Help with battery script for 2S setup!

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BlueWeaselBreath
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Help with battery script for 2S setup!

Post by BlueWeaselBreath » Mon Aug 20, 2018 7:21 am

Hi, all, I am putting a Retropie in a Wii U gamepad, using the following Lithium-Ion 2S 7.4V setup as diagrammed by sudomod community member Banjokazooie on another thread.

Image

Banjokazooie’s own build, as described in that thread, is not this 2S setup (which was diagrammed for another user), but a 3.7V setup using a Powerboost. Therefore, that build is able
to use a setup and script called Pi Power, linked here:
https://github.com/craic/pi_power/blob/master/README.md

The purpose of this script is to allow a series of LEDs to act as battery status indicators; cause a graceful shutdown when the battery charge falls below a certain level; and allow a pushbutton shutdown process. Of these features, it is the first two that I’d like to have in my setup — I can live with the standard software shutdown process.

The problem is, the Pi Power setup relies on the particular pinout of the Powerboost, specifically the Enable control pin, and as you may be able to tell from the above diagram, I am using a stepdown converter, not a Powerboost.

Thus, I am looking for a hardware and/or software solution that is comparable to the Power Pi tutorial, but which is compatible with a 2S setup. Again, all I need is some way to monitor the voltage of the battery (doesn’t have to be LEDs — onscreen status indicator is ok too), and preferably an auto-shutoff feature if the battery drops below a certain level. And of course, I am looking for the most parsimonious solution available, in terms of hardware components.

Thank you in advance to anyone who can point me in the right direction!

cbafun
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Re: Help with battery script for 2S setup!

Post by cbafun » Mon Oct 08, 2018 4:47 am

Hi,

Not sure if this will help. You could potentially replace the power button board you intend to use , with one from the link below (It is intended for a momentary switch, not a latching one).

Im not 100% sure if the EN pinout on the Pollou Buck Converter works in the same way as the PowerBoost, but if it does, this will work for you.

https://github.com/craic/pi_power

Me and my brother made up some PCBs that is based on the circuit form this page. It allows for battery monitoring and all other sorts of goodies. You can also get fancy and implement your analog sticks with the MCP3008 and sell your Teency for a few pints.

As said above, not sure how the EN pin on the Pololu works, but might worth a shot..

Good luck.

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KonnorJ
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Re: Help with battery script for 2S setup!

Post by KonnorJ » Mon Oct 08, 2018 10:29 am

Why are you using 2 cells in series opposed to in parallel? You will get more capacity in parallel so longer play time. Just use a boost converter to 5v.

BlueWeaselBreath
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Re: Help with battery script for 2S setup!

Post by BlueWeaselBreath » Wed Oct 17, 2018 9:04 am

Thank you, cbafun -- the stepdown converter doesn't have that EN pinout, which is the reason I wasn't able to use the craic Pi Power thing, although that was definitely my first thought when I started this build. :-(

KonnorJ, I appreciate your point. I started the build as series rather than parallel -- and ordered all the components accordingly -- because of banjokazooie's comment here that if he could do this build over again, he would use a 2S setup for better battery life and less noise in the signal. At the time, I presumed he was referring to the fact that the lower current draw would more than balance it out, but I suppose it's possible he was imaging a 2S LiPo as opposed to my own rigged two cells, and maybe that would somehow make the difference? I am still trying to get clarity on this.

I am a novice to electronic projects and would welcome any thoughts you may have, though!

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