On 10/20/2011 1:14 PM, swanny wrote:

> On 20/10/2011 1:33 PM, Rheilly Phoull wrote:

>> On 10/20/2011 7:46 AM, Phil Allison wrote:

>>> "Rheilly Phoull"

>>>> I'm trying to use a P type mosfet (IRF 9540) as a PWM switch to charge a

>>>> battery.

>>>> I cant get it to turn on completely, as a test I have connected the +

>>>> supply to the source and the drain to the + of the battery and the

>>>> neg of

>>>> the battery to the neg of the supply. If I take the gate to the neg

>>>> it does not turn on completely, there is a volt drop of several volts

>>>> across it at 2 amps. This happens with the 2 devices I've tried. They

>>>> turn

>>>> off OK when the gate is held high.

>>>> What am I missing here ???

>>>>

>>>

>>> ** What  WE  are missing is the battery type and voltage and the

>>> nature of

>>> the supply.

>>>

>>>      Devil, details .....

>>>

>>>

>>>

>>> ....  Phil

>>>

>>>

>>>

>>>

>>>

>>>

>> Ya right of course, 12v battery and a regulated variable supply that I

>> crank up to set the current flow. The real use will be with solar panels.

>>

>> Cheers ......... Rheilly

>

> What's the measured Vgs when it is supposed to be turned on?

>

Well I just grounded the gate so it was around 14v or 0 depending on how 

you view it.

As it turns out I was ripped off once again by the fiendish oriental

trader :-)

I've just come back with a brand type one and all is well.

(As Phil A and I were discussing)

Cheers ........ Rheilly