A Battery at last!
  • ThomasEgiThomasEgi March 26
    Good news everyone!

    Panasonic released a new battery for micro-applications (wristbands, sunglasses, pens etc).

    here are the quick facts:
    3.65mm diameter
    20mm long
    15mAh 
    discharge up to 15mA, charge up to 11mA
    max allowed charge temp 45°C
    weights about 0.6g

    Given the specs I'd call for organizing a group buy as those things are industrial parts and probably not for sale to individuals. Anyone who has connections to source them please get involved. Alternative would be to source consumer electronics that ship with such battery and aren't overpriced.
  • lolsmcfeelolsmcfee March 26
    dude this looks awesome! great find 
  • ChrisBotChrisBot March 27
    I am fully on board with this!! Yes please! How soon will they be available and when can we organize a group buy?


  • AerisAeris March 27
    Want! Want!

    I work in a research lab so maybe that would be enough to make a purchase, how do we work out if it's possible?
  • ThomasEgiThomasEgi March 27
    I know some people within the electronics industry, so I'll ask them to check on availability and prices.
    I also found some slightly bigger batteries from china but I'd rather not rely on those.
  • JupiterJupiter March 28
    Thanks for the heads up with that, they're smaller than the 35 mAh battery id been using for my Bluetooth communications device. A prototype device is been working on with the device pinned behind the ear and a small wire running (I imagined through a piercing eventually, but just around the bottom when I was developing it) to the ear canal, to allow hearing without significantly obstructing the ability to hear everything else. The battery I'd been using was about the size of three dimes stacked on top of each other.

    The new battery looks great, definitely more compact than my current battery, though it won't last as long for that application. I did put that project on hold a while back, several months, in favor of micro sizing the technology for use in an implant. This battery looks like a good start. Charging is still a never ending issue though.

    I'll do definitely contribute to a group purchase, and I'm curious, how'd you hear about them?
  • The battery itself is really awesome, though I just noticed a thing: Maximum charge voltage:
    4.35V.
    If I recall correctly Qi charging has an output of 5V?

    Just looked it up, on adafruit it says:
    • Output Voltage: 4.8V - 5.2V
    • Current: 500mA
    Both would be too high for the battery without additional electronics, so keep in mind that you are going to need a bit more space than expected.
  • @Chaphasilor. Don't worry Qi charging is designed specifically for lithium batteries and all of that is handled in the charging circuitry. It will work.
  • @ChrisBot Qi is not designed for charging anything. Qi is designed to wirelessly transmit power. 
    @Chaphasilor even tho the specs sais "maximum charge current" this is due to the fact that those things are primarily used for charging phones. So the wording adafruit picked here is misleading. 

    Long story short:
    You will need a proper charge controller to prevent over-current, over-voltage, and under-volting. If you connect a Qi receiver circuit to any lithium battery without a proper charge controller you will damage/destroy the battery. Including the risk of explosion, leakage, fire etc.

    Also when you'r working on minimizing something to the point where using such a small battery starts to make sense you certainly want to build your own pcb. Using pre-made modules is nothing but asking for trouble. In case of this battery, it would perfectly fit into a milled slot on a pcb for maximum protection.
  • JupiterJupiter April 2
    Having done quite a bit of research and a little physical work with Qi charging tech, it's worth noting that the Qi standard utilizes a one-way communication system, that is...
    Qi Charging Pads constantly transmit a minuscule amount of power, similar to an RFID reader.
    When you place a Qi Charging receiver device, such as a phone, on a charging pad, the receiver picks up the small power from the pad.
    The charger "notices" the receiver because the receiver adjusts power output from the receiving coil to the charging circuit, which results in the receiving coil getting "loaded" with power, which results in a lower current draw from the induction field. This adjustable power draw is modulated to achieve unidirectional data transmission from the receiver to the transmitting pad.
    The primary purpose of the communication is to request the charging pad transmit a specific amount of power, by this method the receiver circuit in the device controls "trickle charging" and prevents the transmitting pad from outputting too much power, which also means that when no device is on the pad, it uses significantly less power than when a device is actually being charged.

    I tried to explain that in a way that summed up everything involved without getting so technical that someone might have to look up things I said to understand the whole thing. There much more technical explanations out there for anyone who actually wants to build one of these themselves.

    To solve any concerns, hypothetically you could adjust power transmission to prevent any possible overloading. That said, I suspect that the relatively small 0.5 volts could be decreased with some sort of small resistor in between an unmodified receiver and the battery.

    PS
    As long as the charging mechanism was fairly cheap, easy to build, maybe could be made by modifying a normal Qi charger, I would find it perfectly acceptable at this point in time to not be able to use a standard, unmodified charger. If the implanted device needs a custom charger, I think it'd be plenty worth it.
  • @ThomasEgi, sorry, I abstracted for the sake of conversation.

    I was talking to the NorthStar guys a while back, and they are using this chip. http://www.ti.com/tool/tida-00318

    It's got a receiver and li-ion charger all in one and its only 5mmx5mm. Might be a good option for what ever application these batteries will be involves in
  • @Jupiter This power-regulation mechanism is for the purpose of not brutally over-powering the transmitter in such a way that it would cause damage on the receiver. Also for saving power as you correctly mentioned. This mechanism is by far not accurate or suited to perform charge-control. I can't stress enough you need a dedicated circuitry to do that.

    The module suggested by @ChrisBot features the bq51003 as QI receiver, and bq25100 as dedicated charging controller. They are a great combo and a good example on how things should be done. However I'd very much recommend that you those two chips should be incorporated on the main circuit  board of any device build. They both have a number of parameters you can and should set correctly, especially for such tiny and sensitive batteries. I think i even have some bq25100 around, somewhere in my messed up part storage shelf.
  • RizommaRizomma April 3
    New to this. Can someone explain the purpose of implanting a micro battery into your body?
  • @Rizomma you don't implant only the micro battery. The battery is just part of an implant that does something useful. Finding a suited battery was one of the biggest roadblocks for building proper and useful implants so far.