A question on Inverters

Discussion in 'General Electronics Chat' started by wannabenerd, Jan 15, 2015.

  1. wannabenerd

    Thread Starter New Member

    Jan 15, 2015
    Here's the thing. I had a 250VA rated inverter used with a 12V 40Ah tubular battery. But sometimes the output load would get greater than what the inverter could handle. So I brought a 850VA inverter to meet the load requirements. This is much higher than the expected output load, which would normally run around 250-400VA, and might go beyond that occassionally.
    My question is that will my already available 40Ah battery support the 850VA inverter under normal load conditions? And how long would it last? Can I buy a second battery and use that in series with the existing one to get a voltage of 24V? Is that voltage feasible?

    Thank You. This is my first post here
  2. crutschow


    Mar 14, 2008
    The time the battery will last depends mainly on the load, not the load converter capacity.
    A 40Ah battery has about 12V*40Ah = 480VA capacitor. Assuming 75% efficiency, the battery would last about an hour with your typical load.
    No you can't put two batteries in series unless the inverter is rated for a 24V input, but you can put the batteries in parallel to double the capacity.
    Note that the two batteries should be charged separately to insure equalized charge.
  3. wannabenerd

    Thread Starter New Member

    Jan 15, 2015
    Thank you for the reply.
    So the battery should support a 850VA inverter. Right? And the actual time would depend on the load during that time only.
  4. MikeML

    AAC Fanatic!

    Oct 2, 2009
    You pay a price for running a 850VA inverter lightly loaded. The bigger inverter would discharge the battery faster than the smaller one with no load or light load connected. The lightly-loaded losses in the inverter are higher in the larger inverter.