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So I'm currently using the design & schematic of adafruit's Powerboost 1000c. I've already discovered in a previous thread about which VBUS lines I can remove but will have to find out what I need to do in order ot access an serial terminal/gui via usb micro but that's for another question.

My current question at hand is in the below schematic and board view what VBAT lines do I currently require and what do I not require?

My end priority goal to to be able to recharge the battery which I'm already able to do but whilst also minimzing the amount of vbat in the schematic (by minimize I mean what do I require to make my goals possible and what ones I don't require i.e. I can get rid of). This is because in adafruit's schematic the likes of vbus & vbat connect together and then meet together after connecting to their respective components at their desired pin out with the VBAT pin out depicted by the orange circle and the VBUS pin out depicted by the pink circle.

My 2nd goal is to be able to check the battery level so I can later alert the user in software as to the battery level descending below a specified threshold.

Whether this requires something extra to be added to the schematic I don't know or I can use that VBAT pin and just link it directly to the main computer in my case being a Raspberry Pi Compute Module 3, it would be greatly appreciated if that's the case and you could point that out for me or any alternative routes I will have to take in order to reach this secondary goal.

enter image description here enter image description here

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  • \$\begingroup\$ amount of vbat .... it is unclear what you are quantifying \$\endgroup\$
    – jsotola
    Commented Aug 19, 2018 at 15:37
  • \$\begingroup\$ Oh let me rephrase that wording. what I'm meaning to say is when I look at the schematic that adafruit has supplied for their powerboost 1000c it seems there's alot of lines going to vbat. What I want to find out is which ones are actually what I need in my design such as: The battery providing power to the board, the usb micro providing power to recharge the battery and the ability to check the battery percentile level. And what ones I don't require to make the above work. \$\endgroup\$
    – Dragonfly3r
    Commented Aug 19, 2018 at 16:04
  • \$\begingroup\$ there is only one Vbat in the circuit .... you need to determine if a component requires a connection to Vbat \$\endgroup\$
    – jsotola
    Commented Aug 19, 2018 at 16:25
  • \$\begingroup\$ ^ Sorry that's probably a better rephrasing of it. Still lacking in that department regarding knowledge as you can clearly see. :-) \$\endgroup\$
    – Dragonfly3r
    Commented Aug 19, 2018 at 16:36
  • \$\begingroup\$ LED1 seems to be an indicator, so it may be possible to remove the circuit associated with it \$\endgroup\$
    – jsotola
    Commented Aug 19, 2018 at 16:41

2 Answers 2

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VBATT is preset in the MCP73871 by the factory. The part number determines the value.

enter image description here

You should first understand the safety concerns regarding Li-ion batteries.
Read: Battery University Safety Concerns with Li-ion

You should understand the basics of charging an Li-ion battery.
Read: Battery University Charging Lithium-ion

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You also need to understand the charge characteristics of the target Li-ion battery you are going to charge. This means you need the datasheet for the battery.

To alter the Adafruit Powerboost 1000 you need to FULLY understand is the Microchip MCP73871 battery charger chip.

enter image description here


Rather ironically your name speak truths about your answer. You misunderstand the question I'm asking entirely. 1st and foremost I'm not asking about stuff on the MCP73871. More exactly I'm talking about stuff on the TPS61009RSAR and whether or not I need all of the components it requires on vbat and I can remove some without effecting functionality / performance, whether or not I need a pin out for VBAT using a via and if I can just leave all the vbat connections connected. I'm also asking for help on how I would be able to check the battery level which would be connected via a RPI CM3
– Marc Brooks

My point is you do not understand how this circuit works well enough to even ask the correct question. This makes you dangerous. You have a responsibility for safety of which you are apparently completely unaware.

I'm not asking about stuff... More exactly I'm talking about stuff

Not a statement that inspires confidence you know what you are doing. "Exactly" "Stuff" exactly my point. You should not be working on a Li-ion battery charger is you do not understand how the "stuff" works.

And no, you cannot remove the "stuff" on Vbat otherwise the other "stuff" will not work. Is that exact enough for you?

I'm also asking for help on how I would be able to check the battery level which would be connected via a RPI CM3

I do not know what "RPI CM3" is. You already have two low battery indicators. The LBO on the MCP73871 will work when the USB is disconnected. The MCP73871does this for you. The low battery threshold of the is set with the voltage divided feeding the LBI pin of the TPS61009 so you can set the level to one above or below the LBO on the MCP73871. You can determine the state of charge by monitoring both levels. You need to understand the discharge curve of a Li-ion battery so you know where to set the low battery trigger threshold. Or you can use Adafruit's settings and just look at the two LEDs.

Take a look at the Microchip Demo and Eval boards.

LINK: Microchip Demo Board

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LINK: Microchip Eval Board
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  • \$\begingroup\$ Rather ironically your name speak truths about your answer. You misunderstand the question I'm asking entirely. 1st and foremost I'm not asking about stuff on the MCP73871. More exactly I'm talking about stuff on the TPS61009RSAR and whether or not I need all of the components it requires on vbat and I can remove some without effecting functionality / performance, whether or not I need a pin out for VBAT using a via and if I can just leave all the vbat connections connected. I'm also asking for help on how I would be able to check the battery level which would be connected via a RPI CM3. \$\endgroup\$
    – Dragonfly3r
    Commented Aug 20, 2018 at 8:34
  • \$\begingroup\$ Yes, my name is appropriate and you have substantiated it. See my updated answer. \$\endgroup\$
    – Misunderstood
    Commented Aug 20, 2018 at 17:21
  • \$\begingroup\$ Thank you, your updated answer shines alot more on what I required to know. Particularly "Cannot remove stuff on vbat else it won't work" that's simply all I needed to know. So now I can leave that all connected and just remove the via that was acting as a pin out. Also not currently working with Li-ion as using Lipo although I might change to Li-ion depending on battery space I have available so I will keep your reference to battery in mind. RPI CM3 stands for raspberry pi Compute module 3 & thank you for the insight on battery level checking. \$\endgroup\$
    – Dragonfly3r
    Commented Aug 20, 2018 at 17:36
  • \$\begingroup\$ Li-po stands for Li-ion polymer and uses the same chemistries. batteryuniversity.com/learn/article/… \$\endgroup\$
    – Misunderstood
    Commented Aug 20, 2018 at 18:08
  • \$\begingroup\$ Now I think I understand why you asked about the "pinout". If you wanted to monitor the low battery signals with the Pi, then add output pins to LBO of both chips. The existing LEDs can serve as the pull-up resistance. The LEDs would not be required but if not used, there needs to be a pull-up resistor. Geting back to using Vbat if you can use an ADC to measure the voltage at Vbat then you do not need the low battery signals. You still (more so) would need to understand the charge and discharge curves. \$\endgroup\$
    – Misunderstood
    Commented Aug 20, 2018 at 18:28
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this is not an answer

i highlighted the Vbat net

yellow on one side of the board and light red on the other side

there are some places where the trace switches sides for no reason (pink)

i think that you can streamline the trace routing a lot

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  • \$\begingroup\$ Pink sections on the right are for vbus connections and 1 thermal resistor. They are like that because get when I was doing the routing in Eagle, it was throwing up Earnest airwire errors for the GND's and at the time this was the o my workaround I could think of whilst working single sided. In the 2nd version I've tidied it up as working on both sides for component placement \$\endgroup\$
    – Dragonfly3r
    Commented Aug 19, 2018 at 21:33

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