Power Efficient GSM modules

Question

I am developing a Kit with GSM module which have to receive and send commands. I have gone through many GSM modules(SIM900). All of them consume around 1.5A at burst time. So I am in trouble to develop a power efficient Kit.

My doubt is normally mobile phone battery has the capability of 1000mAh. According to the calculation it has to work around 1 (busy) hour. But normally they stands for 1 day at-least. Are mobile phones uses any low power GSM modules? Is there any specific sleep-wake up mechanism with them?

Your suggestions and helps around this topic is appreciated.

Thank you

Answer 1

Peak current applies to very short pulses. Don't worry about this. In standby mode most GSM modules use much lower current (<50mA).

Long time ago (8 years?) I was using Siemens XT65 GSM/GPRS module and it was pretty energy-efficient (energy consumption was similar/lower than typical GSM phone). There should be no problem to reach 5 day standby on 1000mAh 3.6V battery.

XT65 is very old model now and they probably not sell them anymore, but you can buy modern Siemens modules. They are not so easy to use and relatively expensive but I'm sure that energy efficiency is way better than in low cost modules.

Here is datasheet for XT65 module: link

It says that it uses up to 2A (peak), but this applies to bad signal conditions (when BTS is far).

If you want low cost device - buy some ancient Nokia phone (5110/6110). You can "talk" with them by using UART and AT commands. They can work about 1 week on 3Wh battery (800mAh/3.6V).

Answer 2

Kamil's answer is quite correct that the average standby current for GSM modules is much lower than the peak current so you should get similar standby time to a phone. It depends on your application but another trick you can use is to completely deregister from the network and shutdown the module altogether and then wake it up periodically, say once an hour.

A technique I've often used for GPRS is that the remote devices wake up periodically and send in data they have ready for transmission and at the same time check for any incoming messages / commands waiting on the server. It can take a minute or two to register on the network and current draw for most modules seems higher during that process so it probably only makes sense to go that way if you're waking up say every fifteen minutes or less. Of course that will only work if you can tolerate the latency it introduces between data being sent and received.

If you have a time reference available I'm aware of a GPS tracking system that does something similar for SMS by waking up for certain time periods during the day. So you might set it to wake up for five minutes on the hour and you have that window where you can communicate with the device to change settings etc via SMS.