Discussion in 'General Electronics Chat' started by shivaaa, Jul 3, 2012.

  1. shivaaa

    Thread Starter Member

    Jan 5, 2011

    I have a 600VA UPS for my computer, I have it as an UPS but as soon as the power goes UPS also goes. No back up at all. I can Change the battery but I hope I can get only about 10-15 mins of backup.

    So what I am planning is to get a 100AH battery and use it with the UPS I have. I will remove the battery inside the UPS and connect the 100AH one. I know that the charging current from the UPS will not sufficient to charge the 100AH. So I am planning to buy a seperate charger and connect that charger to 100AH battery and same time I am going to connect the battery terminals to the UPS. Will it workout??

    attached a diagram.
  2. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    Not recommended, as you will be trying to charge the battery from two supplies, also the external charger may damage your UPS system.

    get a better UPS system.
  3. shivaaa

    Thread Starter Member

    Jan 5, 2011
    can I do any external modifications to adopt this? Will it be possible by any chance?
  4. luvv


    May 26, 2011
    Get a external charger, and just swap the batteries around monthly.
    I was doing this w/ 3 UPS and 6 batteries,works fine.
    Couldn't tell you why,but the ups itself sucks at keeping a battery in good condition.
  5. shivaaa

    Thread Starter Member

    Jan 5, 2011
    Swap? Could u tell me more clearly?
  6. electronis whiz

    Well-Known Member

    Jul 29, 2010
    you can do this i have hered of car/ lawnmower bateries being used they say that the charger chould handle it just fine but be relly slow to charge again. having 2 ran may be ok but be safer with one. what i would do is see if you can somhow disconect the charge portion of the UPS. there should be a transformer or posibley some wires for it. just remove a solder from the primary on the trnsformer or clip and tape off the a supply line to that part.
  7. praondevou

    AAC Fanatic!

    Jul 9, 2011
    Why? It would just take longer to charge the battery. Unless the UPS works with some fixed time charge.

    If you can simply put a bigger battery in there depends on how the charger determines that the battery is charged.
  8. DMahalko

    AAC Fanatic!

    Oct 5, 2008
    Generally you should only put about 50% of the rated capacity on a UPS.

    The industry capacity numbers (VA) appear to be a gimmick to inflate what their devices can supposedly do. Some can be as little as 3-5 minutes at max rated load.

    If you are loading it up to the maximum VA, then 15 minutes sounds fairly reasonable.

    With some of the more expensive UPS, you can hang extra battery packs off the back of the UPS to extend the runtime. You don't need to do anything extra to make this work except plug in the battery pack. Though note the recharge time after being depleted may be longer.

    For APC these were called the "XL" line a few years ago, but most UPS manufacturers have extended runtime versions. For this to work, you need to buy a UPS that explicitly has the necessary external battery connectors. The UPS industry name for this is "extended runtime".

    Random Google Shopping search:

    Adding on additional batteries yourself to a UPS not designed to do it, is not a good idea because the batteries may be series strung internally, to be 24v, 36v, 48v etc. You would have to match the correct string voltage or your hack-attached batteries could literally boil, bulge out, or explode, and a plain 12v charger may be back-fed by the higher voltage and be destroyed.

    Also the UPS voltage inverter is often only sized for the specific intended load and battery capacity it was designed to use. Adding batteries beyond what the manufacturer intended may result in the inverter overheating and cooking itself and doing an emergency shutdown, dropping all your "protected" loads. Though you may be able to increase load capacity with an external high-CFM fan over the vents, forcing air through the UPS to cool it more rapidly.
  9. JMW

    Active Member

    Nov 21, 2011
    You must be careful and watch what you are doing. Most UPS' have gel batteries. So you must use gel batteries. The charging rates are different gel, flooded and AGM. As someone else pointed out most have series parallel circuits. I have 8 batteries in mine, they are 6 volts each. They are configured as 4 batteries in series for 24 VDC, times 2, basically I have a 24 volt supply consisting of 2 banks of 4 batts each. I could replace this with 4 12 VDC gel cell batteries. If one of the banks goes "bad" the system won't work, so I need two banks connected. On mine, there is provision for an additional battery pack of 8 more cells.
    Remember you are going to void any warranty. After you configure this, test it outside for several cycles, make certain you are wearing an acid resistant (full face mask and gloves) suit and have a fire extinguisher near by. (CO2). Also be able to disconnect by pulling on a cord with a rope. I would not have this in the house, I would install it near the service panel with appropriate bus transfer/disconnect circuitry. Find the appropriate circuit in the panel, pull it out and install it in a new UPS fuse panel. This panel will be powered by the UPS. I know it sounds like a PITA, but you want it simple for the family to operate safely when you are out chopping the trees that fell on you power line.