5 ch. twin amp system w/ power cap HELP

[Nick Read]

The cheapo 1.5 farad power cap (with digital voltmeter) that I got off ebay has finally arrived, incl instructions, and their wiring diagram looks a bit weird but seems to just about make sense. Basically Im hooking up a 5 channel amplified system, one 4 channel amp running the fronts and rears, and a monoblock running the sub. So I need some advice on the power wiring really, signal wiring is no problem.

Anyway, after a bit of sketching on the back of an envelope my circuit diagram is looking like this...I wonder if any of you out there could just take a peek at it and check that it sounds right to you:

Positive feed (4 gauge) from battery to power cap + terminal.

Positive feed (4 gauge) continues on from + terminal of cap to distribution block.

Pair of fused 8 gauge positive feeds go to the + terminal of each amp.

Individual earthing cables from neg terminal of power cap (4 gauge) and both amps (8 gauge) to common chassis ground.

Main 4 gauge battery cable fused in the engine bay but final amperage not decided yet - 80 A? Distributor block in boot has 60A and 40A fuses to protect wiring (max current draw from amplifiers 43 and 29A respectively)

So what do you lot reckon?

 

[Dink]

yeah that sounds right to me

(apart from the use of the power cap, but i wont go into that)

 

[MaLicE]

have the battery feed coming in to the car in to a dist block, have 1 wire going to poss of the cap and others going to amp... u can have 1 feed going to amp then daisy chain the power from the amp to the other amp if u just have a 2 way dist block, maplin etc sell some 2 and 4 way i think fused dist blocks...

just looks tider than 2 wires going to the cap... and have all the grounds going to 1 point not more than 1 if u get what i mean otherwise u may get interfearance...

 

[Dink]

im lost MaLicE

it sounds better the way nick was going to do it IMO

 

[Pete]

Its right how youve got it Nick.

 

[Nick Read]

Sounds like thats all OK then. I might fiddle with the layout of the cap like what Malice said, running the main feed down to the distribution block rather than the cap and then having another line out of the side of the block to the cap, just for the sake of neatness. Electrically it should be exactly the same. Think Ill leave the power feeds to the amps as two totally separate lines from the block rather than daisy chaining though.

Dink whats wrong with using a power cap? Never used one before, just thought that now Im using a fairly hefty monoblock amp for the sub, it might be worthwhile to save caning the battery if I whack it right up occasionally? Whats the downside of using one?

 

[Pete]

Just remember theyll be slightly more load on the cable by doing it Malices way.

 

[Dink]

say you get 6 bass kicks in 3 secs

the cap will help with the first(output power to the amp) but hinder the other 5 (take power away cos it will need charging)

 

[audio one]

Always good to see people have seen the waste of money that power caps really are... good man dink.

Nick, best think of power cap as another amp that is just another current draw on your alternator.
Your money would be better spent on a good battery and upgrading under bonnet cabling.. i.e alternator to battery etc

Paul
www.audio-one.co.uk

 

[Nick Read]

Very interesting. Well if I tee it off from the distribution block then I can try the system with or without the cap in the circuit, by just undoing one wire. Ill get my alternator checked out anyway.

I only got the cap because it ended up at £15 on ebay LOL

 

[MaLicE]

seeing as your using 4 gague yeh using 1 wire to the cap instead of 2 will draw more load, however its a 1.5 farrad and its 4 gague wire... u aint gonna be cooking ne thing on it.... btw if u looking for cable go to a welding supplies shop can get 0 gague cable at about 30 quid for 5 meters in red and black, alot cheaper than the 100 quid for 3 meters most audio shops supply

 

[Nick Read]

Yeah I hear what youre saying about cost. This time of year its a nightmare getting stuff cheap, cos trade places are shut and you end up having to go to Halfords. Bloody crooks. In the end I found a Maplins and they sell exactly the same stuff for a quarter of the price. Got the 5 metres of 4 gauge for about £15. Plus got all the fancy bits like gold plated distribution blocks, fuseholders, ring terminals etc for a few pounds each and theyre identical to the branded ones that cost the earth.

Example Maplin Shark brand 2 way fuseholder/distribution block in plastic housing, 3x4 gauge in, 2x8 gauge out: £3.99. Halfords Autoleads identical part: £20.99

Example 2: Maplin own brand 4 gauge gold plated ring terminals, 1 black sleeved, one red sleeved: £0.99. Halfords identical product £4.99.

Its actually almost criminal how much profit Halfords must make on this stuff.

 

[Bryan]

all is correct nick

thats how ive wired up systems before, and never had one issue

 

[MaLicE]

i got all my distribution blocks and fuse holders from maplins too, not bad on prices, just recently been thinking of upgrading my 4 gague wire to 0 gague as i have the battery in the boot also, but besides the cable which i can get fairly cheep its the distribution blocks that cost a bundle, i wouldnt mind just running it diect to the battery with an inline fuse but the cheapest 0 gague fuse holders i can find are 30 quid lol, i refuse to pay 30 quid for a friggin fuse holder !

 

[Nick Read]

Well in the end even though I could find 80A AGU fuses exist, I couldnt find anywhere to get them from, 60A seems to be the max I could get. Plus my existing AGU fuse holder only takes 8 gauge and not 4 gauge so Id have to get a new one of those. In the end I just ordered a 100A circuit breaker to do the job...100A will protect the wiring running through the car and then the fuses in the boot will handle the short runs of 8 gauge running to each amp.

The only other thing that Im really thinking about now is the alternator and its wiring. I think that the alternator on my VW is a 65amp job, Ive just put in a brand new battery as well. Ive not checked my alternator output but I suspect that unless it was changed recently its probably not at its best after 20 years of service.

Can I just do a simple voltage check across the terminals of the alternator to see what its producing at idle? If so, what am I looking for? I reckon 12v or less means its knackered; 13v will be adequate, 14-15v would be pretty good. Can someone confirm if this is right?

But even if its actually working, a 65A alternator is surely just designed for the maximum load the cars electrics will draw? So once Im also running an ICE system with 2 amps that could draw 72A max with (or without) a 1.5 farad cap as well, its gonna need an uprated alternator? I think I can get a 90A alternator in there or even a 120A but apart from the initial cost, are there any downsides to bigger alternators, i.e. will they knacker my battery up, will they be harder for the engine to run?

 

[Dink]

i think you will be fine with the alt (if its in good working order)

ill be running a 100A amp in the back of mine soon im sure i wont kill the batt if im careful