ark wrote:
>
> I've got a cell phone Lithium battery that I want to use in one of my
> projects. This particular battery is Motorola SNN4814, 3.6v, but I think my
> questions applies to many other types as well.
>
> The battery package consists of a proper battery and, presumably, some
> protection circuit, and has four terminal plates. My questions are:
>
>     What these four lines are used for? Is there any freely available

Typically Gnd, VCC, temperature and serial comm with the phone to report
capacity.

> specification applicable to this thing?

Nope. You have to scope it.

>     What would be a better way:  to use the battery package as it is,
> connecting it through the existing 4 lines, or to get rid of the

As is. This lets your client go out and purchase replacements,
off-the-shelf after the cycle life is consumed.

You can *probably* get away with just using VCC and GND and
let the pack electronics take care of the 'safety' limits (low
and high charge). I've been using Sony camcorder batteries
this way, without problems, but I am also using an 'official'
external Li battery charger (only 2 wires).
Li batteries are fussy about being over and under charged.
If you want to 'quick charge' you MUST sense temperature
to compensate for the Vmax shift.
If you can measure battery voltage accurately, you can manage
the charge cycle yourself.

electronic
> circuit and use a bare two-terminal battery? (In latter case I will have to
> supply some kind of protection circuit by myself).

And you open yourself to HUGE liability issues.
That's why manufactures will not sell you single cells unless
they have tested and approved your custom charger circuit.
It MUST have hardware charge limits, not just software (at least for
Tadiran).

>     Have somebody used these batteries, and how?

As is, using someone else's 'approved' charged. Then it
becomes THEIR liability if something goes horribly wrong.

You can also purchase unpackaged li-* packs which incorporate
the required charge control electronics as part of the pack.

Robert

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