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Battery maximum output current

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fakhry2002

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Dear All

I'm going to build my 1st UPS it's rated 500 Watt
I'm using a Push Pull DC-DC converter to step up battery up to 300volt
I'm using only 1 battery from powersoinc

the battery specs is 12 volt 8 AH

i found the Push pull satge will need a Peak current about 70 A ( 80% duty cycle, 90% effeciency, 300v/500 watt output)

my question is

dose this battery could supply this 70 peak current or not???
do u have any suggetion for the battery??

the 8AH battery datasheet is attached

thanks
 

Your circuit may not work well with just one battery. You are using a 100 watt-hour battery to produce 500 W. With an ideal battery this will supply only 12 minutes of power. The battery capacity will be much less than 100 Watt-hours under these circumstances. If you look at the data sheet, 16 A is the fastest discharge curve and at these currents the capacity has reduced to 3 Amp-hours. I suspect that at 70 A it will last less than a minute.


As far as peak current, using a shunt capacitor to supply the peaks can help reduce the transient stress on the battery.
 

The jell type batterys are the type that are used in UPS`s. (Yasso) These supplies are only ment to kick in for very short periods of time . The UPS`s that we use have battries twice the size that you have mentioned.

Barrybear
 

Thanks for all

flatulent suggest to use a capacitor to handle peak current , but i think this is no suitable co the duty cycle is 80% so the capacitor discharge time is 80% and capacitor charging time is 20% so i think the peak charging current for the cap will be much larger than the peak discharge so it get worth

is this true?

thanks
 

capacitor

The capacitor with a small inductor to the battery will help a little. It will reduce the peak battery current by about 20%. What will really help is having a larger battery capacity or lower power drain.

After reading the fine print on the data sheet it says maximum current of 80 A for 10 seconds. My one minute estimate was way off. This will require the computer to be able to put all of the things in silicon memory onto the hard drive in a dedicated area in less than 10 seconds as well as shutting down the whole computer.
 

you should burn or explode this battery with 70A discharge !
in best case the output voltage will dramatically fall down, search the internal resistance :roll:
maybe you could use a NiCad battery, high rate RC cells have very small internal resistance
 

You can use 3 batteries from powersonic in series without any problem ... eficiency and losses are mm better, power drivers cheaper etc
 

26 AH battery

The Powersonic 12 V 26 AH battery is rated at 78A for 7 minutes which should allow for the orderly shut down of the computer even after a one minute wait to make sure the AC mains are going to stay off for a while.
 

hi flatulent
if u look at the discharge characteristics, you see #1.5V drop between small discharge and the 16A curve
this means #0.1 ohm resistance, and 7,8V drop @ 78A !!! the battery will unly supply 5V @78A :lol:
so impossible to get the full power (5V x 78 A # 400W) and the inverter must have strong regulation
 

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