Nismo280zEd Posted June 3, 2006 Share Posted June 3, 2006 I thought i'd post this maybe somebody has some sources i'm not aware of. I'm looking for some diodes that can handle 80 amp continous either alone or combined with 2 or the same, etc. Anyway, it needs to be rated for 15 volts as well. I'm going to solder them inline on my alt to stop the voltage draw it has. Everything I can find is for 120 volt which when you do the math doesn't work out for the appropriate amps at 12-15 volts. Any help would be great as i'm kinda following blind sheep on this one hoping that it works. -Ed Quote Link to comment Share on other sites More sharing options...
kcelectronics Posted June 3, 2006 Share Posted June 3, 2006 Could you please explain what you are hoping to achieve by adding the diodes? Quote Link to comment Share on other sites More sharing options...
zcarnut Posted June 3, 2006 Share Posted June 3, 2006 Ed, you mean “current draw” and not “voltage draw”. As an electrical engineer I am always somewhat irked by the interchange of these different electrical properties by the layman. Anyway, there already are diodes in the alternator that should block any reverse current draw. Yes, there is a secondary sense circuit, but it only draws microamps. If you have a problem with reverse current draw then you have an alternator with “leaky” (or defective) diodes. Your series diode “fix” is not practical. Such a diode (or diodes) would have to dissipate an estimated 80W (1.0V x 80A) maximum which would require a large heat sink. Besides, you would need a diode rated at least 50V because it is well know that alternators can produce transients of +40V to -40V at the alternator output terminal when the alternator stops rotating (at engine turn off). Quote Link to comment Share on other sites More sharing options...
alexideways Posted June 3, 2006 Share Posted June 3, 2006 Well if you do decide to go this route anyways you could source some of the diodes fron another alternator. Quote Link to comment Share on other sites More sharing options...
zcarnut Posted June 3, 2006 Share Posted June 3, 2006 Well if you do decide to go this route anyways you could source some of the diodes fron another alternator. There are six diodes in an alternator as all alternators are a three-phase full-bridge configuration. Having six diodes also allows current sharing so one diode does not have to continuously carry the full current. The six alternator diodes use the case of the alternator as a heat sink. However, connecting six alternator type diodes in parallel to handle the 80A is never recommended because of unequal current sharing between the diodes and the negative temperature coefficient of the forward voltage (conduction) drop of a diode. Quote Link to comment Share on other sites More sharing options...
alexideways Posted June 3, 2006 Share Posted June 3, 2006 connecting six alternator type diodes in parallel to handle the 80A is never recommended Well, I'm not sure about what exactly he's trying to do but, I think he said that he would hook it up INLINE with the alt. not parallel. Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted June 4, 2006 Author Share Posted June 4, 2006 yes your right.. it's not volatage draw technically speaking, it is current draw causing a voltage drop from the battery over time. Yes, I'm well aware the alternator already has diodes in it for this purpose, however it's out of 7 alternators that i've had 1 had diodes that actually worked on it. So In my logicall thinking, I thought it would be better to just wire it on the output line from the alternator to the battery. I said 80amps even though the alternator is rated for 125amp. I've run an 80 amp fuse inline from the output post for 3 years now and it's never blown, or even remotly appeared to be near full potential. I'm simply trying to stop the "current draw" from the alternator on the car. It's a 95 DOHC rathed at 125amp wired up the exact same as the maxima diagramns. Yes i'm positive it's the alternator as i have taken every single wire off the terminal block one by one till it no longer had a draw. Previously i rand a large solenoid inline on the alt and this worked, however at the cost of 90 dollars and it only holding up to the elements for about a year, I'm no so sure it was a great cost, plus I thought the diodes would serve a more permanent solution to the problem. Yes I looked into using other diodes from alt, but it seems like all the imports use a series of three diodes at a replacement cost higher than i bought the alt for. Basically... I got a really nice alarm for my car, but can't wire it up cause i can't leave the battery connected right now. I would like to solve this problem before i relocate to the next apartment complex 12 days. -Ed As an electrical engineer zcarnut, maybe you can help me solve this problem. Quote Link to comment Share on other sites More sharing options...
iaconsultants Posted June 4, 2006 Share Posted June 4, 2006 In Houston there are a few what I call electronic stores that sell just about everything like chips, DAC converters, diodes, even many mil spec chips so you should be able to find them fairly easy. I do not recall the names of the places since its been a couple of years since I went to them but I will see if I can dig them up somewhere and they should have what you need. If you called the Electrical Engineering Department and University of Houston they could probably tell you where to go or their EEE group could. Just to let you know if they don't have what you need they could probably order it. Sounds like you are trying to reduce the slow drain on your battery that Z's have a common issue with. There is also one other place that causes the drain is your ignition key swithc with time the workings along with the key wear down and the key can come out even with the car running, well it is easy to not turn the key as far as it should have been turned and pull it out which puts a slow drain on the battery that would drain it enough in 4 or 5 weeks so the car will not start. Just some thoughts and I will see if I can find the places I use to go to and email them to you once I do. Good luck. Robert Quote Link to comment Share on other sites More sharing options...
zcarnut Posted June 4, 2006 Share Posted June 4, 2006 Ed, one thing puzzles me. You said you have the Maxima 125 amp alternator “wired up the exact same as the Maxima diagramsâ€, if that is true then why don’t the Maxima’s have a problem with discharging batteries? Can you tell me exactly how you have your alternator wired up to your Z car? There should be two connector terminals on the alternator plug. One is the “S†or sense terminal which should go directly to the positive post of the battery. The other is the “L†or lamp terminal which should go to a switched 12V source (like the 12V ignition source) through a relay or a diode. If the L terminal of the alternator is connected to a 12V source that is always present, then the result is battery discharging when the engine is not running. I have used the 90 amp and the 105 amp Maxima alternators in Z cars without the battery discharging. I assume that 125 amp version should be configured the same way. Quote Link to comment Share on other sites More sharing options...
alexideways Posted June 4, 2006 Share Posted June 4, 2006 Yes I looked into using other diodes from alt, but it seems like all the imports use a series of three diodes at a replacement cost higher than i bought the alt for. Well I meant go to the crap yard, buy an seized alt. for real cheap and use as many as 6 diodes for almost free. Basically... I got a really nice alarm for my car, but can't wire it up cause i can't leave the battery connected right now. For this you could hook up an kill switch for the batt and you hook up everything that needs constant power (alarme, clock, radio...) before the point were you cut thu current and ook the alt. after, this way no more drain and you get to have that nice alarm working. P.S. I work at BMW and every new cars comes with an HELLA batt. kill switch so, if you whant to pay shipping, I can GIVE you 1 + the unit also comes with about 10 ft of 0 ga. batt cable. P.P.S.: open your alt, you may have an skinned wire in there that grounds itself on the casing. it dos'nt take mutch, only one or two strands of one wire touching ground and you have an not so small drain. Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted June 4, 2006 Author Share Posted June 4, 2006 I have a kill switch but that doesn't solve my problem, yes that will allow the alarm to work, but the alarm also has remote start, which i plan to use in winter, plus it's just a cool feature. I don't want to start my car on battery only cause when i go to work that early, i'll prolly forget to flip the alt kill switch. Zcar nut, You mentioned it has to go through a switched 12 volt source, this might be the problem. The whole car has been rewired except for the tailights basically, my car does not use the ignition switch, as the key thing happened to me and i don't have the money to buy all new locks currently, so i have a series of switches and a push button starter. the main output post goes through an 8ga wire to the 80a fuse to the pos battery terminal. The sensing wires you spoke of... located on the side of my alt, yes it's basically the same as the 90a version, from it mounted in the car there is a top and bottom prong. the TOP prong is 12+ input from my fuse box set for power in ACCESORY for now. the Bottom prong loops back into the 8ga output wire without a switch. So if i understand you correctly, I need to rewired the BOTTOM wire so that it has power for ON only? as it would not be needed for ACESSORY? So once again, output goes to 8ga wire through 80a fuse in the car, then back to the battery. there is an 8ga wire grounded to the back of the alt and the car body. the TOP wire of the two prongs is a 12+ source from the fuse box power in ACCESORY and the BOTTOM wire goes back into the 8ga output wire without a switch. Can I get verification before i cut and splice? -Ed Quote Link to comment Share on other sites More sharing options...
zcarnut Posted June 4, 2006 Share Posted June 4, 2006 ...So once again, output goes to 8ga wire through 80a fuse in the car, then back to the battery. there is an 8ga wire grounded to the back of the alt and the car body. the TOP wire of the two prongs is a 12+ source from the fuse box power in ACCESORY and the BOTTOM wire goes back into the 8ga output wire without a switch.... That should work–provided that the top terminal (prong) is the L terminal and the bottom prong is the S terminal and provided that the voltage on the ACCESSORY buss goes to zero when the car is not running. Have you verified this with a voltmeter? You may have just inadvertently swapped the L and S connections. If you have a multimeter you can confirm the identity of the S and the L terminals (prongs). Unplug the two-pin connector on the alternator and measure the resistance from the alternator prongs to ground. You can use the case of the alternator as ground. The resistance of the S terminal to ground will be high, over 3 megohms, while the resistance of the L terminal will be much lower, typically 5,000 ohms. If you do not have a meter then you can try swapping the two wires going to the connector on the alternator. You will not damage anything by doing this. Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted June 5, 2006 Author Share Posted June 5, 2006 if you swap the two wires "L" and "S" respectively, then it doesn't charge, so i've found out by accident. So I'm guessing the problem lies in the wiring still? ...i really thought we were on to something -Ed Quote Link to comment Share on other sites More sharing options...
ezzzzzzz Posted June 8, 2006 Share Posted June 8, 2006 If memory serves me the Hitachi has a T shaped plug for the F and N leads. The leg of the T is F (field) and the top of the T is N (sensor). The N lead is used to monitor voltage and should go to the fuse block 12+ input. The reason is it provides a better indication of voltage drop in the system here. Many will wire it straight to the alternator output. This works but it doesn't give an accurate indication of voltage drop so charging is not ideal. The F lead goes to a switched (ignition) 12+ source. If you've got this backwards the battery will drain through the alternator with the engine off. It will charge properly however because you are still providing the required 12+ when running. I think zcarnut has it dead-on. If you have 12+ at the F lead when turned off you've found your problem. From your description it sure sounds so. Your alarm should be tied into a constant 12+ source for full time operation. The current draw will be minimal. Quote Link to comment Share on other sites More sharing options...
zcarnut Posted June 8, 2006 Share Posted June 8, 2006 If memory serves me the Hitachi has a T shaped plug for the F and N leads.... Only the early alternators that used an external voltage regulator have the "F" (field) and "N" (neutral) terminals. The later alternators with the internal regulator have the S and L terminals. The terminals have different functions and are not interchangeable. Quote Link to comment Share on other sites More sharing options...
ezzzzzzz Posted June 8, 2006 Share Posted June 8, 2006 I forgot about the internal vs external. Thanks for the correction. I still believe you pointed out the problem. It wouldn't be the first time I've seen this but it was usually on GM products. Quote Link to comment Share on other sites More sharing options...
ezzzzzzz Posted June 8, 2006 Share Posted June 8, 2006 This link over to zhome may answer all of your questions about wiring. http://www.zhome.com/ZCMnL/tech/280Alt.html Quote Link to comment Share on other sites More sharing options...
zcarnut Posted June 8, 2006 Share Posted June 8, 2006 This link over to zhome may answer all of your questions about wiring. [url']http://www.zhome.com/ZCMnL/tech/280Alt.html[/url] Or better yet just ask me as I wrote the above item! Quote Link to comment Share on other sites More sharing options...
ezzzzzzz Posted June 8, 2006 Share Posted June 8, 2006 I can be so goofy sometimes. Maybe I should concentrate on work instead of Z's... Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted June 9, 2006 Author Share Posted June 9, 2006 Well i still don't have this problem fixed and i have a 400$+ alarm sitting in my apartment waiting to be installed. ZCARNUT Since we seem to agree my wiring to the alt is correct, maybe it's the fuse box... Also.. I'd like to talk to you a little bit about my electrical system in my car as i'm sure there are many things that can be improved. Do you have autocad? I might be able to find the time to draw up how the car is wired right now on cad so it's easy to view and trace. -Ed Quote Link to comment Share on other sites More sharing options...
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