Battery choice

[thjnikke]

Hello everyone,

I have an electric circuit that consume around 180mA, I can choose for an AA battery 1.2V/1300mAh or a lithium ion battery 3.6V/2400mAh.
The circuit works on 3.3V and it should last about 1 week. My question is what battery suits best for this circuit?

Thanks in advance.

[JohnnyBerg]

Lithium: 2400mAh / 180mA = 13,3 hrs
3x AA in series : 1300mAh / 180 = 7,2 hrs

If you want to run for a week: none of the above

[sacherjj]

To get the run time you are wanting, you will have to introduce sleep states (if it is a microcontroller based system.)

Does something have to be done continuously, or can you do things in short spurts?  This could be short spurts a few times a second or seconds apart.

These days, 180 mA is a lot of power for most primary battery powered devices. 

1 week = just over 30 Ah battery.  That is huge.  A large cell for a tablet might be 3-4 Ah.

[Rick Law]

Get a car battery or better yet, the marine battery (ie:deep discharge).  Even the ones for small cars can be 50AH.

Assume you just regulate it down to 3.3V,
50AH = 50000mAH @ 180mA => 277.8 hours = 11.57days 

If you buck it down to 3.3V using DC-DC converter, you can easily double or close to 3X that.  A 50AH battery will run it for a month.

[Falcon69]

Here's a 6volt one that is 36Ah

That's 36000/180=8.33 days.  But, when used with a voltage regulator to 3.3v, i was assume you could get around 12-14 days out of it.  Plus, it is deep cycle, fairly small for it's power output, and can be charged over and over again. It has no memory on it like other batteries.

I'm not sure what you are doing, but for me, I was thinking about getting it to run a time lapse camera for a jobsite, and have a small solar cell to trickle charge it.

[thjnikke]

Thank you all, I will look at it!