cap w/digital voltage display

It cannot be denied that when a cap charges, it places load on the electrical system equal to the amount of charge it can store.  It also cannot be denied that any cap will discharge its stored energy when system voltage drops.  The amount of energy that can be stored by even the largest caps is only sufficient to compensate for minor fluctuations in system voltage, so they do help eliminate voltage ripples and provide instantaneous surge capacity for amplifiers, and they can discharge at much faster rates than any battery.  This is why caps are used in all amplifier power supplies.

There is no way to supply long-term (more than one second) power to an amplifier or any other electrical system using capacitors unless they are very large indeed.  But they do have a place in all audio systems.

As to the OPs question concerning using the cap-top voltage meter in some other location, as long as the connections are made safely there is no reason why it wouldn't work.  But as other people have suggested, there are far better solutions that you wouldn't have to ghetto-rig if all you want is a voltage display on your dash.

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ghetto-rig lmao, that pretty much sums it up, that would make a gd sig i was just tryin to put it use it, lites up the inside of my car bright blue an im not really into the brite lite type stuff, imma try an come up with something a little creative for a mount nothin too ghetto lol my 90 amp alt is puttin out its max with both my amps , at least i hope it is, so imma go capless for now thanx every one for all your input1000 watts of lp, now need sum hp an mids

Sorry for the bump, but guess who just installed a new alternator on floridaSPL? Geez (pun intended), all that bashing for nothing. And I'll bet caraudio won't be thanked. But it was good seeing some talented repliers - those Tasmanian Devils are smart. But I like the comment that an alternator "is for the rich kids". Funny, but here an alternator is almost cheaper than a battery. But with the prices I have seen stateside, even an expensive alternator will be cheaper than multiple batteries in the long run (ie, after a few battery replacements). Also, I and J (teenkertoy) and I have exchanged a few PMs. (Multi-discipline & short as usual LOL! Yep, another "sticky" with basic system and design principles.) I explained that I was replying to the "cap (or battery) adds an extra load" which I look at from the overall POV. teenkertoy referred to "energy" (in his second last post in this thread) as I was doing from the overall wasted energy POV, and that of overall strain or load on the alternator. (Not that alternators should strain per se.) But sthrnbmpn, IMO you are doing the right thing having a dash voltmeter. I find it amazing that people ask if they need a bigger alternator for their loads when a dash voltmeter will indicate that. Plus it's a nice way to monitor the state and condition of your battery AND electrical system. Just make sure you wire it across the battery, both poles. Mine is simply relay switched by the ignition, but I'm working on mum's voltmeter which currently has a 3-way switch for Ignition, off, and momentary on. I'm adding a timer so that for both IGN and momentary on, there is a (say) 1 to 3 minute delay before the voltmeter relay turn off.   (The momentary on is to display voltage at any time - not IGN key required.)

(The momentary on is to display voltage at any time - not IGN key required.) that would be real conveniant, is it a simple type circuit? i got relays down pretty gd , but momentary on , imma study up on that one sumthin about push buttons, intersts me1000 watts of lp, now need sum hp an mids

A present it's a 3 position switch - on-off-momentary_on (ie, spring return to the central off position) - a not uncommon mini-switch. I use a small relay whose coil is about 1k Ohms. The switch & relay and voltmeter are housed in a dash blanking plate - just a quick prototype a this stage.       I'm intending to use a MOSFET for the delay, but I need to get a round tuit first. (A round tuit in not a uniquely Aussie expression is it?) And I have until September to complete the job, so it should be done by 2112 (no - not 2012!). I should do that after I replace my faulty alternator (no charge lamp since February) and add MOSFET to buffer my UIBI relay (battery isolator).

ok now i feel kinda noobish again, i know what a momentary on is its just that u made it sound real hi tech an i had a blonde moment an couldnt picture it, lol i can make this happen thanx old spark for the ideas, i dont really want the volt meter to be on everytime the ign is on, just whenevr i wanna check it out 1st position is closed, 2nd position is open an 3rd is momentary now i feel smart again1000 watts of lp, now need sum hp an mids

You always were smart - you want a voltmeter! How many people wonder if their alternator is big enough or they require a priority charging battery isolator (LOL - a bit of a joke, but I just posted elsewhere about WHY have them anyhow - if they did exist!), yet do they have a suitable voltmeter? I think that's why caps have voltmeters - make the user think they have a voltmeter, but make sure it isn't in the dash so that they can see what actually goes on... That way they think they are ok but are really none the wiser. Maybe I should post a pic of my (mum's) meter and switch assembly.... The switch might be this one... from Altronics Switch Mini Toggle SPDT Centre Off Mom; noting that it is On-off-mom not mom-off-mom where mom is ON but spring loaded to return to center - the other positions are latching (or stay in place or whatever "not spring loaded" is - I don't want to use the term "locking" - that's another switch!) Although the switch could switch the voltmeter direct, I used a relay to ensure I had the BATTERY terminal voltage at the voltmeter. Hence the circuit is batt- to relay coil ground (#85) and voltmeter -ve, voltmeter +ve to the NO relay contact (#87) and batt+12V to the Common relay contact (ie, #30) and the momentary switch contact, and whatever "ON" source like IGN or ACC +12V to switch ON contact. The common switch contact goes to the relay coil+ (#86). (Not that I've used a HUGE relay with those terminal labels!) I intend to have the switch-common feed a cap & FET that keeps the relay turned on after it is switched off. The relay coil is ~1kOhms but even then, I prefer a small cap with a FET or transistor to control it.    But that delay circuit is a "cut & insert" that can be added any time withing the next few centuries. (Unless it's not that urgent in which case I'll relax a bit more....) Yeah... maybe a pic, and a circuit....?

so after posting this ive really been doin alot of thinking on this subject, an the term gheto-rigged is the whole goal of my switch/meter install i also have a amp fan wired to a switch under my seat an i was thinkin i could use a clean looking switch bank for accy's. such as meter, fan. so yes pics would help . my post count should be up hi enuff to were i can post sum pics also1000 watts of lp, now need sum hp an mids

sthrnbmpn wrote:  ...my post count should be up hi enuff to were i can post sum pics also

  All active members regardless of post count can upload images. the12volt • Support the12volt.com

what do you think ol spark ineed a way to mount in my ashtray or just buy a voltmeter, its just not doin anything sittin on my parts shelf1000 watts of lp, now need sum hp an mids