Capacity testing for batteries 2

[sabap]

Can somebody help me with capacity testing of the 125 V DC 60 cell battery bank?

The nameplate rating on the C&D batteries is as under:

Model: XT1L-43
Amp-Hour: 3340.9 for 15 min; Final Voltage: 1.67 V

These are Vented Lead Acid batteries.

What i understand from the manual is that AH for the battery is: 3340.9/4 = 835.22 AH

For 8-hour test, we need appr. load of 835.22/8 = 104.4 Amp

At this load we whould reach the nameplate final voltage of 1.67 * 6 = 100.2 V.

Now with 104.4 A current, we should continue the test until the final terminal voltage is 100.2 V

In the mean while if any individual cell voltage falls below 1.5 Volts (or 1 Volts, i am not sure!), we should bypass that cell and continue the test after that with new final voltage , 1.67 * 60 - (no of removed cells).


Please verify if the above procedure is correct. I dont have the copy of IEEE std 450-1995 and cannot afford to buy it. But i have to perform the test as batteries are in service since 1998 and no testing even at the time of commissioning was performed.

Please help!!!

 

[DanDel]

The test amperage is usually provided by the manufacturer in the form of a table or graph showing current values for each test duration.
There is also usually a requirement to equalize charge the batteries about 2 or 3 days before the discharge test.
Why are you dividing the 3340.9AH by 4 to get 835.22AH?
What equipment are you planning to use, since the IEEE standard requires constant current testing?
Is it possible for you to hire a company experienced in this type of testing?

 

[jbartos]

Suggestion: Since no information is provided about the battery types, it is recommended to contact the battery manufacturer tech support. Tech support may have IEEE Std procedures adjusted for their battery product testing.

 

[alehman]

I share Dandel's concerns. There are specific equalization times and voltages, settling times, etc. Equalization parameters depend on temperature. I strongly suggest finding a way to purcahse or borrow a copy of 450. You have a big system and testing it shouldn't be taken lightly. Another approach might be to consult C&D or an qualified battery maintenance organization.

C&D rates this unit at 2142AH at an 8hr rate @25C and 1.75V end-of-discharge, so your constant rate discharge should be somewhere around 2142/8 = 268A, slightly more for 1.67V.

See also

http://www.cdtechno.com/cd/library/manual/f6741/RS1476.htm

 

[jbartos]

I beg your pardon, I overlooked the battery model, XT1L-43. However, the C&D tech support still might be contacted for the calculation approval or refinement.

 

[jbartos]

Suggestion: Please notice that IEEE Std 450 includes under Capacity Test Schedule:
1. Acceptance Test: Made at the factory or upon initial installation. The test should meet the specific discharger rate
2. Performance Tests: Are made within the first two years of battery service. These include Annual Performance Tests of Battery Capacity to any battery that shown sign of degradation or has reached 85% of the service life expected for the application. Degradation is indicated when the battery capacity drops more than 10% of rated capacity from its capacity on the previous performance test, or is below 90% of the manufacturer's rating.
3. Service Tests: May be required by the user to meet a specific application requirement upon completion of the installation. This is a test of the battery's ability as found to satisfy the design requirements (battery duty cycle) of the dc system. This test is performed for Class 1E nuclear power generating station batteries as part of the preoperational and periodic dc system tests described in ANSI/IEEE 308.
Then comes the test procedure.

 

[Kiribanda]

Hi sabap,

As far as I can remember, your testing procedure is correct and also is in accordance with IEEE-450. Please also note the followings.

a)The bad cell should be replaced if any cell is reached 1.67 V + 1 V(or less) and not 1.67V-1 V as you have posted.

b)Modified final voltage is also correct with missing cells. i.e. 1.67 Vx(n-1).

c)When you find a bad cell and the test is stopped don’t take long time to by-pass the bad one. The specified time is 10 % of the total discharge time or 6 minutes whichever is the lowest. We usually keep thick strong jumpers ready before the test is started.

But I too have some questions.

1)Are you going to conduct Constant Current Discharge Test on the battery bank?

2)If so how did you decide the magnitude of the final cell voltage as 1.67? Is it from manufacturer’s battery catalogue?

3)If so how did you decide the magnitude of constant current? Is it from the same catalogue?

4)If so, what is the logic behind your calculation for 104.4 Amps?
Normally these catalogues provide a set of tables for various end voltages with corresponding discharge currents.

Good Luck!
Kiribanda

 

[sabap]

1. Why am i dividing 3340.9 with 4?
Answer: On the nameplate. it is mentioned as under:

capacity: 3340.9 A for 15 min. I am converting this 15 min capacity to AH. Is it wrong?

2. From the website i have already downloaded the specification sheets of XT1L-43 battery. They mention two types capacites, one with high rate and other with low rate. And both AH and final votlages are different for each type. THe data i have given above is given on the nameplate of each individual cell.

THe battery manual does not mention any procedure for testing rather it refers to IEEE 450 which i dont have.

FInally there is no graph or table in the manual.

I have consulted the factory but they are not replying as the batteries are old and they have relocated the distributors. THese batteries were pruchased from Barberton, Ohio. Now they have referred us to Houston office which is not responding.

I have written the question at the forum to get expert opinion from the forum members and i hope i could get somebody to reply who has used these batteries.

 

[sabap]

Sorry, In my confusion i forgot to thanks all who have answered. I once again thank you all for your replies and look forward for further assistance.

 

[alehman]

sabap,
Battery ratings are confusing. I don't understand C&D's lack of response. This model is still in production.

1. Your calculation is correct. However, note this is based on a 15min discharge rate. The AH capacity depends greatly on the discharge rate. You proposed an 8hr discharge rate, so you should use the 8Hr AH rating, which C&D lists as 2142AH to 1.75V. You should not discharge below 1.75V average over an 8hr period. Going lower than this risks damaging the battery.

C&D's web site rates this model at 2802 amps for 15 minutes to 1.75V.

2. C&D provides two general types of ratings - (1) a slow rate which is based on constant current discharge and is given in ampere-hours with 1.75VPC end-of-discharge and (2) a fast rate based on constant current and on constant power discharges with 1.67VPC end-of-discharge. C&D used to provide many more voltage and rate combinations in their literature.

This battery is labeled with the 15min rate because it is optimized for UPS applications.

For discharge temperature correction factors, in the link I posted yesterday and find Part 4, section 1.3. Part 4, section 1.4 has information on capacity testing. IEEE 450 suggests 1V as the cut-off where you jumper a cell out of the string.

 

[jbartos]

Suggestion: IEEE Std 450 includes Discharge Current Correction Factor K for Initial Temperature, e.g.
37.8degC 100degF K=.91
43.3degC 110degF K=.88
etc.
Then, the test discharge current is equal to the rated discharge current divided by K, where K is the discharge current correction factor for the initial electrolyte temperature.
Comment on ""In the mean while if any individual cell voltage falls below 1.5 Volts (or 1 Volts, i am not sure!), we should bypass that cell and continue the test after that with new final voltage , 1.67 * 60 - (no of removed cells).""
If the battery does not meet the design requirements of the dc system, review its rating to see if it is properly sized, equalize the battery, and, if necessary, inspect the battery and take necessary corrective action, and repeat the test.

 

[sabap]

Following is the reply i received from C&D technical support department:

QUOTE

I am in receipt of your Powercom Web Site Information Request dated October 1, 2003. The following is in response to your questions.

1.) The XT1L-43 model is a Lead Calcium Cell.

2.) The final voltage per cell under discharge is dependant on the minimum voltage requirement of the equipment the battery is backing up. Our factory tests as a standard is a constant current discharge at the 15 minute rate down to 1.67 Volts per cell. In general, ratings are provided for the 1.67 Volts per cell for discharge times one hour or less. A 1.75 Volts per cell rating is provided for discharge times from one minute to eight hours.

3.) The 3340.9 value listed on the nameplate is the actual constant current discharge rate used on these cells during the factory acceptance test. All XT models are factory tested for 15 minutes to a 1.67 volt per cell end point. The latest published 15 minute discharge rate is 3288.3 Amps of constant current to 1.67 volts per cell.

C&D recommends Site Battery Testing in accordance with IEEE-450 Std, 2001. It is also recommended to perform the discharge test that represents the actual load on the battery. I have attached a brief write up on Site Testing that provides some guide lines for testing.

I trust that the above information will answer all the questions you have regarding your installation of the XT1L-43, 60 cell battery. Should you require any additional information please feel free to contact us.

UNQUOTE
_______________________________________

They have now referred to IEEE-450-2001 for time adjusted method and rate adjusted method of testing. I think they are talking about site accepting testing.

I beleive i have to buy IEEE-450 somehow!

I would like to know that what is the recommended frequency for capacity and load testing of the batteries.

 

[alehman]

Schedule for discharge testing is a subject of considerable disagreement. Some believe you should not do discharge tests because of the stress of the battery. My feeling is you should test for exactly that reason. I think jbartos mentioned 450 recommends annual tests. That would be adequate for most applications, and is covered by most manufacturer's warranties. Be sure to read your warranty before you implement a schedule.

I agree with the recommendation that the testing should mimic the application as closely as possible, ideally using the actual load.