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Topic: Inrush current limiter for battery based pro mini project (Read 393 times) previous topic - next topic

wonderfuliot

Jul 29, 2019, 10:43 am Last Edit: Jul 29, 2019, 10:44 am by wonderfuliot
Hi,

I am controlling a 9V battery based load using a pro mini. The pro mini is supplied by 3V separately.

The load being switched is as follows:-

9V battery(6XAA cells)->Switching mosfet->LM2596 module(5.5V) ->AMS117(4.0V)->SIM800L

As you can see the 'switching mosfet' switches on SIM800 whenever needed via the 2 regulators. When switched on, there will be a huge inrush current seen by the battery. How do I limit/handle that?

Thanks and Regards,
WI


Robin2

When switched on, there will be a huge inrush current seen by the battery. How do I limit/handle that?
As well as defining what you mean by "huge" you should tell us why you think it may be necessary to limit the inrush current. What problem does it cause?

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

Wawa

Shouldn't a SIM800L be powered directly with a single cell LiPo battery.
A 1117 surrely can't supply the ~2Amp transmit current of that module.
Leo..

wonderfuliot

#4
Jul 29, 2019, 12:26 pm Last Edit: Jul 29, 2019, 12:27 pm by wonderfuliot
Quantify "huge"
As per the SIM800 h/w design guide http://mt-system.ru/sites/default/files/documents/sim800_hardware_design_v1.09.pdf, when sending data, the average consumption is about 450mA,  and during the short bursts of actual data Tx its about 2A.



wonderfuliot

#5
Jul 29, 2019, 12:29 pm Last Edit: Jul 29, 2019, 12:30 pm by wonderfuliot
you should tell us why you think it may be necessary to limit the inrush current. What problem does it cause?

...R
AA cells have 2000mAH rating. Now the maths fall apart when the current consumed is on the higher side. For ex, the AA cell rating means @1A, the cells will last 2000 hrs and @2000mA, it will last 1 hour, but the latter is not true in practice. So I want to prevent inrush peaks.

wonderfuliot

Shouldn't a SIM800L be powered directly with a single cell LiPo battery.
A 1117 surrely can't supply the ~2Amp transmit current of that module.
Leo..
LiPo batteries will not last 1 year which is my target for the batteries. The device is used just once a week to send sms or email

Maybe I will need a different regulator.
The purpose of using this regulator is to remove the ripple.

jackrae

What ripple.  DC current sources (batteries) do not generate ripples.  If you are concerned about the 2A transmit burst then install a 'fat" capacitor in the power feed line after the regulator.

Robin2

AA cells have 2000mAH rating. Now the maths fall apart when the current consumed is on the higher side. For ex, the AA cell rating means @1A, the cells will last 2000 hrs and @2000mA, it will last 1 hour, but the latter is not true in practice. So I want to prevent inrush peaks.
That does not make sense on two levels.

First, the inrush current only lasts for a very short period of time - for battery life you need to consider the average current.

Second, if some device (such as the SIM800L(with which I am not familiar)) needs a high current for a short period then it won't work properly if you deny it that current in order to protect your battery.

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

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