Re: Car stereo capacitor not charging

Connecting 1.5F (or any other cap) into a battery power circuit via a
1k resistor won't do anything. You need VERY low impedance connections
from the cap to the power amp (or whatever) to have it work.

Some supercaps have built-in LEDs, discharge resistors, etc that would
prevent a full charge when fed via a resistor (just as you
experienced). If your 1k resistor drops 7V when feeding the supercap,
that's 7mA, and if you eliminate the resistor, whatever's in the
supercap may draw 20mA or more at 12V, so make sure the circuit is
switched so it doesn't flatten your battery if you leave it unattended
for a month or more.

Does the book mention why they suggest the 1k resistor?

Tony

subliznime@xxxxxxxxx wrote:

I bought a 1.5 F Xpress capacitor for $50 to help stabilize my car's
electrical system when I have my loud music and inverter running. I
hooked it up exactly as the book said, using the 1000 ohm resistor
between the positive terminal of the cap and the positive battery wire,
with the ground connected to the negative terminal of the cap. The
voltage before the resistor is my car's battery voltage, about 13
volts. And the voltage accross the capacitor went somewhat quickly up
to about 4 volts, then seemed to completely stop charging at about 5
volts. So I got pissed, drove all the way back to Fry's, and traded it
for another of the exact same cap. I hooked that up the same way
again, and it is pretty much doing the same thing. I don't know if
that brand is just crap or if I'm missing something here. I did the
calculation online and a 1.5 farad cap with a 1kohm resistor at 12
volts should take about 2 hours to fully charge, although it has been
more than 2 hours and i'm still stuck at 5 volts. Someone please help
me out.

Tony (remove the "_" to reply by email)
.

Relevant Pages

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