Author Topic: Moteino M0 - Remove charge controller?  (Read 424 times)

adam.g

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Moteino M0 - Remove charge controller?
« on: November 30, 2018, 11:30:49 AM »
Hi there,

I was curious, would it be possible to remove the MCP73831 charge controller on the Moteino M0 in order to allow a higher voltage battery to power the board? I don't actually have a need for the charge controller and was hoping to be able to use a 7.4V or 11.1V battery. The MCP1703 LDO can handle 2.7 to 16.0 V, but the charge controller tops out at 6V. Looking at the schematic it appears that I'd also need to disconnect the voltage divider on A5 so as to not expose the pin to greater than 3.3V (I imagine I could make it a 1M/10M ratio to keep the voltage within range).

Would appreciate any feedback!

Cheers,
Adam

Felix

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Re: Moteino M0 - Remove charge controller?
« Reply #1 on: November 30, 2018, 12:05:19 PM »
Yup, if you are brave enough to try this, go ahead, it should work.
The only reason for the 6V max input is the charger MCP73831.
In fact if you're careful, you could just lift the VBAT leg from the trace on the board, and leave the rest of the charger in place - this still assumes VUSB never exceeds 6V (USB power).
Then VBAT only goes to the LDO and you're OK. The VMON divider should also be changed as you already noticed.



Someone else asked about this, and maybe a jumper would help for this purpose but the only room for that would be on the bottom, not sure I want to route VBAT through 2 extra vias.

adam.g

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Re: Moteino M0 - Remove charge controller?
« Reply #2 on: November 30, 2018, 12:55:22 PM »
Thanks Felix!

I just picked up a hot air rework station and have been having fun removing surface mount components from the various damaged components I had laying around.

Could you tell me the size of the SMT resistors on the Moteino M0 (e.g. 0603/0805)?

Cheers,
Adam

Felix

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Re: Moteino M0 - Remove charge controller?
« Reply #3 on: November 30, 2018, 01:17:48 PM »
All resistors are 0603.

As a good practice with hot air - you need to protect the connectors/button/LEDs and non serviced components in general with a piece of sheet metal - I like soda can aluminum since it's easily bendable and has enough thermal mass. Tinfoil as a last resort. Stencil scraps also work well.
This is to draw heat away and prevent them from melting.

mantonakakis

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Re: Moteino M0 - Remove charge controller?
« Reply #4 on: May 21, 2020, 11:47:01 AM »
Yup, if you are brave enough to try this, go ahead, it should work.
The only reason for the 6V max input is the charger MCP73831.
In fact if you're careful, you could just lift the VBAT leg from the trace on the board, and leave the rest of the charger in place - this still assumes VUSB never exceeds 6V (USB power).
Then VBAT only goes to the LDO and you're OK. The VMON divider should also be changed as you already noticed.



Someone else asked about this, and maybe a jumper would help for this purpose but the only room for that would be on the bottom, not sure I want to route VBAT through 2 extra vias.
I'm been having some issue with this - is Q1 able to handle ~12V? Sometimes it works when I use ~12v to battery JST with the charge controller disabled by cutting the trace to pin 3 of the MCP73831, but other times Q1 ends up getting fried and shorts from drain to gate (or VBAT to VUSB). Something else could be going on I suppose, but I wasn't able to find any info on Q1.

Felix

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Re: Moteino M0 - Remove charge controller?
« Reply #5 on: May 22, 2020, 11:36:06 AM »
Unfortunately I just cant process all the hacks that people have in mind. The board is designed to take a 3.7V lipo.
I cant really predict how things will fail and how to fix, undo, properly hack, etc, when higher VINs are connected when 6V max is expected on on the VIN pin.
There is the schematic for reference and any mods and hacks, cut traces and things like that are not endorsed or supported. You might render the board useless.

As a rule of thumb, it is very uncommon and not recommended to supply low power electronics from anything over 5-6V or so. 9V batteries are small capacity and will waste lots of that energy when fed into an LDO, 12v, 15v, 24v situations should be regulated with an external efficient DC/DC regulator, rather than try to feed that into a small linear regulator that is most efficient at around 4V anyway.