[balou]

Hi,
I recently got a vintage cell phone. The phone itself is garbage, but there was a nice 7.2V, 1350mAh LiPo rechargable supplied with it (even reloadable on it's own in the telephone recharger). So... this makes of course a great battery for a portable low-gain high-current-draw amp.

But... it needs to be cut off at 6v, to avoid damage through excessive discharge. A zener diode seems to come in handy, but there are two questions I have:

-Do Zeners have a reverse voltage drop?
-Which value should I choose so that at 6.0v the cell is completely disconnected? cutoff could start as early as at 6.8v. how do the cutoff curves of zener normally look like?

 

[tangent]

You really should be looking for a battery monitor chip instead. Lithium rechargeables are cranky beasts, and hazardous when mistreated.

Also, beware that most lithium battery packs have some sort of active circuitry in them already. You need to test thoroughly to be sure it's not going to interfere with your usage.

 

[villekille]

I think you could try to use a zener AND a JFET. That way any noise from the zener would fade away and when the voltage is too low, the JFET would disconnect the power

 

[MisterX]

Protection circuit Module ( PCB ) for 7.2v(7.4V) Li-Ion Battery Pack (2 Cells with 5A +/-1A Limit) - PCB-S2A5

(they offer a quite a few different protection boards on that site if you do not like that one.

)