A good peak output doesn't necessarily mean good idle output. From my understanding, alternators can be designed for great idle output, great peak output, or a compromise between idle and peak output depending on the application. Something about the winds of wires in them if I remember correctly. I agree, definitely better to charge a battery with a charger than to rely on the alternator to do it.
Minimum acceptable alternator voltage?
- Thread starter Avery4
- Start date
I have an externally regulated alternator, and I have modified my adjustable external voltage regulator, with a knob on my dash, next to my digital Ammeters and voltmeters.
I did this as I often drain my high$$ TPPL agm deeply, and want as much charging as possible whenever I drive with a depleted battery.
So I know the limits of my alternator(s) as I can and do max them out, at the flick of a wrist.
Idle speed when hot, my one 50/120 amp chrysler alternator can just barely make 50 amps, at 525 engine rpm, but can make 68 amps at 600 rpm and maxes out at 122 amps at 2300 rpm when hot, ~ 155f.
My newer Nippon denso style 50/120 amp alternator can barely make 32 amps hot at 525 rpm, but can make 82 amps at 600 engine rpm and maxes out at 109 amps at ~1300 rpm hot.
Two alternators of the same rating, VERY different power curves. Which one would be better, depends on the engine rpm range in the time I drive, as far as fast as possible battery charging, and the difference outside either extreme would be minimal.
If my TPPL AGM battery is well depleted it can easily suck well over 120 amps, and as such, a simple voltmeter might make me think the alternator was not working properly, even if it was making 85 amps, as it takes time for even that much amperage to raise the voltage up above 13.8v when starting at 11.8v.
So even with only one depleted tppl group 31 AGm battery an with either of my '120 amp' alternators, I cannot charge it as fast as it could be charged, even when I send maximum possible field current to either of the alternator's rotors, and rev engine to 2000+ rpm.
My engine requires 12.2 amps at 2000 rpm, leaving ~ 108 amps available to power loads, of which a depleted battery can be considered the biggest., at least in my rig. If I am sitting at a red light at night with blower motor on high, and lights on and stereo running, it cannot maintain much more than 13.4v, depending on the state of charge of the battery, and how long the traffic light is.
If my battery were having to provide 10 amps to keep engine running and all possible loads running, i would be able to idle for about 8 hours before the battery was dangerously depleted. but 200 more rpm and the battery would be charging again instead of powering that which the alternator could not at a lower rpm.
It should be noted a super hot alternator is not a happy alternator, and they get hottest, parked, idling at their maximum output( fully fielded), trying to charge a well depleted battery, and or powering lots of heavy loads, as there is little underhood airflow, and the alternators fan(s) are spinning too slow to keep them cool.
How hot they get varies by alternator and vehicle of course.
I have adhered K type thermocouples to my alternator's casing to find out when mine runs hottest, and basically slow speeds under 25 with low rpms, or parked idling are where the temperature skyrockets towards the 220F danger zone. At 65 mph, ~1975 rpm, making 120 amps, I cant get the casing over 145F, but parked idling maxed out both it and the voltage regulator sending it maximum field current, quickly climb towards 200f. These measurements were before some more recent modifications to better transfer heat from rectifiers to alternator casing. No new data acquired since.
Keep in mind a healthy battery at 80% charged, cannot be recharged to 100% in less than 3.5 hours. This 3.5 hours assume the battery terminals are ~14.5v the entire time, and this does not happen in 99.999% of vehicles, even if they were driven for those 3.5 hours.
You could have a 500 amp rated alternator, its not going to reduce the 3.5 hour timeframe to get a lead acid battery from 80% to 100% charged. Though the 500 amp alternator could get it from 20% to 80% quickly, but Few Lead acid batteries can handle huge charge rates without heating excessively. TPPL AGMS ( Odyssey, Northstar) are fine with it ,and prefer it, when deeply cycled, but they still can get too hot, if they start out hot.
Just because a specific alternator cannot maintain high voltages at idle does not spell instant death for the battery. The reserve capacity rating of a battery is the minutes it can power a 25 amp load ( when new and fully charged). If it hot idle in gear, foot on the brake, it cannot keep up, a few hundred more and it likely can. Put a 25 amp load on a newish fully charged group 24 battery and voltage will fall to ~12.2 in a few to several seconds, and it will take some 80 minutes before it falls below 10.5v, which is considered 100% discharged.
An Alternator with a higher rating, does not necessarily mean it can produce more amperage at hot idle speed, and often higher max rating, sacrifices low speed output.
But without accurate tools to measure and compare output, most will never know, and if the battery is well depleted, and they do not know how much amperage the battery is accepting at the voltage reaching the battery terminals, nor how much of a total combined DC load the other loads are presenting, the picture gets even more foggy.
I've done some wishful shopping for the ultimate alternator for my rig, and for my intended uses, and a 6 phase hairpin wound Mechman alternator rises to the top. but its a 400$+ for the alternator and I'd need to convert to a 10 rib serpentine belt. Not gonna happen.
I intend instead, to run both my 50/120 amp alternators in parallel on Dual V belts. I just got to figure out how to mount the second one, and honestly I can easily get away without doing this, but I would enjoy the capability of having two alternators that I already own, feeding depleted TPPL Agm battery(s) at a high rate, even if the 240 amp 6 phase hairpin wound Mechman, could outperform both.
I did this as I often drain my high$$ TPPL agm deeply, and want as much charging as possible whenever I drive with a depleted battery.
So I know the limits of my alternator(s) as I can and do max them out, at the flick of a wrist.
Idle speed when hot, my one 50/120 amp chrysler alternator can just barely make 50 amps, at 525 engine rpm, but can make 68 amps at 600 rpm and maxes out at 122 amps at 2300 rpm when hot, ~ 155f.
My newer Nippon denso style 50/120 amp alternator can barely make 32 amps hot at 525 rpm, but can make 82 amps at 600 engine rpm and maxes out at 109 amps at ~1300 rpm hot.
Two alternators of the same rating, VERY different power curves. Which one would be better, depends on the engine rpm range in the time I drive, as far as fast as possible battery charging, and the difference outside either extreme would be minimal.
If my TPPL AGM battery is well depleted it can easily suck well over 120 amps, and as such, a simple voltmeter might make me think the alternator was not working properly, even if it was making 85 amps, as it takes time for even that much amperage to raise the voltage up above 13.8v when starting at 11.8v.
So even with only one depleted tppl group 31 AGm battery an with either of my '120 amp' alternators, I cannot charge it as fast as it could be charged, even when I send maximum possible field current to either of the alternator's rotors, and rev engine to 2000+ rpm.
My engine requires 12.2 amps at 2000 rpm, leaving ~ 108 amps available to power loads, of which a depleted battery can be considered the biggest., at least in my rig. If I am sitting at a red light at night with blower motor on high, and lights on and stereo running, it cannot maintain much more than 13.4v, depending on the state of charge of the battery, and how long the traffic light is.
If my battery were having to provide 10 amps to keep engine running and all possible loads running, i would be able to idle for about 8 hours before the battery was dangerously depleted. but 200 more rpm and the battery would be charging again instead of powering that which the alternator could not at a lower rpm.
It should be noted a super hot alternator is not a happy alternator, and they get hottest, parked, idling at their maximum output( fully fielded), trying to charge a well depleted battery, and or powering lots of heavy loads, as there is little underhood airflow, and the alternators fan(s) are spinning too slow to keep them cool.
How hot they get varies by alternator and vehicle of course.
I have adhered K type thermocouples to my alternator's casing to find out when mine runs hottest, and basically slow speeds under 25 with low rpms, or parked idling are where the temperature skyrockets towards the 220F danger zone. At 65 mph, ~1975 rpm, making 120 amps, I cant get the casing over 145F, but parked idling maxed out both it and the voltage regulator sending it maximum field current, quickly climb towards 200f. These measurements were before some more recent modifications to better transfer heat from rectifiers to alternator casing. No new data acquired since.
Keep in mind a healthy battery at 80% charged, cannot be recharged to 100% in less than 3.5 hours. This 3.5 hours assume the battery terminals are ~14.5v the entire time, and this does not happen in 99.999% of vehicles, even if they were driven for those 3.5 hours.
You could have a 500 amp rated alternator, its not going to reduce the 3.5 hour timeframe to get a lead acid battery from 80% to 100% charged. Though the 500 amp alternator could get it from 20% to 80% quickly, but Few Lead acid batteries can handle huge charge rates without heating excessively. TPPL AGMS ( Odyssey, Northstar) are fine with it ,and prefer it, when deeply cycled, but they still can get too hot, if they start out hot.
Just because a specific alternator cannot maintain high voltages at idle does not spell instant death for the battery. The reserve capacity rating of a battery is the minutes it can power a 25 amp load ( when new and fully charged). If it hot idle in gear, foot on the brake, it cannot keep up, a few hundred more and it likely can. Put a 25 amp load on a newish fully charged group 24 battery and voltage will fall to ~12.2 in a few to several seconds, and it will take some 80 minutes before it falls below 10.5v, which is considered 100% discharged.
An Alternator with a higher rating, does not necessarily mean it can produce more amperage at hot idle speed, and often higher max rating, sacrifices low speed output.
But without accurate tools to measure and compare output, most will never know, and if the battery is well depleted, and they do not know how much amperage the battery is accepting at the voltage reaching the battery terminals, nor how much of a total combined DC load the other loads are presenting, the picture gets even more foggy.
I've done some wishful shopping for the ultimate alternator for my rig, and for my intended uses, and a 6 phase hairpin wound Mechman alternator rises to the top. but its a 400$+ for the alternator and I'd need to convert to a 10 rib serpentine belt. Not gonna happen.
I intend instead, to run both my 50/120 amp alternators in parallel on Dual V belts. I just got to figure out how to mount the second one, and honestly I can easily get away without doing this, but I would enjoy the capability of having two alternators that I already own, feeding depleted TPPL Agm battery(s) at a high rate, even if the 240 amp 6 phase hairpin wound Mechman, could outperform both.
Why do cop cars and taxis have heavy duty batteries? It's because the engineers know they idle a lot and need to run accessories. There is only so much even an oversized alternator can do at idle.
It all works out.
This is the electrical equivalent of worrying that your oil pressure drops at high idle. If you get up in the high 13s or preferably 14s driving down the road, your battery is getting charged.
If you want something to worry about, it's those "smart" charging systems that dip voltage to save fuel.
It all works out.
This is the electrical equivalent of worrying that your oil pressure drops at high idle. If you get up in the high 13s or preferably 14s driving down the road, your battery is getting charged.
If you want something to worry about, it's those "smart" charging systems that dip voltage to save fuel.
Well it seems actually adequate alternators do (rarely) exist. I tested the idle output on my K24 swapped 04 Civic and its 15+ year old OEM Denso Acura TSX alternator keeps up beautify. With the engine idling at ~750 RPM and everything electrical on (high beams, rear defroster, blower on high, radio on almost max volume, wipers on high, brake lights, interior lights, and hazards) it still charges the battery at around 13.9 volts with about a 70 amp load. What a concept, an alternator that actually keeps up at idle!
You don't check the alternator at idle. At least 1500RPM.
I once measured the idle output of the alternator in my 2006 Saab 93 at about 120 amps. And Ford's 3G alternators are known to have good output at idle as well. This is probably important in a vehicle with an electric cooling fan that can pull 50 amps or more...
Now, my 1998 Nissan Frontier seems to have a problem with it's alternator. At idle, it only outputs 12.4V (measured with a Fluke 87V at the battery terminals) with the headlights on and the blower fan on high. Going down the road it outputs 14V (measured with a Scangauge). I also notice that the voltage display on the Scangauge bounces around quite a bit, varying as much as 0.5V, making me wonder if maybe it has a bad diode.
Now, my 1998 Nissan Frontier seems to have a problem with it's alternator. At idle, it only outputs 12.4V (measured with a Fluke 87V at the battery terminals) with the headlights on and the blower fan on high. Going down the road it outputs 14V (measured with a Scangauge). I also notice that the voltage display on the Scangauge bounces around quite a bit, varying as much as 0.5V, making me wonder if maybe it has a bad diode.
The only Ford alternator I remember testing the output on was my friend's 1996 Bronco and it wasn't great but it wasn't the worst I have seen either. With everything on at idle, it kept the battery at around 12.5 volts and produced somewhere around 60 amps if I remember correctly. He wanted electric fans and a high end sound system, so I put a Mechman 320 amp alternator on it and I have seen it produce 200+ amps at idle.
Assuming the battery is reasonably charged, 12.4 volts at idle with just the headlights and blower on does seem low. Wouldn't hurt to check the voltage directly at the alternator to rule out possible voltage drops. Also, I have been using a Scangauge since 2016 and although it's a great device, it's voltage has never read very consistently or accurately. I'd say it's accurate to around 0.5 volts or so, which is good enough to see if the alternator is working or not but not much more than that.
There are volt meters that plug into the cigarette lighter and they may be better than the Scangauge, but they aren't necessarily exact either. Depending on how the cigarette lighter circuit is wired, it could have a reasonably significant voltage drop that's affected by other loads independently of actual battery voltage.
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The 1996 Bronco probably had a 90 amp 3G alternator. So getting close to 66% of it's max output at idle.
I'll get a cigarette lighter cord and connect my multimeter to it and see what the voltage looks like that way.
Can you give an example of how it would be wired to cause this droop? This has not been my experience, unless you have other things running on the same, lighter circuit. With no load besides the few mA of the voltmeter, there should be practically zero voltage drop between what it sees and the battery.
Not sure where you guys are getting the idea that alternators put out so much at idle.. They don't, unless the battery voltage is low so it's a VA difference, not a rating of amps at closer to 14.[n]V. It depends on pulley ratio but most alternators at idle, in a good design (crappy would be putting out more than this, overstressing the alternator with higher RPM at high engine RPM) are producing less than half their rated max output. More is not better at idle to the extent that more than needed RPM to meet the load just wears it out faster. If you need to run a lot (more than expected vehicle equipment) at idle you instead get a larger/rated alternator.
One way it could is if the lighter circuit is wired through the ignition switch as many are. If it is, other components that are also wired through the ignition switch will create a voltage drop through the ignition switch as well as its main power feed wires. And if the lighter circuit is powered by an interior fusebox, any other loads on that fusebox will create a voltage drop on its power feed wires. There have been situations where I have measured 14.3 volts at the battery and 13.5 volts at the lighter socket under the same conditions with the same meter, so it's something to be aware of.
I realize that, but I also think a "good" design will at least be capable of generating enough current at idle to keep up with the demands of a stock electrical system rather than forcing the electrical system to draw a significant amount of current from the battery. 13 volt would accomplish this. A higher peak output doesn't necessarily mean more power at idle either. As stated in post #24, it's definitely possible for an OEM alternator at the stock pulley ratio to actually keep up at idle.
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^ Can you provide a diagram that routes the lighter through the ignition switch? This seems very unusual to me, usually the lighter has almost nothing else significant on it because by itself it's at least 10A, usually 15A draw per outlet by itself. It doesn't go through the switch, maybe through an accessory relay but that's just activating it with its own wire lead to it so no voltage drop from that.
The ignition switch itself is just a signal, is not high current to anything rather just a logic level signal. *usually* Go back enough decades and I'm sure that's not the case but we're talking several decades.
Yes, a properly designed electrical system including alternator will not drain the battery at idle with all the factory installed features running, meaning it must be over 12.8V or so. A higher peak output usually does mean more power at idle RPM, all else equal.
Any OEM alternator with the stock pulley should keep up at idle, but it doesn't mean that the lofty amp claims are accurate. It's just not right, the numbers do not add up. That is not amps at 14V+ at idle unless it's wearing out the alternator prematurely at higher engine RPM... can't really have it both ways.
The ignition switch itself is just a signal, is not high current to anything rather just a logic level signal. *usually* Go back enough decades and I'm sure that's not the case but we're talking several decades.
Yes, a properly designed electrical system including alternator will not drain the battery at idle with all the factory installed features running, meaning it must be over 12.8V or so. A higher peak output usually does mean more power at idle RPM, all else equal.
Any OEM alternator with the stock pulley should keep up at idle, but it doesn't mean that the lofty amp claims are accurate. It's just not right, the numbers do not add up. That is not amps at 14V+ at idle unless it's wearing out the alternator prematurely at higher engine RPM... can't really have it both ways.
Sure. Here's a diagram for my Honda Civic. I assume plenty of other cars have a similar setup since the lighter circuit is often only live with the key on and I have never seen a vehicle with a separate relay just for the lighter socket. And since the ignition switch is only fed with about a 12 gauge wire all the way from the underhood fusebox, it's easy to see how there could be a measurable voltage drop at the lighter outlet.
I and several other people in this thread have seen plenty of vehicles with alternators that can't keep up at idle. With everything on and the engine idling, my Civic's stock 70 amp alternator could only keep the voltage in the low 12's. ScannerDanner himself said that it's expected for some alternators to not be able to keep up at idle, which I think is absolutely ridiculous.
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The alternator makes as much amperage as it need to, or is capable of, to meet the voltage demand of the voltage regulator.
At hot idle, in drive, foot on the brake my one alternator is good for ~50 amps. If I apply 55 amps of load it cannot maintain the 14.4v I have chosen and the battery makes up that 5 amps and will slowly drop from 14.4v. 200 more rpm and it can make 68 amps. Sometimes my depleted battery can suck up 55+ amps by itself, so the alternator is fully fielded and system voltage is directly related to engine rpm. When the battery is full, or basically 95% or higher state of charge, all my other loads cannot exceed about 35 amps and the alternator has no issues holding whatever voltage I choose, whether it be 13.6 or 14.7v, as I have modified my external regulators with a dial on my dash to control voltage.
a 12v power port can certainly read well less than a voltage reading right on the battery terminals. The stock ciggy receptacle on my rig was fed through about 3 different connections even before it got to the fuse block from the battery, then that circuit from fuse block was only 18 awg. and Shared with something else, I cannot remember what, as That 18awg was removed and covered and 10AWG run directly to it 12v powerport/ciggy receptacle from the battery, fused at the battery, for 30 amps.
The best voltmeter for monitoring driving down the road and starting voltage, takes its readings right from the battery terminals and shares no wiring with any other product. A powerport voltmeter will drop when one turns on the seat heaters or similar load, but the voltmeter placed directly on teh battery terminals would likely budge very little, and only temporarily, the moment the seat heaters are turned on, or off.
This 3 wire, 5 digit voltmeter is pretty accurate, and samples voltage 5 times per second. Run the yellow to battery +, fused there, run the black to the battery -, run the red to a source which is switched on with the ignition.
Watch it during cold engine starts, and watch it fall lower and lower each cold engine start as the battery ages, or the colder it gets, and Never be surprised by a dead battery again. When it falls into the mid 8's Is when i know the end is near, but some newer vehicles this might be mid 9's.
It will also show the wacky voltage regulation of some vehicles when driving.
Far too many people take one voltage reading at idle, and make blanket statements as to the voltage their 'alternator makes' as if the regulator always demands that voltage or the alternator can make enough amperage to maintain it, when it is but one data point in a sea of variables.
A precision voltmeter attached directly to battery terminals removes the ignorance, for those that don't find that sorry state to be desirable/soothing.
A voltmeter anddigital Ammeter is even better. Slide a battery cable through this, + or -.
The opening in the hall effect sensor is only 3/4 inch though, and I;ve found its voltmeter to be off by 0.15 to 0.18v, but the ammeter more than accurate enough. It can display amps, volts or toggle between both. i only use them for amps and use separate voltmeters. Wish they had red displays. the green is way too bright at night. 2 layers of window tint helps.
You can guess, and hope, or you can know.
Your choice.
At hot idle, in drive, foot on the brake my one alternator is good for ~50 amps. If I apply 55 amps of load it cannot maintain the 14.4v I have chosen and the battery makes up that 5 amps and will slowly drop from 14.4v. 200 more rpm and it can make 68 amps. Sometimes my depleted battery can suck up 55+ amps by itself, so the alternator is fully fielded and system voltage is directly related to engine rpm. When the battery is full, or basically 95% or higher state of charge, all my other loads cannot exceed about 35 amps and the alternator has no issues holding whatever voltage I choose, whether it be 13.6 or 14.7v, as I have modified my external regulators with a dial on my dash to control voltage.
a 12v power port can certainly read well less than a voltage reading right on the battery terminals. The stock ciggy receptacle on my rig was fed through about 3 different connections even before it got to the fuse block from the battery, then that circuit from fuse block was only 18 awg. and Shared with something else, I cannot remember what, as That 18awg was removed and covered and 10AWG run directly to it 12v powerport/ciggy receptacle from the battery, fused at the battery, for 30 amps.
The best voltmeter for monitoring driving down the road and starting voltage, takes its readings right from the battery terminals and shares no wiring with any other product. A powerport voltmeter will drop when one turns on the seat heaters or similar load, but the voltmeter placed directly on teh battery terminals would likely budge very little, and only temporarily, the moment the seat heaters are turned on, or off.
This 3 wire, 5 digit voltmeter is pretty accurate, and samples voltage 5 times per second. Run the yellow to battery +, fused there, run the black to the battery -, run the red to a source which is switched on with the ignition.
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Watch it during cold engine starts, and watch it fall lower and lower each cold engine start as the battery ages, or the colder it gets, and Never be surprised by a dead battery again. When it falls into the mid 8's Is when i know the end is near, but some newer vehicles this might be mid 9's.
It will also show the wacky voltage regulation of some vehicles when driving.
Far too many people take one voltage reading at idle, and make blanket statements as to the voltage their 'alternator makes' as if the regulator always demands that voltage or the alternator can make enough amperage to maintain it, when it is but one data point in a sea of variables.
A precision voltmeter attached directly to battery terminals removes the ignorance, for those that don't find that sorry state to be desirable/soothing.
A voltmeter anddigital Ammeter is even better. Slide a battery cable through this, + or -.
The opening in the hall effect sensor is only 3/4 inch though, and I;ve found its voltmeter to be off by 0.15 to 0.18v, but the ammeter more than accurate enough. It can display amps, volts or toggle between both. i only use them for amps and use separate voltmeters. Wish they had red displays. the green is way too bright at night. 2 layers of window tint helps.
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You can guess, and hope, or you can know.
Your choice.
I'm just going to opt out of this topic now that wrcsixeight has introduced so much utter BS that I can't even begin to (nor want to bother with) the pages and pages of rebuttal at how ludicrous all that nonsense posted was. It's literally absurd, ignorance, and I'll leave it at that and yes, I don't guess, and don't hope, and I know a heck of a lot more than wrcsixeight's nonsense.
Find the fault and fix it, you do not need to consider any of the BS wrcsixeight posted. It's utter stupidity.
Find the fault and fix it, you do not need to consider any of the BS wrcsixeight posted. It's utter stupidity.
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I have a 130 amp 3g alternator in my 96 F250 that reads 14.3v across the terminals at an idle even when when it's putting out 70 plus amps to charge my camper batteries. I don't remember the brand but I got it cheap on rockauto.
Keep in mind a depleted battery can easily accept All of the alternator output at idle, and voltage will only slowly climb.
Some alternators that have their voltage regulators inside the alternator will heat up and reduce target voltage, and thus stress on the alternator, as at lesser electrical pressure the depleted battery will not ask for as much amperage.
Theres a lot of good info in this article on this topic, even if it is outside he strictly automotive domain.
Modern vehicle voltage regulation can be rather convoluted, as to what the regulator is seeking, and when it is seeking higher voltages, and how it is programmed. and what potential variables are used to influence its behavior.
Some alternators that have their voltage regulators inside the alternator will heat up and reduce target voltage, and thus stress on the alternator, as at lesser electrical pressure the depleted battery will not ask for as much amperage.
Theres a lot of good info in this article on this topic, even if it is outside he strictly automotive domain.
Automotive Alternators vs. Deep Cycle Batteries - Marine How To
A Deep Cycle Battery Assassin The alternator pictured here helped to destroy a very expensive bank of TPPL AGM batteries in under two years. These batteries need an absorption voltage of 14.7V. The highest voltage I recorded on this vessel was 13.58V at the battery terminals. At this
marinehowto.com
Modern vehicle voltage regulation can be rather convoluted, as to what the regulator is seeking, and when it is seeking higher voltages, and how it is programmed. and what potential variables are used to influence its behavior.
Can you list a specific example of a vehicle that has a relay for the lighter circuit? I'm not a professional mechanic but I have worked on quite a few vehicles and never saw that. None of my vehicles have one. But even if it did, there will still be some amount of voltage drop across the underdash fusebox's main supply wires and my point still remains valid.
If a design is adequate to begin with, I agree. Unfortunately some designs just aren't adequate.
^ can you list a vehicle that doesn't? Any vehicle where it is not live with ignition or accessory off does this. I do agree that many vehicles have an always live lighter outlet but today, a switched off outlet is also, as common as not to preserve battery.
No, there is not much if any appreciable voltage drop across fuses and wires with the load is only a voltmeter, as the voltage drop is a matter of amount of current drawn, the resistance the circuit causes. If there is OTHER load on that circuit, then yes that other load causes a voltage drop, but a voltmeter alone causes only mA by itself, could be fed by a very small gauge wire and still be plenty accurate if it is the only load across that wire.
On the other hand if someone is measuring on a crusty old lighter outlet, I wonder if oxidation or tobacco tar is fouling the reading.
No, there is not much if any appreciable voltage drop across fuses and wires with the load is only a voltmeter, as the voltage drop is a matter of amount of current drawn, the resistance the circuit causes. If there is OTHER load on that circuit, then yes that other load causes a voltage drop, but a voltmeter alone causes only mA by itself, could be fed by a very small gauge wire and still be plenty accurate if it is the only load across that wire.
On the other hand if someone is measuring on a crusty old lighter outlet, I wonder if oxidation or tobacco tar is fouling the reading.
The 1998 Nissan Frontier does have a relay for the "12V power outlet". It does not have a relay for the "cigarette lighter socket". Yes, it has two sockets. Yes, both are only live when the key is ON (or probably also accessory).
A voltmeter has a high enough internal resistance/impedance (the digital ones say 10 megohms) that it can display an accurate reading with your hand completing the circuit.
One thing I did once was to put a meter probe into the hot slot of electrical outlet, then pick up the other meter probe while touching a grounded object. Meter reads 120V. I don't feel a thing.
