I don´t wanna start a new discussion wheather a CAP is useful or not. I use two of them in my car and I found it to be helpful.
But my Caps dont have any fancy electronics or LED´s . From the values I got from the manf. I think they have real low resistance. My Question is about the autom. charging-curcuits. I found this on the net, can anyone tell me if this is really used by the companies or is it just a DIY-curcuit ?
If so , the FET will add it´s on resistance making the "capacitor-effect" worse. (I know that the FET is used in "wrong" direction, but I heard that it is ok when the FET is fully openend)
But my Caps dont have any fancy electronics or LED´s . From the values I got from the manf. I think they have real low resistance. My Question is about the autom. charging-curcuits. I found this on the net, can anyone tell me if this is really used by the companies or is it just a DIY-curcuit ?
If so , the FET will add it´s on resistance making the "capacitor-effect" worse. (I know that the FET is used in "wrong" direction, but I heard that it is ok when the FET is fully openend)
really used?
sdoom,
I've never opened any of the huge car caps, so I can't comment on whether they are actually used. I've only used standard 25v/100,000uF caps paralleled, and I know they don't have any such gizmo.
It seems counter productive. As you say the fet has a series resistance which is probably greater than cap, so it will always 'get in the way'. The slow start is cool, but any fet the manufacturer can afford to put in with the cap is going to add a few tens to hundreds of milliohms of resistance (RDSon), you only have 12ish volts to push current, if the fet adds even 20milliohms (0.02) of resistance it will drop too much voltage for the cap to be useful for currents in the high 10's to 100 amp range, and as you know big amps draw more than this...
So I'm guessing it is not used by the high end car audio people, perhaps one of them can offer some real info...
Stuart
sdoom,
I've never opened any of the huge car caps, so I can't comment on whether they are actually used. I've only used standard 25v/100,000uF caps paralleled, and I know they don't have any such gizmo.
It seems counter productive. As you say the fet has a series resistance which is probably greater than cap, so it will always 'get in the way'. The slow start is cool, but any fet the manufacturer can afford to put in with the cap is going to add a few tens to hundreds of milliohms of resistance (RDSon), you only have 12ish volts to push current, if the fet adds even 20milliohms (0.02) of resistance it will drop too much voltage for the cap to be useful for currents in the high 10's to 100 amp range, and as you know big amps draw more than this...
So I'm guessing it is not used by the high end car audio people, perhaps one of them can offer some real info...
Stuart
Hi Stuart
Thx for your posting. And this is exactly what I would like to know
I really have no doubt that the cheaper models use curcuits like shown on the picture, maybe that´s the reason why the cheaper ones fail . Probably better ones use more and very good MOSFET´s , as the resistance of paralleled MOSFETS should drop...... but who knows
Thx for your posting. And this is exactly what I would like to know
I really have no doubt that the cheaper models use curcuits like shown on the picture, maybe that´s the reason why the cheaper ones fail . Probably better ones use more and very good MOSFET´s , as the resistance of paralleled MOSFETS should drop...... but who knows
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