li-po low voltage cut off

[sjak]

Hi,

I am converting an old cordless drill to li-po and made a simple low voltage cut off circuit consisting of a power MOS-fet and a 555 IC.
This works fine with a 12 volt lamp, but not with the drill.
I suspect that the problem could be the electronic speed regulator of the drill.
I could solve this by using a relais instead of the MOS-fet, but since the space I have to build the circuit in is limited this is not a good solution.
Can any body help??

sjak

[budm]

Re: li-po low voltage cut off

Can you provide the existing circuit you are using so we can see how you are implementing it.

[sjak]

Re: li-po low voltage cut off

Hello BUDM,

Yes I can.
Help is much appreciated.


Sjak

[eccerr0r]

Re: li-po low voltage cut off

The drill can draw a lot of current and the voltage can droop considerably if the internal resistance of the battery is high... How is the voltage when you use the drill?

Ahh...101 uses for the 555 ...

[sjak]

Re: li-po low voltage cut off

Hello eccerrOr,

The voltage of the not fully charged li-po is 11.38 V
Using the drill it is 10.9 V

Sjak