>Hi,
>I'm just inside this topic for my proper use. I fly some electric glider and
>now i'm studying a Hi-Tech charger with trickle mode, peak detection, charge
>with pulse and controlled current. But this project is waiting in my mind now.
>I'm thinking using a 8031 instead a PIC, because 8031 need only an EPROM and I
>can just program 16C84, 71 , 54..57, and EPROM that's all.
>As these chip seems to have not enought I/O and RAM, (means no RAM extension
>except trought I2C), my design will certainly use a 8031. In addition, most of
>A/D and D/A converter need a data bus sequence and 8031 have already a built
>in one.
>But nothing is fixed yet.
>
>The charger must do:
>        - delta-V charge,

    The charge termination method that is usually employed in the
    industry are:
    i.   minus delta V  - This is applicable to NiCD and NiMH batteries
                          although the NiMH has a smaller drop in
                          its terminal voltage upon full charge
                          Resolution required : -8mV/cell (for normal 6V
                          cellular batteries would be around -20~-40 mV)
                          This method is not applicable to the Li-Ion
                          battery
    ii.  dT/dt          - This method monitors the rate of change in
                          temperature and is very suitable for NiMH
                          batteries with termination at 0.8C/min.
    iii. const V, min I - This method is used for the Li-Ion batteries
                          which requires a constant V charge (you can
                          start as const I but must end with const V) as
                          oppose to constant I charge for the NiMH/NiCD.
                          Method is to charge at the rated voltage and
                          monitors the drop in I until a minimum cutoff.
    iv.  max V, max T & timer cutoff
                        - these are provided as a backup in the event of
                          i, ii & iii termination failure.

>        - pulse charge/measurement

    Pulse charge are suggested to prevent large crystals formation
    in batteries with continuous charge.

>        - cycling a batterie,

    Cycling basically discharges a battery follow by full charge.
    Discharging eliminates "memory effect" which are basically battery
    hysteresis. This is really important only for NiCD batteries.
    Newer batteries like NiMH and Li-Ion does not require discharge before
    charge

>        - discharge with controlled current/voltage

    This is a bit tricky, pulsed discharge (unless you have other method of
    controlling I/V) is not recommend as I heard somewhere that it
    damages the cell materials.

>        - trickle mode
>        - allows to charge more than 16 elements with a car batterie

    Car batteries are made of Lead acids elements, don't have much experience.

>        - allow to charge a minimum of 2 pack simultaneously with different
>        parameter,
>        - record the curve of charge/discharge, (EEPROM or RAM)
>        - be able to comunicate with a PC

    I would recommend that you build a big-banged RS-232-C interface to the
    PC and any data collected on the charge/discharge curve be store on it.

>        - have a LCD panel, some buttons
>
    LCD based on the Hitachi 44780 are quite good, especially if you
    use the 4-bit data interface (which saves you 4 I/Os, only 7 required)

>As you see, I just begin to think it. Seems to need a minimum:
>        - 16K RAM/or EEPROM

    If a PC is used you don't really need that much RAM or EEPROM.

>        - a 12 bit A/D

    For NiMH/NiCD charging, I don't think you require this kind of
    resolution. However, if you plan to charge Li-Ion batteries,
    it is highly recommended, as a difference in 100mV makes a lot of
    difference in the full charge capacity of the Li-Ion.

>        - two 8 bit D/A
    Why would you need a D/A?

>        - a PWM power
    Step down DC-DC convertor under PWM control would be recommended.
    However, check the maximum frequency of the microcontroller PWM
    that you are using as it ultimately dictates the size of your
    filtering components.
>        - an LCD panel
>        - a RS232 interface,
    As above.

>About Ni-Mh and Li-Ion, I don't have any documentation and I don't know what
>are the
>requierment to charge it in the better way.

    For all "normal" purpose, NiMH/NiCD can be charged in the same way.
    This is because NiMH batteries are designed to mimic the characteristic
    of the NiCD. However take note that it has a smaller -delta V termination
    point.
    Li-Ion is a totally type of battery. It can take const I charge but
    must be charged at const V finally. Accuracy of the charging V is
    crucial.

    Hope this gives a brief introduction to battery charging technology.

Regards,

Peter Tiang
tiangcfoon@hitachi.com.my