours.  The objective is to quickly recharge the battery without an excessive temperature rise on the battery.  These batteries typically last 5 to 10 years and have a cycle life of 1000 to 2000 cycles.  The depth of discharge and the how long before recharging are a big influence on battery life.

If a flooded battery is discharged and left in this state, it will sulfate.  The discharge may be by a user or by the battery' self-discharge rate.  This is why manufacturers have requirements for charging batteries in storage for long perions of time.  The battery manufaacturers have published information on how the maintain batteries in storage for months.

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Vishal Prajapati
Vishal Prajapati
1/24/2014 10:25:50 AM
User Rank
Master
Re: Electrochemical noise
Does anyone have FFT of electrochemical noise? What type of spectrum it covers? If battery can be diagnosed with such non invasive menthod, it would be great to see such application. Can it be significant to effect the portable analog electronics like medical equipments?

 

Predicting life of battery has been a very complicated subject. I have tried it using gas gauging ICs available in the market. But no of chargin cycles remaining and amount of sulfation are a bit complecated areas.

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samicksha
samicksha
1/23/2014 4:53:58 AM
User Rank
Student
Re: Chemistry test
We have been talking about batteries discharge and charge, any one remember Peukert's law, wherein he speaks about he capacity of a lead acid battery in terms of the rate at which it is discharged.

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