×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Standby battery bank discharge test
2

Standby battery bank discharge test

Standby battery bank discharge test

(OP)
We have standby battery banks to provide DC power for our generating stations. Recently we started a monthly discharge test where we turn off the battery charger for five minutes to test the capacity/condition of the batteries. There has been some conflicting ideas on whether this is a good practice or not. Any insight?

RE: Standby battery bank discharge test

Monthly is likely too frequent.

How old are your batteries ? What type ?
What was your previous discharge test frequency ? How deep of a discharge did you do in terms of % of its nominal terminal voltage ? How long before you got to the roll off voltage ?

RE: Standby battery bank discharge test

Take a look at the attached Megger Battery testing guide. It appears to give some pretty good information.


Capacity test (capacity test) should be done
▪ at the installation (acceptance test)
▪ Periodically. Intervals should not be greater than 25% of
the expected service life or two years, whichever is less.
▪ Where impedance values has changed significantly
between readings or physically changes has occurred
▪ annually when the battery shows signs of degradation or
has reached 85% of the expected service life. Degradation
is indicated when the battery capacity drops more than
10% from its capacity on the previous capacity test or is
below 90% of manufacturers rating.

RE: Standby battery bank discharge test

(OP)
We have multiple installations with varying ages from 1 year to 20 years. they are vented lead acid battery type. We had not been previuosly doing a discharge test.

RE: Standby battery bank discharge test

A capacity test is much different than turning the charger off for 5 minutes, not sure what that tells you.

You may want to look at Impedence testing, using something like Maggers EBITE system. Works great for monitoring condition of your cells.

RE: Standby battery bank discharge test

Turning the battery charger off will only tell you if there is already something seriously wrong with your battery, ie if the voltage collapses without the support of the battery charger.

RE: Standby battery bank discharge test

Turning the battery charger off will only tell you if there is already something seriously wrong with your batteries, ie if the voltage collapses without the support of the battery charger.

RE: Standby battery bank discharge test

It is amazing how things have changed. Impedance tester was not around 21 years or so ago. We have battery banks approaching 30 years old and with proper maintenance (mostly the addition of distilled water), yearly cell voltage and specific gravity measurement and data analysis if it requires equalization at that time have done OK for us. Capacity test every 3 years down to where voltage starts to roll off without going into deep discharge is how we do it, trending time to reach roll off voltage.

so far that procedure have not changed along with monthly visual inspection to ensure battery are either not being overcharged and floated properly and no visible sign of sulphation.

megger battery what ?

RE: Standby battery bank discharge test

Very well stated, collies99, and a star to boot.

I started in the UPS industry back in about '87. The only way to properly test a battery bank back then was to do a fairly deep discharge and monitor the voltage across each cell. Nearly 30 years later it still hasn't changed :)

Yes, an impedance test can certainly tell you that a battery has failed, or is about to, but it is still nowhere near the certainty that a discharge test will provide.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources