[urq] Electrical Experts - Question re. Capacitor installation
glenahan at vfemail.net
Thu Nov 1 05:23:21 PDT 2007
Yes and no. It will increase the surge at turn-on, but will not
increase constant load, unless the capacitor leaks.
On Oct 31, 2007, at 4:58 PM, Mark R wrote:
> As always Huw is more eloquent than myself on these things. =)
> Let me rephrase.... adding the capacitor is adding more load to the
> system (alternator and supply wiring). Think of a bank of 4 batteries
> in parallel. Yes, resistance is lowered, voltage is the same, but the
> in increased on the charging/supply system. Adding a capacitor adds
> to the
> load (albeit a small load increase). I suspect >IF< Ben is having
> high RPM
> voltage stability problems, it's likely the +12V line is inadequate
> due to
> being undersized, poor quality, corrosion, or poor connections. Or his
> engine ground(s) is(are) poor. A capacitor won't "fix" this kind of
> Hopefully, this is more clear (and I feel stupid for using an
> incorrect term
> earlier in explaining myself.). =)
> Not many lists have such posts! Ben's questions have made us think and
> discuss. How cool is that?
> Thanks Larry and Huw!
> Mark Rosenkrantz
> On 10/31/07, Huw Powell <audi at humanspeakers.com> wrote:
>>> Something new to my realm of expertise.
>>> I would like to install an electrolytic capacitor to act as a buffer
>> an ignition
>>> system – sort of like placing a second battery up close to the
>> load.. Since the
>>> distance of the battery to the coil is about 7-8' and my
>> that a circuit
>>> may lag, it seems installing a large capacitor might be a good idea.
>> If so, it makes
>>> sense that I'd install it in parallel with respect to feed wire and
>> ground, however
>>> diagrams for most stereo AMP installations show the cap to be inline,
>> with no other
>>> current path to the amp.
>>> Is it OK to install an electrolytic cap. as sort of a buffer or quick
>>> batteryin parallel with the circuit? That is basically to connect
>> positive end to
>>> battery post near load and ground as normal, leaving the original
>> positive feed path
>>> intact. I have some 1 and 2 Farad caps and this is mainly to
>> lag at high RPM,
>>> similar to stereo clipping at high volume.
>> Many others have commented, saying most of what I thought in response
>> this, but I figured I'd chime in anyway.
>> 1. Any diagram showing a DC filter/stiffener cap in series with the
>> is simply wrong.
>> 2. If the wire to your coil is too small, replace it. If the wire to
>> the coil is too small to keep battery voltage at the coil, a capacitor
>> is not going to help. The current to keep the cap charged has to come
>> through that wire.
>> 3. It might make things worse, but my head hurts when I try to look at
>> the equations in my old college electronics class notes. But
>> while the coil is "recharging", the capacitor might also be trying to
>> the same, using *more* current. Also, the capacitor will have a
>> "discharge rate" curve, that may not coincide well with the operating
>> cycle speed.
>> 4. So in conclusion, run a bigger wire, and don't do the cap unless
>> figure out a way to get the circuit exactly right for the application.
>> Huw Powell
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>> quattro at audifans.com
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