Simple BIG 12VDC supply ideas wanted

[MadMutt]

Freind has a car audio 'demo board'.
Has been running it off car batteries (with charger) for a while.
I don't believe this is the best idea as he goes through two batteries a year.

He needs a supply (12-14VDC) capable of around 30-50 amps.

I'm thinking a simple unregulated (transformer, bridge rectifier, filter cap) would be fine.

Yes a regulated supply would be better, but at those currents suitable transistor arrays would be expensive.

Is a regulated supply feasible for this current demand ?

No I don't want a switched supply (output noise).

Your thoughts are welcome.

[star882]

Output noise shouldn't be a problem. An automotive electrical system is very noisy.

I suppose if all else fails, you could have an AC motor spinning an alternator.

[MadMutt]

I agree, cars are extremely noisy (electrically).
Hadn't thought of the motor driven alt.
Power wastage doesn't appeal to me though.

He does have one high current (15 A cont.) supply.
It was 'built' by someone with not many brain cells though.
It runs ultra hot and is not really protected at all.
17VAC trans --> bridge --> 10,000uf --> LM317 with two pass transistors.
The design is lifted straight from an application sheet.
So the reg/pass section is dissipating 12 volts to start with.
At a draw of 10A (normal drain) the poor thing is frying in it's tiny case.
The heatsink is barely big enough to mount the three TO3 trannies.

Hence why I'm trying to get him to let me build a proper supply.

I can design/build a regulated supply if he springs the $$$.
Just wondering if anyone has a better sugestion.

Must be as close to short term abuse proof as possible.
He aint always considerate of equipment

[head_spaz]

This is taken directly from National's LM338 data sheet.
This might be worth consideration. It's modular design
lends itself well to scaling.

Anything worth doing, is worth overdoing.



Cut to shape, file to size, pound to fit.

[Notagenius]

i have a shortwave radio supply which is 20 amps continuous, 24 peak. you could clone one of those.

i've tested a car amp with a battery charger. there was a slight hum vs the clean sound of the regulated one. btw, deep cycle batteries would have worked better.

[longthrow]

[QUOTE]Originally posted by MadMutt
[B]
No I don't want a switched supply (output noise).

hi,
a filter is not a problem.
car audio amps already have suppressors.


[QUOTE]Originally posted by star882
[B]Output noise shouldn't be a problem. An automotive electrical system is very noisy.

indeed!..the alternator itself is noisy..


check this out: http://www.meanwellusa.com/search/usp-500/default.htm

i have a mean well rated @ 25A running my car amp for almost 2yrs now w/o any probs..

[Eva]

Originally posted by MadMutt

No I don't want a switched supply (output noise).

You already have one or two switching mode power supplies inside every car audio amplifier so who cares...

[dukep]

Is this supply used for both head units and amplifiers?

Perhaps using the regulated unit for the cd decks. Likely more sensitive to 12v noise.

use the dirty unregulated for the big amps. My supply is unregulated but has 30,000uf in caps to supply power to an amp. For really big amps, a battery is a must to handle the peak amps.

I like the alternator idea. You can get alot of amps cheaper.

[Stuart Easson]

...probably a 50amp car charger/starter with a battery in parallel, huge peak current capacity, but will supply 10-15 amps all day, total cost < $100.

If more average current is needed, parallel another charger. The only obvious drawback is the physical space required to hold the equipment.

HTH

Stuart

[djQUAN]

http://sound.westhost.com/project77.htm