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| Disconnecting generator/alternator; How will this improve MPG? | |
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| Tweet Topic Started: Nov 21 2009, 02:25 PM (2,716 Views) | |
| JohnDN | Jan 3 2010, 10:19 PM Post #16 |
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Metro Fanatic, I was wondering how you rigged up your alternator disable switch. Is it one of the 50amp toggle switches to break the connection between the alternator output (+) post and the battery? I've tried unplugging the connector from the alternator to disable it before, but voltage at the battery was the same before and after I unplugged it, about 13.3 volts, so that must not disable it. |
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| Metro Fanatic | Jan 4 2010, 12:05 AM Post #17 |
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I don't have my schematic in front of me right now but I did use a 50 amp toggle that broke the connection between the generator (I believe the schematic showed a white wire) and the fuse and relay box in the engine compartment. (Where the 30-60 amp fusible links are seated) From there the fusible links are wired to the battery. Simple splice really. I plan and Youtubing the unit in action but with the move coming on fast...priorities will (and should) shift. |
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| snakemeister | Feb 14 2010, 08:53 PM Post #18 |
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New Member
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Hey guys I don't think I'd mess with disconnecting the alternator for several reasons. How's that affecting your computer? It was meant to run on 13+ volts.How far will it run before the battery won't start the car? How hard is the diminished voltage on your starter? How much will it shorten your battery life? |
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| nerys | Feb 14 2010, 10:00 PM Post #19 |
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Grr
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I have to wonder. Do these vehicles not have voltage regulation in them? I thought I remember cars having voltage regulators even as far back as the 50's if you go up or down a volt the computer should not care since the voltage regulation "should" adjust for this as much as it can (of course your going to hit a point where the regulator is not getting enough amps to make the adjustment) I have zero fear over undervolting the ECU it can handle itself just fine. I am however concerned with the initial "spike" when you turn it back on. but then again does this spike not also happen when you suddenly "start" the engine each morning? IE is there not circuitry in place to protect the ECU from these issues? How much solar power are you pushing? When you turn your key in the morning volts to the ECU is around 12.1 to 12.9 volts. while cranking it could in theory drop as low as 9-10 volts. when your engine is running it can push close to 14volts. this is more than a volt difference. Clearly the ecu either does not care IE has a wide range OR more likely it has some form of protection in place ie regulation of some sort. anyone have solid info? Edited by nerys, Feb 14 2010, 10:02 PM.
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| wikityler | Feb 14 2010, 10:32 PM Post #20 |
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Some say...
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The sensitive components in the ECU will be supplied regulated and filtered power at 5v. In theory those parts will operate with an input voltage as low as 6.7v-7.2v. Of more concern is the lights, radio, fan, and ignition system. |
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| mwebb | Feb 14 2010, 11:43 PM Post #21 |
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FOG
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..."anyone have solid info?"... current dogma in the auto repair world says , the networks stop operating 10% up from the low value or 10% down from the high value which may not be system voltage and may not be 5 volt reference most geo metros do not have networks spark stops working at 9.6 volts ( which also happens to be minimum voltage allowed "after" for a carbon pile load test to determine if the battery has the at least the Minimum CCA it is rated at , at 70f ) , when spark stops nothing else matters . but in reality it depends on the system and nothing functions as designed when operating outside of the value s it was designed to function in Edited by mwebb, Feb 14 2010, 11:50 PM.
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| nerys | Feb 15 2010, 12:12 AM Post #22 |
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Grr
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I figured the ECU ran a lot lower than the 14v the car runs at I was not aware it was so low! damn thats USB power though I imagine quite a bit more watts. Then again when I first got my metro and was unaware the alternator was dying (slowly the first day I got it) that night less than 80 miles on the car I notice the lights getting a wee dim and then it would start to "chug" slightly. Put it in neutral and it was fine. Eventually the chugging got worse I pulled over and it ran fine rev it as much as I wanted too and it was fine. Then I said lets see what happens if I turn it off thinking it needed a reboot (remember for whatever reason the BATTERY light did not illuminate! apparently the alt WAS putting out power just not enough) that did it. Not a click when I tried to restart it. Popped the clutch and it was running again. The headlight barely worked at all but damn it if that thing did not keep running. if it were not for the headlights I actually could have made it home but me turning on and off the lights eventually got police attention and I had to get AAA to take me home :-) I really wish I had a meter at the time as I would love to know how low the voltage got. Either way it tells me the car needs VERY little power. I am thinking about trying to run it on two RC car packs and "see" what happens. I rigged up 2 7.2v 3amp sub c cell nimh packs so I could run my 12v stuff portably (camera's etc.. ie 12v car chargers this was before USB and usb chargers became common) I am thinking Car battery for the starter and then disconnect the car battery and run on the Nimh pack and "see" how long it runs. This way I conserve the car battery for starting and don't hammer the lead cells which really hate being depleted. Even Deep Cycle batteries are REALLY deep cycle ie even those get cranky if you go below 80% too often. Might even be interesting to run the ECU directly off its own dedicated power source (rendering it immune from electrical issue) and see "what else" is drawing power. if I run the ECU direct power and "cut off" the alt and battery will the car still run? ie what else does it need to run besides the ECU for the car to function (obviously fuel pump and coil would need power) but is anything else actually critical? Edited by nerys, Feb 15 2010, 12:15 AM.
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| mwebb | Feb 15 2010, 01:01 AM Post #23 |
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FOG
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..." will the car still run? ie what else does it need to run besides the ECU for the car to function (obviously fuel pump and coil would need power) but is anything else actually critical? "... on a Geo Metro AIRBAG s - most cars will code for low system voltage in AIRBAG module before any other module on other cars ; depends on what car and what system s , the throttle body motors are running on system voltage on many cars , ask toyota how sensitive those systems can be some cars have electric brake and power steering .... most / all newer cars have networks that communicate between systems except Geo Metro |
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| Woodie | Feb 15 2010, 07:11 AM Post #24 |
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You're right, the ECM/PCM has a power supply in it that reduces the available voltage to the 5 volts it uses. It's designed to deal with the 14.4 the alternator puts out, the 12 the battery puts out, or the 11 the battery has when cranking. Sensors, solenoids, motors, and coil are going to have problems long before the ECM itself. There is a voltage regulator but it doesn't regulate the available battery voltage, it turns the alternator on and off in order to keep the battery charged. That's right, it automatically does what the original poster is installing a manual switch to do. Just like installing an injector cutoff switch, there's no point, the car came from the factory already doing that. |
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| nerys | Feb 16 2010, 12:53 AM Post #25 |
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Grr
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well not really. The alternator is ALWAYS ON. its never off. Ever. unless the engine is off. Come on we should all know this. Cars do not run on the battery. They start on the battery and then RUN off the alternator. you can remove the battery entirely and nothing bad would happen at all (this is NOT so on some of the newer more computerized cars) my geo has no electrics in the brakes no electrics in the tranny no electrics in the steering (manual steering) what are body motors? I am guessing thats something mine won't have either. If your car is using electricity YOUR ALTERNATOR IS APPLYING A LOAD. Period. so switching off the alt is not pointless. at this point your forcing your car to run off just the battery and not the alternator. if you charge the battery at home your trading gas to run the alt versus your home power to charge the battery. assuming your battery has enough capacity for your commute this might be net positive for you since home power is a lot cheaper by many orders of magnitude than gasoline is. but also be warned batteries do not like this. that starter battery is not intended to be worn down and charged up ie "cycled" to any depth of discharge. you will greatly shorten its lifespan. How much I have no idea. you will need to figure this out and make sure you save more in gas than the cost of the shorter lifespan of that battery and the E to charge it up at home. I have a feeling with a deep cycle battery it would still be net positive plus you get bragging rights of higher mpg which IS important too :-) I have no doubt I could commute on just the deep cycle battery my stereo is a pig not sure how much power it would need :-) |
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| mwebb | Feb 18 2010, 10:11 PM Post #26 |
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FOG
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>>> ...."The alternator is ALWAYS ON. its never off. Ever."... <<<< the thought above is false the voltage regulator has the ability to make the alternator charge at 100% or at 0% or anywhere in between depending on the needs of the system at the time the load that alternator puts on the engine is minimized and very small when the voltage regulator has the alternator charging at 0% , but there is still some slight load . many newer cars and systems switch the alternator off for many conditions depending on how the system is programmed like when the TPS shows system is at WOT . many have over running pulley s so on decel is alternator speed exceeds belt speed , the alternator just spins freely charging at 100% until the belt catches up. a burst of free energy ... sorta |
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| nerys | Feb 18 2010, 11:38 PM Post #27 |
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Grr
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I am sorry mwebb but you are simply not correct in this instance. The moment the alternator goes to 0% the battery would discharge and that would cause the alternator to increase above 0% and this would happen over and over rapidly. now I notice you use the word CHARGE. that is the wrong word in this discussion. The right word is apply a load. the alternator is ALWAYS applying a working load to the engine because it has to generate the needed amps the car is demanding at any given time. the battery does NOT supply these amps. The alternator does. To confirm (again this is on MY older cars this will not work or may damage some newer cars though I doubt anything as old as a metro) I can go outside RIGHT NOW and remove the battery from my Metro. I can roll the car pop the clutch and drive anywhere I want to go without issues or repercussion. the battery has one purpose only. Start the engine. Once the engine is running the battery is finished and does nothing more. SO you yourself listed the amp draws of basic components in our metro's ECU etc.. turn everything in the car off. so its only the spark plugs fuel pump and ECU and related stuff running. whatever amount of amps that stuff required. THAT is what your alternator is putting out. While the regulator MAY be able to goto 0% it never will since that would require the battery to then supply amps which is bad for the battery. What you describe in the second half of your post is a programmed system to "defeat" the normal operation of the charging system in order to gain some sort of bonus. I am pretty certain no metro has such functionality and I KNOW my metro has no such function. it was not a thought merely a statement of fact. I noted in my statement that newer cars might be exceptions. so removing the alternator WILL net a continuous bonus if you can manage the power requirements and if the savings exceeds the E to recharge the system and the faster replacement rate of the batteries etc.. but your mpg SHOULD go up. |
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| mwebb | Feb 19 2010, 12:56 AM Post #28 |
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FOG
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I am sorry mwebb but you are simply not correct in this instance. The moment the alternator goes to 0% the battery would discharge and that would cause the alternator to increase above 0% and this would happen over and over rapidly. now I notice you use the word CHARGE. that is the wrong word in this discussion. The right word is apply a load. the alternator is ALWAYS applying a working load to the engine because it has to generate the needed amps the car is demanding at any given time. the above poster is entitled to his own opinion but not his own facts that is NOT how it works |
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| nerys | Feb 19 2010, 12:27 PM Post #29 |
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Grr
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Alas that is how my car works mwebb. Its not an opinion it is in reality an "observed fact" the load the alternator applies in my car is always non zero. that is a fact not an opinion. A battery NEVER puts out 14v this is a fact. SECONDS after removing the charging source a battery will rapidly fall to its normal voltage region. so if the voltage measured is HIGHER than the sustained voltage of the battery this means the ALTERNATOR is supplying that power NOT the battery. This is really simple. It is in fact how you TEST your alternator in the simplest manner to see if its functioning at all. You can plug a meter into a car like mine and as long as the alternator is functioning properly the voltages WILL ALWAYS 100% of the time show higher than the battery standard. This means it is APPLYING a load. I am not sure what is unclear about this. While the "charging" circuit may drop to 0% I could care less about the charging circuit. I only care about the load it applies to the engine (in this discussion) and this is 100% of the time non zero. My details may not be accurate. my figures may be off. My wording may be incorrect technically or otherwise. I am by no means an expert but the following statement I can say with 100% certainty The Alternator in a car such as mine is 100% of the time supplying power to the system and therefore 100% of the time is applying some non zero load to the engine. Edited by nerys, Feb 19 2010, 12:30 PM.
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