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Propeller Li-Ion Battery Controller — Parallax Forums

Propeller Li-Ion Battery Controller

Bobb FwedBobb Fwed Posts: 1,119
edited 2009-04-22 05:21 in Propeller 1
Are there any tutorials or instructions on how I could create a Lithium Ion/Polymer multi-cell battery controller with (or without) the Propeller?
Someone has had to create a controller.

Here are some specs:
Charge on each cell cannot exceed 0.5A
Discharge on each cell cannot exceed 1.5A (not necessary, as I will be in 100% control of the load circuit)
Charging of the cell will be at 4.2V
Each cell cannot deplete below 2.75V

Obviously, in this multi-cell setup, each cell doesn't have to be monitored, but a measurement of the whole "battery" can be measured, and values determined with a knowledge of the number/arrangement of the cells.

Here is what I am planning, a Li-Ion/Polymer battery integrated in a mobile device I have, with a 2-by-3 setup. Explanation: 2 sets of 3 cells. With 3.7V 2.4Ah cells, I intend to get 7.4V with 7.2Ah.

If anyone can point me in the right direction. I'm kind of curious on how to build my own, but I guess pre-fab controllers (or complete battery/controller packages) would be very helpful as well.

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April, 2008: when I discovered the answers to all my micro-computational-botherations!

Comments

  • Mike HuseltonMike Huselton Posts: 746
    edited 2009-04-20 23:58
    Check SparkFun web site. I have purchased several chargers and batteries from them and the quality is superb.



    www.sparkfun.com/

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    JMH
  • Fred HawkinsFred Hawkins Posts: 997
    edited 2009-04-21 03:21
    TI's power management link page: http://focus.ti.com/analog/docs/powerhome.tsp?familyId=64&contentType=4
  • Bobb FwedBobb Fwed Posts: 1,119
    edited 2009-04-21 21:08
    Well, I ended up using this: www.alliedelec.com/Images/Products/Datasheets/BM/MICROCHIP/383-1410.PDF I am going to build one. There are a few external parts, and it is only a one-way controller (doesn't monitor/affect output of battery), but that is where the Prop comes in, it will monitor the output voltage and whatnot while it is doing its other chores.

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    April, 2008: when I discovered the answers to all my micro-computational-botherations!
  • mctriviamctrivia Posts: 3,772
    edited 2009-04-22 00:27
    would either of these systems be safe for full time use? have a project that will run on wal power most of the time but needs a battery backup. My hope is to have this project run non stop for 50 years so I am over building everything.

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    Need to make your prop design easier or secure? Get a PropMod has crystal, eeprom, and programing header in a 40 pin dip 0.7" pitch module with uSD reader, and RTC options.
  • Bobb FwedBobb Fwed Posts: 1,119
    edited 2009-04-22 01:03
    From my understanding, Li-Ion batteries will not last that long. Normal shelf life is 10-15 years (at best), but with normal use, the battery life cycle will eventually diminish to next to nothing after 4-6 years. Heavy use will reduce the time.
    As for the rest of your device: I would assume most simple components if used at the suggested 50%-max-load (or less) would last that long. I'm not sure if there is some known deterioration time of ICs or transistor-based devices in general. I would (as you say) over-build everything, and stay away from electrolytic capacitors and anything that is not solid state.

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    April, 2008: when I discovered the answers to all my micro-computational-botherations!
  • mctriviamctrivia Posts: 3,772
    edited 2009-04-22 01:19
    yes everything is solid state and changing out the bateries once a decade is not a problem. I actually have 2 separate redundant backup supplies so even if the power goes out while changing a battery pack it will be ok.

    So it will not kill the batteries if I keep them hooked to the charge circuit and never draw any power(or almost never)

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    Need to make your prop design easier or secure? Get a PropMod has crystal, eeprom, and programing header in a 40 pin dip 0.7" pitch module with uSD reader, and RTC options.
  • Bobb FwedBobb Fwed Posts: 1,119
    edited 2009-04-22 01:24
    I think most Li-Ion cell voltage degrade something like 5% per month (without use). So periodically it will have to charge, but it looks like on the IC (on the datasheet above) it completely disconnects the battery from the circuit when not in use. And if you add a diode or two (in the right spots) the voltage will have to swing even more before the battery is engaged, depending on the stability of the power, this could also reduce the use of the battery.

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    April, 2008: when I discovered the answers to all my micro-computational-botherations!
  • SRLMSRLM Posts: 5,045
    edited 2009-04-22 02:02
    @mctrivia

    You may want to try and design in triplicate. I believe that's the way that the mars landers are designed. That way, if one copy goes bad the other two good ones will indicate that there is bad data from the ruined copy. Plus, it will allow you to maintain one system, while still having a backup for the running components.

    50 years? Are you sure that your descendants will be willing to keep it running that long? By the time you have enough knowledge to build something like this, you'll have to be at least 20. Since I know that you're getting married soon (from the Prop Galore thread), I'll take that you're getting married at the average age, ~27 years old. The average life expectancy of (Americans, at least) is ~78 years, so you'll finish this experiment one year before your death. Cutting it close... [noparse]:)[/noparse]
  • mctriviamctrivia Posts: 3,772
    edited 2009-04-22 02:18
    i am 26 and in my family average life is 95. The project is a gift. A clock counting in seconds from the moment we get married hopefully to the day I die.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Need to make your prop design easier or secure? Get a PropMod has crystal, eeprom, and programing header in a 40 pin dip 0.7" pitch module with uSD reader, and RTC options.
  • SRLMSRLM Posts: 5,045
    edited 2009-04-22 03:34
    That's a pretty good project idea!
  • mctriviamctrivia Posts: 3,772
    edited 2009-04-22 03:42
    i will write it up when I am done. Who knows maybe I can get it in circuit cellar. Probably not but worth trying.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Need to make your prop design easier or secure? Get a PropMod has crystal, eeprom, and programing header in a 40 pin dip 0.7" pitch module with uSD reader, and RTC options.
  • Bobb FwedBobb Fwed Posts: 1,119
    edited 2009-04-22 05:07
    Another simpler idea would be to get one of those real-time "clock" counter ICs (I don't know how to describe them, but I have seen them). They run off of main power until it is cut. At that point it switches over to a "super-cap" or backup battery. I think they could operate as low as 1V. This allows you to use those flat batteries like you see on your motherboard.
    Of course, if you want to actually be able to see the time tick by even when the power is out, you would be out of luck. But at least you know the time is backed up.
    Tomorrow when I am wasting company time, I will attempt to look for the IC I am thinking of.

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    April, 2008: when I discovered the answers to all my micro-computational-botherations!
  • mctriviamctrivia Posts: 3,772
    edited 2009-04-22 05:21
    Yes I am using a 1340 RTC as my secondary backup and 2 lithium cells for my primary. primary lets me still see the time and play sound(alarm clock feature)

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Need to make your prop design easier or secure? Get a PropMod has crystal, eeprom, and programing header in a 40 pin dip 0.7" pitch module with uSD reader, and RTC options.
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