Question about Powerware 9355 UPS System

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Battery Packs for Powerware 9355 UPS

I am working with a number of Powerware 9355 UPS systems. One of the systems gives an ''error message'' that ''no battery is installed'' The system operates correctly otherwise. The DC battery breaker was cycled several times and finally we tested the voltage output of the six battery pack and found that each pack had discharged to a voltage (for the entire pack) of about 130 volts instead of the normal 230 volts. The battery packs are relatively new and have not been cycled very many times. 
Questions: Is there any way I can get the Powerware 9355 to recognize the battery and have it begin to recharge the battery?
Can I remove the battery pack and recharge it external to the Powerware 9355 and then reinstall the battery pack? Or, are the battery packs dead?
Any other suggestions on getting the Powerware 9355 up and running.
Another question:
When I entered the battery test mode on the Powerware 9355, I was unable to start the test. Is there a secret to starting the battery test?
Many thanks in advance.

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  • jproth Jul 15, 2010

    Batteries were removed from UPS and charged externally. After the charged batteries were replaced the UPS started normally and is in service.



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If you battery packs are all at 130volts DC, then all of the packs will have become dead, and the batteries are not recoverable. Your battery DC bus voltage on a Powerware 9355 20 to 40kVA rated UPS is nominal 432 volts DC - 36 batteries in series in each string at 12 volts DC per battery. If batteries go below 10.5 volts DC each, or 378 volts DC bus voltage, no amount of charging will recover these batteries. You should not be recycling the DC battery breaker, unless you felt the battery breaker was faulty. The UPS would have given you an alarm message of either battery breaker Off, Charger Failure, or Low DC Bus Voltage long before the these batteries failed.
The battery test will not proceed if the batteries are dead.

Posted on Feb 11, 2011

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The Batts can be charged externally, then refitted, usually I extend the DC cables so I can work with the batt outside the unit. This is ONLY to be done if you understand the risk and what may happen if you get it wrong.

Batts are always live and can cause fire/explosion/severe burns if shorted!

OK so the UPS will not normally recognise a very low batt pack, that is the reason you can not start the test, this test will back of the rectifier so the batt pack takes the load for a short period.

If the batt pack is out of range then this will make the load go off, so the UPS is designed not to allow the test,unless the batt is at the right level.

If you can get the batt pack up close to normal then the unit will recharge it to full.,Wait until it is fully charged before testing.
If this is sucessful the cyle the batt a few times allowing it to reach around low batt warning before recharging. This will assist the batt in recovery. During this process if possible monitor with a test intrument(fluke 123 or 43B will do) the batt pack discharge curve , once the batt pack has dropped to its charge level from float, it should be a smooth decay.
depending on the state of the batts you may be ok, if there are weak ones in the string then you may have to replace all of them depending on the age of the batt pack.


Check you manual for safety procedures, BEFORE working on Batteries.

hope this helps

thanks for using Fixya

Posted on Jul 13, 2010


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