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I want to charge an 100AH battery with a UPS of 220V Ac input and output. On the back of the UPS there are not enough information provided regarding how much ampheres it provide for charging the battery however it has 1250VA written on the back side. In my desired setup, I will have the following,

An 100AH battery connected with my 1250VA UPS whereas the UPS will only charge the battery I.e will not provide any AC output (a spare UPS that I want to use as a charger only, instead of purchasing a new charger). I will connect a DC fan to the battery in this setup whose power is 48-50 watts. The UPS as a charger will be supplying charge almost 10 hours a day as there is at least 14 hours electric power cut-off in our area. I need to know below: 1. Is the UPS power capacity OK for the battery I.e it will not damage my 100 ah battery. 2. For 10 hours daily the UPS will have electric power to charge the battery and during when it is charging I may be using my DC fan connected with to the battery, will it work without getting damaged ? enter image description hereenter image description here

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  • \$\begingroup\$ It's a lead battery you have there for sure. These are charged with constant voltage, not constant current. Check the battery voltage given in the charger description. \$\endgroup\$
    – Janka
    Commented May 20, 2017 at 12:29
  • \$\begingroup\$ Its Acid battery of 12V \$\endgroup\$
    – Daniel
    Commented May 20, 2017 at 12:31
  • \$\begingroup\$ So it's Pb - lead. Check the voltage of the battery matches that of the UPS and you are ok. \$\endgroup\$
    – Janka
    Commented May 20, 2017 at 12:34
  • \$\begingroup\$ The UPS is meant to charge 12V battery that is what I can say with 100% surety \$\endgroup\$
    – Daniel
    Commented May 20, 2017 at 12:36
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    \$\begingroup\$ VA (as in 1250 VA) means Volts x Ampere. So 1250 VA at 220 V means 5.7 A. But that is irrelevant for the battery !! Other than that the battery should be able to deliver 1250 VA/ 12 V = 104 A then. That 1250 VA (or 1250 Watt) means that the UPS can deliver 1250 W maximum. It bares no relation to the battery capacity nor how much current is used to charge the battery. \$\endgroup\$
    – Bimpelrekkie
    Commented May 20, 2017 at 12:39

2 Answers 2

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The adequacy of your UPS as a charger depends upon the type of battery for which the charger was designed. Most UPS's are made to charge gelled electrolyte batteries. If this is the case, you may find that it takes longer to charge your wet chemistry battery or that the battery never fully charges. But it most likely will not damage your battery as long as everything is a 12 volt system.

There is no problem running your fan when the battery is charging. It may take a little while longer to charge the battery as a result but nothing will get damaged in the process.

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First find out the Line to Neutral Voltage . Assuming that is V_x then AC current is 1250 / V_x. (V_x is written to be 220 on the backside )

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