Need help understanding batteries??

System · September 2007

I have a 2500 watt inverter and am going to power a computer, monitor and gas sampling instrument with it. I figure I have a total draw of about 8 amps. Would like for this system to have about a three hour reserve. So, how many batteries and how many amp hours do they need?
Thank you,

boB · September 2007

Re: Need help understanding batteries??

johnlarn wrote: »

I have a 2500 watt inverter and am going to power a computer, monitor and gas sampling instrument with it. I figure I have a total draw of about 8 amps. Would like for this system to have about a three hour reserve. So, how many batteries and how many amp hours do they need?
Thank you,

Theoretically, 8Amps X 3 Hours = 24 Amp-Hours of reserve battery.

But, make it more than that cuz you don't want to drain the batteries every time if possible. How many batteries ?? Depends on the voltage and amp-hour rating of each battery and how many of them you have to series-parallel.

Is this for battery backup and the inverter is going to keep the batteries charged until an outage ?? If so, then just multiply by two, or around 50Amp-Hours of batteries should be great.

boB

BB. · September 2007

Re: Need help understanding batteries??

A 2.5 kW inverter is a pretty big beast... Is the 8 amp draw at 240 VAC, 120 VAC, or 12 VDC (i.e., the input or the output of the inverter)?

8amps * 12 VDC = 96 watts (battery bus)
8amps * 24 VDC = 192 watts (battery bus)
8amps * 48 VDC = 384 watts (battery bus)
8amps * 120 VAC = 960 watts (instrument power bus)
8amps * 240 VAC = 1,920 watts (instrument power bus)

So, the sizing of the battery really depends on what power level you are talking about...

Also, how often do you need to run for 3 hours on battery... If this is a one time deal (during a power failure), you can have a small(ish) battery that would get used up with just a few cycles of power failures.

If this is a system that will do the 3 hours on battery for multiple times (say a mobile sampling station that does not want a generator to pollute the readings), then a larger battery (or even a different battery chemistry--NiCad vs Lead Acid vs AGM) may be better.

-Bill

System2 · September 2007

Re: Need help understanding batteries??

First, thanks for the replies and information. My situation is that I will be using the batteries in a floating situation. Will run charger from a dirty source of power (drilling rig generator) just need to have this system to clean up the current and act as a battery backup. Keep the suggestions coming.
Thanks

Need help understanding batteries??

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