I wrote about FETs, and went ahead - with a BUZ100, seems better than BUZ72.
From my source,supplies with a LED for monitoring, and not pulse charing of a battery. It charges
But when I loose my power, the battery powers my LED on the other side of the FET.
Here it is: power in - to a LM555, output pin 3 directly to Gate and a resistor to ground. The power LED parralel with the LM555. Finally the FET between 0V and the battery connected to +V.
My problem is, that my BUZ100 is able to supply the other circuit when power is off, my LED is always on drainign the battery. I used the FET in order to avoid a diode and the loss involved.
It's hard to figure out what your circuit is, but you probably have leakage through the 555 too. There is a body diode with anode at the source and cathode at the drain which conducts reverse current through the FET without a gate volatge present. You need to do something like this:
Used a 555? Or did you use a 7555 or CMOS version? Please draw a circuit and post it, LTSpice is free, as is the ascii circuit software some here use (AAcircuit).
Very useful information here. I was surprised that the 555 seems to cosume app 10ma, which for a solar project is a lot. I will try it with a 7555 ASAP to reduce power consuption. Thx
And for the programmes I have will check them out. Thx again. Schematic to come.
I hope you're talking about lead acid batteries and not something else- last week it was a Sony Walkman. There are bunches of reference ciruits for PV charging of lead acid cells out there. If you visualize the body diode as in shunt with D-S terminals, then the back-to-back setup puts them in opposition, it is the only way to control bidirectional current flow with MOSFETs.
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