Commissioning of New Battery Banks 1

[zaza123]

Is Discharging test required for the commissioning of Battery Bank for UPS.What are the test required before commissioning & during commisssioning of New Batteries,

thanks in advance

 

[DanEE]

Well in our case with customers in the USA, it would be what the customer demands. We've never had one ask for that..

At a miniumum, the battery internal resistance is measured (Alber Cellcorder) to establish the reference for later measurements during the life of the batteries..

We do quarterly load tests at several joint commission certified hospitals here in the USA. It's specificly called for and specifies the type of load test to be done.

http://www.jointcommission.org/

 

[zaza123]

We are ordering New Batteries, we have requested the Manufacturer to send the Batteries in charged condition & ready for use.at our site we will check the voltage of each cell & specific gravity. Is the load bank testing, ie Discharging & charging the batteries is also required.I think as per IEEE it is once in year.

 

[rbulsara]

For all the UPS jobs we did in last 12 years (including at my past employers) , we had battery discharge test as mandatory requirement. To me that is the only reasonable way of knowing if the batteries are good, at least for a while. In fact, we as consultant would insist on it and no one ever has resisted.

I have seen a whole set of batteries (a few years old) last a total of 0.5 sec after all the passive tests were being passed on as good or acceptable!

Check out IEEE 450 for wet cells and IEEE 1188 for dry. While there is no "law" requiring it, it is a matter of prudence.

Rafiq Bulsara

http://www.srengineersct.com

 

[dpc]

FWIW, a large utility here in the Northwest no longer does battery discharge testing in their substations because they concluded it does more harm than good.

"Theory is when you know all and nothing works. Practice is when all works and nobody knows why. In this case we have put together theory and practice: nothing works... and nobody knows why! (Albert Einstein)

 

[marks1080]

An alternative to a discharge test could just be a load test... Connect the batteries to a load and measure the rate of change of charge on the batteries.

 

[Zogzog]

Or an impedance test, many specs allow for it in leiu of load test.

 

[rbulsara]

Ahh, to me load test is the discharge test.

To clarify: We did not do the DC load bank test, which mostly is useless as it does not test the final system and connections.

Our discharge tests are on a load bank connected to UPS output and kill the ups input power to see the load is served via the UPS inverters on battery for the designed duration. Thus the actual system is tested with final connections.



Rafiq Bulsara

http://www.srengineersct.com

 

[zaza123]

rbulsara
you mean to say that the Load needs to be connected with UPS output.Normally we connect the Resistive load to Battery banks whihc are charged & discharge the battery through them.While keeping a constant load , the rate of reduction of voltage with time is monitored.

 

[rbulsara]

We connect the resistive load bank to the UPS output. It is a much better, useful and less expensive test. Any battery connections disturbed after the load test renders much of the system integrity test useless.

Rafiq Bulsara

http://www.srengineersct.com

 

[Zogzog]

Don't they do impedence testing in the UK?

http://www.megger.com/common/documents/bite/BITE2P_WMV.htm

 

[waross]

I like your approach to system testing, Rafiq.
It reminded my of a standby generator installation I did in Central America. The gen-set worked fine and everything tested good. I was due to leave for Canada in a few days. All testing had been done with the test switches on the Automatic Transfer Switch. On the way out the last time, I decided to give the set one last test by opening the main incoming breaker instead of using the test switch. NOTHING. It turned out that there was a relay that was Not in the circuit when the test switch was used but was used during a utility failure and the relay was defective. Had it not been for the final breaker test, I would have been back in Canada when the next power failure hit and the generator failed to start.
I heartily support your total system testing method.
Yours
Bill

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Pikoplatt]

Is there a maximum allowable recharge current(following a battery load test) specified by the battery manufacturer for VRLA batteries? If yes, how is this current controlled in the case of a UPS system, so that it does not exceed this maximum limit? Can the VRLA Battery be damaged if the re-charge current is allowed to exceed this limit?

 

[sibeen]

Normally for a VRLA battery the maximum recharge current is limited to 10% of the C10 rating of the battery.

In a UPS this is done by controlling the DC voltage of the rectifier, for systems that have the batteried directly connected to the DC bus.

Many newer UPSs don't directly connect the batteries. In this case there will be a seperate charger for the batteries. Again the maximum current will be limited to 10% of the C10 rating.

Basically there is two stages to the charging cycle.

1. Constant current. The current is limited to the maximum charging rate by adjusting the voltage to the battery. Depending upon the depth of discharge this can last up to an few hours or so.

2. Constant voltage. At the end of the constant current cycle the voltage across the battery has reached the nominal charging voltage. Current will still flow for about 24 hours with the voltage kept at the float level. At the end of this period the battery will then stay in trickle current mode.

Charging a VRLA battery at higher currents will result in 'gassing' of the battery which will shorten the operational life of the system.

 

[Pikoplatt]

Is the C10 Rating published by the Manufacturer as part of the VRLA battery technical data? If yes, do we set the current limit on the battery charger equal to 10% of the C10 rating to avoid damage to battery during recharge, following a deep discharge?

 

[rbulsara]

Thanks, Bill. There is no substitute for a comprehensive system testing. There can be and should be some pretesting of individual equipment, like factory witness testing, but they cannot be the final answer.

Rafiq Bulsara

http://www.srengineersct.com

 

[raithrovers1]

The customer dictates what the current limit to a battery is by specifying a certain recharge time. This is then calculated by the ampere hour rating of the battery. It must be mentioned that as long as the float voltage of the rectifier in the system is not above 2.28V per cell (for powersafe batteries) then any charging current can be used. It depends on how fast you want to recharge the batteries.
The majority of battery manufacturer's require a full battery discharge test in the UK to be completed before any warranty claims can be made.
And yes we do do cellcorder or midtronics testing in the UK but it does not replace a discharge for warranty claims.


UPS engineer

http://www.powerups.co.uk

 

[ScottyUK]

"...any charging current can be used. It depends on how fast you want to recharge the batteries."

Phew, that's brave! A few of the battery manufacturers might have something to say about that, especially if they are covering the cells under warranty.

See Section 2.6 for Hoppecke's recommendations: no limit on current below 2.4V / cell, then roughly C/10 to C/20 depending on the type. The figures are fairly typical for flooded lead-acid cells.


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If we learn from our mistakes I'm getting a great education!

 

[raithrovers1]

The reason I say any charging current can be used is that all of the battery manufacturers that I have spoken to have said that the internal resistance of the battery will limit the current to a level that is safe for the battery.
I have always thought this was dubious as there are obviously mechanical connections that have to carry the current. But I was only passing on what I have been told by people who work at the battery companies!
Obviously I would never advocate pumping a 100Ah battery with 800A!!!!!!!! (Which after reading my post again - I suppose I did.)

UPS engineer

http://www.powerups.co.uk

 

[raithrovers1]

Here is a quote from the Powersafe VRLA manual:
"There is no limit on the charging current provided the float
voltage is set at the recommended value as the battery itself
will regulate the current, accepting only as much as is
required to reach float voltage."

UPS engineer

http://www.powerups.co.uk