Rating of UPS

Depends how everything is connected.

Hi Khawaja;

Do you have 12 each (2) Volt Cells you wish to use? If not how many of these cells do you have? Also, how old are these batteries you have that you wish to use? The domestic UPS charging circuit has how many amperes capability? Please answer these questions so I may more know how to advise you concerning your questions? Thank You!

Professor Lowell A Morton

Hi Professor,

Thanks for quick response. Answer to your qurries as under

1. I have 6 cells, Each of 2 Volts, 410 Ampere Hours (Series Connection)= 12 Volts, 410 A.H

2. These are 2yrs old and always used very much under load.

3. The Domestic UPS charging Capicity 10 amps

4. The Cells are Sealed, Gel Type, nonmaintainable.

My fear is UPS charging Circuit will be able to charge the 410 AH battery cells or we will add additional battery charger.

Your suggestions / advise awaited

Khawajaraisuddin

Hi Khawaja;

The answer to your question related to the charge time is totally dependent on the duty cycle of the UPS. If the UPS is only used on standby then you must know how often will it be needed and for how long a time it will be required to operate? Also, is it it a true sine wave ups, and is it frequency synchronous? One last question is - do you have any loads operating on ups supported lines that are computer/microprocessor dependent which must be switched on immediately without loosing a single cycle in a power failure, and missing that one cycle could and or would in that case either interrupt and/or reset their microprocessors? All of these questions are to a greater and/or a lesser degree important to gage the level of priority the UPS's operation and all of them must be answered to address that. Please see if you can obtain all of this information I have requested so that we can estimate the appoximate charge rate which will be required for your UPS. If the batteries you have are lead calcium station batteries then their servicable life should be around 10-20 years under float standby service. If you have never discharged them more than 10% of their rated capacity they should work just fine for your use, but I won't know that for sure until you are able to supply the other information I requested here in my email to you. Godspeed!

Professor Lowell A Morton

Administrator of Virtual Universities

Regards.

These cells seem to be of larg UPS systems. Why these cannot be used.

But the problem in Pakistan is the repeated or recurring and long outages and full charge between outages may not be possible.

So you need to use external charger.

It will be safe to disconnect the built-in charging circuit.

A 10 amp charger in the UPS would keep the cells charged, and could recharge the cells in about 40 hours, if they were completely drained. If this recharge time is too long, then you would need to use an external charger.

The cutoff voltage of the 10 amp charger is a possible additional concern. If it is designed for a different battery, the cutoff voltage could be too high (or possible too low). Lead acid batteries are similar, but not identical in this regard, and with big expensive cells, you would do well to make sure that the float voltage is as advised by the battery maker.