Power supply for GM862-GPS Charger

[tasosmi]

Hello,

i have built a tracking system with the module GM862-GPS. In the manufacturer's datasheet i have read that the input for the charger (which is embodied to GM862-GPS) must be 5 - 7 volts and 400 mA maximum current.

I have built a power supply, which when i measure it standalone, i have 5,5 V and 370 mA.

When i connect it with the charger pin of GM862-GPS module, the values drops at 3.96 V and 100 mA. :-?

I want also to say that i am using a Li-Ion rechargeable battery 3,7 V and 2200 mAh.
So, what am i doing wrong? Has anybody used before the charger of that module? :?:

Sorry for my English and thank you in advance!!!

 

[tasosmi]

Please Anybody?

 

[arthur0]

I’m not familiar with this particular GSM module, but after searching it I found this application note.

It would seem that the module doesn’t provide a fully-featured charger and so your power supply should be a current generator (similar to the ones for hi-power LEDs).
In any case, the module can draw up to 1A (which is more power that your supply can give, hence the drop in voltage), so you’ll be in charge (no pun intended) with limiting the current.
All this according to the application note provided above.
Your power supply could still work, but it can take days to recharge the battery. Give it a bit more juice so the current settles at above 0.1C (220mA to 1A for your pack).

Arthur

 

[tasosmi]

Hi Arthur,

the power supply that i have build gives to gm862-gps 370 mA. But gm862-gps uses only 100 mA. Do you think that if i give more than 370 mA (let's say 1 A), the module gm862-gps would use more than 100 mA?

Also i am thinking to use a battery with less capacity. I will buy a Li-ion 3,7 V at around 800mAh and i will test it.

Thank you,
Tasos

 

[AbdullahQ8]

Hello tasosmi,

I am in a similar situation, I built a switching power regulator based on a TI chip. The output was designed to produce 6V at 1.2A. But when connected to the GM862-GPS module, it drops to around 3.9V. Then the module restarts continuously (guessing its because of inadequate power).

It is worth mentioning that I have connected the power supply to the CHARGE pin (not VBATT), and a 900mAh battery is on VBATT - but it does not seem to be charging at all.

Please let me know if you figure out a solution. Thnx.

 

[tasosmi]

Hi AbdullahQ8,

first of all, if you have connected 6V at 1.2A in the CHARGE pin, it is WRONG! The maximum amperes should not be above 400 mA. But if you use 5 to 5,5 Volts, then you can use maximum 1 A.
The battery that you connect to VBATT pin should have the ability to give 2 A.
The voltage that drops to 3.9V is normal, because that is the right charging voltage for the battery. The module restarts continuously because the battery could not give at least 1,8 A. So you should use a battery with at least 1800 mAh. I guess that the 900 mAh battery that you use, could give only 0,9V -> it is not enough!
To see if the battery is charging, you could use the at command AT#CBC and AT+CBC (i am not completely sure about those commands, so check the appropriate guide)