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165.21.155.13
In Reply to: RE: bank of capacitors posted by audioeyedoc on November 12, 2007 at 20:04:17
that's too much electrolytic capacitance to be in parallel with batteries.
If you leave them connected to the batteries, the leakage current will drain and damage the batteries over time, unless you leave the charger on at all times. The trouble is, you can't really be sure the charger will be on at all times 24/7 can you?
If you switch them in as and when, the large in-rush current over many duty cycles will stress and damage the switch contacts and the batteries over time, unless you implement some form of soft-start (initial charging through a resistor).
Follow Ups:
What size resistor should I use and would it be in series on positive leg for soft start?What would be the maximum capacitance you would recommend?Presently using SLA 12/18aH and will be switching to Optima yellow top or Odyssey PC2150 or PC1500.All are deep cycle low impedance car batteries.
Mike
a few ohms I guess. It's simple Ohm's law. For a 12V supply, a 12ohm resistor will limit the charging current to 1A. Use a high power resistor 15W, 20W or more. The resistor gets switched out of the circuit (shorted across with a manually-thrown switch or timer-based relay) after a couple of seconds. Note again this is necessary only for "huge" capacitor banks.
I don't see a problem with increasing capacitance, as long as you hard-wire the cap array between the terminals and just switch the battery back and forth between the charger and the application.
Like I said, if you can be sure the charger is always on 24/7 (no prolonged power outages, and no unplugging of the equipment to put aside even just for a few days), then it's fine to hardwire a huge electrolytics bank to the batteries.
Hi.
Up to 1F huge cap, size like a 2-litre bottle, are commonly used by car-amp lovers to top up the amp performance.
Let me quote an unbelievable enormous 'lytic cap consuming Hi-end intergrated SS amp: the Germany Hi-End Award winner: Emitter II Exclusive Battery model, made by ASR Audiosysteme, Germany. Probably the most expensive intergrated amp in the world now!
This SS amp used many many 'lytic caps in parallel, totally: 1,140,000uF
housed in a see-thru acrylic housing !! Weighting 32Kgs !!
Thess caps are for the different stages, powered by an outboard battery-bank/charger with 400,000uF filter cap bank to supply up to 200VA DC power to the integrated amp.
To answer the question: would too many 'lytic caps parallel slow down the amp? Here is the anwer: the rise time of this very very expensive
German made SS integrated amp is only 0.8uS.
c-J
I use a 100AH SLA battery with low 2 milliohm internal resistance to power a CDP that draws less than 1A. There was audible improvement after adding a large electrolytic cap array between the battery terminals, futher improvement after adding a second smaller electrolytic array inside the CDP, and improvement once more after placing .1uf teflon and .47uf film bypass caps at the chipsets. Film bypass caps by themselves are not enough with batteries. There seems to be no diminishing return on capacitance, even with a large battery powering a light load.
Hi.
Now you've tempted to try some large 'lytic caps with my SLA cells for my phonostage tube heaters as well as the batteries for my SS phonostage, as I have got already AC oil cap & film caps bypass.
c-J
I think you will be pleasantly suprised in the improvement.It took these about a week to sound their best but right off the bat-improvement is evident.
Mike
1. Car audio "stiffening" capacitors are designed with low leakage current in mind, usually based on carbon aerogel technology. They are not electrolytics.
2. You'll find that "big" amps that have huge capacitor banks implement some form of soft-start. Either timer-relay based switching-out of series resistor, or simply an NTC (negative temp coefficient) in-rush limiter for class-A amps, or tube rectifiers (the heating up of the filament provides the slow ramp-up) for tube amps.
Hi.
I hate to put any current limiter or even a serie resistor upstream of the tube heater circuit, maybe for sonic reason.
So instead of putting a resistive current limiter downstream of the SLA cell powering the tube heaters of my phonostage, I do it the tedious way.
I add a basic 6V AC-DC adapter, which I found sleeping for ever in my dump bin, & hook it up outboard to the phonostage so that I can pre-heat the tube heaters first with the 6V adapter, before the SLA cell kicks in. So the damaging surge to the cold heaters is eliminated, and the tubes will last longer (IMO, long enough already - these are the original 50-year vintage tubes came as stock with the phonostage.)
c-J
c-J
Therefore-would the smaller 680uf bank be quicker than the 1500mf bank-looks like it may-even if I double up on the 680mf(possibly not)in theory?
Mike
.
Rubycon ZL series.
HI.
Rubycon makes excellent 'lytic caps, including Black Gates which are considered by many tube/SS builders king of caps.
In fact, I've & am using wideband fastspeed 'lytic caps made by Rubycon for my tube HV filters: 80uF-160uF 330V. They all sound very fast & transparent.
Who said 'ltyic caps sound crappy ????
c-J
680mf bank 293760mf and 1500mf bank 378000mf!!WOW!!
Mike
Hi.
Since you already got both banks built. Just try them both & see if you could hear the difference. IMO, I doubt yu could.
c-J
I only have one 1500mf bank built for now.That's why I posted to get opinions on the matter.That's a lot of caps Granpa!!
Mike
Hi.
A cap in theory would be pure capacitive. But any realworld cap is a very complex AC network comprising series & parallel resistance DCR, inductance L & capacitance C. So by parallel multi caps, the resultant impedance of the cap bank would be reduced due to reduced internal DCRs & inductances vs a single cap of same size.
If an amp with 1.4 million uF 'lytic caps in parallel can give 0.8uS rise time as I posted above, why you worry?
c-J
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