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Topic: Power - Step Converter for SIM800 (Read 57 times) previous topic - next topic

zstergios

Apr 20, 2018, 06:38 pm Last Edit: Apr 20, 2018, 06:44 pm by zstergios
Hi,
I'm working with SIM800L module that works on 3.4 - 4.4 volts. I activate the module with N-CHANNEL mosfet to minimize the battery drain.

I'm using arduino pro mini 3.3V 8HZ + some sensors (all working on 3.3-5V)

I'm powering the project with 2 x 18650 3.7 (4.2 fully charged) 3.400 mAh (parallel), so I have 4.2V with 6800 mAh.
 
18650 Voltages
Stop 3.0V
Nominal 3.7V
Max 4.2V
The problem
====================
Sim800L is unstable when the battery is bellow 3.65 Volts. I have also placed capacitor.

So the minium voltage limit is arround 3.7, so I unable to use the 50% of battery.

So I would like to suggest me or review my possible solutions bellow

Solution 1
=====================
1) Use auto-ajustable step up boost module to fixed value of 3.8Volts
2) Remove arduino regulator


Solution 2
======================
1) Connect the batteries in series, so 8.4 Volts and use auto ajustable step down module to 3.8Volts
1) Remove arduino regulator


Arduino wakes only for 30secs-60secs per day, so the drain is low.
When it is awake, with simple multimiter I get 0,10 mA and when is sleeping probably some few uA (multimeter dispays zero on 200μ measurement)


What are the pros & cons of each solution?
How you would handle the issue in my possition?
Which is the most efficient converter per solution?


The target is stability and maximize the duration of batteries.




zstergios

I have this in my hands "DC-DC Auto Boost Buck step Up step down Converter Module Solar Voltage LM2577 "

https://www.ebay.com/itm/DC-DC-Auto-Boost-Buck-step-Up-step-down-Converter-Module-Solar-Voltage-LM2577/201422600692?hash=item2ee5b8f9f4:g:EKMAAOSwMmBV7EYq

jremington

Quote
I'm working with SIM800L module that works on 3.4 - 4.4 volts.
Quote
Sim800L is unstable when the battery is bellow 3.65 Volts.
?

zstergios

I have not missed typed.

Under 3.65 Volts some times SIM800L restarts itself. That's why I said is not stable.

jremington

#4
Apr 25, 2018, 09:31 pm Last Edit: Apr 25, 2018, 09:33 pm by jremington
Then it does not work at 3.4V, contrary to the very first statement in your post.

Buy a better battery. Typical measured discharge curves for 18650 cells:



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