Hello all,
I got a GSM shield and testing it for couple of days. When I power the GSM shield using the wall power adapter (5V with max 2A load) all is working fine. But I would like to use this GSM shield on my Garden Project where there is no possibility to use this wall adapter. I was searching the internet for same solution and found that the best would be probably to power it up with Li Ion batery as they can provide enough current for the modul. Specificatins of the GSM shield is 3,4 - 4,5 V with peak of 2A current. I saw couple of Li Ion bateries wher specification says that it can provide even more then 2A (at 3,7V). But I also see that Li Ion bateries need to be handeled carefully to avoid explosion or damage of the batery. So I would like to ask you if somebody could help me with it. If there is any board which would manage all the stuff to protect the Li Ion batery + possibility to charge it. And what Li Ion battery I should choose. Or if there is some other solution how to power it. I already tried to use 3 x NiMH battery with the supercap (2 x 10F - 2.5V in series) without success. Actually the best solution for the project would be to charge the battery from sollar cell (it would be perfect, but not necessary in this stage of the project).
Super caps are used for this problem. However, if you connect the cap in SERIES it won't work since it will essentially be an open circuit between the battery and your GSM!!! You are meant to connect it in parallel. That way the battery can charge it up slowly at low current and the CAP can provide a large burst of current when its needed by the GSM. The cap must go across the battery probably with a series resistor between them to slow up the charging process. On the other side is your GSM that can draw current from the battery and the CAP if it needs a high current burst. IT HAS TO WORK even if it doesn't solve your problem which it should. It's what is done.
ProfRon:
if you connect the cap in SERIES it won't work since it will essentially be an open circuit between the battery and your GSM
I think that OP means is that he will connect two Supercaps in series to overcome the 2.5V-rating of them.
OP needs to study what this involves - maybe some kind of balancing circuit, because if the charge-state and internal resistance of the caps is different, one may see more tham 2.5V at some point, which would be a bad idea.
OP: Generally, any reasonable sized Lithium-cell (600mAh and up) can supply a GSM-shield. Think of the sizes of Lithium-cells in cellphones.