# Need to figure out power consumption...

Discussion in 'General Electronics Chat' started by jsmith24, May 18, 2015.

1. ### jsmith24 Thread Starter New Member

Jul 10, 2013
23
0
Hi all,

I'm trying to figure out my power consumption so that I can estimate run time for a given battery. Normally this would be pretty straight forward - I'd get a crude estimate by dividing AH by current. However, the current is only a few times per day, as follows:

Current draw:
220 mA for 30 seconds per day.
35 mA for 2 minutes per day.
3.5 mA for 12 hours per day.
20 mA for 12 hours per day.

Battery: 12V, 9AH SLA.

Can someone help untangle my brain to see the obvious thing that I'm missing?

Thanks,

Jack

2. ### Alec_t AAC Fanatic!

Sep 17, 2013
9,934
2,401
As an approximation, ignore the first two quantities. That leaves ~23.5mA x 12 hours, = 0.282AH per day. If you discharge the battery, say, half way (it's bad for the battery to flatten it) you have 4.5Ah capacity; so the life-time would be 4.5/0.282 = ~16 days.

3. ### dl324 AAC Fanatic!

Mar 30, 2015
8,524
2,049
I wouldn't run the battery lower than 10.5V. Using SLA 0.05C discharge data and extrapolating; 16-20 days ballpark...

4. ### paulktreg AAC Fanatic!

Jun 2, 2008
756
166
Your discharge rate is low and I'd like to increase the bid to 20~25 days.

Last edited: May 18, 2015