alternator rpm question?
08-03-2006, 10:51 PM
#1
Honda-Tech Member
Thread Starter
Join Date: Apr 2003
Posts: 2,550
Likes: 0
Received 0 Likes
on
0 Posts
alternator rpm question?
Today a friend and i were talking about alternators/charging systems becuase of a delima i am having with space in my car and both brought up an idea.
Its a given that once an alternator produces 14.4 volts (give or take a tenth or so) the voltage regulator kicks in and doesn't allow any more voltage to be produced. What rpm this voltage is produced depends on the load that is put on the charging system. Well charging system tests are usually done at around 2k rpm and this is usually when the system will put out around 14.4-14.6ish volts varying on vehicle and load.
So the idea is this, If an alternator was always spun at a constant rpm (say 4k rpm) while a car was running, would it be able to keep up withthe demands of the cars electrical system?
In short i'll explain my situation. h-series in a dc2 chassis+ bigturbo=very very limited space for alternator and alternator belt routing. So i was thinking of hooking up an electric motor that would hold a consistant rpm (around 4k i figured to be best) so that it would charge plenty at idle, and would be spun fast enough so that it could keep up on multiple gear pulls.
Because it pretty much comes down to that i don't have space for an alternator without it being placed in an area that it would have to withstand mass amounts of heat (from the manifold). which means i would have to replace it all the time. which isn;t logical. i'm looking for any alternatives to driving the alternator off of the motor pretty much
any ideas, suggestions, thoughts?
Its a given that once an alternator produces 14.4 volts (give or take a tenth or so) the voltage regulator kicks in and doesn't allow any more voltage to be produced. What rpm this voltage is produced depends on the load that is put on the charging system. Well charging system tests are usually done at around 2k rpm and this is usually when the system will put out around 14.4-14.6ish volts varying on vehicle and load.
So the idea is this, If an alternator was always spun at a constant rpm (say 4k rpm) while a car was running, would it be able to keep up withthe demands of the cars electrical system?
In short i'll explain my situation. h-series in a dc2 chassis+ bigturbo=very very limited space for alternator and alternator belt routing. So i was thinking of hooking up an electric motor that would hold a consistant rpm (around 4k i figured to be best) so that it would charge plenty at idle, and would be spun fast enough so that it could keep up on multiple gear pulls.
Because it pretty much comes down to that i don't have space for an alternator without it being placed in an area that it would have to withstand mass amounts of heat (from the manifold). which means i would have to replace it all the time. which isn;t logical. i'm looking for any alternatives to driving the alternator off of the motor pretty much
any ideas, suggestions, thoughts?
08-04-2006, 02:58 PM
#2
Honda-Tech Member
Join Date: Aug 2004
Location: Sterling Heights, MI, USA
Posts: 2,006
Likes: 0
Received 4 Likes
on
3 Posts
Re: alternator rpm question? (b16hybridsol)
The electric motor will eat up more power than your alternator will produce. And then you also have to feed the car's electrical system....
08-04-2006, 07:58 PM
#3
Re: alternator rpm question? (02 accord)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 02 accord »</TD></TR><TR><TD CLASS="quote">The electric motor will eat up more power than your alternator will produce...</TD></TR></TABLE>EXACTLY!
08-04-2006, 10:18 PM
#5
Honda-Tech Member
Join Date: Aug 2004
Location: Sterling Heights, MI, USA
Posts: 2,006
Likes: 0
Received 4 Likes
on
3 Posts
Re: alternator rpm question? (b16hybridsol)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by b16hybridsol »</TD></TR><TR><TD CLASS="quote">i can't see a small 12v motor pulling anymore than like 10-15 amps. </TD></TR></TABLE>
A small 12v motor that pulls 15 amps will not put out enough torque to drive your alternator.
Side note: as you increase the load on the alternator, it gets harder to drive.
Why don't they use small 25cc weedeater motors to drive 1 kw generators? Not enough torque. Look here: http://www.lowes.com/lowes/lkn...=none. 8kw generator, 15 hp.
Your small motor:
12v * 15a = 180 watts
180 watts/746 watts = 0.24hp.
Comparing engine power to output power:
15hp/.24hp = 8kw/x
x = 128 watts
128 watts / 12v = 10.7 amps.
So according to this simple example (just picked a random generator for numbers), your alternator will put out 10 amps while the motor driving it will pull 15. I don't see how this will work.
If it was possible to run a generator off an electric motor (generator powers the motor) and still have power left over, we wouldn't be burning up fossil fuels to produce power, would we?
Modified by 02 accord at 2:46 AM 8/5/2006
A small 12v motor that pulls 15 amps will not put out enough torque to drive your alternator.
Side note: as you increase the load on the alternator, it gets harder to drive.
Why don't they use small 25cc weedeater motors to drive 1 kw generators? Not enough torque. Look here: http://www.lowes.com/lowes/lkn...=none. 8kw generator, 15 hp.
Your small motor:
12v * 15a = 180 watts
180 watts/746 watts = 0.24hp.
Comparing engine power to output power:
15hp/.24hp = 8kw/x
x = 128 watts
128 watts / 12v = 10.7 amps.
So according to this simple example (just picked a random generator for numbers), your alternator will put out 10 amps while the motor driving it will pull 15. I don't see how this will work.
If it was possible to run a generator off an electric motor (generator powers the motor) and still have power left over, we wouldn't be burning up fossil fuels to produce power, would we?
Modified by 02 accord at 2:46 AM 8/5/2006
Thread
Thread Starter
Forum
Replies
Last Post