apc inverter battery change

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har297

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hi, to all of you guys>>>

i had an apc backup ups es 500, it's battery died, it was originally having 12v 7.5Ah sealed battery, now for extra backup time, i installed 12v 18Ah battery(sealed),

i have read that it needs extra time for charging, have any one done this??
how much time do i need to charge, any idea on how much backup i can expect for a load of 40 watts


ThAnX
 

practically it wont support, all low cost UPS are designed to work only 10-15 min,

if you want use only 40w it is ok in inverter mode but for charging you have to make external charger if less than 1.5 1.8A ( 1/10 A of battery capacity) charging current
 

thank you for your reply,

can you suggest any circuit for charging, preferably having a auto cutoff system in it.
 

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do not charge more than 2.5 to 3 amp for 18AH battery, you can use two LM317 in parallel is the simple solution, just search in google varies circuits are available including switch mode charging
 

i am currently charging with around 2A, manually i am taking out connection after charging current falls to zero,
now the problem is that the inverter provides only 5 minutes of backup time irrespective of load(tested with no load and and full load) so i'm confused now,
is there any modification that i can do,
i just wanna run a small aquarium pump rated at 20W for around 1.5Hrs, if it's not possible to mod this particulr ups please provide any idea that can be implemented>>


thank you
 

if the backup is only for 5 min then check the battery, what is your charging limit volt mostly it will be 13.8V and can go up-to 14.4 volt

your 5 minutes backup time is with 7AH or 18AH battery?

there is no further modification is needed if the transformer is good

or you can make a inverter with 12-0-12v 2A to 230V transformer , using relay you can make the same transformer for charging/inverter
 

As per my knowledge, APC inverter , checked by me can take more than 80% of rated load safely. Moreover, The charging circuit is really good. Not be able to charge like 70/90/120/150/180 AH Battery but surely can charge upto 24AH Safely.

I Recomended no need for separate charging if not large car battery fixed.

Thanks
 

the 5min backup time is with 18Ah battery as well as 7Ah battery,
i did charge the 18Ah battery externally at 14.4 volts for almost 18 hrs,

after 12 hrs the charging current dropped to around 20mA, even after 16 Hrs the current drawing was the same,,so took out after 18 hrs,,

is it enough? when to know that battery is fully charged,
should i charge till the current drawing is ZERO

thank you

Added after 52 minutes:

@BADFLOPPY
have you done the same mod? if yes please post the details it will be helpful

thanks
 

guys, please help, i'm not able to get backup time>>




thanks
 

HI

Backup is solely dependent on Battery capaacity, Higher the AH more the Back up. Your 18AH battery may not be new one. One more point to consider is that 500 VA UPS are designed economically and transformer is rated for 10-15 minutes only. If you increase the Battery size, the transformer may burn b'cos it has to deliver higher charging current and also working time in backup mode will increase.

Thanks
 

if the low battery beep is coming from the ups .then the fault is in battery.
otherwise check the ups.
to incrase the charging currnet you need a 3amp transformer, make bridge rectifier
using in5408, 4700mfd cap, build a regulator of series pass using 2n3055, adjust
o/p cutoff of 14.4vdc. this ckt will work upto 25ah of battery.
 

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