Charging system gurus, help with dual alt wiring
02-24-2006, 01:57 PM
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Charging system gurus, help with dual alt wiring A buddy and I fabbed up some brackets to run twin alts in my truck (still have only one battery), and now I have some questions that some of you can hopefully answer. I have the output posts wired in parallel, I have one alt running off the PCM. For the other, I took a switched ignition wire and ran it through a test light then to the L terminal. The PCM sees one alternator working as it should, hooked up to both F and L terminals, and the second one runs fine independent of the other. The PCM is not throwing any codes, and the test light illuminates when the ignition is on but the engine is not running, and goes out (as it should) as soon as the motor starts. Both alts are 140 amp Delphi units (same part number even) out of the newer trucks.
Here's where it gets tricky. I am not sure that both are running at the same time, and here is why. When I hook up a voltmeter to the battery posts, I see 14-14.5 volts when everything is all warmed up. Now, when I unplug the connector from the PCM-monitored alternator, nothing happens to the voltage, which is what I expected. The other alt is still running and should maintain the voltage, and it does. No problem there.
Start again with both alts plugged in. Now when I pull the connector off the independent alternator, the voltage drops to 13 or so and I can hear the engine bog as the PCM-monitored alt kicks in, then after a second or so the voltage will come back up to 14+. I have tested the voltage on the L-terminal wire on the PCM connector when the independent alt is running, and it is 12v, so it seems like both should be on all the time, but I have a feeling that only one is running at any given time. I don't know if there is some strange interaction between the two or what, and I don't know how to test them independently when they are both hooked up to see if they are both sharing the electrical load from the system.
Is there anyone that has experience with this kind of thing, or can give me some ideas for testing or whatever? My understanding is that the way I have it hooked up is technically correct, but I think there's something that I am missing.
Here's some pics
Here's where it gets tricky. I am not sure that both are running at the same time, and here is why. When I hook up a voltmeter to the battery posts, I see 14-14.5 volts when everything is all warmed up. Now, when I unplug the connector from the PCM-monitored alternator, nothing happens to the voltage, which is what I expected. The other alt is still running and should maintain the voltage, and it does. No problem there.
Start again with both alts plugged in. Now when I pull the connector off the independent alternator, the voltage drops to 13 or so and I can hear the engine bog as the PCM-monitored alt kicks in, then after a second or so the voltage will come back up to 14+. I have tested the voltage on the L-terminal wire on the PCM connector when the independent alt is running, and it is 12v, so it seems like both should be on all the time, but I have a feeling that only one is running at any given time. I don't know if there is some strange interaction between the two or what, and I don't know how to test them independently when they are both hooked up to see if they are both sharing the electrical load from the system.
Is there anyone that has experience with this kind of thing, or can give me some ideas for testing or whatever? My understanding is that the way I have it hooked up is technically correct, but I think there's something that I am missing.
Here's some pics
02-24-2006, 06:33 PM
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I just checked it out again and played with some different configurations. The PCM vs independent control doesn't seem to make a difference. I get the same thing when I swap the plugs on the alts, and it's always the inside alt (furthest from the battery) that seems to be off until I unplug the outer one. I turned on some loud-*** music to get a good load on the alt, and when the bass hits really hard the engine RPM fluctuates as the inner alt starts up due to the voltage drop. It's clear to me that the inner one will not turn on until the voltage of the entire system drops to around 13.5 volts or less. I also experiemented with removing the PCM completely from the equation (running both through their own test light), and it's still the same.
02-24-2006, 08:00 PM
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First of all I would like to say nice job on fabricating the brackets and installing the dual alternators, you made a very clean install. I have never heard of anyone trying to run automotive generators in parallel nor do I have any experience of my own with this,
but it sounds as if one voltage regulators is "kicking in" at a higher voltage threshold than the other due either to the line voltage that it is sensing or because of manufacturing tolerances at the factory. It seems like you are doing this to provide your sound system with enough power to wake-up your neighbors over in Flagstaff.
If so, maybe you should install that second battery, keep it charged with your second alternator, isolate it from the rest of the trucks electrical system and use it only to run the sound system.
You would want to be sure that every thing is properly fused, and you might even want to install a relay that would allow you to turn it on and off with the key switch.
OR
You could just get a larger (single) aftermarket alternator.
Just a couple of ideas, because I think you are going to have a very difficult time getting the two internal voltage regulators to properly share the load.
but it sounds as if one voltage regulators is "kicking in" at a higher voltage threshold than the other due either to the line voltage that it is sensing or because of manufacturing tolerances at the factory. It seems like you are doing this to provide your sound system with enough power to wake-up your neighbors over in Flagstaff.
If so, maybe you should install that second battery, keep it charged with your second alternator, isolate it from the rest of the trucks electrical system and use it only to run the sound system.
You would want to be sure that every thing is properly fused, and you might even want to install a relay that would allow you to turn it on and off with the key switch.
OR
You could just get a larger (single) aftermarket alternator.
Just a couple of ideas, because I think you are going to have a very difficult time getting the two internal voltage regulators to properly share the load.
02-24-2006, 08:26 PM
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Originally Posted by Fireberg
First of all I would like to say nice job on fabricating the brackets and installing the dual alternators, you made a very clean install. I have never heard of anyone trying to run automotive generators in parallel nor do I have any experience of my own with this,
but it sounds as if one voltage regulators is "kicking in" at a higher voltage threshold than the other due either to the line voltage that it is sensing or because of manufacturing tolerances at the factory. It seems like you are doing this to provide your sound system with enough power to wake-up your neighbors over in Flagstaff.
If so, maybe you should install that second battery, keep it charged with your second alternator, isolate it from the rest of the trucks electrical system and use it only to run the sound system.
You would want to be sure that every thing is properly fused, and you might even want to install a relay that would allow you to turn it on and off with the key switch.
OR
You could just get a larger (single) aftermarket alternator.
Just a couple of ideas, because I think you are going to have a very difficult time getting the two internal voltage regulators to properly share the load.
but it sounds as if one voltage regulators is "kicking in" at a higher voltage threshold than the other due either to the line voltage that it is sensing or because of manufacturing tolerances at the factory. It seems like you are doing this to provide your sound system with enough power to wake-up your neighbors over in Flagstaff.
If so, maybe you should install that second battery, keep it charged with your second alternator, isolate it from the rest of the trucks electrical system and use it only to run the sound system.
You would want to be sure that every thing is properly fused, and you might even want to install a relay that would allow you to turn it on and off with the key switch.
OR
You could just get a larger (single) aftermarket alternator.
Just a couple of ideas, because I think you are going to have a very difficult time getting the two internal voltage regulators to properly share the load.
heres a similar set-up, thought you might be interested
02-25-2006, 12:57 PM
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Originally Posted by Fireberg
If so, maybe you should install that second battery, keep it charged with your second alternator, isolate it from the rest of the trucks electrical system and use it only to run the sound system.
You would want to be sure that every thing is properly fused, and you might even want to install a relay that would allow you to turn it on and off with the key switch.
You would want to be sure that every thing is properly fused, and you might even want to install a relay that would allow you to turn it on and off with the key switch.
02-27-2006, 12:14 AM
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I really don't want to run 2 batteries...I'm sure there's a way to do what I want to do, but whether or not I have the right equipment is another matter. Can anyone explain to me exactly how the regulators work, input voltage on L terminal, PWM output on F terminal, interaction between either of those and output voltage, etc etc?
Electrical draw: 2500 watts RMS stereo, electric fans, offroad lights. I hate it when the voltage drops when the fans kick in, and during the summer with the a/c on at night, at idle in traffic, or whatever, I know I'm loading up the single alt pretty high, and I want to make sure that I have plenty of output all across the board. Matt, I have seen pics of that setup, Steve Meade I believe....I'll have to send him a PM and find out how he wired up the connectors. Thanks for the feedback so far guys!
Electrical draw: 2500 watts RMS stereo, electric fans, offroad lights. I hate it when the voltage drops when the fans kick in, and during the summer with the a/c on at night, at idle in traffic, or whatever, I know I'm loading up the single alt pretty high, and I want to make sure that I have plenty of output all across the board. Matt, I have seen pics of that setup, Steve Meade I believe....I'll have to send him a PM and find out how he wired up the connectors. Thanks for the feedback so far guys!
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02-27-2006, 12:23 AM
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BTW...the reason I decided to go with 2 alts is to get plenty of current at idle. It seems like the higher you go with an aftermarket, the more you give up at idle. I have a 180 amp aftermarket one sitting in my garage, but it won't maintain voltage at idle. I don't want to give up my idle capacity. I believe the factory 140 amp units are rated at 100 amps idle, 140 peak. That would give me 200 amps at idle, 280 peak.
03-04-2006, 11:45 PM
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how the hell are you running 2500 RMS? if you are running this all the time you need to look into some sort of ear protection, hah...
that aside, the stock computers only draws what it needs from the system and the 14.4/12 volt regulator only takes what it needs and the way its wired currently in parallel that is won't allow for more voltage...hope that makes sense
Here is what I did..Im going to keep running the stock alt. and got 2 batteries and a relay that will not allow the truck battery to take any load from my system asside from what the truck needs (inc. the HU) now both my amps are running off of a red top (b/c the discharge/recharge faster than a deepcycle) any system is not always at max or even RMS wattage usage 100% of the time, and if it were w/ the volume up at a level to really drain that system all the time I would be deaf or have serious hearing damage.
But this way the alternator works @ the same duty and charges both batteries normally pushing more current to the second battery b/c thats where a majority of the drain is...the ecu dosn't really know the second battery is there and this seems to be the best system for me...
the only way I can think of getting both of your alts. to work at their potential for that rpm is to run the sec. alt straight to the amps w/ a few fuses in the way also but im not sure how that will really affect the amp? I would assume that you would need the posweline from the battery also ?? I dunno
but long story short w/ the 2 alts and the way its currently wired it is only going to pull what it needs for power requirements...
that aside, the stock computers only draws what it needs from the system and the 14.4/12 volt regulator only takes what it needs and the way its wired currently in parallel that is won't allow for more voltage...hope that makes sense
Here is what I did..Im going to keep running the stock alt. and got 2 batteries and a relay that will not allow the truck battery to take any load from my system asside from what the truck needs (inc. the HU) now both my amps are running off of a red top (b/c the discharge/recharge faster than a deepcycle) any system is not always at max or even RMS wattage usage 100% of the time, and if it were w/ the volume up at a level to really drain that system all the time I would be deaf or have serious hearing damage.
But this way the alternator works @ the same duty and charges both batteries normally pushing more current to the second battery b/c thats where a majority of the drain is...the ecu dosn't really know the second battery is there and this seems to be the best system for me...
the only way I can think of getting both of your alts. to work at their potential for that rpm is to run the sec. alt straight to the amps w/ a few fuses in the way also but im not sure how that will really affect the amp? I would assume that you would need the posweline from the battery also ?? I dunno
but long story short w/ the 2 alts and the way its currently wired it is only going to pull what it needs for power requirements...
03-04-2006, 11:46 PM
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if i confused you more send me an email @ justin073@mac.com b/c i don't check these boards as often as i should
03-06-2006, 01:02 PM
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Nah I don't run it all the time, but that's the potential. I just like to play overkill so I don't have to worry about running out of power.
But....I decided that I am not gonna be able to do what I want without a significant investment of time, research, and money, so I am gonna go back to a single 145 amp alt and call that good enough. Thanks for the replies....
But....I decided that I am not gonna be able to do what I want without a significant investment of time, research, and money, so I am gonna go back to a single 145 amp alt and call that good enough. Thanks for the replies....
03-06-2006, 06:24 PM
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Not really, but I think most guys who are making power have 1-wire alternators. I don't think the factory stuff is really compatible with the setup I was hoing to run.
