Ok so I've added a sub, some dynamat, new speakers in a 2008 package 6 (JBL + NAV + SKS). I can feel a bit of a draw on the inverter when the system is turned up (its surprisingly good from stock head unit). I've ordered a 3.5F 20V cap (for $33 shipped), and now I am wondering if I should wire the capacitor after the battery (between the battery and sub -- a normal install) or if I should wire it between the inverter and 12V battery. In short does the inverter charge in such a way that it could take advantage of charging a large Capacitor which would then charge the battery. There are a few advantages to such a schematic: 1) Increase 12V energy storage capacity for the entire car 2) It would not drain the battery over long periods of time. Are there any disadvantages to wiring a capacitor between the inverter (12v charger) and battery? Looking forward to answers with roots in experience or education (e.g. EE). Thanks, Cliff
Follow up: 1) the sub is in the trunk with a short wire run. 2) if I run the Cap after the battery as ususal is there a way I could also run the stock audio system off the Cap too? -- I can hear the stock audio system run out of head room on some loud portions of songs @ volumes 49-62 -- I think the stock system would benefit from the cap (voltage stiffining etc) too
Your two options are identical. The 12V battery sits across the 12V bus. The capacitor will do the same, whether wired before or after the battery. They are in parallel, as is the inverter. The only real difference involves voltage drop over the bus, which shouldn't be an issue. If you really feel that you need this extra capacitor because of the power draw from the power amplifier, then you should wire the capacitor as close to the amplifier as possible. Tom
A capacitor only helps for a few seconds at a time. It won't compensate for a weak battery or battery charging capability. If you need to use one, put it close to your amplifier where it will also help make up for wiring loses at peak power. I seriously doubt that the stock audio system would benefit from a capacitor. The only reason it might benefit would be because of skimpy stock wiring. If that's the case, a separate capacitor at the stock audio system would be the best approach.
Thanks guys -- a follow up question. Is the battery big enough to handle a cap wired after it? It seems a little weak (no offence intended).
Any cap you can buy for an audio system is insignificant compared to any car battery. Those capacitors are usually used to make up for inadequate wiring between the battery and audio equipment or for their placebo effect.
3.5F times 12V = 42 amp*seconds, or 0.012 amp-hours. If the 12V battery can handle the headlights for more than a few seconds when not in Ready mode, it can handle this cap. BTW, what is the ESR spec of this cap, and how does it compare to the battery and wiring resistances? I've seen far too many caps in other applications where the primary benefit was the placebo effect.
We generally specify self-sealing conductors to avoid this problem, but I suppose a pan might make sense for a retrofit. Unfortunately, most of the legacy circuits used imperial dimensions, and now all you can find are metric grid pans. The other problem, of course, is disposal. In the old days you just dumped the electrons down the drain. You don't want to get caught doing that these days. There are some disposal outfits, but the cost per coulomb is pretty high. Tom
To keep the Cathode above the Grid, just throw a Hi Wattage Cathode Bias Resistor in the line and use the surplus heat in winter! Just use up those excess electrons!
Okay, I'll try to give some real info. First: Define "feel". Is this by some telepathic link? Second: Electrolytic capacitors have a number of real life concerns. Electrolytic capacitors will reduce capacity, and short or open after some period of time. [ame="http://www.youtube.com/watch?v=-K3PTlybroc"]100,000[/ame] Note there are many factors that determine the life and failure mode of a capaitor! You can search for use of Electrolytic capacitors documents under the sites nasa.gov and *.gov to see some real info (often very technical). https://www.google.com/search?q=site:nasa.gov+electrolytic+capacitor+use+space+applications http://nepp.nasa.gov/files/20389/09_005_GSFC_Williams_Liu%20APC%20Final%20Report.pdf Basically, because of the short failure/deterioration mode for Electrolytic capacitors, they do not get used on satellites unless they are in non critical areas, can't crowbar the main/important power buses, or have an inline resistor to take the voltage drop and/or act as a fuse in case the capacitor fails. And, yes, I've been doing Defense electronic design for over a dozen years and Space for 8+ years. So, how does that make you feel about putting some POS CR*P CHEAP *SS high value capacitor inline with your battery on your hybrid car? Third: The use for a capacitor: You use a capacitor for local/close energy storage because in real life, wires have resistance (inductance, capacitance, etc). Also, in real life, it takes the electronic voltage regulator "some amount of time" to respond to an increase in current demand (let's say ~~1/20th sec so it's visible on any lights). So, for an automotive sound/electronic system, a local very close capacitor can help smooth over short high current demands by the circuit. It actually gets much more involved. For one thing, the speed at which the actual capacitor can deliver power/current to the actual circuit. Having a capacitor that's "too big" will limit how fast the current can be delivered. For a sound system, they have the smaller higher frequency capacitors inside the electronics. So, they might be aided by a slower, bigger, lower frequency capacitors that is right at the power input of the device. Again, I'm talking about real life devices and their proper use by a real engineer. I'm not talking about some BS propaganda by some company that's out their to make money off of people. I tried to avoid getting too technical, while at the same time, assuming that the people reading this are not 10 year old grade school kids. And, therefore they want some more real semi-detailed info, and not some hand waving BS. Good Luck!
