Very high output alternator (200A+)

[nightfire]

Hi everyone,

So I've been defrauded now twice while trying to order A/C parts from two people here. If you're reading this .. I hope you feel bad.

Anyway, I'm giving up on that route, and I'm going to try to build a Peltier solid state A/C unit. I just ordered some 500W stacks from ebay, and I've already got some massive heat sinks and fans ready. I figure that at 1500W (just over 100A @ 13.5V) I should be able to make enough cold air to at least keep the temperature bearable in the summer. Assuming 33-50% efficiency that should have the cooling effect of around 5000-7500BTU/h, which should be sufficient.

I plan to put the whole thing in a box where the normal A/C unit is supposed to go and run some water exchange hoses to a front mounted radiator.

The immediate problem, obviously.. is where do I get the power from?

I know very little about alternators, other than it's a motor and a rectifier. Does anyone know what's involved in upping the maximum current handling capacity to something insane... like 200+ amps? I know there are 140A alternators out that but that just won't cut it. My carputer and amps alone draw between 15-20A constant (core2 duo @ 3.6ghz), so with lights, ECU, blower motor, engine fan, etc... I'll easily draw a nominal 150A.

I googled around but didn't find anything specific.. does anyone make a generic kit (or better yet one for our alternators) that might help? Or is it just a matter of upgrading the rectifier and caps? Will the stock windings handle the load? Also, do I need to worry about alternator belt strength? If I tighten it enough so that it doesn't slip, is it likely to snap?

[Ryan]

You could go talk to an Alternator shop, I know people have had them rewound upto 120A. See what they can do...

[Daninski]

The guy at a shop here was going to up mine to 160 amps for about $160 bucks. I asked to only have it upped to 120 amps as the more amps you go with the more power it takes to drive the alt.

As a side note I went to pick up my alt and the shop is closed, out of business and my alt is gone. I knew I shouldn't of waited 3 months to go get it. lol

[wytbishop]

Dan makes a good point. Every bit of energy you take from the charging system costs you energy from the crankshaft. I actually thing that a 200A alternator would probably cause problems with the engine. It would take an enormous amount of power to drive an alternator that large.

[nightfire]

Sure, under full load. But it can't be any worse than an A/C compressor. Even at 200A, assuming 50% efficiency (and it's gotta be better than that) we're still only talking ~6-8hp. I imagine A/C's gotta be ~10.

[Ryan]

AC is 20, rule of thumb. Ever thought of a AC mounted alty? haha...

[wytbishop]

Well I'm not doing any calculations or anything (I hated electrical/power engineering) but I can say that upgrading from a stock 90 to 110A alternator is noticeable so going from 90 to 200A would be very very noticeable.

[Ryan]

So, it seems like a bust idea.

Go the Jesse way and start thinking about running a little gas generator in the back seat

[wytbishop]

I'd be interested to know how many amps those competition stereo guys run with their multiple alt set ups and if you can even drive those cars with all the alternators turning.

[Daninski]

Hijack;

Ok, I went to boost start a friends car. The battery was dead and the alt was not putting out any volts (I found out after) so, as I was trying to boost start the car and it kept dying the booster cables were getting hotter and hotter then my coolant starting flowing out of the overflow reservior. I've had no problems since so I've surmised the alternator load caused the engine to over heat. Does this sound right? As such could a heavily loaded alt cause an engine to run hotter?

[nightfire]

Not for a properly functioning engine. An A/C will load up the engine as much or more than a 300A alternator, let alone a 110A one. Hell.. just the friction in the engine probably loads in excess of a 10HP at idle.

I'm not worried about the alternator causing the engine to stall (even at full load). The IAC will certainly have enough control to keep the engine at a reasonable idle. I'm more worried about the belt. :/

[Daninski]

Excellant sumassion Sherock but as we already know a vehicle with A/C has and extra radiator fan so. Will an engine with an overrated alt (assuming your drawing load from it) need to have additional cooling. My question remains; why did my engine over heat when the alt was being asked to max out during that boost? Anyone?

[nightfire]

Excellant sumassion Sherock but as we already know a vehicle with A/C has and extra radiator fan so. Will an engine with an overrated alt (assuming your drawing load from it) need to have additional cooling. My question remains; why did my engine over heat when the alt was being asked to max out during that boost? Anyone?

That extra radiator isn't for the engine.. it's to cool the freon from the A/C. And no way it'll need additional cooling; that radiator is good enough to cool the engine running continuously at full load, so the only question is airflow... and the fans are quite strong. So I still doubt it.

[Inodoro Pereyra]

Daninski: Nightfire is right. The car doesn't have an additional radiator. That's the A/C condenser, and it actually hinders (when the A/C is in use) engine cooling (being that it heats up the air right in front of the radiator), so if you get rid of it, your issue would probably be the engine overcooling, not overheating.

Nightfire: I hate to be the bearer of bad news, but, as far as I know, Peltier chips have an efficiency of 5 to 10%, and that's 5-10% of an ideal refrigerator's CARNOT NUMBER, not its electrical consumption.

[Daninski]

Correction. I meant to say vehicles with AC have an extra fan. I know the front 'rad' is the condensor so my appologies for misstating my question. Anyone care to comment, I'm still curious why my engine over heated while trying to boost a friends SUV.