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Can cells be charged this way? — Parallax Forums

Can cells be charged this way?

lardomlardom Posts: 1,659
in General Discussion
Every balance charging connector I've seen has multiple pins. The only advantage I can see for multiple pins is speed of charging.
Is it possible to design a battery pack that is wired both in parallel for charging 'and' in series for discharge? You could then have two XT60 connectors, one for low voltage charging and a second for powering your device.
Balance charge.PNG
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Comments

  • DigitalBobDigitalBob Posts: 1,513
    What type of cells are they??
  • DigitalBobDigitalBob Posts: 1,513
    If they are lithium Ion you what to avoid surge currents
  • lardomlardom Posts: 1,659
    DigitalBob wrote: »
    If they are lithium Ion you what to avoid surge currents
    I inherited a partial carton of backup lithium Ion battery packs designed for obsolete routers. I still have a bunch of things to learn before I attempt to build a battery pack but one of the things that crossed my mind was would a low voltage charging configuration allow solar charging?
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    I think you might need some sort of balancing circuit to charge them in "parallel." IOW, I doubt that you can just connect them in parallel as you've shown.

    -Phil
  • tonyp12tonyp12 Posts: 1,951
    The problem is how to float each battery or how to float each 5V supply.
    Some half-h bridges could probably do it.
    YKqYU.png
  • lardomlardom Posts: 1,659
    edited 2017-10-09 01:27
    @tonyp12, I just did a quick search on tp4046. It looks like that's the way to go. Thanks
    @Phil Pilgrim, after thinking about bus charging a bit more one of the things that popped out was that you wouldn't have any data on the discharge condition which means I have to discard the idea. Always appreciate your input. Thanks.
  • DigitalBobDigitalBob Posts: 1,513
    This auto correct is anything but correct . " you want to avoid surges"
  • lardomlardom Posts: 1,659
    DigitalBob wrote: »
    This auto correct is anything but correct . " you want to avoid surges"
    Auto-correct will catch spelling errors but I rely on 'Preview' to try to make my posts as clear as possible. :smile:
  • Heater.Heater. Posts: 21,230
    If I understand correctly lithium Ion cells are a bit fussy about how they are charged.

    For example one should not exceed 4.2 volts when charging an empty cell at constant current. When you hit that voltage you switch to a constant voltage mode until it's charged.

    All of this is hard to do, hence all the pins on a multi-cell charger. They even make chips to manage it for you.

    All in all, it is not something I would think of building myself.

    There is a ton of articles about charging such cells around the net if you like.
  • lardomlardom Posts: 1,659
    Heater. wrote: »
    If I understand correctly lithium Ion cells are a bit fussy about how they are charged.

    For example one should not exceed 4.2 volts when charging an empty cell at constant current. When you hit that voltage you switch to a constant voltage mode until it's charged.

    All of this is hard to do, hence all the pins on a multi-cell charger. They even make chips to manage it for you.

    All in all, it is not something I would think of building myself.

    There is a ton of articles about charging such cells around the net if you like.
    That answers one of the big questions I had which made me believe a low voltage charger was possible.
    My other interest is that I have a project collecting dust for over a year because it's to small to do any work. I built a wireless, mobile robotic arm with pan/tilt camera 'but' it runs on AA cells. It's a toy. For starters I want to scale it up to 24V and attach a cart behind it. Lithium cells would help but I don't yet know enough to include them in my projects.
  • kwinnkwinn Posts: 8,697
    lardom wrote: »
    Heater. wrote: »
    If I understand correctly lithium Ion cells are a bit fussy about how they are charged.

    For example one should not exceed 4.2 volts when charging an empty cell at constant current. When you hit that voltage you switch to a constant voltage mode until it's charged.

    All of this is hard to do, hence all the pins on a multi-cell charger. They even make chips to manage it for you.

    All in all, it is not something I would think of building myself.

    There is a ton of articles about charging such cells around the net if you like.
    That answers one of the big questions I had which made me believe a low voltage charger was possible.
    My other interest is that I have a project collecting dust for over a year because it's to small to do any work. I built a wireless, mobile robotic arm with pan/tilt camera 'but' it runs on AA cells. It's a toy. For starters I want to scale it up to 24V and attach a cart behind it. Lithium cells would help but I don't yet know enough to include them in my projects.

    Have you considered using the lithium battery from a cordless drill for this? I use the 19V battery from mine to extend the run time of my laptop for some tasks.
  • lardomlardom Posts: 1,659
    kwinn wrote: »

    Have you considered using the lithium battery from a cordless drill for this? I use the 19V battery from mine to extend the run time of my laptop for some tasks.

    That sounds pretty clever. How did you modify the connector?
  • koehlerkoehler Posts: 598
    kwinn wrote: »
    lardom wrote: »
    [
    Have you considered using the lithium battery from a cordless drill for this? I use the 19V battery from mine to extend the run time of my laptop for some tasks.

    Doh!

    Brilliant.
  • kwinnkwinn Posts: 8,697
    lardom wrote: »
    kwinn wrote: »

    Have you considered using the lithium battery from a cordless drill for this? I use the 19V battery from mine to extend the run time of my laptop for some tasks.

    That sounds pretty clever. How did you modify the connector?

    With my old cordless I used the receptacle portion from a defective charger. With my new DeWalt all I needed was two spade connectors on the end of my laptop power cord.
  • lardomlardom Posts: 1,659
    @tonyp12, the TP4056 would be perfect for charging a cell phone battery through a computer USB. Both my wife and I have have problems getting our cell phones to charge without jiggling the USB cable. I could easily put together an adapter for the battery on a pcb. On top of thst they're cheap so I'll get a few of them.
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