APC ups 3 stage charging

Hello everybody,

i recently installed APC ups 1500i. In bulk charge voltage gradually rises and reach to 27.73v and then absorption period starts in which voltage decrease to 27.61v with declining of current. when current reaches to approx 0.5-0.6a, i think this is the float charge in this stage the the voltage again rises to 27.71v.

now there are few points which i want to clear up.

1. on many websites they say that on bulk charge when it reached to set voltage then absorption stage starts with constant voltage, WHY DECREASE VOLTAGE FROM 27.73 TO 27.61. .

2. in float charge, the voltage must be lowered than absorption stage. WHY iNCREASE VOLTAGE FROM 27.61 TO 27.71

is there any problem in the charger of ups.

here is the picture also

clead1.jpg

Thanks

there is no problem.. that is how dry batteries are supposed to absorb the power provided.. voltages are only an indicator of how much PD is present / required to push the desired amount of amps through the battery. these vary according to the stages of charging, and hence there are those 3 stages of charging.

Thanks farhan. my batteries are brand new wet/flooded. sp gravity of all cells of both batteries are 1.29

gravity is a bit high.. it should be 1.25-1.27 max..

when batteries are fully charged,. check the terminal voltage, and then see how many DC amps are going through the red wire.. it should be within decimals.. when in decimals, it is in float mode..

the pd should be around 27V.

the sp gravity should be 1.26-1.27 max.

sp in all cells should be equal.

see if voltage decreases by disconnecting all the load from it...

bateries model and power? were they bought together? same time installed?

Usually the absorption level is 29V and float is 27V.

The voltages mentioned above are measured on batteries terminals or on the APC display ?

Check on the APC how much it is showing at these three stages.

@farhan

when batteries are fully charged,. check the terminal voltage, 27.73v

and then see how many DC amps are going through the red wire.. it should be within decimals.. when in decimals, it is in float mode.. its about 0.5-0.6amp

see if voltage decreases by disconnecting all the load from it... Yes it decreases to 26.10v

bateries model and power? were they bought together? same time installed? AGS GX175. BOUGHT TOGETHER AND INSTALLED AT SAME TIME ABOUT 20 DAYS AGO

@tufail_74

Voltages are measured at batteries terminal. Apc sua1500i does not have a display.

your batteries are in larger capacity than the 1500 can handle.. it will keep a little bit ore charging than is required to top them up. and since these are over capcity, you should be fine with over charging.

just check that when ups has almost depleted the batteries and then wapda comes back back, how many amps of max charging does the apc give.. you can also check by shutting off wapda and using ups for an hour or 3 and then switch back on wapda when light comes.

^ when batteries are fully dischaged, ups charges @ 10-10.20amps.

when light goes for an hour and comes back then it charges @ 8-9amps

ur charging is fine.. and your ups is ok too.. when it is modified to work with wet batteries its constants are changed to match local batteries, so values might differ a bit, which is all within normal range

2 months old scenario: Brand new batteries (2 x 175ah AGS) in bulk charge voltage gradually rises and reach to 27.73v and then absorption period starts

Current scenario: Now after 2 months in bulk charge apc ups voltage gradually rises and reach to 27.45v and then absorption period starts.

is this usual behavior of apc to change voltage from 27.73 to 27.45 as the batteries are getting older.

Thanks and reply awaited.

Yes !!!!!!!!!!!