Battery Datasheet Confusion

Thread Starter

odm4286

Joined Sep 20, 2009
243
Hello, I have a project presentation Friday. Unfortunately my current draw calculation was WAY off and I've just now realized this thing guzzles down 9v batteries very fast! I'm looking for a quick fix to get me through Friday and it seems switching from a alkaline to Lithium 9v battery will do the trick. My device draws about 60mA in its idle state and a little over half and amp in its active state.

The good news is it doesn't have to last very long, 30 minutes tops, the bad news is I'm having some trouble understanding the Capacity Characterization chart on the following datasheet

https://cellpacksolutions.co.uk/wp-content/uploads/2015/06/ultralife-u9vl-jp-technical-data-sheet.pdf

My device has two regulators, a 7805C and a MCP1827S-3302E/AB so I NEED the 9v battery to maintain at least 7.5 volts for about 30 minutes. This thing will only be in its active state one time during presentation so I won't have to worry about a large current draw.

So just to sum it all up, can I draw about 60mA for 25 minutes and still have enough juice to enter my active state? Could someone clarify for me? Thanks!
 

crutschow

Joined Mar 14, 2008
23,734
That lithium battery data sheet states the maximum current draw is 150mA so it won't readily provide the 1½ amps your load requires in the active state.
The fastest fix is just to 6 AA alkaline batteries in series. They can readily provide 1½ A for a short period.
 

crutschow

Joined Mar 14, 2008
23,734
Luckily that 1/2 amp draw is only pulsed. So on for a second off for a second, hopefully that helps?
Yes, I misread your post for the peak current.
The 9V lithium battery will handle half amp pulses for a short time.
How often will you pulse it and how many pulses in a row?
 

Thread Starter

odm4286

Joined Sep 20, 2009
243
only at the end of the presentation, to show the device's alarm/active state. It triggers an annoying Piezo buzzer as well, so I'll only let it run for a few seconds at the absolute max 10 seconds.
 

crutschow

Joined Mar 14, 2008
23,734
only at the end of the presentation, to show the device's alarm/active state. It triggers an annoying Piezo buzzer as well, so I'll only let it run for a few seconds at the absolute max 10 seconds.
Then the 9V lithium battery should work fine.
 

ScottWang

Joined Aug 23, 2012
6,843
According what you want then we can calculate the time, assuming that when the voltage drop to 7.5V and the current still has over 0.8A, here we just use 0.8A, when you draw 60 mA then the using time as :

T = (I_Total - I_Last) / I_draw
= (1.2A - 0.8A) / 60 mA
= 400 mA/ 60mA
= 6.67 Hrs

9Vfor60mA25mins_7500mV_odm4286.gif

So, it is enough to use for your application,
 
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