Battery advice for my battery powered gps tracker

Hi,

I have made a prototype for gps tracking my sheeps in the mountains.

MCU: Arduino pro mini 5v 16mHz.
GPS & GPRS = SIM808 breakout board ← PWRIN range: 5 - 10V.
DS3231 for having MCU sleeping and waking up once in a day sending the GPS position to my server.

The plan is to use a mosfet for cutting all power to SIM808 module before going to sleep.
Also using a MCP1702 for giving stable 5V to Arduino.

What i need obviously is a good battery, range 6 - 10V. Which could last for a long time.

I have been searching around the forums and google. And i couldn’t come up with a good battery for my project. I guess i will need a battery with loads of mAH. I would appreciate if someone could share their experience regarding battery powered iOT.

Cheers,

You need to measure the average current draw.

If everything is sleeping or off most of the time, the average current draw should be well approximated by (average current draw while ON)*(total seconds ON per day)/(seconds per day).

A rough estimate of battery lifetime in hours is (battery capacity in mAh)/(average current draw in mA)

Don't forget that some GPS units can take several minutes to get a fix, depending on the satellite configuration and the amount of time the GPS has been off, or whether it has been moved.

If you can, run everything from one 3.7 V cell (if using LiPo).

If you use a 3.7V (nominal, 4.2V freshly charged) LiPo cell you will need a boost converter to get the minimum 6V for your cellular modem. If you put two cells in series (7.4V nominal, 8.4V freshly charged). you could use it directly. A holder with two common 18650 (18mm diameter x 65mm tall) cells might be enough. They typically have a capacity of about 2000 mAh. If not, a "2S" (two cells in series) LiPo battery for a quadcopter can be found in almost any capacity. You can get 5000 mAh or more for under $50.

sindrevr:
What i need obviously is a good battery, range 6 - 10V. Which could last for a long time.

Define a long time? days? weeks? months?
How will you recharge the Batteries?
How will you attach to your “Sheeps”

I am not convinced LiPo is appropriate for attaching to a sheep in the wilds, one little failure and roast lamb?

Kiwi_Bloke:
Define a long time? days? weeks? months?
How will you recharge the Batteries?
How will you attach to your "Sheeps"

I am not convinced LiPo is appropriate for attaching to a sheep in the wilds, one little failure and roast lamb?

Thank you all for participating this discussion.

Months (min. 3 months), waking up only once in a day.

2 & 3:
As this is only a few prototypes this year i will install all the components in a "Pelicase" (100% waterproof).
The pelicase will be attached to the back of the sheep (behind the neck).
Therefore the battery´s should be easy to recharge when needed.

Have ordered some 18650 batteries with PCB, dual 18650 battery case (serial) and Pololu step down converter..

This should work?

This should work?

At least for a short while.

If you send SMS-es once a day, you send several recorded GPS positions during that day? Then you should count these partial (GPS + Arduino) startups into overall power used.

If the case on the sheep's back is big enough (8x8cm or 3x3inches) you may want to consider a 300-500mW solar cell mounted on it. I thin it's enough for one daily 5 minute power-on at 2-3watts. Batteries can get much smaller. And happier sheeps I guess