Hi,
want to put an Arduino UNO with GPS and GSM in a backpack.
What is the best way to provide it with power to work up to 3 hours.
Idea is that always when I want to know the location of the backpack I send SMS to UNO and it send me back the SMS with coordinates.
thnx
Have you measured how much current your Arduino + GPS + GSM consumes when it is powered up?
You will need that information to figure out how much energy is required for 3 hours usage.
There are various ways to reduce energy consumption if it is not essential to have everything working all the time. See Nick Gammon's power saving tutorial
If the weight of the batteries matters then LiPo cells have the best energy to weight ratio - but they need to be charged carefully and NEVER short circuited.
...R
The SIM900 Board Input is 5-26V 2A, in passive mode it uses cc 2mA. Does not say what A it uses per sending but assume it is a function of signal strength.
GPS around 50mA, Arduino around 50mA.
The SIM900 is my concern...
jegesd:
The SIM900 Board Input is 5-26V 2A, in passive mode it uses cc 2mA. Does not say what A it uses per sending but assume it is a function of signal strength.GPS around 50mA, Arduino around 50mA.
The SIM900 is my concern...
Why not connect everything together, run your program and measure the current with your multimeter?
...R
you are right regarding your suggestion.
just ordered GSM it took to arrive 30-40 days if then i measure and then order going to wait again a 30-40 days... 
had idea if can got some suggestion and order now that i can save some time.
jegesd:
just ordered GSM it took to arrive 30-40 days if then i measure and then order going to wait again a 30-40 days...
Buy from a local supplier?
Why not try a pack of 6 x AA alkaline cells?
...R
from local supplier we had only Conrad where prices are 3-4 times higher then china, sometimes even more then that.
Due my firs hobby is baying medication I am quite price sensitive.
I am good in SW development but HW is new for me, not sure that AA can provide enough A to GSM module, but going to try.
jegesd:
from local supplier we had only Conrad where prices are 3-4 times higher then china, sometimes even more then that.
Due my firs hobby is baying medication I am quite price sensitive.
I reckon you need to balance that against the question of supporting local jobs. Would you like your customer to abandon you in favour of buying from China (or whererever).
not sure that AA can provide enough A to GSM module, but going to try.
Think about it. 6 x AA cells are a helluva lot bigger than the battery in your phone.
...R
Saw that most AA batteries goes up to 1.5 A draw, i need 2A.
Can it still work e.g. they are going to overheat but can handle those few seconds ?
I agree. We vote with our $ (where/what we bay) but C is a web shop neither jobs, neither profit remains in local community, in such case i bay cheaper.
Otherwise we are on the same page.
jegesd:
Saw that most AA batteries goes up to 1.5 A draw, i need 2A.
Put a big capacitor on the circuit to act as a reservoir?
...R
Just use a USB power bank of decent size and be done.
Something around 10.000mAh should be sufficient for several hours of continuous use. If not, there's always larger ones... 
This way, you have a rechargeable energy store and a lot less stuff to think about.
Just need to make sure that the minimum draw of your stuff is high enough to prevent the power bank from switching off, some of them do that unfortunately. Since the larger powerbanks usually have at least two ports, you could connect the SIM module to a port by itself, making sure it can draw its 2A if it really needs to.
Cheers,
Shuzz
P.S.: Nobody buys their stuff at Conrad if they can help it. Maybe try Reichelt?
jegesd:
want to put an Arduino UNO with GPS and GSM in a backpack.
What is the best way to provide it with power to work up to 3 hours.
Safest is to use a linear supply, lithium batteries or a pack of AA Alkalines.
Any switching power supplies, such as USB power banks can produce enough interferance to significantly reduce the sensitivity of radio devices such as GPSs, so the GPS might not work reliably.